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Nightingale, Kathryn Radabaugh

Overview:

The goals of our laboratory are to investigate and improve ultrasonic imaging methods for clinically-relevant problems. We do this through theoretical, experimental, and simulation methods. The main focus of our recent work is the development of novel, acoustic radiation force impulse (ARFI)-based elasticity imaging methods to generate images of the mechanical properties of tissue, involving interdisciplinary research in ultrasonics and tissue biomechanics. We have access to the engineering interfaces of several commercial ultrasound systems which allows us to design, rapidly prototype, and experimentally demonstrate custom sequences to explore novel beamforming and imaging concepts. We employ FEM modeling methods to simulate the behavior of tissues during mechanical excitation, and we have integrated these tools with ultrasonic imaging modeling tools to simulate the ARFI imaging process. We maintain strong collaborations with the Duke University Medical Center where we work to translate our technologies to clinical practice. The ARFI imaging technologies we have developed have served as the basis for commercial imaging technologies that are now being used in clinics throughout the world.  We are also studying the risks and benefits of increasing acoustic output energy for specific clinical imaging scenarios, with the goal of improving ultrasonic image quality in the difficult-to-image patient.

Positions:

James L. and Elizabeth M. Vincent Professor of Biomedical Engineering

Biomedical Engineering
Pratt School of Engineering

Professor in the Department of Biomedical Engineering

Biomedical Engineering
Pratt School of Engineering

Member of the Duke Cancer Institute

Duke Cancer Institute
School of Medicine

Education:

B.S. 1989

B.S. — Duke University

Ph.D. 1997

Ph.D. — Duke University

News:

Grants:

Improved ultrasound imaging using elevated acoustic output

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
March 01, 2016
End Date
December 31, 2019

Early Detection of Clinically Significant Prostate Cancer using Ultrasonic Acoustic Radiation Force Impulse (ARFI) Imaging

Administered By
Biomedical Engineering
AwardedBy
United States Army Medical Research Acquisition Activity
Role
Principal Investigator
Start Date
September 15, 2016
End Date
September 14, 2019

Training in Medical Imaging

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
July 15, 2003
End Date
August 31, 2019

Acoustic Radiation Force Impulse (ARFI) Imaging of Cardiac Tissue

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Investigator
Start Date
May 15, 2009
End Date
March 31, 2019

Acoustic Radiation Force Based Hepatic Elasticity Quantification and Imaging

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
September 10, 2001
End Date
July 31, 2017

Medical Scientist Training Program

Administered By
School of Medicine
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
July 01, 1997
End Date
June 30, 2017

Radiation Force Imaging of Prostate Cancer and Guidance of Biopsy Procedures

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
January 18, 2010
End Date
December 31, 2015

Acoustic Radiation Force Impulse (ARFI) Imaging of Cardiac Tissue

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Investigator
Start Date
May 15, 2009
End Date
March 31, 2014

Assessing Use of Acoustic Radiation Force to Noninvasively Measure Liver Pressure

Administered By
School of Medicine
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
March 01, 2012
End Date
February 28, 2014

Acoustic Radiation Force Impulse (AFRI) Imaging for Prostate Cancer

Administered By
Biomedical Engineering
AwardedBy
United States Army Medical Research and Materiel Command
Role
Principal Investigator
Start Date
March 01, 2008
End Date
March 31, 2011

Acoustic Radiation Force Imaging of Colorectal Tissues

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
April 04, 2005
End Date
January 31, 2011

Laboratory Renovation for Teaching and Research

Administered By
Biomedical Engineering
AwardedBy
Lord Foundation of North Carolina
Role
Principal Investigator
Start Date
May 01, 1998
End Date
June 30, 1999
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Publications:

Robust characterization of viscoelastic materials from measurements of group shear wave speeds

© 2016 IEEE.This study describes a new method to determine the stiffness μ0 and viscosity η of viscoelastic materials by observing shear wave propagation following localized, impulsive excitations and measuring the group shear wave speeds Vdisp and Vvel determined using the shear wave displacement and velocity signals, respectively. The stiffness and viscosity are found by analytically solving the equation of motion describing shear wave propagation and calculating lookup tables μ0(Vdisp, Vvel) and η(Vdisp, Vvel) to give μ0 and η from the measured shear wave speeds. Results are presented for three viscoelastic phantoms and one approximately elastic phantom. The method is robust because group shear wave speeds are easily measured experimentally, the lookup tables are relatively insensitive to the size and shape of the excitation, and the difference ΔV = Vvel - Vdisp gives a first order measure of viscosity in the same way that the group shear wave speed gives a measure of the material stiffness.

Authors
Rouze, NC; Deng, Y; Palmeri, ML; Nightingale, KR
MLA Citation
Rouze, NC, Deng, Y, Palmeri, ML, and Nightingale, KR. "Robust characterization of viscoelastic materials from measurements of group shear wave speeds." November 1, 2016.
Source
scopus
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Volume
2016-November
Publish Date
2016
DOI
10.1109/ULTSYM.2016.7728832

Comparison between 3D ARFI imaging and mpMRI in detecting clinically-significant prostate cancer lesions

© 2016 IEEE.Current prostate cancer screening methods involve non-targeted needle biopsies and detection of clinically-insignificant lesions that receive excessive treatments, exposing patients to unnecessary adverse side effects and placing a burden on our health care systems. There is a strong clinical need for improved prostate imaging methods that are sensitive and specific for clinically-significant prostate cancer lesions to guide needle biopsies, target focal treatments, and improve overall patient outcomes. In this study, we compared 3D in vivo Acoustic Radiation Force Impulse (ARFI) imaging with 3 Tesla, endorectal coil, multi-parametric magnetic resonance imaging (mpMRI) to correlate the ability for each modality to identify clinically-significant prostate cancer lesions. We also correlated Apparent Diffusion Coefficient (ADC) values from Diffusion Weighted Imaging (DWI) MR sequences with ARFI indices of suspicion and MR Prostate Imaging - Reporting and Data Systems (PI-RADS) scores, testing the hypothesis that increased cellular density is associated with regions suspicious for prostate cancer in ARFI images. Overall, ARFI and mpMR imaging were well-correlated in identifying clinically-significant prostate cancer lesions. There were several cases where only one of the imaging modalities was able to identify the prostate cancer lesion, highlighting the potential to further improve prostate cancer lesion detection and localization with a fused ARFI:mpMRI imaging system. ADC values were decreased in all prostate cancer lesions identified with mpMRI, but there were no obvious trends between the absolute ADC values and the ARFI image indices of suspicion.

Authors
Palmeri, M; Glass, T; Gupta, R; McCormick, M; Brown, A; Polascik, T; Rosenzweig, S; Buck, A; Nightingale, K
MLA Citation
Palmeri, M, Glass, T, Gupta, R, McCormick, M, Brown, A, Polascik, T, Rosenzweig, S, Buck, A, and Nightingale, K. "Comparison between 3D ARFI imaging and mpMRI in detecting clinically-significant prostate cancer lesions." November 1, 2016.
Source
scopus
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Volume
2016-November
Publish Date
2016
DOI
10.1109/ULTSYM.2016.7728618

Dispersion analysis in skin using FEM: Characterizing the effects of the lower boundary material on the propagation of shear waves

© 2016 IEEE.Skin represents a complex structure for the quantification of viscoelastic (VE) properties using shear waves. Wave propagation through skin has been modeled as propagating both as a Lamb wave and as a Rayleigh wave, but both assumptions are limited due to the structure of the skin, which is a multi-layered tissue. This complexity of structure makes it difficult to accurately assess the relative contributions of geometry and viscosity to shear wave dispersion. In this study we used finite element modeling (FEM) to simulate the layering and VE properties of skin and subcutaneous tissues to assess characteristics of shear wave propagation through skin. Results were compared to the expected solutions using pure Rayleigh wave or Lamb wave models. From the simulation it was established that under most physiological circumstances the Lamb wave model is more appropriate than the Rayleigh wave model, higher frequencies should be used for viscoelasticity characterization, and imaging thicker regions of skin facilitates higher accuracy for characterizing its VE properties.

Authors
Pely, A; Nightingale, KR; Palmeri, ML
MLA Citation
Pely, A, Nightingale, KR, and Palmeri, ML. "Dispersion analysis in skin using FEM: Characterizing the effects of the lower boundary material on the propagation of shear waves." November 1, 2016.
Source
scopus
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Volume
2016-November
Publish Date
2016
DOI
10.1109/ULTSYM.2016.7728410

On the feasibility of estimating ultrasonic shear wave attenuation using amplitude-based methods

© 2016 IEEE.Human tissues are known to be viscoelastic (VE), a type of material described by two behaviors: dispersion and attenuation. Several methods have been developed to measure shear wave dispersion, but quantifying shear wave attenuation (α) has been less successful, particularly using amplitude-based methods. Shear wave displacement amplitudes are dependent on several factors including geometric spreading, shear attenuation, and bias in ultrasonic displacement amplitude estimation. Recent developments using 3D single track location (STL) shear wave imaging have significantly reduced the error in effective tracking location arising from speckle bias, preserving the relative amplitudes of the shear wave. Using a cylindrically symmetric source, the shear wave can be modeled as a cylindrical wave, whose geometric decay is 1/√r. Shear wave displacements were generated from an analytic model and Gaussian white noise was added to the temporal shear wave velocity profiles to mimic jitter (25 dB SNR). One hundred realizations of noise were combined to model different radial trajectories from the excitation in the lateral-elevation plane of a volumetric acquisition. The time-domain Fourier Transform (FT) of these profiles was computed and shear attenuation as a function of frequency was estimated from the amplitude decay after correcting for geometric spreading. The results are compared with shear attenuation estimation obtained using the spectral spreading 2D-FT attenuation method. Root-mean-square-error (RMSE) compared to the analytic solution was calculated for both methods over the frequency range of 100 to 300 Hz. Both methods perform comparably with a large spatial extent (>40 mm); however the 2D-FT methods exhibit considerable bias with smaller window sizes.

Authors
Lipman, SL; Rouze, NC; Palmeri, ML; Nightingale, KR
MLA Citation
Lipman, SL, Rouze, NC, Palmeri, ML, and Nightingale, KR. "On the feasibility of estimating ultrasonic shear wave attenuation using amplitude-based methods." November 1, 2016.
Source
scopus
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Volume
2016-November
Publish Date
2016
DOI
10.1109/ULTSYM.2016.7728789

Evaluating the Improvement in Shear Wave Speed Image Quality Using Multidimensional Directional Filters in the Presence of Reflection Artifacts

Authors
Lipman, SL; Rouze, NC; Palmeri, ML; Nightingale, KR
MLA Citation
Lipman, SL, Rouze, NC, Palmeri, ML, and Nightingale, KR. "Evaluating the Improvement in Shear Wave Speed Image Quality Using Multidimensional Directional Filters in the Presence of Reflection Artifacts." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 63.8 (August 2016): 1049-1063.
Source
crossref
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
63
Issue
8
Publish Date
2016
Start Page
1049
End Page
1063
DOI
10.1109/TUFFC.2016.2558662

Identifying Clinically Significant Prostate Cancers using 3-D In Vivo Acoustic Radiation Force Impulse Imaging with Whole-Mount Histology Validation.

Overly aggressive prostate cancer (PCa) treatment adversely affects patients and places an unnecessary burden on our health care system. The inability to identify and grade clinically significant PCa lesions is a factor contributing to excessively aggressive PCa treatment, such as radical prostatectomy, instead of more focal, prostate-sparing procedures such as cryotherapy and high-dose radiation therapy. We have performed 3-D in vivo B-mode and acoustic radiation force impulse (ARFI) imaging using a mechanically rotated, side-fire endorectal imaging array to identify regions suspicious for PCa in 29 patients being treated with radical prostatectomies for biopsy-confirmed PCa. Whole-mount histopathology analyses were performed to identify regions of clinically significant/insignificant PCa lesions, atrophy and benign prostatic hyperplasia. Regions of suspicion for PCa were reader-identified in ARFI images based on boundary delineation, contrast, texture and location. These regions of suspicion were compared with histopathology identified lesions using a nearest-neighbor regional localization approach. Of all clinically significant lesions identified on histopathology, 71.4% were also identified using ARFI imaging, including 79.3% of posterior and 33.3% of anterior lesions. Among the ARFI-identified lesions, 79.3% corresponded to clinically significant PCa lesions, with these lesions having higher indices of suspicion than clinically insignificant PCa. ARFI imaging had greater sensitivity for posterior versus anterior lesions because of greater displacement signal-to-noise ratio and finer spatial sampling. Atrophy and benign prostatic hyperplasia can cause appreciable prostate anatomy distortion and heterogeneity that confounds ARFI PCa lesion identification; however, in general, ARFI regions of suspicion did not coincide with these benign pathologies.

Authors
Palmeri, ML; Glass, TJ; Miller, ZA; Rosenzweig, SJ; Buck, A; Polascik, TJ; Gupta, RT; Brown, AF; Madden, J; Nightingale, KR
MLA Citation
Palmeri, ML, Glass, TJ, Miller, ZA, Rosenzweig, SJ, Buck, A, Polascik, TJ, Gupta, RT, Brown, AF, Madden, J, and Nightingale, KR. "Identifying Clinically Significant Prostate Cancers using 3-D In Vivo Acoustic Radiation Force Impulse Imaging with Whole-Mount Histology Validation." Ultrasound in medicine & biology 42.6 (June 2016): 1251-1262.
PMID
26947445
Source
epmc
Published In
Ultrasound in Medicine & Biology
Volume
42
Issue
6
Publish Date
2016
Start Page
1251
End Page
1262
DOI
10.1016/j.ultrasmedbio.2016.01.004

On System-Dependent Sources of Uncertainty and Bias in Ultrasonic Quantitative Shear-Wave Imaging.

Ultrasonic quantitative shear-wave imaging methods have been developed over the last decade to estimate tissue elasticity by measuring the speed of propagating shear waves following acoustic radiation force excitation. This work discusses eight sources of uncertainty and bias arising from ultrasound system-dependent parameters in ultrasound shear-wave speed (SWS) measurements. Each of the eight sources of error is discussed in the context of a linear, isotropic, elastic, homogeneous medium, combining previously reported analyses with Field II simulations, full-wave 2-D acoustic propagation simulations, and experimental studies. Errors arising from both spatial and temporal sources lead to errors in SWS measurements. Arrival time estimation noise, speckle bias, hardware fluctuations, and phase aberration cause uncertainties (variance) in SWS measurements, while pulse repetition frequency (PRF) and beamforming errors, as well as coupling medium sound speed mismatch, cause biases in SWS measurements (accuracy errors). Calibration of the sources of bias is an important step in the development of shear-wave imaging systems. In a well-calibrated system, where the sources of bias are minimized, and averaging over a region of interest (ROI) is employed to reduce the sources of uncertainty, an SWS error can be expected.

Authors
Deng, Y; Rouze, NC; Palmeri, ML; Nightingale, KR
MLA Citation
Deng, Y, Rouze, NC, Palmeri, ML, and Nightingale, KR. "On System-Dependent Sources of Uncertainty and Bias in Ultrasonic Quantitative Shear-Wave Imaging." IEEE transactions on ultrasonics, ferroelectrics, and frequency control 63.3 (March 2016): 381-393.
PMID
26886980
Source
epmc
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
63
Issue
3
Publish Date
2016
Start Page
381
End Page
393
DOI
10.1109/tuffc.2016.2524260

Ultrasonic Shear Wave Elasticity Imaging (SWEI) Sequencing and Data Processing Using a Verasonics Research Scanner

Authors
Deng, Y; Rouze, NC; Palmeri, ML; Nightingale, KR
MLA Citation
Deng, Y, Rouze, NC, Palmeri, ML, and Nightingale, KR. "Ultrasonic Shear Wave Elasticity Imaging (SWEI) Sequencing and Data Processing Using a Verasonics Research Scanner." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (2016): 1-1.
Source
crossref
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Publish Date
2016
Start Page
1
End Page
1
DOI
10.1109/TUFFC.2016.2614944

Quantifying the benefit of elevated acoustic output in harmonic imaging

© 2015 IEEE.Tissue harmonic imaging (THI) has been widely used in abdominal imaging due to its significant reduction in acoustic noise compared to fundamental imaging. However, THI can be both signal-to-noise ratio (SNR) and penetration-depth limited during clinical imaging, resulting in decreased diagnostic utility. A logical approach is to increase the source pressure, but the in situ pressures used in diagnostic imaging have been subject to a de facto upper limit based upon the Food and Drug Administration (FDA) guideline for the Mechanical Index (MI < 1.9) since 1992. A recent AIUM report concluded that exceeding MI of 1.9 up to an estimated in situ value of 4.0, could be warranted without concern for increased risk of cavitation in non-fetal tissues without gas bodies. This work quantifies the benefit of elevated acoustic output in hepatic harmonic imaging. Increasing MI values were shown to be associated with increases in harmonic signal content, penetration depth, and vessel Contrast-to-noise ratio in THI images. Obese patients who suffer from poor ultrasound image quality are more likely to benefit from elevated acoustic output to enable better THI performance.

Authors
Deng, Y; Palmeri, ML; Rouze, NC; Haysteady, CM; Nightingale, KR
MLA Citation
Deng, Y, Palmeri, ML, Rouze, NC, Haysteady, CM, and Nightingale, KR. "Quantifying the benefit of elevated acoustic output in harmonic imaging." November 13, 2015.
Source
scopus
Published In
2015 IEEE International Ultrasonics Symposium, IUS 2015
Publish Date
2015
DOI
10.1109/ULTSYM.2015.0299

System dependent sources of error in time-of-flight shear wave speed measurements

© 2015 IEEE.This work discusses eight sources of uncertainty and bias arising from system dependent parameters in ultrasound shear wave speed (SWS) measurement. Each of the eight error sources of error we have identified is discussed in the context of a linear, isotropic, elastic, homogeneous medium, combining previously reported analyses with Field II simulations, full-wave 2D acoustic propagation simulations and experimental studies. Errors arising from both spatial and temporal sources lead to errors in SWS measurements. Arrival time estimation noise, speckle bias, master clock jitter, and phase aberration cause uncertainties (variance) in SWS measurements, while pulse repetition frequency and beamforming errors, as well as coupling medium sound speed mismatch cause biases in SWS measurements (accuracy errors). Calibration of these sources of error is an important step in the development of shear wave imaging systems. In a well-calibrated system, where the sources of biases are minimized, and averaging over an ROI is employed to reduce the sources of uncertainty, a SWS error < 3% can be expected.

Authors
Deng, Y; Rouze, NC; Palmeri, ML; Nightingale, KR
MLA Citation
Deng, Y, Rouze, NC, Palmeri, ML, and Nightingale, KR. "System dependent sources of error in time-of-flight shear wave speed measurements." November 13, 2015.
Source
scopus
Published In
2015 IEEE International Ultrasonics Symposium, IUS 2015
Publish Date
2015
DOI
10.1109/ULTSYM.2015.0267

Measurement of the frequency dependent phase velocity and attenuation from the Fourier description of shear wave propagation: Addressing geometric spreading arising from spatially asymmetric Gaussian excitations

© 2015 IEEE.Observations of shear wave propagation in a viscoelastic (VE) tissue are typically analyzed by assuming the wave is described as a plane wave, or as the asymptotic form of a wave expanding radially from a cylindrically symmetric source. In this study we present an exact expression for the two dimensional Fourier transform (2D-FT) description of shear wave propagation in a VE material following an asymmetric Gaussian excitation. This expression is used to evaluate the bias in 2D-FT measurements obtained using the plane or cylindrical wave assumptions. A wide range of biases are observed depending on specific values of frequency and aspect ratio R of the source asymmetry. These biases can be reduced significantly by weighting the shear wave signal in the spatial domain to correct for the geometric spreading of the shear wavefront using a factor of xp. The optimal weighting power p is found to be near the theoretical value of 0.5 for the case of a cylindrical source with R = 1, and decreases for asymmetric sources with R > 1.

Authors
Rouze, NC; Palmeri, ML; Nightingale, KR
MLA Citation
Rouze, NC, Palmeri, ML, and Nightingale, KR. "Measurement of the frequency dependent phase velocity and attenuation from the Fourier description of shear wave propagation: Addressing geometric spreading arising from spatially asymmetric Gaussian excitations." November 13, 2015.
Source
scopus
Published In
2015 IEEE International Ultrasonics Symposium, IUS 2015
Publish Date
2015
DOI
10.1109/ULTSYM.2015.0199

Characterizing sclerotic skin stiffness with Acoustic Radiation Force Impulse (ARFI) and Shear Wave Elasticity Imaging (SWEI)

© 2015 IEEE.Sclerotic skin diseases are associated with inflammation and fibrosis in the dermis, and these changes in collagen content with disease progression make this pathology amenable to being characterized with Acoustic Radiation Force Impulse (ARFI) and Shear Wave Elasticity Imaging (SWEI) methods. We characterized skin stiffness in healthy individuals at repeated three month intervals and compared sclerotic to healthy skin stiffness. ARFI and SWEI were implemented using a Siemens 14L5 linear array on an ACUSON S2000™ scanner. A single dermatologist performed all imaging in twenty-two patients. Normal and sclerotic skin stiffnesses were characterized by (1) mean ARFI displacement magnitude, and (2) group shear wave speed estimated using a Radon sum of shear wave velocity data. Imaging was performed at different anatomic sites, including the upper and lower back, arm, forearm, abdomen, thigh and calf. Five repeat data acquisitions were performed in each anatomic location. ARFI displacement and SWEI shear wave speeds were reconstructed in 96% of all acquisitions when the region of interest was exclusively contained in the dermis. Overall, ARFI and SWEI metrics showed no significant difference between contralateral imaging locations across different anatomic sites in healthy skin (p < 0.05). Mean shear wave speeds were >200% greater in sclerotic lesions than in contralateral healthy skin in patients with graft-versus-host disease (GVHD) (p < 0.01), and 25% greater in patients with morphea. ARFI displacements exhibited greater variability than shear wave speed in characterizing sclerotic skin, showing a 61% decrease compared to healthy skin in GVHD patients (p < 0.05) and a 19% decrease in morphea patients (p < 0.05). ARFI and SWEI are able differentiate sclerotic skin lesions from healthy skin, and studies are underway to evaluate their utility in longitudinally-monitoring disease progression and response to therapy. Additional study details, data and conclusions can be found in the full-length manuscript describing this work [1].

Authors
Lee, SY; Cardones, AR; Nightingale, K; Palmeri, M
MLA Citation
Lee, SY, Cardones, AR, Nightingale, K, and Palmeri, M. "Characterizing sclerotic skin stiffness with Acoustic Radiation Force Impulse (ARFI) and Shear Wave Elasticity Imaging (SWEI)." November 13, 2015.
Source
scopus
Published In
2015 IEEE International Ultrasonics Symposium, IUS 2015
Publish Date
2015
DOI
10.1109/ULTSYM.2015.0098

RSNA QIBA ultrasound shear wave speed Phase II phantom study in viscoelastic media

© 2015 IEEE.Using ultrasonic shear wave speed (SWS) estimates has become popular to noninvasively evaluate liver fibrosis, but significant inter-system variability in liver SWS measurements can preclude meaningful comparison of measurements performed with different systems. The RSNA Quantitative Imaging Biomarker Alliance (QIBA) ultrasound SWS committee has been developing elastic and viscoelastic (VE) phantoms to evaluate system dependencies of SWS estimates. The objective of this study is to compare SWS measurements between commercially-available systems using phantoms that have viscoelastic properties similar to those observed in normal and fibrotic liver. CIRS, Inc. fabricated three phantoms using a proprietary oil-water emulsion infused in a Zerdine® hydrogel that were matched in viscoelastic behavior to healthy and fibrotic human liver data. Phantoms were measured at academic, clinical, government and vendor sites using different systems with curvilinear arrays at multiple focal depths (3.0, 4.5 & 7.0 cm). The results of this study show that current-generation ultrasound SWS measurement systems are able to differentiate viscoelastic materials that span healthy to fibrotic liver. The deepest focal depth (7.0 cm) yielded the greatest inter-system variability for each phantom (maximum of 17.7%) as evaluated by IQR. Inter-system variability was consistent across all 3 phantoms and was not a function of stiffness. Median SWS estimates for the greatest outlier system for each phantom/focal depth combination ranged from 12.7-17.6%. Future efforts will include performing more robust statistical analyses of these data, comparing these phantom data trends with viscoelastic digital phantom data, providing vendors with study site data to refine their systems to have more consistent measurements, and integrating these data into the QIBA ultrasound shear wave speed measurement profile.

Authors
Palmeri, M; Nightingale, K; Fielding, S; Rouze, N; Deng, Y; Lynch, T; Chen, S; Song, P; Urban, M; Xie, H; Wear, K; Garra, B; Milkowski, A; Rosenzweig, S; Carson, P; Barr, R; Shamdasani, V; MacDonald, M; Wang, M; Guenette, G; Miyajima, Y; Okamura, Y; Dhyani, M; Samir, A; Hah, Z; McLaughlin, G; Gee, A; Chen, Y; Napolitano, D; McAleavey, S; Obuchowski, N; Hall, T
MLA Citation
Palmeri, M, Nightingale, K, Fielding, S, Rouze, N, Deng, Y, Lynch, T, Chen, S, Song, P, Urban, M, Xie, H, Wear, K, Garra, B, Milkowski, A, Rosenzweig, S, Carson, P, Barr, R, Shamdasani, V, MacDonald, M, Wang, M, Guenette, G, Miyajima, Y, Okamura, Y, Dhyani, M, Samir, A, Hah, Z, McLaughlin, G, Gee, A, Chen, Y, Napolitano, D, McAleavey, S, Obuchowski, N, and Hall, T. "RSNA QIBA ultrasound shear wave speed Phase II phantom study in viscoelastic media." November 13, 2015.
Source
scopus
Published In
2015 IEEE International Ultrasonics Symposium, IUS 2015
Publish Date
2015
DOI
10.1109/ULTSYM.2015.0283

Preliminary Results on the Feasibility of Using ARFI/SWEI to Assess Cutaneous Sclerotic Diseases.

In this study, acoustic radiation force impulse (ARFI) and shear wave elasticity imaging (SWEI) were applied to the skin to investigate the feasibility of their use in assessing sclerotic skin diseases. Our motivation was to develop a non-invasive imaging technology with real-time feedback of sclerotic skin disease diagnosis. This paper shows representative results from an ongoing study, recruiting patients with and without sclerosis. The stiffness of the imaged site was evaluated using two metrics: mean ARFI displacement magnitude and bulk shear wave speed inside the region of interest (ROI). In a subject with localized graft versus host disease (GVHD), the mean ARFI displacement inside sclerotic skin was 61% lower (p < 0.01) and shear wave speed 128% higher (p < 0.005) compared to those in normal skin-indicating stiffer mechanical properties in the sclerotic skin. This trend persisted through disease types. We conclude ARFI and SWEI can successfully differentiate sclerotic lesions from normal dermis.

Authors
Lee, SY; Cardones, AR; Doherty, J; Nightingale, K; Palmeri, M
MLA Citation
Lee, SY, Cardones, AR, Doherty, J, Nightingale, K, and Palmeri, M. "Preliminary Results on the Feasibility of Using ARFI/SWEI to Assess Cutaneous Sclerotic Diseases." Ultrasound in medicine & biology 41.11 (November 2015): 2806-2819.
PMID
26259888
Source
epmc
Published In
Ultrasound in Medicine & Biology
Volume
41
Issue
11
Publish Date
2015
Start Page
2806
End Page
2819
DOI
10.1016/j.ultrasmedbio.2015.06.007

An analytic, Fourier domain description of shear wave propagation in a viscoelastic medium using asymmetric Gaussian sources.

Recent measurements of shear wave propagation in viscoelastic materials have been analyzed by constructing the two-dimensional Fourier transform (2D-FT) of the spatial-temporal shear wave signal and using an analysis procedure derived under the assumption the wave is described as a plane wave, or as the asymptotic form of a wave expanding radially from a cylindrically symmetric source. This study presents an exact, analytic expression for the 2D-FT description of shear wave propagation in viscoelastic materials following asymmetric Gaussian excitations and uses this expression to evaluate the bias in 2D-FT measurements obtained using the plane or cylindrical wave assumptions. A wide range of biases are observed depending on specific values of frequency, aspect ratio R of the source asymmetry, and material properties. These biases can be reduced significantly by weighting the shear wave signal in the spatial domain to correct for the geometric spreading of the shear wavefront using a factor of x(p). The optimal weighting power p is found to be near the theoretical value of 0.5 for the case of a cylindrical source with R = 1, and decreases for asymmetric sources with R > 1.

Authors
Rouze, NC; Palmeri, ML; Nightingale, KR
MLA Citation
Rouze, NC, Palmeri, ML, and Nightingale, KR. "An analytic, Fourier domain description of shear wave propagation in a viscoelastic medium using asymmetric Gaussian sources." The Journal of the Acoustical Society of America 138.2 (August 2015): 1012-1022.
PMID
26328717
Source
epmc
Published In
The Journal of the Acoustical Society of America
Volume
138
Issue
2
Publish Date
2015
Start Page
1012
End Page
1022
DOI
10.1121/1.4927492

Analyzing the Impact of Increasing Mechanical Index and Energy Deposition on Shear Wave Speed Reconstruction in Human Liver.

Shear wave elasticity imaging (SWEI) has found success in liver fibrosis staging. This work evaluates hepatic SWEI measurement success as a function of push pulse energy using two mechanical index (MI) values (1.6 and 2.2) over a range of pulse durations. Shear wave speed (SWS) was measured in the livers of 26 study subjects with known or potential chronic liver diseases. Each measurement consisted of eight SWEI sequences, each with different push energy configurations. The rate of successful SWS estimation was linearly proportional to the push energy. SWEI measurements with higher push energy were successful in patients for whom standard push energy levels failed. The findings also suggest that liver capsule depth could be used prospectively to identify patients who would benefit from elevated output. We conclude that there is clinical benefit to using elevated acoustic output for hepatic SWS measurement in patients with deeper livers.

Authors
Deng, Y; Palmeri, ML; Rouze, NC; Rosenzweig, SJ; Abdelmalek, MF; Nightingale, KR
MLA Citation
Deng, Y, Palmeri, ML, Rouze, NC, Rosenzweig, SJ, Abdelmalek, MF, and Nightingale, KR. "Analyzing the Impact of Increasing Mechanical Index and Energy Deposition on Shear Wave Speed Reconstruction in Human Liver." Ultrasound in medicine & biology 41.7 (July 2015): 1948-1957.
PMID
25896024
Source
epmc
Published In
Ultrasound in Medicine & Biology
Volume
41
Issue
7
Publish Date
2015
Start Page
1948
End Page
1957
DOI
10.1016/j.ultrasmedbio.2015.02.019

Conditionally Increased Acoustic Pressures in Nonfetal Diagnostic Ultrasound Examinations Without Contrast Agents: A Preliminary Assessment.

The mechanical index (MI) has been used by the US Food and Drug Administration (FDA) since 1992 for regulatory decisions regarding the acoustic output of diagnostic ultrasound equipment. Its formula is based on predictions of acoustic cavitation under specific conditions. Since its implementation over 2 decades ago, new imaging modes have been developed that employ unique beam sequences exploiting higher-order acoustic phenomena, and, concurrently, studies of the bioeffects of ultrasound under a range of imaging scenarios have been conducted. In 2012, the American Institute of Ultrasound in Medicine Technical Standards Committee convened a working group of its Output Standards Subcommittee to examine and report on the potential risks and benefits of the use of conditionally increased acoustic pressures (CIP) under specific diagnostic imaging scenarios. The term "conditionally" is included to indicate that CIP would be considered on a per-patient basis for the duration required to obtain the necessary diagnostic information. This document is a result of that effort. In summary, a fundamental assumption in the MI calculation is the presence of a preexisting gas body. For tissues not known to contain preexisting gas bodies, based on theoretical predications and experimentally reported cavitation thresholds, we find this assumption to be invalid. We thus conclude that exceeding the recommended maximum MI level given in the FDA guidance could be warranted without concern for increased risk of cavitation in these tissues. However, there is limited literature assessing the potential clinical benefit of exceeding the MI guidelines in these tissues. The report proposes a 3-tiered approach for CIP that follows the model for employing elevated output in magnetic resonance imaging and concludes with summary recommendations to facilitate Institutional Review Board (IRB)-monitored clinical studies investigating CIP in specific tissues.

Authors
Nightingale, KR; Church, CC; Harris, G; Wear, KA; Bailey, MR; Carson, PL; Jiang, H; Sandstrom, KL; Szabo, TL; Ziskin, MC
MLA Citation
Nightingale, KR, Church, CC, Harris, G, Wear, KA, Bailey, MR, Carson, PL, Jiang, H, Sandstrom, KL, Szabo, TL, and Ziskin, MC. "Conditionally Increased Acoustic Pressures in Nonfetal Diagnostic Ultrasound Examinations Without Contrast Agents: A Preliminary Assessment." Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine 34.7 (July 2015): 1-41. (Review)
PMID
26112617
Source
epmc
Published In
Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine
Volume
34
Issue
7
Publish Date
2015
Start Page
1
End Page
41
DOI
10.7863/ultra.34.7.15.13.0001

WFUMB guidelines and recommendations for clinical use of ultrasound elastography: Part 1: Basic principles and terminology

© 2015.Conventional diagnostic ultrasound images of the anatomy (as opposed to blood flow) reveal differences in the acoustic properties of soft tissues (mainly echogenicity but also, to some extent, attenuation), whereas ultrasound-based elasticity images are able to reveal the differences in the elastic properties of soft tissues (e.g., elasticity and viscosity). The benefit of elasticity imaging lies in the fact that many soft tissues can share similar ultrasonic echogenicities but may have different mechanical properties that can be used to clearly visualize normal anatomy and delineate pathologic lesions. Typically, all elasticity measurement and imaging methods introduce a mechanical excitation and monitor the resulting tissue response. Some of the most widely available commercial elasticity imaging methods are 'quasi-static' and use external tissue compression to generate images of the resulting tissue strain (or deformation). In addition, many manufacturers now provide shear wave imaging and measurement methods, which deliver stiffness images based upon the shear wave propagation speed. The goal of this review is to describe the fundamental physics and the associated terminology underlying these technologies. We have included a questions and answers section, an extensive appendix, and a glossary of terms in this manuscript. We have also endeavored to ensure that the terminology and descriptions, although not identical, are broadly compatible across the WFUMB and EFSUMB sets of guidelines on elastography (Bamber etal. 2013; Cosgrove etal. 2013).

Authors
Shiina, T; Nightingale, KR; Palmeri, ML; Hall, TJ; Bamber, JC; Barr, RG; Castera, L; Choi, BI; Chou, YH; Cosgrove, D; Dietrich, CF; Ding, H; Amy, D; Farrokh, A; Ferraioli, G; Filice, C; Friedrich-Rust, M; Nakashima, K; Schafer, F; Sporea, I; Suzuki, S; Wilson, S; Kudo, M
MLA Citation
Shiina, T, Nightingale, KR, Palmeri, ML, Hall, TJ, Bamber, JC, Barr, RG, Castera, L, Choi, BI, Chou, YH, Cosgrove, D, Dietrich, CF, Ding, H, Amy, D, Farrokh, A, Ferraioli, G, Filice, C, Friedrich-Rust, M, Nakashima, K, Schafer, F, Sporea, I, Suzuki, S, Wilson, S, and Kudo, M. "WFUMB guidelines and recommendations for clinical use of ultrasound elastography: Part 1: Basic principles and terminology." Ultrasound in Medicine and Biology 41.5 (May 1, 2015): 1126-1147.
Source
scopus
Published In
Ultrasound in Medicine & Biology
Volume
41
Issue
5
Publish Date
2015
Start Page
1126
End Page
1147
DOI
10.1016/j.ultrasmedbio.2015.03.009

WFUMB guidelines and recommendations for clinical use of ultrasound elastography: Part 2: Breast

© 2015.The breast section of these Guidelines and Recommendations for Elastography produced under the auspices of the World Federation of Ultrasound in Medicine and Biology (WFUMB) assesses the clinically used applications of all forms of elastography used in breast imaging. The literature on various breast elastography techniques is reviewed, and recommendations are made on evidence-based results. Practical advice is given on how to perform and interpret breast elastography for optimal results, with emphasis placed on avoiding pitfalls. Artifacts are reviewed, and the clinical utility of some artifacts is discussed. Both strain and shear wave techniques have been shown to be highly accurate in characterizing breast lesions as benign or malignant. The relationship between the various techniques is discussed, and recommended interpretation based on a BI-RADS-like malignancy probability scale is provided. This document is intended to be used as a reference and to guide clinical users in a practical way.

Authors
Barr, RG; Nakashima, K; Amy, D; Cosgrove, D; Farrokh, A; Schafer, F; Bamber, JC; Castera, L; Choi, BI; Chou, YH; Dietrich, CF; Ding, H; Ferraioli, G; Filice, C; Friedrich-Rust, M; Hall, TJ; Nightingale, KR; Palmeri, ML; Shiina, T; Suzuki, S; Sporea, I; Wilson, S; Kudo, M
MLA Citation
Barr, RG, Nakashima, K, Amy, D, Cosgrove, D, Farrokh, A, Schafer, F, Bamber, JC, Castera, L, Choi, BI, Chou, YH, Dietrich, CF, Ding, H, Ferraioli, G, Filice, C, Friedrich-Rust, M, Hall, TJ, Nightingale, KR, Palmeri, ML, Shiina, T, Suzuki, S, Sporea, I, Wilson, S, and Kudo, M. "WFUMB guidelines and recommendations for clinical use of ultrasound elastography: Part 2: Breast." Ultrasound in Medicine and Biology 41.5 (May 1, 2015): 1148-1160.
Source
scopus
Published In
Ultrasound in Medicine & Biology
Volume
41
Issue
5
Publish Date
2015
Start Page
1148
End Page
1160
DOI
10.1016/j.ultrasmedbio.2015.03.008

WFUMB guidelines and recommendations for clinical use of ultrasound elastography: Part 3: Liver

© 2015.The World Federation for Ultrasound in Medicine and Biology (WFUMB) has produced these guidelines for the use of elastography techniques in liver disease. For each available technique, the reproducibility, results, and limitations are analyzed, and recommendations are given. Finally, recommendations based on the international literature and the findings of the WFUMB expert group are established as answers to common questions. The document has a clinical perspective and is aimed at assessing the usefulness of elastography in the management of liver diseases.

Authors
Ferraioli, G; Filice, C; Castera, L; Choi, BI; Sporea, I; Wilson, SR; Cosgrove, D; Dietrich, CF; Amy, D; Bamber, JC; Barr, R; Chou, YH; Ding, H; Farrokh, A; Friedrich-Rust, M; Hall, TJ; Nakashima, K; Nightingale, KR; Palmeri, ML; Schafer, F; Shiina, T; Suzuki, S; Kudo, M
MLA Citation
Ferraioli, G, Filice, C, Castera, L, Choi, BI, Sporea, I, Wilson, SR, Cosgrove, D, Dietrich, CF, Amy, D, Bamber, JC, Barr, R, Chou, YH, Ding, H, Farrokh, A, Friedrich-Rust, M, Hall, TJ, Nakashima, K, Nightingale, KR, Palmeri, ML, Schafer, F, Shiina, T, Suzuki, S, and Kudo, M. "WFUMB guidelines and recommendations for clinical use of ultrasound elastography: Part 3: Liver." Ultrasound in Medicine and Biology 41.5 (May 1, 2015): 1161-1179.
Source
scopus
Published In
Ultrasound in Medicine & Biology
Volume
41
Issue
5
Publish Date
2015
Start Page
1161
End Page
1179
DOI
10.1016/j.ultrasmedbio.2015.03.007

WFUMB guidelines and recommendations for clinical use of ultrasound elastography: Part 3: liver.

The World Federation for Ultrasound in Medicine and Biology (WFUMB) has produced these guidelines for the use of elastography techniques in liver disease. For each available technique, the reproducibility, results, and limitations are analyzed, and recommendations are given. Finally, recommendations based on the international literature and the findings of the WFUMB expert group are established as answers to common questions. The document has a clinical perspective and is aimed at assessing the usefulness of elastography in the management of liver diseases.

Authors
Ferraioli, G; Filice, C; Castera, L; Choi, BI; Sporea, I; Wilson, SR; Cosgrove, D; Dietrich, CF; Amy, D; Bamber, JC; Barr, R; Chou, Y-H; Ding, H; Farrokh, A; Friedrich-Rust, M; Hall, TJ; Nakashima, K; Nightingale, KR; Palmeri, ML; Schafer, F; Shiina, T; Suzuki, S; Kudo, M
MLA Citation
Ferraioli, G, Filice, C, Castera, L, Choi, BI, Sporea, I, Wilson, SR, Cosgrove, D, Dietrich, CF, Amy, D, Bamber, JC, Barr, R, Chou, Y-H, Ding, H, Farrokh, A, Friedrich-Rust, M, Hall, TJ, Nakashima, K, Nightingale, KR, Palmeri, ML, Schafer, F, Shiina, T, Suzuki, S, and Kudo, M. "WFUMB guidelines and recommendations for clinical use of ultrasound elastography: Part 3: liver." Ultrasound in medicine & biology 41.5 (May 2015): 1161-1179.
PMID
25800942
Source
epmc
Published In
Ultrasound in Medicine & Biology
Volume
41
Issue
5
Publish Date
2015
Start Page
1161
End Page
1179
DOI
10.1016/j.ultrasmedbio.2015.03.007

WFUMB guidelines and recommendations for clinical use of ultrasound elastography: Part 1: basic principles and terminology.

Conventional diagnostic ultrasound images of the anatomy (as opposed to blood flow) reveal differences in the acoustic properties of soft tissues (mainly echogenicity but also, to some extent, attenuation), whereas ultrasound-based elasticity images are able to reveal the differences in the elastic properties of soft tissues (e.g., elasticity and viscosity). The benefit of elasticity imaging lies in the fact that many soft tissues can share similar ultrasonic echogenicities but may have different mechanical properties that can be used to clearly visualize normal anatomy and delineate pathologic lesions. Typically, all elasticity measurement and imaging methods introduce a mechanical excitation and monitor the resulting tissue response. Some of the most widely available commercial elasticity imaging methods are 'quasi-static' and use external tissue compression to generate images of the resulting tissue strain (or deformation). In addition, many manufacturers now provide shear wave imaging and measurement methods, which deliver stiffness images based upon the shear wave propagation speed. The goal of this review is to describe the fundamental physics and the associated terminology underlying these technologies. We have included a questions and answers section, an extensive appendix, and a glossary of terms in this manuscript. We have also endeavored to ensure that the terminology and descriptions, although not identical, are broadly compatible across the WFUMB and EFSUMB sets of guidelines on elastography (Bamber et al. 2013; Cosgrove et al. 2013).

Authors
Shiina, T; Nightingale, KR; Palmeri, ML; Hall, TJ; Bamber, JC; Barr, RG; Castera, L; Choi, BI; Chou, Y-H; Cosgrove, D; Dietrich, CF; Ding, H; Amy, D; Farrokh, A; Ferraioli, G; Filice, C; Friedrich-Rust, M; Nakashima, K; Schafer, F; Sporea, I; Suzuki, S; Wilson, S; Kudo, M
MLA Citation
Shiina, T, Nightingale, KR, Palmeri, ML, Hall, TJ, Bamber, JC, Barr, RG, Castera, L, Choi, BI, Chou, Y-H, Cosgrove, D, Dietrich, CF, Ding, H, Amy, D, Farrokh, A, Ferraioli, G, Filice, C, Friedrich-Rust, M, Nakashima, K, Schafer, F, Sporea, I, Suzuki, S, Wilson, S, and Kudo, M. "WFUMB guidelines and recommendations for clinical use of ultrasound elastography: Part 1: basic principles and terminology." Ultrasound in medicine & biology 41.5 (May 2015): 1126-1147.
PMID
25805059
Source
epmc
Published In
Ultrasound in Medicine & Biology
Volume
41
Issue
5
Publish Date
2015
Start Page
1126
End Page
1147
DOI
10.1016/j.ultrasmedbio.2015.03.009

WFUMB guidelines and recommendations for clinical use of ultrasound elastography: Part 2: breast.

The breast section of these Guidelines and Recommendations for Elastography produced under the auspices of the World Federation of Ultrasound in Medicine and Biology (WFUMB) assesses the clinically used applications of all forms of elastography used in breast imaging. The literature on various breast elastography techniques is reviewed, and recommendations are made on evidence-based results. Practical advice is given on how to perform and interpret breast elastography for optimal results, with emphasis placed on avoiding pitfalls. Artifacts are reviewed, and the clinical utility of some artifacts is discussed. Both strain and shear wave techniques have been shown to be highly accurate in characterizing breast lesions as benign or malignant. The relationship between the various techniques is discussed, and recommended interpretation based on a BI-RADS-like malignancy probability scale is provided. This document is intended to be used as a reference and to guide clinical users in a practical way.

Authors
Barr, RG; Nakashima, K; Amy, D; Cosgrove, D; Farrokh, A; Schafer, F; Bamber, JC; Castera, L; Choi, BI; Chou, Y-H; Dietrich, CF; Ding, H; Ferraioli, G; Filice, C; Friedrich-Rust, M; Hall, TJ; Nightingale, KR; Palmeri, ML; Shiina, T; Suzuki, S; Sporea, I; Wilson, S; Kudo, M
MLA Citation
Barr, RG, Nakashima, K, Amy, D, Cosgrove, D, Farrokh, A, Schafer, F, Bamber, JC, Castera, L, Choi, BI, Chou, Y-H, Dietrich, CF, Ding, H, Ferraioli, G, Filice, C, Friedrich-Rust, M, Hall, TJ, Nightingale, KR, Palmeri, ML, Shiina, T, Suzuki, S, Sporea, I, Wilson, S, and Kudo, M. "WFUMB guidelines and recommendations for clinical use of ultrasound elastography: Part 2: breast." Ultrasound in medicine & biology 41.5 (May 2015): 1148-1160.
PMID
25795620
Source
epmc
Published In
Ultrasound in Medicine & Biology
Volume
41
Issue
5
Publish Date
2015
Start Page
1148
End Page
1160
DOI
10.1016/j.ultrasmedbio.2015.03.008

Single- and Multiple-Track-Location Shear Wave and Acoustic Radiation Force Impulse Imaging: Matched Comparison of Contrast, Contrast-to-Noise Ratio and Resolution

© 2015 World Federation for Ultrasound in Medicine & Biology.Acoustic radiation force impulse imaging and shear wave elasticity imaging (SWEI) use the dynamic response of tissue to impulsive mechanical stimulus to characterize local elasticity. A variant of conventional, multiple-track-location SWEI, denoted single-track-location SWEI, offers the promise of creating speckle-free shear wave images. This work compares the three imaging modalities using a high push and track beam density combined acquisition sequence to image inclusions of different sizes and contrasts. Single-track-location SWEI is found to have a significantly higher contrast-to-noise ratio than multiple-track-location SWEI, allowing for operation at higher resolution. Acoustic radiation force impulse imaging and single-track-location SWEI perform similarly in the larger inclusions, with single-track-location SWEI providing better visualization of small targets ≤2.5mm in diameter. The processing of each modality introduces different trade-offs between smoothness and resolution of edges and structures; these are discussed in detail.

Authors
Hollender, PJ; Rosenzweig, SJ; Nightingale, KR; Trahey, GE
MLA Citation
Hollender, PJ, Rosenzweig, SJ, Nightingale, KR, and Trahey, GE. "Single- and Multiple-Track-Location Shear Wave and Acoustic Radiation Force Impulse Imaging: Matched Comparison of Contrast, Contrast-to-Noise Ratio and Resolution." Ultrasound in Medicine and Biology 41.4 (April 1, 2015): 1043-1057.
Source
scopus
Published In
Ultrasound in Medicine & Biology
Volume
41
Issue
4
Publish Date
2015
Start Page
1043
End Page
1057
DOI
10.1016/j.ultrasmedbio.2014.11.006

Single- and multiple-track-location shear wave and acoustic radiation force impulse imaging: matched comparison of contrast, contrast-to-noise ratio and resolution.

Acoustic radiation force impulse imaging and shear wave elasticity imaging (SWEI) use the dynamic response of tissue to impulsive mechanical stimulus to characterize local elasticity. A variant of conventional, multiple-track-location SWEI, denoted single-track-location SWEI, offers the promise of creating speckle-free shear wave images. This work compares the three imaging modalities using a high push and track beam density combined acquisition sequence to image inclusions of different sizes and contrasts. Single-track-location SWEI is found to have a significantly higher contrast-to-noise ratio than multiple-track-location SWEI, allowing for operation at higher resolution. Acoustic radiation force impulse imaging and single-track-location SWEI perform similarly in the larger inclusions, with single-track-location SWEI providing better visualization of small targets ≤ 2.5 mm in diameter. The processing of each modality introduces different trade-offs between smoothness and resolution of edges and structures; these are discussed in detail.

Authors
Hollender, PJ; Rosenzweig, SJ; Nightingale, KR; Trahey, GE
MLA Citation
Hollender, PJ, Rosenzweig, SJ, Nightingale, KR, and Trahey, GE. "Single- and multiple-track-location shear wave and acoustic radiation force impulse imaging: matched comparison of contrast, contrast-to-noise ratio and resolution." Ultrasound in medicine & biology 41.4 (April 2015): 1043-1057.
PMID
25701531
Source
epmc
Published In
Ultrasound in Medicine & Biology
Volume
41
Issue
4
Publish Date
2015
Start Page
1043
End Page
1057
DOI
10.1016/j.ultrasmedbio.2014.11.006

A theoretical study of inertial cavitation from acoustic radiation force impulse imaging and implications for the mechanical index.

The mechanical index (MI) attempts to quantify the likelihood that exposure to diagnostic ultrasound will produce an adverse biological effect by a non-thermal mechanism. The current formulation of the MI implicitly assumes that the acoustic field is generated using the short pulse durations appropriate to B-mode imaging. However, acoustic radiation force impulse (ARFI) imaging employs high-intensity pulses up to several hundred acoustic periods long. The effect of increased pulse durations on the thresholds for inertial cavitation was studied computationally in water, urine, blood, cardiac and skeletal muscle, brain, kidney, liver and skin. The results indicate that, although the effect of pulse duration on cavitation thresholds in the three liquids can be considerable, reducing them by, for example, 6%-24% at 1 MHz, the effect on tissue is minor. More importantly, the frequency dependence of the MI appears to be unnecessarily conservative; that is, the magnitude of the exponent on frequency could be increased to 0.75. Comparison of these theoretical results with experimental measurements suggests that some tissues do not contain the pre-existing, optimally sized bubbles assumed for the MI. This means that in these tissues, the MI is not necessarily a strong predictor of the probability of an adverse biological effect.

Authors
Church, CC; Labuda, C; Nightingale, K
MLA Citation
Church, CC, Labuda, C, and Nightingale, K. "A theoretical study of inertial cavitation from acoustic radiation force impulse imaging and implications for the mechanical index." Ultrasound in medicine & biology 41.2 (February 2015): 472-485.
PMID
25592457
Source
epmc
Published In
Ultrasound in Medicine & Biology
Volume
41
Issue
2
Publish Date
2015
Start Page
472
End Page
485
DOI
10.1016/j.ultrasmedbio.2014.09.012

Analysis of rapid multi-focal-zone ARFI imaging.

Acoustic radiation force impulse (ARFI) imaging has shown promise for visualizing structure and pathology within multiple organs; however, because the contrast depends on the push beam excitation width, image quality suffers outside of the region of excitation. Multi-focal-zone ARFI imaging has previously been used to extend the region of excitation (ROE), but the increased acquisition duration and acoustic exposure have limited its utility. Supersonic shear wave imaging has previously demonstrated that through technological improvements in ultrasound scanners and power supplies, it is possible to rapidly push at multiple locations before tracking displacements, facilitating extended depth of field shear wave sources. Similarly, ARFI imaging can utilize these same radiation force excitations to achieve tight pushing beams with a large depth of field. Finite element method simulations and experimental data are presented, demonstrating that single- and rapid multi-focal-zone ARFI have comparable image quality (less than 20% loss in contrast), but the multi-focal-zone approach has an extended axial region of excitation. Additionally, as compared with single-push sequences, the rapid multi-focalzone acquisitions improve the contrast-to-noise ratio by up to 40% in an example 4-mm-diameter lesion.

Authors
Rosenzweig, S; Palmeri, M; Nightingale, K
MLA Citation
Rosenzweig, S, Palmeri, M, and Nightingale, K. "Analysis of rapid multi-focal-zone ARFI imaging." IEEE transactions on ultrasonics, ferroelectrics, and frequency control 62.2 (February 2015): 280-289.
PMID
25643078
Source
epmc
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
62
Issue
2
Publish Date
2015
Start Page
280
End Page
289
DOI
10.1109/tuffc.2014.006594

Prostate elastography

© Springer Science+Business Media New York 2015.Conventional B-mode transrectal ultrasound (TRUS) generates images of the acoustic properties of tissues (density and sound speed). TRUS is used extensively to aid in visualizing the prostate gland and needle during biopsy. However, TRUS has limited sensitivity and specificity for prostate cancer (PCa) detection/visualization [1, 2], and therefore advanced ultrasonic methods are currently being investigated to improve PCa detection. One promising approach, called elastography, generates images of the elastic properties of tissues (i.e., tissue stiffness), providing complementary information to B-mode images. This approach has promise for PCa imaging due to the inherent differences in stiffness between normal and pathologic tissues in the prostate.

Authors
Rosenzweig, S; Miller, Z; Polascik, T; Nightingale, K
MLA Citation
Rosenzweig, S, Miller, Z, Polascik, T, and Nightingale, K. "Prostate elastography." Prostate Ultrasound: Current Practice and Future Directions. January 1, 2015. 163-172.
Source
scopus
Publish Date
2015
Start Page
163
End Page
172
DOI
10.1007/978-1-4939-1948-2_12

B-mode and acoustic radiation force impulse (ARFI) imaging of prostate zonal anatomy: comparison with 3T T2-weighted MR imaging.

Prostate cancer (PCa) is the most common non-cutaneous malignancy among men in the United States and the second leading cause of cancer-related death. Multi-parametric magnetic resonance imaging (mpMRI) has gained recent popularity to characterize PCa. Acoustic Radiation Force Impulse (ARFI) imaging has the potential to aid PCa diagnosis and management by using tissue stiffness to evaluate prostate zonal anatomy and lesions. MR and B-mode/ARFI in vivo imaging datasets were compared with one another and with gross pathology measurements made immediately after radical prostatectomy. Images were manually segmented in 3D Slicer to delineate the central gland (CG) and prostate capsule, and 3D models were rendered to evaluate zonal anatomy dimensions and volumes. Both imaging modalities showed good correlation between estimated organ volume and gross pathologic weights. Ultrasound and MR total prostate volumes were well correlated (R(2) = 0.77), but B-mode images yielded prostate volumes that were larger (16.82% ± 22.45%) than MR images, due to overestimation of the lateral dimension (18.4% ± 13.9%), with less significant differences in the other dimensions (7.4% ± 17.6%, anterior-to-posterior, and -10.8% ± 13.9%, apex-to-base). ARFI and MR CG volumes were also well correlated (R(2) = 0.85). CG volume differences were attributed to ARFI underestimation of the apex-to-base axis (-28.8% ± 9.4%) and ARFI overestimation of the lateral dimension (21.5% ± 14.3%). B-mode/ARFI imaging yielded prostate volumes and dimensions that were well correlated with MR T2-weighted image (T2WI) estimates, with biases in the lateral dimension due to poor contrast caused by extraprostatic fat. B-mode combined with ARFI imaging is a promising low-cost, portable, real-time modality that can complement mpMRI for PCa diagnosis, treatment planning, and management.

Authors
Palmeri, ML; Miller, ZA; Glass, TJ; Garcia-Reyes, K; Gupta, RT; Rosenzweig, SJ; Kauffman, C; Polascik, TJ; Buck, A; Kulbacki, E; Madden, J; Lipman, SL; Rouze, NC; Nightingale, KR
MLA Citation
Palmeri, ML, Miller, ZA, Glass, TJ, Garcia-Reyes, K, Gupta, RT, Rosenzweig, SJ, Kauffman, C, Polascik, TJ, Buck, A, Kulbacki, E, Madden, J, Lipman, SL, Rouze, NC, and Nightingale, KR. "B-mode and acoustic radiation force impulse (ARFI) imaging of prostate zonal anatomy: comparison with 3T T2-weighted MR imaging." Ultrasonic imaging 37.1 (January 2015): 22-41.
PMID
25060914
Source
epmc
Published In
Ultrasonic Imaging
Volume
37
Issue
1
Publish Date
2015
Start Page
22
End Page
41
DOI
10.1177/0161734614542177

Derivation and analysis of viscoelastic properties in human liver: impact of frequency on fibrosis and steatosis staging.

Commercially-available shear wave imaging systems measure group shear wave speed (SWS) and often report stiffness parameters applying purely elastic material models. Soft tissues, however, are viscoelastic, and higher-order material models are necessary to characterize the dispersion associated with broadband shear waves. In this paper, we describe a robust, model-based algorithm and use a linear dispersion model to perform shear wave dispersion analysis in traditionally difficult-to-image subjects. In a cohort of 135 non-alcoholic fatty liver disease patients, we compare the performance of group SWS with dispersion analysis-derived phase velocity c(200 Hz) and dispersion slope dc/df parameters to stage hepatic fibrosis and steatosis. Area under the ROC curve (AUROC) analysis demonstrates correlation between all parameters [group SWS, c(200 Hz), and, to a lesser extent dc/df ] and fibrosis stage, whereas no correlation was observed between steatosis stage and any of the material parameters. Interestingly, optimal AUROC threshold SWS values separating advanced liver fibrosis (≥F3) from mild-to-moderate fibrosis (≤F2) were shown to be frequency-dependent, and to increase from 1.8 to 3.3 m/s over the 0 to 400 Hz shear wave frequency range.

Authors
Nightingale, KR; Rouze, NC; Rosenzweig, SJ; Wang, MH; Abdelmalek, MF; Guy, CD; Palmeri, ML
MLA Citation
Nightingale, KR, Rouze, NC, Rosenzweig, SJ, Wang, MH, Abdelmalek, MF, Guy, CD, and Palmeri, ML. "Derivation and analysis of viscoelastic properties in human liver: impact of frequency on fibrosis and steatosis staging." IEEE transactions on ultrasonics, ferroelectrics, and frequency control 62.1 (January 2015): 165-175.
PMID
25585400
Source
epmc
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
62
Issue
1
Publish Date
2015
Start Page
165
End Page
175
DOI
10.1109/tuffc.2014.006653

Analyzing the impact of increasing Mechanical Index (MI) and energy deposition on shear wave speed (SWS) reconstruction in human liver

© 2014 IEEE.Shear wave elasticity imaging (SWEI) has found success in liver fibrosis staging. However, technical failure and unreliable shear wave speed (SWS) estimation have been reported to increase both with elevated patient body mass index (BMI) and in the presence of significant hepatic fibrosis. Elevated BMI results in a significant amount of subcutaneous fat which attenuates acoustic radiation force (ARF) and abberates tracking beams. Advanced fibrosis results in small displacement amplitudes in stiff livers. This work evaluates hepatic SWEI measurement success as a function of push pulse energy using 2 Mechanical Index (MI) values (1.6 and 2.2) over a range of pulse durations. The rate of successful SWS estimation for 8 repeated measurements is linearly proportional to the push energy level. As expected, elevated push energy in SWEI measurements results in higher displacement signal-to-noise ratio (SNR). SWEI measurements with elevated push energy are successful in patients for whom standard push energy levels failed. Deep liver capsule is shown to be an indicator for lower yield of SWS estimation. Patients with deep liver capsules are likely to benefit from elevated push energies. We conclude that there is clinical benefit to using elevated acoustic output for hepatic SWS measurement in 'difficult to image' patients.

Authors
Deng, Y; Palmeri, ML; Rouze, NC; Rosenzweig, SJ; Abdelmalek, MF; Nightingale, KR
MLA Citation
Deng, Y, Palmeri, ML, Rouze, NC, Rosenzweig, SJ, Abdelmalek, MF, and Nightingale, KR. "Analyzing the impact of increasing Mechanical Index (MI) and energy deposition on shear wave speed (SWS) reconstruction in human liver." January 1, 2014.
Source
scopus
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2014
Start Page
719
End Page
722
DOI
10.1109/ULTSYM.2014.0177

3D in vivo ARFI imaging: Prostate cancer sensitivity

© 2014 IEEE.Imaging tools that reliably visualize prostate cancer (PCa) are increasingly needed in the urological community. The objective of this research was to evaluate the ability of Acoustic Radiation Force Impulse (ARFI) imaging to localize PCa in 29 patients with biopsy-confirmed PCa who underwent radical prostatectomy and whole mount histopathology analysis. B-mode, ARFI imaging and whole mount histopathology volumes were acquired for each patient. Regions of suspicion (ROS) for PCa were reader-identified in ARFI images based on boundary delineation, contrast, texture and location, and compared to lesions identified in histopathology. ARFI imaging identified a total of 29 ROSs, 27 of which were correctly identified as cancer (PPV: 93%). ARFI imaging's overall sensitivity was 55%; however, there was significant variation in sensitivity depending on lesion type. We found that ARFI imaging was much more sensitive to posterior lesions (63%) than anterior lesions (12.5%). Posterior index lesions were identified with greater sensitivity (81%) than clinically-insignificant lesions (33%).

Authors
Miller, ZA; Palmeri, ML; Rosenzweig, SJ; Glass, TJ; Nightingale, KR; Polascik, TJ; Buck, A; Madden, J
MLA Citation
Miller, ZA, Palmeri, ML, Rosenzweig, SJ, Glass, TJ, Nightingale, KR, Polascik, TJ, Buck, A, and Madden, J. "3D in vivo ARFI imaging: Prostate cancer sensitivity." January 1, 2014.
Source
scopus
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2014
Start Page
209
End Page
212
DOI
10.1109/ULTSYM.2014.0053

Dependence of shear wave spectral content on acoustic radiation force excitation duration and spatial beamwidth

© 2014 IEEE.Shear Wave Elasticity Imaging (SWEI) has become increasingly popular to non-invasively characterize liver fibrosis. Generating adequate shear wave displacements in human liver in vivo can be challenging, especially in the high Body Mass Index (BMI) population being evaluated for Non-Alcoholic Fatty Liver Disease (NAFLD). Technical approaches to improve ARF-induced displacements include (1) using more aggressive focal configurations to generate higher peak force amplitudes, and (2) increasing the duration of the acoustic radiation force excitation. Using finite element method (FEM) models of Gaussian ARF excitations of varying spatial extent and temporal duration, we have demonstrated that shear wave velocity spectra are affected by both the spatial distribution and temporal duration of acoustic radiation force shear wave excitation sources. Shear wave spectra can be affected by the ARF spatial extent in the orthogonal dimension, which can be important when lateral:elevation excitation beamwidth anisotropies exist as a function of depth. Shear wave spectral content differences in different stiffness media are minimized for tightly-focused ARF excitations when using longer excitation durations, decreasing from ∼60% for 100 μs excitations to ∼10% for 1.5 ms excitations. These absolute and relative differences are significantly reduced for broader excitations. We have demonstrated similar trends experimentally using tissue-mimicking phantoms.

Authors
Palmeri, ML; Deng, Y; Rouze, NC; Nightingale, KR
MLA Citation
Palmeri, ML, Deng, Y, Rouze, NC, and Nightingale, KR. "Dependence of shear wave spectral content on acoustic radiation force excitation duration and spatial beamwidth." January 1, 2014.
Source
scopus
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2014
Start Page
1105
End Page
1108
DOI
10.1109/ULTSYM.2014.0271

Estimation of model parameters characterizing dispersion in ARFI induced shear waves in in vivo human liver

© 2014 IEEE.We consider the analysis of shear wave dispersion following ARFI excitation in a cohort of 135 Non-Alcoholic Fatty Liver Disease patients traditionally characterized as 'difficult-to-image.' Three analysis methods are considered: (1) measuring k(ω) by locating the maximum signal from the two-dimensional Fourier transform (2D-FT) of propagating shear wave data, (2) an extension of this method using model-based sums through 2D-FT data, and (3) shear wave spectroscopy. A linear dispersion model is used to characterize the frequency-dependent phase velocity. The analysis methods are evaluated in terms of robustness as determined by the rate of successful measurements in the patient data, and by the degrees of correlation and bias inherent with each method as determined by viscoelastic FEM validation studies. For these patient data and analysis procedures, although the 2D-FT methods are more robust than the shear wave spectroscopy method, they are also systematically biased. Even so, they can be used can be used to characterize the relative viscoelastic properties of liver.

Authors
Rouze, NC; Palmeri, ML; Nightingale, KR
MLA Citation
Rouze, NC, Palmeri, ML, and Nightingale, KR. "Estimation of model parameters characterizing dispersion in ARFI induced shear waves in in vivo human liver." January 1, 2014.
Source
scopus
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2014
Start Page
983
End Page
986
DOI
10.1109/ULTSYM.2014.0241

Improving the accuracy of shear wave speed reconstructions using 4D directional filters in the presence of reflection artifacts

© 2014 IEEE.Reflected waves from stiffness boundaries can lead to artifacts in shear wave speed (SWS) reconstructions. 2D directional filters are commonly used with planar imaging systems to reduce in-plane reflected waves; however SWS artifacts arise from both in and out-of imaging plane reflected waves. Herein, we quantify the reduction in image artifacts afforded by the use of volumetric SWS monitoring and 4D directional filters. A Gaussian acoustic radiation force impulse was simulated in a phantom with a Young's modulus (E) of 3 kPa with a 5 mm spherical lesion with E = 6, 12 or 18.75 kPa. 2D, 3D, and 4D directional filters were applied to the displacement profiles to reduce in and out-of-plane reflected wave artifacts. SWS images were reconstructed and RMS error and CNR were calculated for each image to evaluate the image accuracy and quality. Applying 3D directional filters as compared to 2D led to larger improvements in image accuracy and quality than the improvements seen using 4D directional filters over 3D. This improvement in image accuracy is significant because the processing of these data could be performed on displacement data from a traditional 1D linear array with reasonable computational time and resources. Although 4D directional filters can further reduce the impact of large magnitude out-of-plane reflection artifacts in SWS images, computational overhead and transducer costs may outweigh the modest improvements in image quality.

Authors
Lipman, SL; Rouze, NC; Palmeri, ML; Nightingale, KR
MLA Citation
Lipman, SL, Rouze, NC, Palmeri, ML, and Nightingale, KR. "Improving the accuracy of shear wave speed reconstructions using 4D directional filters in the presence of reflection artifacts." January 1, 2014.
Source
scopus
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2014
Start Page
2312
End Page
2315
DOI
10.1109/ULTSYM.2014.0576

Micro-elasticity (μ-E): CNR and resolution of acoustic radiation force impulse imaging and single- and multiple track location shear wave elasticity imaging for visualizing small targets

© 2014 IEEE.Acoustic radiation force impulse (ARFI) imaging and shear wave elasticity imaging (SWEI) use the dynamic response of tissue to impulsive mechanical stimulus to characterize local elasticity. A variant of conventional, multiple track location SWEI (MTL-SWEI), denoted single track location SWEI (STL-SWEI) offers the promise of creating speckle-free shear wave images. This work compares the three imaging modalities using a high push and track beam density combined acquisition sequence to image stiff inclusions with diameters of 1.5 and 6 mm. STL-SWEI is shown to have significantly higher CNR than MTL-SWEI, allowing for operation at higher resolution. ARFI and STL-SWEI perform similarly in the 6 mm inclusions, but STL-SWEI images the 1.5 mm targets with the highest CNR and best resolution. The processing trade-offs between CNR and resolution for each modality are discussed.

Authors
Hollender, P; Rosenzweig, S; Nightingale, K; Trahey, G
MLA Citation
Hollender, P, Rosenzweig, S, Nightingale, K, and Trahey, G. "Micro-elasticity (μ-E): CNR and resolution of acoustic radiation force impulse imaging and single- and multiple track location shear wave elasticity imaging for visualizing small targets." January 1, 2014.
Source
scopus
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2014
Start Page
703
End Page
706
DOI
10.1109/ULTSYM.2014.0173

3D elasticity imaging with acoustic radiation force

Acoustic radiation force impulse (ARFI) based elasticity imaging methods have been under development for the past 15 years, and both qualitative on-axis (ARFI imaging) and quantitative shear wave speed (SWEI) methods have been introduced into the commercial market. On-axis methods employ less processing and provide higher spatial resolution, whereas SWEI methods employ reconstruction algorithms that afford higher contrast and provide quantitative estimates of the underlying material stiffness. Each approach can be optimized through custom beam sequences and processing algorithms for specific clinical applications. We discuss three specific applications herein: 1) hepatic fibrosis and steatosis staging through SWEI, 2) 3D SWEI for characterizing material anisotropy, and 3) 3D prostatic SWEI and ARFI imaging. © 2013 IEEE.

Authors
Nightingale, KR; Rouze, NC; Wang, MH; Rosenzweig, SJ; Palmeri, ML
MLA Citation
Nightingale, KR, Rouze, NC, Wang, MH, Rosenzweig, SJ, and Palmeri, ML. "3D elasticity imaging with acoustic radiation force." December 1, 2013.
Source
scopus
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2013
Start Page
531
End Page
536
DOI
10.1109/ULTSYM.2013.0138

Bayesian shear wave speed estimation for in vivo 3D imaging of the prostate

Shear wave elasticity imaging (SWEI) has shown promise for visualizing structure and pathology within multiple organs; however, due to the assumptions of time of flight algorithms, artifacts caused by reflected waves at structural boundaries may be present in the images. The maximum a posteriori (MAP) estimator provides a framework for Bayesian estimation of the shear wave speed in order to reduce the artifacts and noise in SWEI images. Finite element method simulations and data acquired in a calibrated CIRS phantom show reductions in the bias and variance of the shear wave speed estimates compared to least squares linear regression. In vivo data are presented along with concurrently acquired acoustic radiation force impulse (ARFI) images demonstrating correlation between the elasticity imaging modalities. © 2013 IEEE.

Authors
Rosenzweig, S; Rouze, N; Byram, B; Palmeri, M; Polascik, T; Nightingale, K
MLA Citation
Rosenzweig, S, Rouze, N, Byram, B, Palmeri, M, Polascik, T, and Nightingale, K. "Bayesian shear wave speed estimation for in vivo 3D imaging of the prostate." December 1, 2013.
Source
scopus
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2013
Start Page
1260
End Page
1263
DOI
10.1109/ULTSYM.2013.0322

RSNA/QIBA: Shear wave speed as a biomarker for liver fibrosis staging

An interlaboratory study of shear wave speed (SWS) estimation was performed. Commercial shear wave elastography systems from Fibroscan, Philips, Siemens and Supersonic Imagine, as well as several custom laboratory systems, were involved. Fifteen sites were included in the study. CIRS manufactured and donated 11 pairs of custom phantoms designed for the purposes of this investigation. Dynamic mechanical tests of equivalent phantom materials were also performed. The results of this study demonstrate that there is very good agreement among SWS estimation systems, but there are several sources of bias and variance that can be addressed to improve consistency of measurement results. © 2013 IEEE.

Authors
Hall, TJ; Milkowski, A; Garra, B; Carson, P; Palmeri, M; Nightingale, K; Lynch, T; Alturki, A; Andre, M; Audiere, S; Bamber, J; Barr, R; Bercoff, J; Bercoff, J; Bernal, M; Brum, J; Chan, HW; Chen, S; Cohen-Bacrie, C; Couade, M; Daniels, A; Dewall, R; Dillman, J; Ehman, R; Franchi-Abella, S; Fromageau, J; Gennisson, JL; Henry, JP; Ivancevich, N; Kalin, J; Kohn, S; Kugel, J; Lee, K; Liu, N; Loupas, T; Mazernik, J; McAleavey, S; Miette, V; Metz, S; Morel, B; Nelson, T; Nordberg, E; Oudry, J et al.
MLA Citation
Hall, TJ, Milkowski, A, Garra, B, Carson, P, Palmeri, M, Nightingale, K, Lynch, T, Alturki, A, Andre, M, Audiere, S, Bamber, J, Barr, R, Bercoff, J, Bercoff, J, Bernal, M, Brum, J, Chan, HW, Chen, S, Cohen-Bacrie, C, Couade, M, Daniels, A, Dewall, R, Dillman, J, Ehman, R, Franchi-Abella, S, Fromageau, J, Gennisson, JL, Henry, JP, Ivancevich, N, Kalin, J, Kohn, S, Kugel, J, Lee, K, Liu, N, Loupas, T, Mazernik, J, McAleavey, S, Miette, V, Metz, S, Morel, B, Nelson, T, Nordberg, E, and Oudry, J et al. "RSNA/QIBA: Shear wave speed as a biomarker for liver fibrosis staging." December 1, 2013.
Source
scopus
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2013
Start Page
397
End Page
400
DOI
10.1109/ULTSYM.2013.0103

Finite element modeling of impulsive excitation and shear wave propagation in an incompressible, transversely isotropic medium

Elastic properties of materials can be measured by observing shear wave propagation following localized, impulsive excitations and relating the propagation velocity to a model of the material. However, characterization of anisotropic materials is difficult because of the number of elasticity constants in the material model and the complex dependence of propagation velocity relative to the excitation axis, material symmetries, and propagation directions. In this study, we develop a model of wave propagation following impulsive excitation in an incompressible, transversely isotropic (TI) material such as muscle. Wave motion is described in terms of three propagation modes identified by their polarization relative to the material symmetry axis and propagation direction. Phase velocities for these propagation modes are expressed in terms of five elasticity constants needed to describe a general TI material, and also in terms of three constants after the application of two constraints that hold in the limit of an incompressible material. Group propagation velocities are derived from the phase velocities to describe the propagation of wave packets away from the excitation region following localized excitation. The theoretical model is compared to the results of finite element (FE) simulations performed using a nearly incompressible material model with the five elasticity constants chosen to preserve the essential properties of the material in the incompressible limit. Propagation velocities calculated from the FE displacement data show complex structure that agrees quantitatively with the theoretical model and demonstrates the possibility of measuring all three elasticity constants needed to characterize an incompressible, TI material. © 2013 Elsevier Ltd.

Authors
Rouze, NC; Wang, MH; Palmeri, ML; Nightingale, KR
MLA Citation
Rouze, NC, Wang, MH, Palmeri, ML, and Nightingale, KR. "Finite element modeling of impulsive excitation and shear wave propagation in an incompressible, transversely isotropic medium." Journal of Biomechanics 46.16 (November 15, 2013): 2761-2768.
Source
scopus
Published In
Journal of Biomechanics
Volume
46
Issue
16
Publish Date
2013
Start Page
2761
End Page
2768
DOI
10.1016/j.jbiomech.2013.09.008

Finite element modeling of impulsive excitation and shear wave propagation in an incompressible, transversely isotropic medium.

Elastic properties of materials can be measured by observing shear wave propagation following localized, impulsive excitations and relating the propagation velocity to a model of the material. However, characterization of anisotropic materials is difficult because of the number of elasticity constants in the material model and the complex dependence of propagation velocity relative to the excitation axis, material symmetries, and propagation directions. In this study, we develop a model of wave propagation following impulsive excitation in an incompressible, transversely isotropic (TI) material such as muscle. Wave motion is described in terms of three propagation modes identified by their polarization relative to the material symmetry axis and propagation direction. Phase velocities for these propagation modes are expressed in terms of five elasticity constants needed to describe a general TI material, and also in terms of three constants after the application of two constraints that hold in the limit of an incompressible material. Group propagation velocities are derived from the phase velocities to describe the propagation of wave packets away from the excitation region following localized excitation. The theoretical model is compared to the results of finite element (FE) simulations performed using a nearly incompressible material model with the five elasticity constants chosen to preserve the essential properties of the material in the incompressible limit. Propagation velocities calculated from the FE displacement data show complex structure that agrees quantitatively with the theoretical model and demonstrates the possibility of measuring all three elasticity constants needed to characterize an incompressible, TI material.

Authors
Rouze, NC; Wang, MH; Palmeri, ML; Nightingale, KR
MLA Citation
Rouze, NC, Wang, MH, Palmeri, ML, and Nightingale, KR. "Finite element modeling of impulsive excitation and shear wave propagation in an incompressible, transversely isotropic medium." J Biomech 46.16 (November 15, 2013): 2761-2768.
PMID
24094454
Source
pubmed
Published In
Journal of Biomechanics
Volume
46
Issue
16
Publish Date
2013
Start Page
2761
End Page
2768
DOI
10.1016/j.jbiomech.2013.09.008

Acoustic radiation force elasticity imaging in diagnostic ultrasound.

The development of ultrasound-based elasticity imaging methods has been the focus of intense research activity since the mid-1990s. In characterizing the mechanical properties of soft tissues, these techniques image an entirely new subset of tissue properties that cannot be derived with conventional ultrasound techniques. Clinically, tissue elasticity is known to be associated with pathological condition and with the ability to image these features in vivo; elasticity imaging methods may prove to be invaluable tools for the diagnosis and/or monitoring of disease. This review focuses on ultrasound-based elasticity imaging methods that generate an acoustic radiation force to induce tissue displacements. These methods can be performed noninvasively during routine exams to provide either qualitative or quantitative metrics of tissue elasticity. A brief overview of soft tissue mechanics relevant to elasticity imaging is provided, including a derivation of acoustic radiation force, and an overview of the various acoustic radiation force elasticity imaging methods.

Authors
Doherty, JR; Trahey, GE; Nightingale, KR; Palmeri, ML
MLA Citation
Doherty, JR, Trahey, GE, Nightingale, KR, and Palmeri, ML. "Acoustic radiation force elasticity imaging in diagnostic ultrasound." IEEE Trans Ultrason Ferroelectr Freq Control 60.4 (April 2013): 685-701. (Review)
PMID
23549529
Source
pubmed
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
60
Issue
4
Publish Date
2013
Start Page
685
End Page
701
DOI
10.1109/TUFFC.2013.2617

On the precision of time-of-flight shear wave speed estimation in homogeneous soft solids: Initial results using a matrix array transducer

A system capable of tracking radiation-forceinduced shear wave propagation in a 3-D volume using ultrasound is presented. In contrast to existing systems, which use 1-D array transducers, a 2-D matrix array is used for tracking shear wave displacements. A separate single-element transducer is used for radiation force excitation. This system allows shear wave propagation in all directions away from the push to be observed. It is shown that for a limit of 64 tracking beams, by placing the beams at the edges of the measurement region of interest (ROI) at multiple directions from the push, timeof-flight (TOF) shear wave speed (SWS) measurement uncertainty can theoretically be reduced by 40% compared with equally spacing the tracking beams within the ROI along a single plane, as is typical when using a 1-D array for tracking. This was verified by simulation, and a reduction of 30% was experimentally observed on a homogeneous phantom. Analytical expressions are presented for the relationship between TOF SWS measurement uncertainty and various shear wave imaging parameters. It is shown that TOF SWS uncertainty is inversely proportional to ROI size, and inversely proportional to the square root of the number of tracking locations for a given distribution of beam locations relative to the push. TOF SWS uncertainty is shown to increase with the square of the SWS, indicating that TOF SWS measurements are intrinsically less precise for stiffer materials. © 1986-2012 IEEE.

Authors
Wang, M; Byram, B; Palmeri, M; Rouze, N; Nightingale, K
MLA Citation
Wang, M, Byram, B, Palmeri, M, Rouze, N, and Nightingale, K. "On the precision of time-of-flight shear wave speed estimation in homogeneous soft solids: Initial results using a matrix array transducer." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 60.4 (2013): 758-770.
PMID
23549536
Source
scival
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
60
Issue
4
Publish Date
2013
Start Page
758
End Page
770
DOI
10.1109/TUFFC.2013.2624

Ultrasonic characterization of the nonlinear properties of canine livers by measuring shear wave speed and axial strain with increasing portal venous pressure

Elevated hepatic venous pressure is the primary source of complications in advancing liver disease. Ultrasound imaging is ideal for potential noninvasive hepatic pressure measurements as it is widely used for liver imaging. Specifically, ultrasound based stiffness measures may be useful for clinically monitoring pressure, but the mechanism by which liver stiffness increases with hepatic pressure has not been well characterized. This study is designed to elucidate the nonlinear properties of the liver during pressurization by measuring both hepatic shear wave speed (SWS) and strain with increasing pressure. Tissue deformation during hepatic pressurization was tracked in 8 canine livers using successively acquired 3-D B-mode volumes and compared with concurrently measured SWS. When portal venous pressure was increased from clinically normal (0-5 mmHg) to pressures representing highly diseased states at 20 mmHg, the liver was observed to expand with axial strain measures up to 10%. At the same time, SWS estimates were observed to increase from 1.5-2 m/s at 0-5 mmHg (baseline) to 3.25-3.5 m/s at 20 mmHg. © 2013 Elsevier Ltd. All rights reserved.

Authors
Rotemberg, V; Byram, B; Palmeri, M; Wang, M; Nightingale, K
MLA Citation
Rotemberg, V, Byram, B, Palmeri, M, Wang, M, and Nightingale, K. "Ultrasonic characterization of the nonlinear properties of canine livers by measuring shear wave speed and axial strain with increasing portal venous pressure." Journal of Biomechanics (2013).
PMID
23726184
Source
scival
Published In
Journal of Biomechanics
Publish Date
2013
DOI
10.1016/j.jbiomech.2013.04.027

Imaging transverse isotropic properties of muscle by monitoring acoustic radiation force induced shear waves using a 2-D matrix ultrasound array

A 2-D matrix ultrasound array is used to monitor acoustic radiation force impulse (ARFI) induced shear wave propagation in 3-D in excised canine muscle. From a single acquisition, both the shear wave phase and group velocity can be calculated to estimate the shear wave speed (SWS) along and across the fibers, as well as the fiber orientation in 3-D. The true fiber orientation found using the 3-D radon transform on B-mode volumes of the muscle was used to verify the fiber direction estimated from shear wave data. For the simplified imaging case when the ARFI push can be oriented perpendicular to the fibers, the error in estimating the fiber orientation using phase and group velocity measurements was 3.5\pm 2.6\circ and 3.4\pm 1.4\circ (mean \pmstandard deviation), respectively, over six acquisitions in different muscle samples. For the more general case when the push is oblique to the fibers, the angle between the push and the fibers is found using the dominant orientation of the shear wave displacement magnitude. In 30 acquisitions on six different muscle samples with oblique push angles up to 40\circ, the error in the estimated fiber orientation using phase and group velocity measurements was 5.4\pm 2.9\circ and 5.3\pm 3.2\circ , respectively, after estimating and accounting for the additional unknown push angle. Either the phase or group velocity measurements can be used to estimate fiber orientation and SWS along and across the fibers. Although it is possible to perform these measurements when the push is not perpendicular to the fibers, highly oblique push angles induce lower shear wave amplitudes which can cause inaccurate SWS measurements. © 2012 IEEE.

Authors
Wang, M; Byram, B; Palmeri, M; Rouze, N; Nightingale, K
MLA Citation
Wang, M, Byram, B, Palmeri, M, Rouze, N, and Nightingale, K. "Imaging transverse isotropic properties of muscle by monitoring acoustic radiation force induced shear waves using a 2-D matrix ultrasound array." IEEE Transactions on Medical Imaging 32.9 (2013): 1671-1684.
PMID
23686942
Source
scival
Published In
IEEE Transactions on Medical Imaging
Volume
32
Issue
9
Publish Date
2013
Start Page
1671
End Page
1684
DOI
10.1109/TMI.2013.2262948

Parameters affecting the resolution and accuracy of 2-D quantitative shear wave images.

Time-of-flight methods allow quantitative measurement of shear wave speed (SWS) from ultrasonically tracked displacements following impulsive acoustic radiation force excitation in tissue. In heterogeneous materials, reflections at boundaries can distort the wave shape and confound determination of the wave arrival time. The magnitude of these effects depends on the shear wavelength of the excitation, the kernel size used to calculate the SWS, and the method used to determine the wave arrival time. In this study, we perform a parametric analysis of these factors using finite element modeling of the tissue response and simulated ultrasonic tracking. Two geometries are used, a stiff vertical layer and a stiff spherical inclusion, each in a uniform background. Wave arrival times are estimated using the peak displacement, peak slope of the leading edge, and cross-correlation methods. Results are evaluated in terms of reconstruction accuracy, resolution, contrast, and contrast-to-noise ratio of reconstructed SWS images. Superior results are obtained using narrower excitation widths and arrival time estimators which identify the leading edge of the propagating wave. The optimal kernel size is determined by a tradeoff between improved accuracy for larger kernels at the expense of spatial resolution.

Authors
Rouze, NC; Wang, MH; Palmeri, ML; Nightingale, KR
MLA Citation
Rouze, NC, Wang, MH, Palmeri, ML, and Nightingale, KR. "Parameters affecting the resolution and accuracy of 2-D quantitative shear wave images." IEEE Trans Ultrason Ferroelectr Freq Control 59.8 (August 2012): 1729-1740.
PMID
22899119
Source
pubmed
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
59
Issue
8
Publish Date
2012
Start Page
1729
End Page
1740
DOI
10.1109/TUFFC.2012.2377

Acoustic Radiation Force Based Imaging: An Overview

Authors
Nightingale, K; Wang, M; Rosenzweig, S; Rotemberg, V; Rouze, N; Palmeri, M
MLA Citation
Nightingale, K, Wang, M, Rosenzweig, S, Rotemberg, V, Rouze, N, and Palmeri, M. "Acoustic Radiation Force Based Imaging: An Overview." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
4004
End Page
4004

Acoustic radiation force impulse imaging of human prostates: initial in vivo demonstration.

Reliably detecting prostate cancer (PCa) has been a challenge for current imaging modalities. Acoustic radiation force impulse (ARFI) imaging is an elasticity imaging method that uses remotely generated, focused acoustic beams to probe tissue stiffness. A previous study on excised human prostates demonstrated ARFI images portray various prostatic structures and has the potential to guide prostate needle biopsy with improved sampling accuracy. The goal of this study is to demonstrate the feasibility of ARFI imaging to portray internal structures and PCa in the human prostate in vivo. Custom ARFI imaging sequences were designed and implemented using a modified Siemens Antares™ scanner with a three-dimensional (3-D) wobbler, end-firing, trans-cavity transducer, EV9F4. Nineteen patients were consented and imaged immediately preceding surgical prostatectomy. Pathologies and anatomic structures were identified in histologic slides by a pathologist blinded to ARFI data and were then registered with structures found in ARFI images. The results demonstrated that when PCa is visible, it generally appears as bilaterally asymmetric stiff structures; benign prostatic hyperplasia (BPH) appears heterogeneous with a nodular texture; the verumontanum and ejaculatory ducts appears softer compared with surrounding tissue, which form a unique 'V' shape; and the boundary of the transitional zone (TZ) forms a stiff rim separating the TZ from the peripheral zone (PZ). These characteristic appearances of prostatic structures are consistent with those found in our previous study of prostate ARFI imaging on excised human prostates. Compared with the matched B-mode images, ARFI images, in general, portray prostate structures with higher contrast. With the end-firing transducer used for this study, ARFI depth penetration was limited to 22 mm. Image contrast and resolution were decreased as compared with the previous ex vivo study due to the small transducer aperture. Even with these limitations, this study suggests ARFI imaging holds promise for guidance of targeted prostate needle biopsy and focal therapy, as well as aiding assessment of changes during watchful waiting/active surveillance.

Authors
Zhai, L; Polascik, TJ; Foo, W-C; Rosenzweig, S; Palmeri, ML; Madden, J; Nightingale, KR
MLA Citation
Zhai, L, Polascik, TJ, Foo, W-C, Rosenzweig, S, Palmeri, ML, Madden, J, and Nightingale, KR. "Acoustic radiation force impulse imaging of human prostates: initial in vivo demonstration." Ultrasound Med Biol 38.1 (January 2012): 50-61.
PMID
22104533
Source
pubmed
Published In
Ultrasound in Medicine and Biology
Volume
38
Issue
1
Publish Date
2012
Start Page
50
End Page
61
DOI
10.1016/j.ultrasmedbio.2011.10.002

Reply to: The use of acoustic radiation force-based shear stiffness in non-alcoholic fatty liver disease

Authors
Palmeri, ML; Abdelmalek, MF; Nightingale, KR
MLA Citation
Palmeri, ML, Abdelmalek, MF, and Nightingale, KR. "Reply to: The use of acoustic radiation force-based shear stiffness in non-alcoholic fatty liver disease." Journal of Hepatology 56.4 (2012): 996--.
Source
scival
Published In
Journal of Hepatology
Volume
56
Issue
4
Publish Date
2012
Start Page
996-
DOI
10.1016/j.jhep.2011.09.007

Functional neuroimaging using ultrasonic blood-brain barrier disruption and manganese-enhanced MRI

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains technically challenging. One approach, Activation-Induced Manganese-enhanced MRI (AIM MRI), has been used successfully to map neuronal activity in rodents 1-5. In AIM MRI, Mn 2+ acts a calcium analog and accumulates in depolarized neurons 6,7. Because Mn 2+ shortens the T 1 tissue property, regions of elevated neuronal activity will enhance in MRI. Furthermore, Mn 2+ clears slowly from the activated regions; therefore, stimulation can be performed outside the magnet prior to imaging, enabling greater experimental flexibility. However, because Mn 2+ does not readily cross the blood-brain barrier (BBB), the need to open the BBB has limited the use of AIM MRI, especially in mice. One tool for opening the BBB is ultrasound. Though potentially damaging, if ultrasound is administered in combination with gas-filled microbubbles (i.e., ultrasound contrast agents), the acoustic pressure required for BBB opening is considerably lower. This combination of ultrasound and microbubbles can be used to reliably open the BBB without causing tissue damage 8-11. Here, a method is presented for performing AIM MRI by using microbubbles and ultrasound to open the BBB. After an intravenous injection of perflutren microbubbles, an unfocused pulsed ultrasound beam is applied to the shaved mouse head for 3 minutes. For simplicity, we refer to this technique of BBB Opening with Microbubbles and UltraSound as BOMUS 12. Using BOMUS to open the BBB throughout both cerebral hemispheres, manganese is administered to the whole mouse brain. After experimental stimulation of the lightly sedated mice, AIM MRI is used to map the neuronal response. To demonstrate this approach, herein BOMUS and AIM MRI are used to map unilateral mechanical stimulation of the vibrissae in lightly sedated mice 13. Because BOMUS can open the BBB throughout both hemispheres, the unstimulated side of the brain is used to control for nonspecific background stimulation. The resultant 3D activation map agrees well with published representations of the vibrissae regions of the barrel field cortex 14. The ultrasonic opening of the BBB is fast, noninvasive, and reversible; and thus this approach is suitable for high-throughput and/or longitudinal studies in awake mice.

Authors
Howles, GP; Qi, Y; Rosenzweig, SJ; Nightingale, KR; Johnson, GA
MLA Citation
Howles, GP, Qi, Y, Rosenzweig, SJ, Nightingale, KR, and Johnson, GA. "Functional neuroimaging using ultrasonic blood-brain barrier disruption and manganese-enhanced MRI." Journal of Visualized Experiments 65 (2012).
PMID
22825127
Source
scival
Published In
Journal of Visualized Experiments
Issue
65
Publish Date
2012
DOI
10.3791/4055

The impact of hepatic pressurization on liver shear wave speed estimates in constrained versus unconstrained conditions

Increased hepatic venous pressure can be observed in patients with advanced liver disease and congestive heart failure. This elevated portal pressure also leads to variation in acoustic radiation-force-derived shear wave-based liver stiffness estimates. These changes in stiffness metrics with hepatic interstitial pressure may confound stiffness-based predictions of liver fibrosis stage. The underlying mechanism for this observed stiffening behavior with pressurization is not well understood and is not explained with commonly used linear elastic mechanical models. An experiment was designed to determine whether the stiffness increase exhibited with hepatic pressurization results from a strain-dependent hyperelastic behavior. Six excised canine livers were subjected to variations in interstitial pressure through cannulation of the portal vein and closure of the hepatic artery and hepatic vein under constrained conditions (in which the liver was not free to expand) and unconstrained conditions. Radiation-force-derived shear wave speed estimates were obtained and correlated with pressure. Estimates of hepatic shear stiffness increased with changes in interstitial pressure over a physiologically relevant range of pressures (035 mmHg) from 1.5 to 3.5 m s 1. These increases were observed only under conditions in which the liver was free to expand while pressurized. This behavior is consistent with hyperelastic nonlinear material models that could be used in the future to explore methods for estimating hepatic interstitial pressure noninvasively. © 2012 Institute of Physics and Engineering in Medicine.

Authors
Rotemberg, V; Palmeri, M; Nightingale, R; Rouze, N; Nightingale, K
MLA Citation
Rotemberg, V, Palmeri, M, Nightingale, R, Rouze, N, and Nightingale, K. "The impact of hepatic pressurization on liver shear wave speed estimates in constrained versus unconstrained conditions." Physics in Medicine and Biology 57.2 (2012): 329-341.
PMID
22170769
Source
scival
Published In
Physics in Medicine and Biology
Volume
57
Issue
2
Publish Date
2012
Start Page
329
End Page
341
DOI
10.1088/0031-9155/57/2/329

Should the mechanical index be revised for ARFI imaging?

The mechanical index (MI) quantifies the likelihood that exposure to diagnostic ultrasound will produce an adverse biological effect by a nonthermal mechanism. The current formulation of the MI is based on inertial cavitation thresholds in two liquids, water and blood, as calculated by a formalism assuming very short pulse durations. Although tissue contains a high proportion of water, it is not a liquid but a viscoelastic solid. Further, acoustic radiation force impulse imaging employs high-intensity pulses up to several hundred acoustic periods long. The effect of these differences was studied in water, blood and five representative tissues. © 2012 IEEE.

Authors
Church, CC; Labuda, C; Nightingale, K
MLA Citation
Church, CC, Labuda, C, and Nightingale, K. "Should the mechanical index be revised for ARFI imaging?." IEEE International Ultrasonics Symposium, IUS (2012): 17-20.
PMID
24533174
Source
scival
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2012
Start Page
17
End Page
20
DOI
10.1109/ULTSYM.2012.0005

Characterizing expansion and stiffening of the canine liver with increasing hepatic pressure

Hepatic venous pressure is increased in advancing liver disease and is considered the primary source of of complications (such as variceal bleeding and ascites). Measurement of clinically significant increases in portal pressure is important for managing liver disease and is performed using the invasive method, hepatic venous pressure gradient (HVPG). We have previously reported that ARFI based shear wave speed (SWS) estimate increases with increasing hepatic venous pressure require an underlying tissue deformation. However, the mechanical behavior of the liver during pressurization is not well understood. In this work, tissue deformation during hepatic pressurization was tracked using successively acquired 3-D B-mode volumes and compared with concurrently accrued SWS datasets. © 2012 IEEE.

Authors
Rotemberg, V; Byram, B; Wang, M; Palmeri, ML; Nightingale, KR
MLA Citation
Rotemberg, V, Byram, B, Wang, M, Palmeri, ML, and Nightingale, KR. "Characterizing expansion and stiffening of the canine liver with increasing hepatic pressure." 2012.
Source
scival
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2012
Start Page
101
End Page
104
DOI
10.1109/ULTSYM.2012.0025

3D shear wave imaging of anisotropic mechanical properties of muscle using a 2D matrix array transducer

A 2D matrix array is used to monitor acoustic radiation force impulse (ARFI) induced shear wave propagation in 3D in excised canine muscle. From a single acquisition, both the shear wave phase and group velocity can be calculated within a plane of symmetry to estimate the shear wave speed (SWS) along and across the fibers, as well as the fiber orientation in 3D. The true fiber orientation found using the 3D Radon Transform (3D RT) on B-mode volumes of the muscle was used to verify the fiber direction. For the simplified imaging case when the ARFI push can be oriented perpendicular to the fibers, the error in estimating the fiber orientation using phase and group velocity measurements was 3.5 ± 2.6°and 3.4 ± 1.4°(mean ± standard deviation), over six acquisitions in different muscle samples. For the more general case when the push is oblique to the fibers, the angle between the push and the fibers (or orientation of the plane of symmetry) is found using the dominant orientation of the shear wave displacement magnitude. In 30 acquisitions on six different muscle samples with oblique push angles up to 40°, the median error in the estimated fiber orientation using phase and group velocity measurements was 5.2°and 4.7°, respectively, after accounting for the additional unknown push angle. Either the phase or group velocity measurements can be used to estimate fiber orientation and SWS along and across the fibers in a plane of symmetry. Although it is possible to estimate the orientation of the plane of symmetry when the push is oblique to the fibers, inaccurate measurements of fiber orientation and SWS along and across the fibers occurred for highly oblique push angles (>25°). © 2012 IEEE.

Authors
Wang, MH; Byram, BC; Palmeri, ML; Rouze, NC; Nightingale, KR
MLA Citation
Wang, MH, Byram, BC, Palmeri, ML, Rouze, NC, and Nightingale, KR. "3D shear wave imaging of anisotropic mechanical properties of muscle using a 2D matrix array transducer." 2012.
Source
scival
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2012
Start Page
5
End Page
8
DOI
10.1109/ULTSYM.2012.0002

Comparison of concurrently acquired in vivo 3D ARFI and SWEI images of the prostate

In the prostate, ARFI and SWEI imaging methods have reported that cancer and other pathologies as being stiffer than the surrounding tissue. A three-dimensional in vivo prostatic imaging system capable of concurrently acquiring ARFI and SWEI data was developed to compare the information available in the two image types. Data were acquired in a calibrated CIRS phantom to analyze the contrast, contrast to noise ratio (CNR), and resolution between the ARFI and SWEI images; SWEI images provided improved contrast and CNR, but lower spatial resolution than ARFI images. Challenges and potential artifacts in both the ARFI and SWEI images have been identified and reduced by viewing coronal sections and maximum value SWEI images, resulting in high correlation between the normalized ARFI displacement magnitude and the estimated shear wave speed. We have demonstrated that this combined ARFI and SWEI imaging system can image the anatomy of the prostate. © 2012 IEEE.

Authors
Rosenzweig, S; Palmeri, M; Rouze, N; Lipman, S; Kulbacki, E; Madden, J; Polascik, T; Nightingale, K
MLA Citation
Rosenzweig, S, Palmeri, M, Rouze, N, Lipman, S, Kulbacki, E, Madden, J, Polascik, T, and Nightingale, K. "Comparison of concurrently acquired in vivo 3D ARFI and SWEI images of the prostate." 2012.
Source
scival
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2012
Start Page
97
End Page
100
DOI
10.1109/ULTSYM.2012.0024

Noninvasive evaluation of hepatic fibrosis using acoustic radiation force-based shear stiffness in patients with nonalcoholic fatty liver disease.

BACKGROUND & AIMS: Nonalcoholic fatty liver disease (NAFLD), the most common form of chronic liver disease in developed countries, may progress to nonalcoholic steatohepatitis (NASH) in a minority of people. Those with NASH are at increased risk for cirrhosis and hepatocellular carcinoma. The potential risk and economic burden of utilizing liver biopsy to stage NAFLD in an overwhelmingly large at-risk population are enormous; thus, the discovery of sensitive, inexpensive, and reliable noninvasive diagnostic modalities is essential for population-based screening. METHODS: Acoustic Radiation Force Impulse (ARFI) shear wave imaging, a noninvasive method of assessing tissue stiffness, was used to evaluate liver fibrosis in 172 patients diagnosed with NAFLD. Liver shear stiffness measures in three different imaging locations were reconstructed and compared to the histologic features of NAFLD and AST-to-platelet ratio indices (APRI). RESULTS: Reconstructed shear stiffnesses were not associated with ballooned hepatocytes (p=0.11), inflammation (p=0.69), nor imaging location (p=0.11). Using a predictive shear stiffness threshold of 4.24kPa, shear stiffness distinguished low (fibrosis stage 0-2) from high (fibrosis stage 3-4) fibrosis stages with a sensitivity of 90% and a specificity of 90% (AUC of 0.90). Shear stiffness had a mild correlation with APRI (R(2)=0.22). BMI>40kg/m(2) was not a limiting factor for ARFI imaging, and no correlation was noted between BMI and shear stiffness (R(2)=0.05). CONCLUSIONS: ARFI imaging is a promising imaging modality for assessing the presence or absence of advanced fibrosis in patients with obesity-related liver disease.

Authors
Palmeri, ML; Wang, MH; Rouze, NC; Abdelmalek, MF; Guy, CD; Moser, B; Diehl, AM; Nightingale, KR
MLA Citation
Palmeri, ML, Wang, MH, Rouze, NC, Abdelmalek, MF, Guy, CD, Moser, B, Diehl, AM, and Nightingale, KR. "Noninvasive evaluation of hepatic fibrosis using acoustic radiation force-based shear stiffness in patients with nonalcoholic fatty liver disease." J Hepatol 55.3 (September 2011): 666-672.
PMID
21256907
Source
pubmed
Published In
Journal of Hepatology
Volume
55
Issue
3
Publish Date
2011
Start Page
666
End Page
672
DOI
10.1016/j.jhep.2010.12.019

Acoustic radiation force-based elasticity imaging methods.

Conventional diagnostic ultrasound images portray differences in the acoustic properties of soft tissues, whereas ultrasound-based elasticity images portray differences in the elastic properties of soft tissues (i.e. stiffness, viscosity). The benefit of elasticity imaging lies in the fact that many soft tissues can share similar ultrasonic echogenicities, but may have different mechanical properties that can be used to clearly visualize normal anatomy and delineate pathological lesions. Acoustic radiation force-based elasticity imaging methods use acoustic radiation force to transiently deform soft tissues, and the dynamic displacement response of those tissues is measured ultrasonically and is used to estimate the tissue's mechanical properties. Both qualitative images and quantitative elasticity metrics can be reconstructed from these measured data, providing complimentary information to both diagnose and longitudinally monitor disease progression. Recently, acoustic radiation force-based elasticity imaging techniques have moved from the laboratory to the clinical setting, where clinicians are beginning to characterize tissue stiffness as a diagnostic metric, and commercial implementations of radiation force-based ultrasonic elasticity imaging are beginning to appear on the commercial market. This article provides an overview of acoustic radiation force-based elasticity imaging, including a review of the relevant soft tissue material properties, a review of radiation force-based methods that have been proposed for elasticity imaging, and a discussion of current research and commercial realizations of radiation force based-elasticity imaging technologies.

Authors
Palmeri, ML; Nightingale, KR
MLA Citation
Palmeri, ML, and Nightingale, KR. "Acoustic radiation force-based elasticity imaging methods." Interface Focus 1.4 (August 6, 2011): 553-564.
PMID
22419986
Source
pubmed
Published In
Interface Focus
Volume
1
Issue
4
Publish Date
2011
Start Page
553
End Page
564
DOI
10.1098/rsfs.2011.0023

What challenges must be overcome before ultrasound elasticity imaging is ready for the clinic?

Ultrasound elasticity imaging has been a research interest for the past 20 years with the goal of generating novel images of soft tissues based on their material properties (i.e., stiffness and viscosity). The motivation for such an imaging modality lies in the fact that many soft tissues can share similar ultrasonic echogenicities, but may have very different mechanical properties that can be used to clearly visualize normal anatomy and delineate diseased tissues and masses. Recently, elasticity imaging techniques have moved from the laboratory to the clinical setting, where clinicians are beginning to characterize tissue stiffness as a diagnostic metric and commercial implementations of ultrasonic elasticity imaging are beginning to appear on the market. This article provides a foundation for elasticity imaging, an overview of current research and commercial realizations of elasticity imaging technology and a perspective on the current successes, limitations and potential for improvement of these imaging technologies.

Authors
Palmeri, ML; Nightingale, KR
MLA Citation
Palmeri, ML, and Nightingale, KR. "What challenges must be overcome before ultrasound elasticity imaging is ready for the clinic?." Imaging Med 3.4 (August 2011): 433-444.
PMID
22171226
Source
pubmed
Published In
Imaging in Medicine
Volume
3
Issue
4
Publish Date
2011
Start Page
433
End Page
444
DOI
10.2217/iim.11.41

Acoustic radiation force-driven assessment of myocardial elasticity using the displacement ratio rate (DRR) method.

A noninvasive method of characterizing myocardial stiffness could have significant implications in diagnosing cardiac disease. Acoustic radiation force (ARF)-driven techniques have demonstrated their ability to discern elastic properties of soft tissue. For the purpose of myocardial elasticity imaging, a novel ARF-based imaging technique, the displacement ratio rate (DRR) method, was developed to rank the relative stiffnesses of dynamically varying tissue. The basis and performance of this technique was demonstrated through numerical and phantom imaging results. This new method requires a relatively small temporal (<1 ms) and spatial (tenths of mm(2)) sampling window and appears to be independent of applied ARF magnitude. The DRR method was implemented in two in vivo canine studies, during which data were acquired through the full cardiac cycle by imaging directly on the exposed epicardium. These data were then compared with results obtained by acoustic radiation force impulse (ARFI) imaging and shear wave velocimetry, with the latter being used as the gold standard. Through the cardiac cycle, velocimetry results portray a range of shear wave velocities from 0.76-1.97 m/s, with the highest velocities observed during systole and the lowest observed during diastole. If a basic shear wave elasticity model is assumed, such a velocity result would suggest a period of increased stiffness during systole (when compared with diastole). Despite drawbacks of the DRR method (i.e., sensitivity to noise and limited stiffness range), its results predicted a similar cyclic stiffness variation to that offered by velocimetry while being insensitive to variations in applied radiation force.

Authors
Bouchard, RR; Hsu, SJ; Palmeri, ML; Rouze, NC; Nightingale, KR; Trahey, GE
MLA Citation
Bouchard, RR, Hsu, SJ, Palmeri, ML, Rouze, NC, Nightingale, KR, and Trahey, GE. "Acoustic radiation force-driven assessment of myocardial elasticity using the displacement ratio rate (DRR) method." Ultrasound Med Biol 37.7 (July 2011): 1087-1100.
PMID
21645966
Source
pubmed
Published In
Ultrasound in Medicine and Biology
Volume
37
Issue
7
Publish Date
2011
Start Page
1087
End Page
1100
DOI
10.1016/j.ultrasmedbio.2011.04.005

Acoustic radiation force impulse (ARFI) imaging-based needle visualization

Ultrasound-guided needle placement is widely used in the clinical setting, particularly for central venous catheter placement, tissue biopsy and regional anesthesia. Difficulties with ultrasound guidance in these areas often result from steep needle insertion angles and spatial offsets between the imaging plane and the needle. Acoustic Radiation Force Impulse (ARPI) imaging leads to improved needle visualization because it uses a standard diagnostic scanner to perform radiation force based elasticity imaging, creating a displacement map that displays tissue stiffness variations. The needle visualization in ARFI images is independent of needle-insertion angle and also extends needle visibility out of plane. Although ARFI images portray needles well, they often do not contain the usual B-mode landmarks. Therefore, a three-step segmentation algorithm has been developed to identify a needle in an ARFI image and overlay the needle prediction on a coregistered B-mode image. The steps are: (1) contrast enhancement by median filtration and Laplacian operator filtration, (2) noise suppression through displacement estimate correlation coefficient thresholding and (3) smoothing by removal of outliers and best-fit line prediction. The algorithm was applied to data sets from horizontal 18,21 and 25 gauge needles between 0-4 mm offset in elevation from the transducer imaging plane and to 18G needles on the transducer axis (in plane) between 10° and 35° from the horizontal. Needle tips were visualized within 2 mm of their actual position for both horizontal needle orientations up to 1.5 mm offset in elevation from the transducer imaging plane and on-axis angled needles between 10°-35° above the horizontal orientation. We conclude that segmented ARFI images overlaid on matched B-mode images hold promise for improved needle visibility in many clinical applications. Copyright 2011 by Dynamedia, Inc.

Authors
Rotemberg, V; Palmeri, M; Rosenzweig, S; Grant, S; Macleod, D; Nightingale, K
MLA Citation
Rotemberg, V, Palmeri, M, Rosenzweig, S, Grant, S, Macleod, D, and Nightingale, K. "Acoustic radiation force impulse (ARFI) imaging-based needle visualization." Ultrasonic Imaging 33.1 (2011): 1-16.
PMID
21608445
Source
scival
Published In
Ultrasonic Imaging
Volume
33
Issue
1
Publish Date
2011
Start Page
1
End Page
16

Methodology to register prostate B-mode and ARFI images to MR and histology

Acoustic Radiation Force Impulse (ARFI) imaging is being developed for guiding needle biopsy and focal therapy of Prostate cancer (PCa). In vivo ARFI images portray internal structures in the prostate with higher contrast than matched B-mode images. Given the heterogeneity of the prostate and the poor visualization provided by B-mode, another gold standard for determining what is being visualized in ARFI images is necessary. In this study, we present image registration techniques that facilitate correlation of in vivo ARFI, B-mode ultrasound (US), and Magnetic Resonance (MR) images obtained prior to radical prostatectomy with whole mount histology data. Pathology and structures were identified and segmented in the different datasets. The segmented datasets were used to form 3D mesh models of the prostate and the node and element information was extrapolated into a 3D image matrix of equivalent size for all modalities. Non-rigid registration of the different models was performed and the registered images were evaluated for co-localization of confirmed pathology. The methodology was validated using simulated prostate anatomy and finite-element techniques and found to improve the average displacement of registration markers by 76% in the MR simulation and 58% in the US simulation. When implemented on the patient data, the registration methodology was found to simplify multi-modality image comparison and analysis. Confirmed pathology was found to align with similarly suspicious regions in both ARFI and MR images. With its improved anatomical visualization over traditional B-mode imaging, ARFI holds promise for providing targeted image guidance of prostate focal therapy and needle biopsy. © 2011 IEEE.

Authors
Hsu, CML; Polascik, TJ; Davenport, MS; Kauffman, C; Gupta, RT; Kulbacki, E; Madden, J; Lipman, SL; Palmeri, ML; Nightingale, KR
MLA Citation
Hsu, CML, Polascik, TJ, Davenport, MS, Kauffman, C, Gupta, RT, Kulbacki, E, Madden, J, Lipman, SL, Palmeri, ML, and Nightingale, KR. "Methodology to register prostate B-mode and ARFI images to MR and histology." 2011.
Source
scival
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2011
Start Page
1866
End Page
1869
DOI
10.1109/ULTSYM.2011.0466

Combined ultrasonic thermal ablation with interleaved ARFI Image monitoring using a single diagnostic curvilinear array: A feasibility study

The goal of this work is to demonstrate the feasibility of using a diagnostic ultrasound system (Siemens Antares™ and CH6-2 curvilinear array) to ablate ex vivo liver with a custom M-mode sequence and monitor the resulting tissue stiffening with 2-D Acoustic Radiation Force Impulse (ARFI) imaging. Images were taken before and after ablation, as well as in 5-s intervals during the ablation sequence in order to monitor the ablation lesion formation temporally. Ablation lesions were generated at depths up to 1.5 cm from the surface of the liver and were not visible in B-mode. ARFI images showed liver stiffening with heating that corresponded to discolored regions in gross pathology. As expected, the contrast of ablation lesions in ARFI images is observed to increase with ablation lesion size. This study demonstrated the ability of a diagnostic system using custom beam sequences to localize an ablation site, heat the site to the point of irreversible damage and monitor the formation of the ablation lesion with ARFI imaging. Copyright 2011/2012 by Dynamedia, Inc. All rights of reproduction in any form reserved.

Authors
Bing, KF; Rouze, NC; Palmeri, ML; Rotemberg, VM; Nightingale, KR
MLA Citation
Bing, KF, Rouze, NC, Palmeri, ML, Rotemberg, VM, and Nightingale, KR. "Combined ultrasonic thermal ablation with interleaved ARFI Image monitoring using a single diagnostic curvilinear array: A feasibility study." Ultrasonic Imaging 33.4 (2011): 217-232.
PMID
22518953
Source
scival
Published In
Ultrasonic Imaging
Volume
33
Issue
4
Publish Date
2011
Start Page
217
End Page
232

Acoustic radiation force impulse (ARFI) imaging: A review

Acoustic radiation force based elasticity imaging methods are under investigation by many groups. These methods differ from traditional ultrasonic elasticity imaging methods in that they do not require compression of the transducer, and are thus expected to be less operator dependent. Methods have been developed that utilize impulsive (i.e. < 1 ms), harmonic (pulsed), and steady state radiation force excitations. The work discussed in this paper utilizes impulsive methods, for which two imaging approaches have been pursued: 1) monitoring the tissue response within the radiation force region of excitation (ROE) and generating images of relative differences in tissue stiffness (Acoustic Radiation Force Impulse (ARFI) imaging); and 2) monitoring the speed of shear wave propagation away from the ROE to quantify tissue stiffness (Shear Wave Elasticity Imaging (SWEI)). For these methods, a single ultrasound transducer on a commercial ultrasound system can be used to both generate acoustic radiation force in tissue, and to monitor the tissue displacement response. The response of tissue to this transient excitation is complicated and depends upon tissue geometry, radiation force field geometry, and tissue mechanical and acoustic properties. Higher shear wave speeds and smaller displacements are associated with stiffer tissues, and slower shear wave speeds and larger displacements occur with more compliant tissues. ARFI images have spatial resolution comparable to that of B-mode, often with greater contrast, providing matched, adjunctive information. SWEI images provide quantitative information about the tissue stiffness, typically with lower spatial resolution. A review these methods and examples of clinical applications are presented herein. © 2011 Bentham Science Publishers.

Authors
Nightingale, K
MLA Citation
Nightingale, K. "Acoustic radiation force impulse (ARFI) imaging: A review." Current Medical Imaging Reviews 7.4 (2011): 328-339.
PMID
22545033
Source
scival
Published In
Current medical imaging reviews
Volume
7
Issue
4
Publish Date
2011
Start Page
328
End Page
339
DOI
10.2174/157340511798038657

GPU-based real-time small displacement estimation with ultrasound

General purpose computing on graphics processing units (GPUs) has been previously shown to speed up computationally intensive data processing and image reconstruction algorithms for computed tomography (CT), magnetic resonance (MR), and ultrasound images. Although some algorithms in ultrasound have been converted to GPU processing, many investigative ultrasound research systems still use serial processing on a single CPU. One such ultrasound modality is acoustic radiation force impulse (ARFI) imaging, which investigates the mechanical properties of soft tissue. Traditionally, the raw data are processed offline to estimate the displacement of the tissue after the application of radiation force. It is highly advantageous to process the data in real-time to assess their quality and make modifications during a study. In this paper, we present algorithms for efficient GPU parallel processing of two widely used tools in ultrasound: cubic spline interpolation and Loupas' two-dimensional autocorrelator for displacement estimation. It is shown that a commercially available graphics card can be used for these computations, achieving speed increases up to 40× compared with single CPU processing. Thus, we conclude that the GPU-based data processing approach facilitates real-time (i.e.,<1 second) display of ARFI data and is a promising approach for ultrasonic research systems. © 2006 IEEE.

Authors
Rosenzweig, S; Palmeri, M; Nightingale, K
MLA Citation
Rosenzweig, S, Palmeri, M, and Nightingale, K. "GPU-based real-time small displacement estimation with ultrasound." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 58.2 (2011): 399-405.
PMID
21342825
Source
scival
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
58
Issue
2
Publish Date
2011
Start Page
399
End Page
405
DOI
10.1109/TUFFC.2011.1817

Comparison between Acoustic Radiation Force Impulse (ARFI)-based hepatic stiffness quantification in deformed and undeformed pressurized canine livers

Increased hepatic interstitial pressure can be observed in patients with advanced liver disease and is associated with worsened clinical outcomes. Elevated hepatic stiffness has been reported clinically with increases in hepatic venous pressure gradient (HVPG). An experiment was designed to determine whether stiffness increase exhibited with hepatic pressurization results from a strain-dependent hyperelastic behavior. Six excised canine livers were subjected to variations in interstitial pressure through cannulation of the portal vein and closure of the hepatic artery and hepatic vein under constrained conditions (in which the liver was not free to expand) and unconstrained conditions. Radiation force derived shear wave speed estimates were obtained and correlated with pressure. Estimates of hepatic shear stiffness increased with changes in interstitial pressure over a physiologically relevant range of pressures (0-35mmHg) from 1.5 to 3.5 m/s. These increases were observed only under conditions in which the liver was free to expand while pressurized. © 2011 IEEE.

Authors
Rotemberg, V; Palmeri, ML; Rouze, NC; Nightingale, R; Nightingale, KR
MLA Citation
Rotemberg, V, Palmeri, ML, Rouze, NC, Nightingale, R, and Nightingale, KR. "Comparison between Acoustic Radiation Force Impulse (ARFI)-based hepatic stiffness quantification in deformed and undeformed pressurized canine livers." IEEE International Ultrasonics Symposium, IUS (2011): 2090-2093.
Source
scival
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2011
Start Page
2090
End Page
2093
DOI
10.1109/ULTSYM.2011.0518

Improving shear wave speed estimation precision in homogeneous media by tracking shear wave propagation in 3D using a real-time volumetric imaging transducer

A system capable of tracking radiation force induced shear wave propagation in 3D using ultrasound is presented. In contrast to existing systems, which use 1D array transducers, a 2D matrix array is used for tracking shear wave displacements. A HIFU piston is used for radiation force excitation. This system allows shear wave propagation in all directions away from the push to be observed, for the first time. It is shown that for a limit of 64 tracking beams and a given reconstruction kernel size, by placing the tracking beams at the edges of the kernel at multiple directions from the push, time-of-flight (TOF) shear wave speed (SWS) measurement uncertainty can theoretically be reduced by 40% compared to equally spacing the tracking beams within the kernel along a single plane, as is typical when using a 1D array for tracking. This was verified by simulation, and a reduction of 30% was experimentally observed on a homogeneous phantom. © 2011 IEEE.

Authors
Wang, MH; Byram, BC; Palmeri, ML; Rouze, NC; Nightingale, KR
MLA Citation
Wang, MH, Byram, BC, Palmeri, ML, Rouze, NC, and Nightingale, KR. "Improving shear wave speed estimation precision in homogeneous media by tracking shear wave propagation in 3D using a real-time volumetric imaging transducer." IEEE International Ultrasonics Symposium, IUS (2011): 1262-1265.
Source
scival
Published In
IEEE International Ultrasonics Symposium : [proceedings]. IEEE International Ultrasonics Symposium
Publish Date
2011
Start Page
1262
End Page
1265
DOI
10.1109/ULTSYM.2011.0311

Comparison of qualitative and quantitative acoustic radiation force based elasticity imaging methods

Acoustic radiation force based elasticity imaging methods utilize focused acoustic beams to mechanically excite tissue and ultrasonic correlation based methods to monitor the dynamic response of the tissue, which reflects the underlying tissue stiffness. Both qualitative images and quantitative images can be derived depending upon the selected beam sequences and data processing algorithms. Qualitative images provide good spatial resolution and contrast, but reflect only relative differences in tissue stiffness. Quantitative measurements of tissue stiffness can be obtained by measuring the speed of propagating shear waves induced in tissue by acoustic radiation force. In homogeneous media, time-of-flight (TOF) measurements of shear wave speed (SWS) ideally are independent of the size of the region of interest (or reconstruction kernel), thus extensive averaging can be performed to improve estimate accuracy and precision. However, in heterogeneous media, shear wave morphology is altered by discontinuities in stiffness due to reflections or boundary conditions which introduce error to the measured SWS. In addition, the size of the reconstruction kernel limits the spatial resolution, or ability to precisely localize changes in stiffness. This study investigates the impact of: arrival time estimation method, shear wavelength, and reconstruction kernel size on the accuracy and spatial resolution of TOF SWS reconstruction in heterogeneous media using finite element method (FEM) simulations. © 2011 IEEE.

Authors
Nightingale, KR; Rouze, NC; Wang, MH; Zhai, L; Palmeri, ML
MLA Citation
Nightingale, KR, Rouze, NC, Wang, MH, Zhai, L, and Palmeri, ML. "Comparison of qualitative and quantitative acoustic radiation force based elasticity imaging methods." 2011.
Source
scival
Published In
Proceedings / IEEE International Symposium on Biomedical Imaging: from nano to macro. IEEE International Symposium on Biomedical Imaging
Publish Date
2011
Start Page
1606
End Page
1609
DOI
10.1109/ISBI.2011.5872710

Robust estimation of time-of-flight shear wave speed using a radon sum transformation.

Time-of-flight methods allow quantitative measurement of shear wave speed (SWS) from ultrasonically tracked displacements following impulsive excitation in tissue. However, application of these methods to in vivo data are challenging because of the presence of gross outlier data resulting from sources such as physiological motion or spatial inhomogeneities. This paper describes a new method for estimating SWS by considering a solution space of trajectories and evaluating each trajectory using a metric that characterizes wave motion along the entire trajectory. The metric used here is found by summing displacement data along the trajectory as in the calculation of projection data in the Radon transformation. The algorithm is evaluated using data acquired in calibrated phantoms and in vivo human liver. Results are compared with SWS estimates using a random sample consensus (RANSAC) algorithm described by Wang et al. Good agreement is found between the Radon sum and RANSAC SWS estimates with a correlation coefficient of greater than 0.99 for phantom data and 0.91 for in vivo liver data. The Radon sum transformation is suitable for use in situations requiring real-time feedback and is comparably robust to the RANSAC algorithm with respect to outlier data.

Authors
Rouze, NC; Wang, MH; Palmeri, ML; Nightingale, KR
MLA Citation
Rouze, NC, Wang, MH, Palmeri, ML, and Nightingale, KR. "Robust estimation of time-of-flight shear wave speed using a radon sum transformation." IEEE Trans Ultrason Ferroelectr Freq Control 57.12 (December 2010): 2662-2670.
PMID
21156362
Source
pubmed
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
57
Issue
12
Publish Date
2010
Start Page
2662
End Page
2670
DOI
10.1109/TUFFC.2010.1740

Contrast-enhanced in vivo magnetic resonance microscopy of the mouse brain enabled by noninvasive opening of the blood-brain barrier with ultrasound.

The use of contrast agents for neuroimaging is limited by the blood-brain barrier (BBB), which restricts entry into the brain. To administer imaging agents to the brain of rats, intracarotid infusions of hypertonic mannitol have been used to open the BBB. However, this technically challenging approach is invasive, opens only a limited region of the BBB, and is difficult to extend to mice. In this work, the BBB was opened in mice, using unfocused ultrasound combined with an injection of microbubbles. This technique has several notable features: it (a) can be performed transcranially in mice; (b) takes only 3 min and uses only commercially available components; (c) opens the BBB throughout the brain; (d) causes no observed histologic damage or changes in behavior (with peak-negative acoustic pressures of 0.36 MPa); and (e) allows recovery of the BBB within 4 h. Using this technique, Gadopentetate Dimeglumine (Gd-DTPA) was administered to the mouse brain parenchyma, thereby shortening T(1) and enabling the acquisition of high-resolution (52 × 52 × 100 micrometers(3)) images in 51 min in vivo. By enabling the administration of both existing anatomic contrast agents and the newer molecular/sensing contrast agents, this technique may be useful for the study of mouse models of neurologic function and pathology with MRI.

Authors
Howles, GP; Bing, KF; Qi, Y; Rosenzweig, SJ; Nightingale, KR; Johnson, GA
MLA Citation
Howles, GP, Bing, KF, Qi, Y, Rosenzweig, SJ, Nightingale, KR, and Johnson, GA. "Contrast-enhanced in vivo magnetic resonance microscopy of the mouse brain enabled by noninvasive opening of the blood-brain barrier with ultrasound." Magn Reson Med 64.4 (October 2010): 995-1004.
PMID
20740666
Source
pubmed
Published In
Magnetic Resonance in Medicine
Volume
64
Issue
4
Publish Date
2010
Start Page
995
End Page
1004
DOI
10.1002/mrm.22411

Characterizing stiffness of human prostates using acoustic radiation force.

Acoustic Radiation Force Impulse (ARFI) imaging has been previously reported to portray normal anatomic structures and pathologies in ex vivo human prostates with good contrast and resolution. These findings were based on comparison with histological slides and McNeal's zonal anatomy. In ARFI images, the central zone (CZ) appears darker (smaller displacement) than other anatomic zones and prostate cancer (PCa) is darker than normal tissue in the peripheral zone (PZ). Since displacement amplitudes in ARFI images are determined by both the underlying tissue stiffness and the amplitude of acoustic radiation force that varies with acoustic attenuation, one question that arises is how the relative displacements in prostate ARFI images are related to the underlying prostatic tissue stiffness. In linear, isotropic elastic materials and in tissues that are relatively uniform in acoustic attenuation (e.g., liver), relative displacement in ARFI images has been shown to be correlated with underlying tissue stiffness. However, the prostate is known to be heterogeneous. Variations in acoustic attenuation of prostatic structures could confound the interpretation of ARFI images due to the associated variations in the applied acoustic radiation force. Therefore, in this study, co-registered three-dimensional (3D) ARFI datasets and quantitative shear wave elasticity imaging (SWEI) datasets were acquired in freshly-excised human prostates to investigate the relationship between displacement amplitudes in ARFI prostate images and the matched reconstructed shear moduli. The lateral time-to-peak (LTTP) algorithm was applied to the SWEI data to compute the shear-wave speed and reconstruct the shear moduli. Five types of prostatic tissue (PZ, CZ, transition zone (TZ) and benign prostatic hyperplasia (BPH), PCa and atrophy) were identified, whose shear moduli were quantified to be 4.1 +/- 0.8 kPa, 9.9 +/- 0.9 kPa, 4.8 +/- 0.6 kPa, 10.0 +/- 1.0 kPa and 8.0 kPa, respectively. Linear regression was performed to compare ARFI displacement amplitudes and the inverse of the corresponding reconstructed shear moduli at multiple depths. The results indicate an inverse relation between ARFI displacement amplitude and reconstructed shear modulus at all depths. These findings support the conclusion that ARFI prostate images portray underlying tissue stiffness variations.

Authors
Zhai, L; Madden, J; Foo, W-C; Mouraviev, V; Polascik, TJ; Palmeri, ML; Nightingale, KR
MLA Citation
Zhai, L, Madden, J, Foo, W-C, Mouraviev, V, Polascik, TJ, Palmeri, ML, and Nightingale, KR. "Characterizing stiffness of human prostates using acoustic radiation force." Ultrason Imaging 32.4 (October 2010): 201-213.
PMID
21213566
Source
pubmed
Published In
Ultrasonic Imaging
Volume
32
Issue
4
Publish Date
2010
Start Page
201
End Page
213
DOI
10.1177/016173461003200401

Improving the robustness of time-of-flight based shear wave speed reconstruction methods using RANSAC in human liver in vivo.

The stiffness of tissue can be quantified by measuring the shear wave speed (SWS) within the medium. Ultrasound is a real-time imaging modality capable of tracking the propagation of shear waves in soft tissue. Time-of-flight (TOF) methods have previously been shown to be effective for quantifying SWS from ultrasonically tracked displacements. However, the application of these methods to in vivo data is challenging due to the presence of additional sources of error, such as physiologic motion or spatial inhomogeneities in tissue. This article introduces the use of random sample consensus (RANSAC), a model fitting paradigm robust to the presence of gross outlier data, for estimating the SWS from ultrasonically tracked tissue displacements in vivo. SWS reconstruction is posed as a parameter estimation problem and the RANSAC solution to this problem is described. Simulations using synthetic TOF data show that RANSAC is capable of good stiffness reconstruction accuracy (mean error 0.5 kPa) and precision (standard deviation 0.6 kPa) over a range of shear stiffness (0.6-10 kPa) and proportion of inlier data (50%-95%). As with all TOF SWS estimation methods, the accuracy and precision of the RANSAC reconstructed shear modulus decreases with increasing tissue stiffness. The RANSAC SWS estimator was applied to radiation force induced shear wave data from 123 human patient livers acquired with a modified SONOLINE Antares ultrasound system (Siemens Healthcare, Ultrasound Business Unit, Mountain View, CA, USA) in a clinical setting before liver biopsy was performed. Stiffness measurements were not possible in 19 patients due to the absence of shear wave propagation inside the liver. The mean liver stiffness for the remaining 104 patients ranged from 1.3 to 24.2 kPa and the proportion of inliers for the successful reconstructions ranged between 42% to 99%. Using RANSAC for SWS estimation improved the diagnostic accuracy of liver stiffness for delineating fibrosis stage compared with ordinary least squares (OLS) without outlier removal (AUROC = 0.94 for F >or= 3 and AUROC = 0.98 for F = 4). These results show that RANSAC is a suitable method for estimating the SWS from noisy in vivo shear wave displacements tracked by ultrasound.

Authors
Wang, MH; Palmeri, ML; Rotemberg, VM; Rouze, NC; Nightingale, KR
MLA Citation
Wang, MH, Palmeri, ML, Rotemberg, VM, Rouze, NC, and Nightingale, KR. "Improving the robustness of time-of-flight based shear wave speed reconstruction methods using RANSAC in human liver in vivo." Ultrasound Med Biol 36.5 (May 2010): 802-813.
PMID
20381950
Source
pubmed
Published In
Ultrasound in Medicine and Biology
Volume
36
Issue
5
Publish Date
2010
Start Page
802
End Page
813
DOI
10.1016/j.ultrasmedbio.2010.02.007

Acoustic radiation force impulse imaging of human prostates ex vivo.

It has been challenging for clinicians using current imaging modalities to visualize internal structures and detect lesions inside human prostates. Lack of contrast among prostatic tissues and high false positive or negative detection rates of prostate lesions have limited the use of current imaging modalities in the diagnosis of prostate cancer. In this study, acoustic radiation force impulse (ARFI) imaging is introduced to visualize the anatomical and abnormal structures in freshly excised human prostates. A modified Siemens Antares ultrasound scanner (Siemens Medical Solutions USA Inc., Malvern, PA) and a Siemens VF10-5 linear array were used to acquire ARFI images. The transducer was attached to a three-dimensional (3-D) translation stage, which was programmed to automate volumetric data acquisition. A depth dependent gain (DDG) method was developed and applied to 3-D ARFI datasets to compensate for the displacement gradients associated with spatially varying radiation force magnitudes as a function of depth. Nine human prostate specimens were collected and imaged immediately after surgical excision. Prostate anatomical structures such as seminal vesicles, ejaculatory ducts, peripheral zone, central zone, transition zone and verumontanum were visualized with high spatial resolution and in good agreement with McNeal's zonal anatomy. The characteristic appearance of prostate pathologies, such as prostate cancerous lesions, benign prostatic hyperplasia, calcified tissues and atrophy were identified in ARFI images based upon correlation with the corresponding histologic slides. This study demonstrates that ARFI imaging can be used to visualize internal structures and detecting suspicious lesions in the prostate and appears promising for image guidance of prostate biopsy.

Authors
Zhai, L; Madden, J; Foo, W-C; Palmeri, ML; Mouraviev, V; Polascik, TJ; Nightingale, KR
MLA Citation
Zhai, L, Madden, J, Foo, W-C, Palmeri, ML, Mouraviev, V, Polascik, TJ, and Nightingale, KR. "Acoustic radiation force impulse imaging of human prostates ex vivo." Ultrasound Med Biol 36.4 (April 2010): 576-588.
PMID
20350685
Source
pubmed
Published In
Ultrasound in Medicine and Biology
Volume
36
Issue
4
Publish Date
2010
Start Page
576
End Page
588
DOI
10.1016/j.ultrasmedbio.2009.12.006

Imaging arrays with improved transmit power capability

Bonded multilayer ceramics and composites incorporating low-loss piezoceramics have been applied to arrays for ultrasound imaging to improve acoustic transmit power levels and to reduce internal heating. Commercially available hard PZT from multiple vendors has been characterized for microstructure, ability to be processed, and electroacoustic properties. Multilayers using the best materials demonstrate the tradeoffs compared with the softer PZT5-H typically used for imaging arrays. Three-layer PZT4 composites exhibit an effective dielectric constant that is three times that of single layer PZT5H, a 50% higher mechanical Q, a 30% lower acoustic impedance, and only a 10% lower coupling coefficient. Application of low-loss multilayers to linear phased and large curved arrays results in equivalent or better element performance. A 3-layer PZT4 composite array achieved the same transmit intensity at 40% lower transmit voltage and with a 35% lower face temperature increase than the PZT-5 control. Although B-mode images show similar quality, acoustic radiation force impulse (ARFI) images show increased displacement for a given drive voltage. An increased failure rate for the multilayers following extended operation indicates that further development of the bond process will be necessary. In conclusion, bonded multilayer ceramics and composites allow additional design freedom to optimize arrays and improve the overall performance for increased acoustic output while maintaining image quality. © 2010 IEEE.

Authors
Zipparo, MJ; Bing, KF; Nightingale, KR
MLA Citation
Zipparo, MJ, Bing, KF, and Nightingale, KR. "Imaging arrays with improved transmit power capability." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 57.9 (2010): 2076-2090.
PMID
20875996
Source
scival
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
57
Issue
9
Publish Date
2010
Start Page
2076
End Page
2090
DOI
10.1109/TUFFC.2010.1655

Robust estimation of time-of-flight shear wave speed using a Radon sum transformation

Time-of-flight methods allow quantitative measurement of shear wave speed (SWS) from ultrasonically tracked displacements following impulsive excitation in tissue. However, application of these methods to in vivo data is challenging due to the presence of gross outlier data resulting from sources such as physiological motion or spatial in homogeneities. This paper describes a new method for estimating SWS by considering a solution space of trajectories and evaluating each trajectory using a metric that characterizes wave motion along the entire trajectory. The metric used here is found by summing displacement data along the trajectory as in the calculation of projection data in the Radon transformation. The algorithm is evaluated using data acquired in calibrated phantoms and in vivo human liver. Results are compared to SWS estimates using a random sample consensus (RANSAC) algorithm described by Wang, et al. Good agreement is found between the Radon sum and RANSAC SWS estimates with a correlation coefficient of greater than 0.99 for phantom data and 0.91 for in vivo liver data. The Radon sum transformation is suitable for use in situations requiring realtime feedback and is comparably robust to the RANSAC algorithm with respect to outlier data. © 2010 IEEE.

Authors
Rouze, NC; Wang, MH; Palmeri, ML; Nightingale, KR
MLA Citation
Rouze, NC, Wang, MH, Palmeri, ML, and Nightingale, KR. "Robust estimation of time-of-flight shear wave speed using a Radon sum transformation." Proceedings - IEEE Ultrasonics Symposium (2010): 21-24.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Publish Date
2010
Start Page
21
End Page
24
DOI
10.1109/ULTSYM.2010.5935919

Quantifying the impact of shear wavelength and kernel size on shear wave speed estimation

Quantitative measurements of tissue stiffness can be obtained by measuring the speed of shear waves induced in tissue by acoustic radiation force. In homogeneous media, time-of-flight (TOF) measurements of shear wave speed (SWS) ideally are independent of the size of the region of interest (or reconstruction kernel). However, in heterogeneous media, shear wave morphology is altered by discontinuities in stiffness due to reflections or boundary conditions, which introduce error to the measured SWS. In addition, the size of the reconstruction kernel limits the spatial resolution, or ability to precisely localize changes in stiffness. This study investigated the impact of shear wavelength, and reconstruction kernel size on the accuracy and spatial resolution of TOF SWS reconstruction in heterogeneous media using finite element method (FEM) simulations. SWS estimation error was found to be most severe at locations where the shear wave travels through a stiff-to-soft interface, where reflections with the same polarity as the incident wave occur. The magnitude and spatial extent of errors near stiffness discontinuities in the direction of shear wave propagation increase as the shear wavelength increases, due to the larger size of the reflected wave. The SWS reconstruction error near stiffness discontinuities orthogonal to the direction of shear wave propagation was also found to be more severe for larger shear wavelengths. The ability of the shear wave to conform to discontinuities in stiffness in this orientation is limited by the boundary condition that the shear wave displacements must remain continuous. The spatial resolution of SWS estimates, as measured using edge widths at stiffness discontinuities, was found to be directly related to the reconstruction kernel size. Although SWS images represent quantitative measurements of stiffness, their spatial resolution is inherently inferior to ARFI images, since reconstruction kernels of finite spatial extent must always be used. © 2010 IEEE.

Authors
Palmeri, ML; Rouze, NC; Wang, MH; Ding, X; Nightingale, KR
MLA Citation
Palmeri, ML, Rouze, NC, Wang, MH, Ding, X, and Nightingale, KR. "Quantifying the impact of shear wavelength and kernel size on shear wave speed estimation." 2010.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Publish Date
2010
Start Page
13
End Page
16
DOI
10.1109/ULTSYM.2010.5935798

Quantitative images of elastic modulus using tissue dynamics in the region of impulsive acoustic radiation force excitation

Focused, impulsive, acoustic radiation force excitations can generate shear waves with microns of displacement in tissue. The speed of shear wave propagation is directly related to the tissue's shear modulus, which can be correlated with tissue pathology to diagnose disease and to follow disease progression. Shear wave speed reconstruction has conventionally been measured over spatial domains that are spatially-offset from the region of excitation (ROE). While these methods are very robust in clinical studies characterizing large, homogeneous organs, their spatial resolution can be limited when generating quantitative images of shear elasticity. The ROETTP algorithm measures time-to-peak (TTP) displacements along the axis-of-symmetry in the ROE of an impulsive acoustic radiation force excitation. These TTP displacements are inversely proportional to shear stiffness and are dependent on the excitation-beam geometry. Lookup tables (LUTs) specific to an excitation/displacement tracking transducer configuration were generated from simulated data, and shear stiffnesses were estimated from experimental data as a function of depth using the LUTs. Quantitative ROETTP shear elasticity images of spherical inclusions in a calibrated tissue-mimicking phantom have been generated. Shear wave reflections and interference can lead to an underestimation of the absolute reconstructed shear modulus (20-25%), but the ratio of absolute shear stiffnesses is well-preserved (3.3 vs. 3.5). Copyright © 2010 by ASME.

Authors
Palmeri, ML; Xu, D; Wang, M; Nightingale, K
MLA Citation
Palmeri, ML, Xu, D, Wang, M, and Nightingale, K. "Quantitative images of elastic modulus using tissue dynamics in the region of impulsive acoustic radiation force excitation." ASME International Mechanical Engineering Congress and Exposition, Proceedings 2 (2010): 487-491.
Source
scival
Published In
ASME International Mechanical Engineering Congress and Exposition, Proceedings
Volume
2
Publish Date
2010
Start Page
487
End Page
491
DOI
10.1115/IMECE2009-12695

Improving precision of tissue shear modulus quantification within theregion of acoustic radiation force excitation with compounded displacementestimates

The time-to-peak (TTP) displacement within the region of acoustic radiationforce excitation (ROE) is directly related to the tissue shear modulus. It haspreviously been shown that the ROE TTP can be directly converted to shearmodulus using a look-up table (LUT) for a given radiation force excitation focalconfiguration. While this method has the advantages of requiring less inputdata for stiffness reconstruction, ease of experimental implementation, and highspatial resolution, it suffers from lack of precision due to jitter inultrasonically tracked TTP displacement estimates. To reduce the variance of TTPmeasurements, compounding of TTP values obtained using different receiveapertures was investigated. A previously validated 3D FEM model was used tocalculate tissue displacement from impulsive radiation force excitation usingthe Siemens CH4-1 transducer and a fixed focal configuration (focal depth 49 mm,f/2, 2.2 MHz). Tissue was modeled as a linear elastic isotropic material withshear modulus from 1.5-20 kPa. Ultrasonic tracking of this displacement field inthe ROE was simulated in FIELD II using a receive spatial compoundingbeamforming technique. A single f/2 transmit aperture using 52 elements with afocal depth of 49 mm and 3.1 MHz center frequency was used. A total of 96elements were used for receive. These were grouped to form 9 overlapping receiveapertures each of 32 elements. The magnitude of TTP jitter after averaging TTPvalues from all 9 receive apertures was 0.250.02 ms for a simulated shearmodulus of 1.5 kPa and 0.12 mm displacement tracking kernel. In comparison, theTTP jitter without compounding using all 96 elements in a single receiveaperture was 0.560.07 ms. By using these compounded TTP values, the average ROETTP stiffness reconstruction error was 0.3 kPa, compared to 1.0 kPa withoutcompounding. Compounding TTP values from the different receive aperturesachieved TTP jitter reduction despite the fact that 1) speckle observed by thedifferent apertures is not fully decorrelated, and 2) receive aperture locationsoffset from the ROE axis have inherently higher TTP jitter. Moreover, thistechnique does not compromise spatial resolution, and can be experimentallyimplemented on a scanner capable of parallel beamforming without reduction ofpulse repetition frequency (PRF). © 2010 IEEE.

Authors
Wang, MH; Palmeri, ML; Rouze, NC; Xu, D; Nightingale, KR
MLA Citation
Wang, MH, Palmeri, ML, Rouze, NC, Xu, D, and Nightingale, KR. "Improving precision of tissue shear modulus quantification within theregion of acoustic radiation force excitation with compounded displacementestimates." 2010.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Publish Date
2010
Start Page
1600
End Page
1603
DOI
10.1109/ULTSYM.2010.5935944

In vivo quantification of liver stiffness in a rat model of hepatic fibrosis with acoustic radiation force.

Liver fibrosis is currently staged using needle biopsy, a highly invasive procedure with a number of disadvantages. Measurement of liver stiffness changes that accompany progression of the disease may provide a quantitative and noninvasive method to assess the health of the liver. The purpose of this study is to investigate the correlation between liver stiffness measured by radiation force induced shear waves and disease related changes in the liver. An additional aim is to present initial findings on the effects of liver viscosity on radiation force induced shear wave morphology. Liver fibrosis was induced in 10 rats using carbon tetrachloride (CCl(4)), while five rats acted as controls. Liver stiffness was measured in vivo in all rats after a treatment period of 8 weeks using a modified Siemens SONOLINE Antares scanner (Siemens Medical Solutions USA, Ultrasound Division, Issaquah, WA, USA). The spatial coherence of radiation force induced shear waves propagating in the viscoelastic rat liver decreased significantly with propagation distance, compared with shear waves in an elastic phantom and a finite element model of a purely elastic medium. Animals were sacrificed after imaging and liver samples were taken for histopathologic analysis and collagen quantification using picrosirius red staining and hydroxyproline assay. At the end of the treatment period, five rats had healthy livers (stage F0), while six had severe fibrosis (F3) and the rest had light to moderate fibrosis (F1 and F2). The measured liver stiffness for the F0 group was 1.5+/-0.1 kPa (mean+/-95% confidence interval) and for F3 livers was 1.8+/-0.2 kPa. In this study, liver stiffness was found to be linearly correlated with the amount of collagen in the liver measured by picrosirius red staining (r(2)=0.43, p=0.008). In addition, stiffness spatial heterogeneity was also linearly correlated with liver collagen content (r(2)=0.58, p=0.001) by picrosirius red staining. These results are consistent with those obtained by Salameh et al. (2007) and Yin et al. (2007b) using animal models of liver fibrosis and MR elastography. This suggests that stiffness measurement using acoustic radiation force can provide a quantitative assessment of the extent of fibrosis in the liver and can be potentially used for the diagnosis, management and study of liver fibrosis.

Authors
Wang, MH; Palmeri, ML; Guy, CD; Yang, L; Hedlund, LW; Diehl, AM; Nightingale, KR
MLA Citation
Wang, MH, Palmeri, ML, Guy, CD, Yang, L, Hedlund, LW, Diehl, AM, and Nightingale, KR. "In vivo quantification of liver stiffness in a rat model of hepatic fibrosis with acoustic radiation force." Ultrasound Med Biol 35.10 (October 2009): 1709-1721.
PMID
19683381
Source
pubmed
Published In
Ultrasound in Medicine and Biology
Volume
35
Issue
10
Publish Date
2009
Start Page
1709
End Page
1721
DOI
10.1016/j.ultrasmedbio.2009.04.019

NON-INVASIVE ASSESSMENT OF LIVER FIBROSIS WITH QUANTITATIVE ACOUSTIC RADIATION FORCE METHODS

Authors
Wang, M; Palmeri, M; Rouze, N; Rotemberg, V; Moser, B; Guy, CD; Diehl, AM; Abdelmalek, MF; Nightingale, K
MLA Citation
Wang, M, Palmeri, M, Rouze, N, Rotemberg, V, Moser, B, Guy, CD, Diehl, AM, Abdelmalek, MF, and Nightingale, K. "NON-INVASIVE ASSESSMENT OF LIVER FIBROSIS WITH QUANTITATIVE ACOUSTIC RADIATION FORCE METHODS." October 2009.
Source
wos-lite
Published In
Hepatology
Volume
50
Issue
4
Publish Date
2009
Start Page
743A
End Page
744A

Blood-brain barrier (BBB) disruption using a diagnostic ultrasound scanner and Definity in Mice.

The objective of this work was to determine whether diagnostic ultrasound and contrast agent could be used to transcranially and nondestructively disrupt the blood-brain barrier (BBB) in mice under ultrasound image guidance and to quantify that disruption using magnetic resonance imaging (MRI) and magnetic resonance (MR) contrast agent. Each mouse was placed under isoflurane anesthesia and the hair on top of its skull was removed before treatment. A diagnostic ultrasound transducer was placed in a water bag coupled with gel on the mouse skull. Definity (ultrasound [US] contrast) and Magnevist (MR contrast) were injected concurrent with the start of a custom ultrasound transmission sequence. The transducer was translated along the rostral-caudal axis to insonify three spatial locations (2mm apart) along one half of the brain for each sequence. T1-weighted MR images were used to quantify the volume of tissue over which the BBB disruption allowed Magnevist to enter the brain, based upon increases in MR contrast-to-noise ratio (CNR) compared with the noninsonified portions of the brain. Ultrasonic frequency, pressure and pulse duration, as well as Definity dose and injection time were varied. Preliminary results suggest that a threshold exists for BBB opening dependent upon both pressure and pulse duration (consistent with reports in the literature performed at lower frequencies). A range of typical diagnostic frequencies (e.g., 5.0-8.0 MHz) generated BBB disruption. Comparable BBB opening was noted with varied delays between Definity injection and insonification (0-2 min) for a range of Definity concentrations (400-2400 microL/kg). The low-pressure, custom sequences (mechanical index [MI]< or =0.65) had minimal blood cell extravasation as determined by histologic evaluation. This study has shown the ability of a diagnostic ultrasound system, in conjunction with Definity, to open the BBB transcranially in a mouse model for molecules approximately 0.5 kDa in size. Opening was achieved at higher frequencies than previously reported and was localized under ultrasound image guidance. A typical, ultrasound imaging mode (pulsed wave [PW] Doppler) with specific settings (transmit frequency=5.7 MHz, gate size=15 mm, pulse repetition frequency=100 Hz, system power=15%) successfully opened the BBB, which facilitates implementation using the most of commercially available clinical diagnostic scanners. Localized opening of the BBB may have potential clinical utility for the delivery of diagnostic or therapeutic agents to the brain.

Authors
Bing, KF; Howles, GP; Qi, Y; Palmeri, ML; Nightingale, KR
MLA Citation
Bing, KF, Howles, GP, Qi, Y, Palmeri, ML, and Nightingale, KR. "Blood-brain barrier (BBB) disruption using a diagnostic ultrasound scanner and Definity in Mice." Ultrasound Med Biol 35.8 (August 2009): 1298-1308.
PMID
19545939
Source
pubmed
Published In
Ultrasound in Medicine and Biology
Volume
35
Issue
8
Publish Date
2009
Start Page
1298
End Page
1308
DOI
10.1016/j.ultrasmedbio.2009.03.012

On the feasibility of imaging peripheral nerves using acoustic radiation force impulse imaging.

Regional anesthesia is preferred over general anesthesia for many surgical procedures; however, challenges associated with poor image guidance limit its widespread acceptance as a viable alternative. In B-mode ultrasound images, the current standard for guidance, nerves can be difficult to visualize due to their similar acoustic impedance with surrounding tissues and needles must be aligned within the imaging plane at limited angles of approach that can impede successful peripheral nerve anesthesia. These challenges lead to inadequate regional anesthesia, necessitating intraoperative interventions, and can cause complications, including hemorrhage, intraneural injections and even nerve paralysis. ARFI imaging utilizes acoustic radiation force to generate images that portray relative tissue stiffness differences. Peripheral nerves are typically surrounded by many different tissue types (e.g., muscle, fat and fascia) that provide a mechanical basis for improved image contrast using ARFI imaging over conventional B-mode images. ARFI images of peripheral nerves and needles have been generated in cadaveric specimens and in humans in vivo. Contrast improvements of >600% have been achieved for distal sciatic nerve structures. The brachial plexus has been visualized with improved contrast over B-mode images in vivo during saline injection and ARFI images can delineate nerve bundle substructures to aid injection guidance. Physiologic motion during ARFI imaging of nerves near arterial structures has been successfully suppressed using ECG-triggered image acquisition and motion filters. This work demonstrates the feasibility of using ARFI imaging to improve the visualization of peripheral nerves during regional anesthesia procedures.

Authors
Palmeri, ML; Dahl, JJ; MacLeod, DB; Grant, SA; Nightingale, KR
MLA Citation
Palmeri, ML, Dahl, JJ, MacLeod, DB, Grant, SA, and Nightingale, KR. "On the feasibility of imaging peripheral nerves using acoustic radiation force impulse imaging." Ultrason Imaging 31.3 (July 2009): 172-182.
PMID
19771960
Source
pubmed
Published In
Ultrasonic Imaging
Volume
31
Issue
3
Publish Date
2009
Start Page
172
End Page
182
DOI
10.1177/016173460903100303

Correlation between SWEI and ARFI image findings in ex vivo human prostates

Acoustic Radiation Force Impulse (ARFI) imaging has previously been used to visualize normal anatomic structures and pathologies in both ex vivo and in vivo human prostates. Based on the relative displacement amplitudes in ARFI images and comparison with histological slides and McNeal's zonal anatomy, it seems that the central zone (CZ) is stiffer than other anatomic zones, and prostate cancer (PCa) is stiffer than normal tissue in the peripheral zone and benign prostatic hyperplasia (BPH). Since displacement amplitudes in ARFI images are determined by both the underlying tissue stiffness and the amplitude of acoustic radiation force, one question that arises is: how are the relative displacements in ARFI images related to the underlying tissue stiffness? In this study, co-registered three-dimensional (3D) ARFI datasets and shear wave elasticity imaging (SWEI) datasets were acquired to investigate the relationship between displacement amplitudes in ARFI images and the underlying tissue stiffness. Six freshly excised human prostates were collected and imaged. The lateral time-to-peak (TTP) algorithm was used to reconstruct the tissue stiffness. Linear regression was performed between ARFI displacement amplitudes and the inverse of the corresponding reconstructed shear moduli. Five types of prostatic tissues were identified in ARFI images, and their stiffnesses were quantified. ©2009 IEEE.

Authors
Zhai, L; Madden, J; Mouraviev, V; Polascik, T; Nightingale, K
MLA Citation
Zhai, L, Madden, J, Mouraviev, V, Polascik, T, and Nightingale, K. "Correlation between SWEI and ARFI image findings in ex vivo human prostates." 2009.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Publish Date
2009
DOI
10.1109/ULTSYM.2009.5441796

Robust hepatic shear modulus reconstruction using acoustic radiation force and RANSAC

Liver stiffness may be useful for the staging and management of hepatic fibrosis. Liver shear modulus can be quantified by measuring the shear wave speed (SWS) in the liver using time-of-flight (TOF) methods. In in vivo patient data, this approach is susceptible to gross outliers in the measured shear wave arrival times due to inhomogeneities in the liver and physiological motion. Linear regression and averaging are not suitable for dealing with this type of error, which can lead to skewed SWS reconstructions. Therefore, the use of random sample consensus (RANSAC), an iterative fitting approach robust to outliers, was investigated for estimating SWS from patient livers. Shear waves were generated in the livers of 105 patients immediately before biopsy using acoustic radiation force and were tracked by ultrasound. 6-12 shear wave acquisitions were performed on each patient. RANSAC was able to reconstruct the shear modulus in 86 patients (82%). Unsuccessful reconstructions were typically associated with shear wave displacements of low amplitude. The biopsy results for 79 patients with at least one valid stiffness measurement were available. The stiffness for healthy to mildly fibrotic (F0-F2) livers (N=64) was 3.03±1.1kPa (mean ± standard deviation), for severely fibrotic (F3) livers (N=12) was 6.3 ± 2.8kPa, and for cirrhotic (F4) livers (N=3) was 17.8 ± 7.8kPa. This trend of increasing liver stiffness with fibrosis stage has also been observed by other groups using alternative modalities of shear wave imaging. These results show that RANSAC is a suitable method for SWS estimation from in vivo ultrasonically tracked shear wave displacements. ©2009 IEEE.

Authors
Wang, MH; Palmeri, ML; Rotemberg, VM; Rouze, NC; Nightingale, KR
MLA Citation
Wang, MH, Palmeri, ML, Rotemberg, VM, Rouze, NC, and Nightingale, KR. "Robust hepatic shear modulus reconstruction using acoustic radiation force and RANSAC." 2009.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Publish Date
2009
DOI
10.1109/ULTSYM.2009.5441567

Concurrent ARFI imaging and HIFU ablation using a diagnostic transducer array and ultrasound system with custom beam sequences

Background, Motivation and Objective: High-intensity focused ultrasound (HIFU) has primarily been performed using a specialized ultrasound transducer for therapy and either a separate transducer for imaging or a different imaging modality. Accurate localization and monitoring of HIFU treatment is important to improving the efficacy of the treatment as well as minimizing complications. The goal of this work was to demonstrate the feasibility of using a diagnostic ultrasound system to perform spot ablations in liver with concurrent Acoustic Radiation Force Impulse (ARFI) stiffness imaging in order to monitor lesion formation. Statement of Contribution/Methods: A diagnostic ultrasound system (Siemens Antares™ and CH6-2 curvilinear array) was used to both: 1) ablate ex vivo liver samples with a custom M-mode sequence and 2) to monitor the resulting tissue stiffening with 2-D ARFI imaging. Ablation patterns were generated using a grid of varying numbers of heating locations. Results: ARFI images showed irreversible liver stiffening with heating that corresponded to discolored regions in gross pathology. Images were taken before and after ablation, as well as in 5-second intervals during ablation to monitor the increase in stiffness contrast and extent with time. No gaseous body formation was observed during the ablations in B-mode, thus lesions were not visualized in matched B-mode images. In order to mimic the presence of a stiffer tumor, bovine muscle tissue was inserted into a liver sample, and subtraction images (pre-post ARFI) clearly distinguished the ablated (stiffened) liver tissue from the stiffer bovine tissue. Discussion and Conclusions: This study demonstrated the ability of a diagnostic system using custom beam sequences to localize an ablation site, heat the site to the point of irreversible damage, and monitor the formation of the ablation lesion. Future work will involve testing this treatment system in vivo. ©2009 IEEE.

Authors
Bing, KF; Rotemberg, VM; Palmeri, ML; Nightingale, KR
MLA Citation
Bing, KF, Rotemberg, VM, Palmeri, ML, and Nightingale, KR. "Concurrent ARFI imaging and HIFU ablation using a diagnostic transducer array and ultrasound system with custom beam sequences." 2009.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Publish Date
2009
DOI
10.1109/ULTSYM.2009.5441759

An integrated indenter-ARFI imaging system for tissue stiffness quantification.

The goal of this work is to develop and characterize an integrated indenter-ARFI (acoustic radiation force impulse) imaging system. This system is capable of acquiring matched datasets of ARFI images and stiffness profiles from ex vivo tissue samples, which will facilitate correlation of ARFI images of tissue samples with independently-characterized material properties. For large and homogeneous samples, the indenter can be used to measure the Young's moduli by using Boussinesq's solution for a load on the surface ofa semi-infinite isotropic elastic medium. Experiments and finite element method (FEM) models were designed to determine the maximum indentation depth and minimum sample size for accurate modulus reconstruction using this solution. Applying these findings, indentation measurements were performed on three calibrated commercial tissue-mimicking phantoms and the results were in good agreement with the calibrated stiffness. For heterogeneous tissue samples, indentation can be used independently to characterize relative stiffness variation across the sample surface, which can then be used to validate the stiffness variation in registered ARFI images. Tests were performed on heterogeneous phantoms and freshly-excised colon cancer specimens to detect the relative stiffness and lesion sizes using the combined system. Normalized displacement curves across the lesion surface were calculated and compared. Good agreement ofthe lesion profiles was observed between indentation and ARFI imaging.

Authors
Zhai, L; Palmeri, ML; Bouchard, RR; Nightingale, RW; Nightingale, KR
MLA Citation
Zhai, L, Palmeri, ML, Bouchard, RR, Nightingale, RW, and Nightingale, KR. "An integrated indenter-ARFI imaging system for tissue stiffness quantification." Ultrason Imaging 30.2 (April 2008): 95-111.
PMID
18939611
Source
pubmed
Published In
Ultrasonic Imaging
Volume
30
Issue
2
Publish Date
2008
Start Page
95
End Page
111
DOI
10.1177/016173460803000203

Quantifying hepatic shear modulus in vivo using acoustic radiation force.

The speed at which shear waves propagate in tissue can be used to quantify the shear modulus of the tissue. As many groups have shown, shear waves can be generated within tissues using focused, impulsive, acoustic radiation force excitations, and the resulting displacement response can be ultrasonically tracked through time. The goals of the work herein are twofold: (i) to develop and validate an algorithm to quantify shear wave speed from radiation force-induced, ultrasonically-detected displacement data that is robust in the presence of poor displacement signal-to-noise ratio and (ii) to apply this algorithm to in vivo datasets acquired in human volunteers to demonstrate the clinical feasibility of using this method to quantify the shear modulus of liver tissue in longitudinal studies. The ultimate clinical application of this work is noninvasive quantification of liver stiffness in the setting of fibrosis and steatosis. In the proposed algorithm, time-to-peak displacement data in response to impulsive acoustic radiation force outside the region of excitation are used to characterize the shear wave speed of a material, which is used to reconstruct the material's shear modulus. The algorithm is developed and validated using finite element method simulations. By using this algorithm on simulated displacement fields, reconstructions for materials with shear moduli (mu) ranging from 1.3-5 kPa are accurate to within 0.3 kPa, whereas stiffer shear moduli ranging from 10-16 kPa are accurate to within 1.0 kPa. Ultrasonically tracking the displacement data, which introduces jitter in the displacement estimates, does not impede the use of this algorithm to reconstruct accurate shear moduli. By using in vivo data acquired intercostally in 20 volunteers with body mass indices ranging from normal to obese, liver shear moduli have been reconstructed between 0.9 and 3.0 kPa, with an average precision of +/-0.4 kPa. These reconstructed liver moduli are consistent with those reported in the literature (mu = 0.75-2.5 kPa) with a similar precision (+/-0.3 kPa). Repeated intercostal liver shear modulus reconstructions were performed on nine different days in two volunteers over a 105-day period, yielding an average shear modulus of 1.9 +/- 0.50 kPa (1.3-2.5 kPa) in the first volunteer and 1.8 +/- 0.4 kPa (1.1-3.0 kPa) in the second volunteer. The simulation and in vivo data to date demonstrate that this method is capable of generating accurate and repeatable liver stiffness measurements and appears promising as a clinical tool for quantifying liver stiffness.

Authors
Palmeri, ML; Wang, MH; Dahl, JJ; Frinkley, KD; Nightingale, KR
MLA Citation
Palmeri, ML, Wang, MH, Dahl, JJ, Frinkley, KD, and Nightingale, KR. "Quantifying hepatic shear modulus in vivo using acoustic radiation force." Ultrasound Med Biol 34.4 (April 2008): 546-558.
PMID
18222031
Source
pubmed
Published In
Ultrasound in Medicine & Biology
Volume
34
Issue
4
Publish Date
2008
Start Page
546
End Page
558
DOI
10.1016/j.ultrasmedbio.2007.10.009

Three-dimensional acoustic radiation force impulse (ARFI) imaging of human prostates in vivo

We are investigating utilizing ARFI imaging to guide prostate needle biopsy. Our previous ex vivo study demonstrated that ARFI imaging using a VF10-5 linear array was able to visualize the internal anatomy and suspicious lesions in the prostate, which may help improve the diagnostic accuracy of prostate needle biopsy. The objective of this study is to implement ARFI techniques on a 3D wobbler rectal probe and image human prostates in vivo. Three patients were imaged. The initial in vivo results are reported. © 2008 IEEE.

Authors
Zhai, L; Dahl, J; Madden, J; Mouraviev, V; Polascik, T; Palmeri, M; Nightingale, K
MLA Citation
Zhai, L, Dahl, J, Madden, J, Mouraviev, V, Polascik, T, Palmeri, M, and Nightingale, K. "Three-dimensional acoustic radiation force impulse (ARFI) imaging of human prostates in vivo." 2008.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Publish Date
2008
Start Page
540
End Page
543
DOI
10.ll09/ULTSYM.2008.0131

Acoustic radiation force based quantification of tissue shear modulus within the region of excitation

The speed of shear wave propagation in tissue is directly related to the tissue's shear modulus. Shear waves can be generated in tissue using focused, impulsive, acoustic radiation force excitations. Shear modulus reconstruction has typically been performed by monitoring shear wave propagation in regions that are spatially offset from the region of excitation (ROE), but such methods require greater radiation forces than methods that work within the ROE. Previously validated 3D FEM models of soft tissue response to impulsive radiation force excitations, coupled with Field II simulations of ultrasonic displacement tracking, were utilized for this work. Simulations were performed for a given focal geometry (Siemens CH41 transducer) for a range of tissue stiffnesses (μ = 1-15 kPa). Linear, elastic, isotropic material properties were assumed, making the time-to-peak (TTP) displacements along the axis of symmetry in the ROE proportional to the tissue's shear wave speed and the excitation beam geometry. Lookup tables specific to an excitation/tracking focal configuration were generated from simulated data, and stiffness estimates as a function of depth were possible using experimental data in calibrated phantoms and soft tissues in vivo, These stiffness estimates were compared with estimates using our previously validated Lateral TTP method. Simulation data indicate that the reconstructed shear moduli are independent of variations in tissue attenuation that impact the spatial distribution of radiation force in the ROE. Phantom reconstructions yielded ROE TTP shear modulus estimates within 0.15 kPa to those using the Lateral TTP method. The axial ROI for each method is similar, but the lateral ROI is ~30x smaller for the ROE TTP method (0.2 vs. 6 mm). The ROE TTP algorithm applied to in vivo data yielded similar mean shear stiffness estimates (μ = 1.7 kPa), but with increased variance (0.9 vs. 0.2 kPa) compared to the Lateral TTP algorithm. Greater displacement magnitudes are present within the ROE compared with spatially-offset locations, producing greater displacement SNR and reducing the acoustic energy needed to generate accurate displacement estimates. Reduced acoustic output leads to decreased transducer and tissue heating. Measuring TTP values within the ROE, instead of at multiple offset locations, also reduces data acquisition times, limiting displacement motion artifacts. The ROE TTP precision is jitter dependent; material shear moduli can be reconstructed within <0.5 kPa. © 2008 IEEE.

Authors
Palmeri, ML; Xu, D; Zhai, L; Nightingale, KR
MLA Citation
Palmeri, ML, Xu, D, Zhai, L, and Nightingale, KR. "Acoustic radiation force based quantification of tissue shear modulus within the region of excitation." 2008.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Publish Date
2008
Start Page
2009
End Page
2012
DOI
10.1109/ULTSYM.2008.0495

A combined ARFI sequence for 2D displacement imaging and shear wave velocity mapping

As pathological changes are normally accompanied with changes of mechanical properties, tissue elasticity is a potential diagnostic metric for a number of diseases. While elasticity imaging techniques have been successfully applied to delineate different tissues and malignancies based on their relative structural stiffness compared with surrounding tissues, a matched absolute tissue modulus map will provide complimentary and validating information in these relative stiffness images. Acoustic radiation force impulse (ARFI) imaging is a method of imaging the relative stiffness variations inside tissue. By using an impulse acoustic radiation force excitation, ARFI excitation pulses not only generate an on-axis displacement response, but also initiate shear wave propagation away from the region of excitation (ROE), which can be used to estimate the shear wave speed, and thus quantify the shear modulus of tissue. The goal of this study is to design and implement a combined sequence capable of acquiring 2D ARFI images (relative stiffness) and shear wave elasticity images (SWEI) (quantitative method). By utilizing parallel receive tracking techniques and temporal interleaving, the sequences developed herein monitor the on-axis displacements and subsequent lateral shear wave propagation serially without increasing the total number of excitation pulses compared to conventional ARFI imaging sequences. ©2008 IEEE.

Authors
Zhai, L; Hsu, S; Bouchard, R; Nightingale, K
MLA Citation
Zhai, L, Hsu, S, Bouchard, R, and Nightingale, K. "A combined ARFI sequence for 2D displacement imaging and shear wave velocity mapping." 2008.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Publish Date
2008
Start Page
2013
End Page
2016
DOI
10.1109/ULTSYM.2008.0496

Investigating the effects of viscosity on focused, impulsive, acoustic radiation force induced shear wave morphology

The effect of dispersion on the morphology of impulsive acoustic radiation force induced shear waves propagating in viscoelastic (VE) media is investigated. Change in shear wave morphology was quantified by calculating its spatial coherence. The magnitude of the slope of the spatial coherence as a function of propagation distance, or decorrelation rate, was used to compare the VE behavior of different materials. Shear waves in VE media with a range of material properties were simulated using Finite Element Method (FEM) models and a three parameter standard linear solid model of viscoelasticity. Shear wave decorrelation rate increased with the amount of stress relaxation occurring within the temporal extent of the shear wave. Shear wave decorrelation rate can therefore be used to discriminate ranges of VE behavior. In experimental data collected using a modified Siemens AntaresTM scanner, the shear wave decorrelation rate was significantly higher for a VE phantom than one constructed of an elastic materia . In preliminary in vivo human liver data, shear wave decorrelation was found to be present and variable among different patients. The relationship between liver viscosity as quantified by shear wave spatial coherence and disease states is being investigated. ©2008 IEEE.

Authors
Wang, M; Palmeri, M; Rouze, N; Nightingale, K; Hobson, M
MLA Citation
Wang, M, Palmeri, M, Rouze, N, Nightingale, K, and Hobson, M. "Investigating the effects of viscosity on focused, impulsive, acoustic radiation force induced shear wave morphology." 2008.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Publish Date
2008
Start Page
647
End Page
650
DOI
10.1109/ULTSYM.2008.0155

Three-Dimensional Acoustic Radiation Force Impulse (ARFI) Imaging of Human Prostates in vivo

Authors
Zhai, L; Dahl, J; Madden, J; Mouraviev, V; Polascik, T; Palmeri, M; Nightingale, K; IEEE,
MLA Citation
Zhai, L, Dahl, J, Madden, J, Mouraviev, V, Polascik, T, Palmeri, M, Nightingale, K, and IEEE, . "Three-Dimensional Acoustic Radiation Force Impulse (ARFI) Imaging of Human Prostates in vivo." 2008.
Source
wos-lite
Published In
Proceedings of the IEEE Ultrasonics Symposium
Publish Date
2008
Start Page
540
End Page
543
DOI
10.1109/ULTSYM.2008.0131

A parallel tracking method for acoustic radiation force impulse imaging.

Radiation force-based techniques have been developed by several groups for imaging the mechanical properties of tissue. Acoustic Radiation Force Impulse (ARFI) imaging is one such method that uses commercially available scanners to generate localized radiation forces in tissue. The response of the tissue to the radiation force is determined using conventional B-mode imaging pulses to track micron-scale displacements in tissue. Current research in ARFI imaging is focused on producing real-time images of tissue displacements and related mechanical properties. Obstacles to producing a real-time ARFI imaging modality include data acquisition, processing power, data transfer rates, heating of the transducer, and patient safety concerns. We propose a parallel receive beamforming technique to reduce transducer heating and patient acoustic exposure, and to facilitate data acquisition for real-time ARFI imaging. Custom beam sequencing was used with a commercially available scanner to track tissue displacements with parallel-receive beamforming in tissue-mimicking phantoms. Using simulations, the effects of material properties on parallel tracking are observed. Transducer and tissue heating for parallel tracking are compared to standard ARFI beam sequencing. The effects of tracking beam position and size of the tracked region are also discussed in relation to the size and temporal response of the region of applied force, and the impact on ARFI image contrast and signal-to-noise ratio are quantified.

Authors
Dahl, JJ; Pinton, GF; Palmeri, ML; Agrawal, V; Nightingale, KR; Trahey, GE
MLA Citation
Dahl, JJ, Pinton, GF, Palmeri, ML, Agrawal, V, Nightingale, KR, and Trahey, GE. "A parallel tracking method for acoustic radiation force impulse imaging." IEEE Trans Ultrason Ferroelectr Freq Control 54.2 (February 2007): 301-312.
PMID
17328327
Source
pubmed
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
54
Issue
2
Publish Date
2007
Start Page
301
End Page
312

Dependence of in vivo, radiation force derived hepatic shear modulus estimates on imaging approach: Intercostal vs. subcostal

The speed at which shear waves propagate can be used to quantify the shear modulus of tissue. Focused, impulsive, acoustic radiation force excitations can be used to generate transient displacement fields in soft tissue that create shear waves that propagate away from the region of excitation (ROE). These shear wave displacements can be ultrasonically tracked through time. The speed at which these shear waves propagate away from the ROE can be estimated using a time of flight-based method that estimates linear trends in times to peak (TTP) displacement at locations laterally offset from the ROE. This method has been previously described as the Lateral TTP algorithm. The purpose of this study is to evaluate the differences that may exist when reconstructing liver shear moduli from subcostal and intercostal approaches using acoustic radiation force excitations with the Lateral TTP algorithm, and to evaluate the repeatability of such measurements. Liver shear moduli have been reconstructed between 0.9 and 3.0 kPa in vivo, with an average precision of ± 0.4 kPa in a 20 volunteer study with body mass indices ranging from normal to obese. Repeated intercostal liver shear modulus reconstructions were performed on 9 different days in 2 volunteers over a 105 day period, yielding an average shear modulus of 1.9 ± 0.5 kPa (1.3-2.5 kPa) in the first volunteer, and 1.8 ± 0.4 kPa (1.1-3.0 kPa) in the second volunteer. Shear moduli have been successfully reconstructed in patients undergoing liver biopsy with BMI > 40. Dynamic linear motion filters are capable of removing physiologic and hand-held transducer motion artifacts without needing ECG data acquisition triggering. The in vivo data to date demonstrate that this method is capable of generating accurate and repeatable liver stiffness measurements and is promising as a clinical tool for quantifying liver stiffness. ©2007 IEEE.

Authors
Palmeri, ML; Wang, MH; Frinkley, KD; Nightingale, KR; Abdelmalek, MF; Diehl, AM
MLA Citation
Palmeri, ML, Wang, MH, Frinkley, KD, Nightingale, KR, Abdelmalek, MF, and Diehl, AM. "Dependence of in vivo, radiation force derived hepatic shear modulus estimates on imaging approach: Intercostal vs. subcostal." Proceedings - IEEE Ultrasonics Symposium (2007): 566-569.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Publish Date
2007
Start Page
566
End Page
569
DOI
10.1109/ULTSYM.2007.147

Radiation force imaging: Challenges and opportunities

A number of novel imaging modalities have been developed to interrogate the mechanical properties of tissue. A subset of these methods utilize acoustic radiation force to mechanically excite tissue and form images from the local responses of tissue to these excitations. These methods are attractive because of the ability to focus and steer the excitatory beams and to control their spatial and temporal characteristics using techniques similar to those employed in conventional ultrasonic imaging. These capabilities allow for a wide variety of imaging methods whose features are only beginning to be explored. However, radiation force based methods also present significant challenges. Tissue and transducer heating limit the tissue displacements achievable with radiation force applications and restrict image frame rates and fields-of-view. The small tissue displacements are difficult to detect and may be obscured by physiologic tissue motion. We review the fundamental limits of imaging methods based on radiation force generated by patient safety concerns and the impact of these limits on achievable image signal-to-noise ratios and frame rates. We also review our progress to date in the development and clinical evaluation of one class of radiation force imaging methods employing very brief impulses of radiation force.

Authors
Trahey, GE; Palmeri, M; Nightingale, K; Dahl, J
MLA Citation
Trahey, GE, Palmeri, M, Nightingale, K, and Dahl, J. "Radiation force imaging: Challenges and opportunities." 2007.
Source
scival
Published In
Proceedings of SPIE
Volume
6513
Publish Date
2007
DOI
10.1117/12.719470

On the potential for guidance of ablation therapy using acoustic radiation force impulse imaging

Acoustic radiation force imaging methods utilize acoustic radiation force to mechanically excite tissue, and the tissue response is monitored with conventional imaging methods. Radiation force based methods comprise a subset of elasticity imaging, in which images reflect relative differences in tissue stiffness. Acoustic Radiation Force Impulse (ARFI) imaging is one such method that is implemented on a modified diagnostic ultrasound scanner, using the same transducer for the excitation and monitoring of the tissue response. ARFI imaging is under investigation for its potential to monitor thermal ablation procedures because thermal lesions are associated with considerable (>4 times) stiffness increases as compared to viable tissue. Applications include monitoring radio-frequency ablation procedures in the liver, kidney, and heart, and monitoring focused ultrasound ablation procedures. We present results from ongoing studies in these areas. © 2007 IEEE.

Authors
Nightingale, K; Fahey, B; Hsu, S; Frinkley, K; Dahl, J; Palmeri, M; Zhai, L; Pinton, G; Trahey, G
MLA Citation
Nightingale, K, Fahey, B, Hsu, S, Frinkley, K, Dahl, J, Palmeri, M, Zhai, L, Pinton, G, and Trahey, G. "On the potential for guidance of ablation therapy using acoustic radiation force impulse imaging." 2007 4th IEEE International Symposium on Biomedical Imaging: From Nano to Macro - Proceedings (2007): 1116-1119.
Source
scival
Published In
2007 4th IEEE International Symposium on Biomedical Imaging: From Nano to Macro - Proceedings
Publish Date
2007
Start Page
1116
End Page
1119
DOI
10.1109/ISBI.2007.357052

In-vivo staging of liver fibrosis in a rat model using acoustic radiation force

Liver fibrosis is currently staged using needle biopsy, a highly invasive procedure with a number of disadvantages. Measurement of liver stiffness changes which accompany progression of the disease may provide a quantitative and noninvasive method to assess the health of the liver. The purpose of this study is to investigate the correlation between radiation force derived shear wave speed and disease related changes in the liver. Liver fibrosis was induced in 10 rats using carbon tetrachloride (CCl4), while 5 rats acted as controls. Liver stiffness was measured in vivo in all rats after a treatment period of 8 weeks using a modified Siemens SONOLINE Antares™ scanner. The animals were sacrificed after imaging and liver samples were taken for fibrosis staging using the Batts and Ludwig scale and collagen quantification using Sirius red staining. At the end of the treatment period, 4 rats had healthy livers (stage F0), while 8 had severe fibrosis (F3), and the rest had light to moderate fibrosis (Fl and F2). The mean measured liver stiffness for the F0 group was 1.2±0.1kPa, and for F3 livers was 1.6±0.2kPa. The difference in population means of FO and F3 liver stiffness was significant (p < 0.01), suggesting that radiation force can be used to differentiate F0 and F3 livers. However, the nonquantitative nature of fibrosis staging using the Batts and Ludwig method coupled with the relatively small changes in liver stiffness between F0 and F3 livers may make detecting stiffness differences between livers with light to moderate stage fibrosis (F1 and F2) difficult. Nevertheless, other quantitative measures of the liver health exist, which may better reflect changes observed in liver stiffness than fibrosis stage. In this study, liver stiffness was found to be strongly correlated with the amount of collagen in the liver measured by Sirius red staining (r = 0.7, p < 0.01). The relationship between radiation force measured liver stiffness and other quantitative parameters characterizing the liver health are currently being explored. ©2007 IEEE.

Authors
Wang, MH; Hedlund, LW; Palmeri, ML; Guy, CD; Yang, L; Diehl, AM; Nightingale, KR
MLA Citation
Wang, MH, Hedlund, LW, Palmeri, ML, Guy, CD, Yang, L, Diehl, AM, and Nightingale, KR. "In-vivo staging of liver fibrosis in a rat model using acoustic radiation force." Proceedings - IEEE Ultrasonics Symposium (2007): 562-565.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Publish Date
2007
Start Page
562
End Page
565
DOI
10.1109/ULTSYM.2007.146

Transcending the traditional: Using tablet PCs to enhance engineering and computer science instruction

Traditional instructional methods present many obstacles to effective teaching and learning in engineering and computer science courses. These include a reliance on text-based or static mediums to convey equation- and graphics-heavy concepts, a disconnect between theoretical lecture presentations and applied laboratory or homework exercises, and a difficulty in promoting collaborative activities that more accurately reflect an engineering approach to problem solving. Additionally, technical courses can suffer, like any other course, when students are not actively engaged in the learning and when instructors cannot gauge student understanding. This project has explored the utility of Tablet PCs for overcoming these challenges within a sample of courses in engineering and computer science. There were three primary questions: which knowledge domains benefit from the use of Tablet PCs; whether observed benefits are derived from Tablet PC-specific activities; and what problems limit the effectiveness of Tablet PCs in educational settings? The evaluation of assessment data using regression approaches demonstrated that Tablet-PC-specific activities had a consistent, meaningful, and positive impact upon engineering and computer science courses. © 2007 IEEE.

Authors
Huettel, LG; Forbes, J; Franzoni, L; Malkin, R; Nadeau, J; Nightingale, K; Ybarra, GA
MLA Citation
Huettel, LG, Forbes, J, Franzoni, L, Malkin, R, Nadeau, J, Nightingale, K, and Ybarra, GA. "Transcending the traditional: Using tablet PCs to enhance engineering and computer science instruction." 2007.
Source
scival
Published In
Proceedings - Frontiers in Education Conference, FIE
Publish Date
2007
Start Page
S4J1
End Page
S4J6
DOI
10.1109/FIE.2007.4417869

Visualizing the anatomic structures of human prostates using Acoustic Radiation Force Impulse (ARFI) imaging

McNeal's zonal anatomy for prostate has been the standard anatomical model for human prostate for about 30 years. It divides a human prostate into one non-glandular zone (the anterior flbromuscular stroma), and three glandular zones (central zone (CZ), transitional zone (TZ) and peripheral zone (PZ)). Visualizing these zones is of great importance for diagnosing prostate diseases. However, they are not well visualized by current ultrasound techniques. In this study, 3D Acoustic Radiation Force Impulse (ARFI) imaging has been implemented in order to visualize anatomic structures of excised human prostates. Prostate specimens were obtained immediately after radical prostatectomy and put in an isotonic saline bath at room temperature. ARFI data were acquired from the posterior side of the prostate using a Siemens Antares scanner and a VF10-5 linear array, whose imaging plane is the axial/lateral view in the normal anatomy. The position of the imaging transducer was controlled by a 3D translation stage. The scanner and the translation stage were programmed to scan the entire prostate specimen automatically with 1 mm spacing between elevation planes. 3D ARFI images with high spatial resolution were acquired for each specimen. Different zones and structures within the prostates have been well visualized in 3D ARFI images, which are in agreement with McNeal's zonal anatomy. Prostate lesions and benign prostatic hyperplasia were also detected and correlated with histopathological results. This study demonstrated that ARFI imaging is capable of visualizing internal structures and detecting suspicious lesions in the prostate.

Authors
Zhai, L; Madden, J; Mouraviev, V; Polascik, T; Nightingale, K
MLA Citation
Zhai, L, Madden, J, Mouraviev, V, Polascik, T, and Nightingale, K. "Visualizing the anatomic structures of human prostates using Acoustic Radiation Force Impulse (ARFI) imaging." 2007.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Publish Date
2007
Start Page
432
End Page
435
DOI
10.1109/ULTSYM.2007.117

Therapeutic potential metric for diagnostic transducers

The goal of this work is to develop a 'therapeutic potential' metric and experimental protocol to define the expected efficacy of commercial, diagnostic transducers for thermal therapy. Temperature rises at the transducer face were measured using thin-film thermocouples (TFTs) on a tissue mimicking phantom for sequences with moderate acoustic output as an indicator of the risk of damage to the transducer during therapeutic applications. Several measurements were then taken to evaluate the focal heating of the transducer and compared with thermocouple measurements. The acoustic power was measured near the surface of the transducer. Spatial peak and spatial average intensities were measured in the focal plane at low system voltages to avoid nonlinear effects. Finally, ARFI imaging displacements within ±25% of the focus in a tissue-mimicking phantom were evaluated. Four transducers were compared using these protocols (two curvilinear arrays, one phased array, and one two-dimensional array). Without focal gain considerations, acoustic power is an inaccurate predictor of focal heating. ARFI displacement cannot easily be used to estimate focal heating, primarily due to confounding mechanical phenomena. After normalizing each measurement by the ultrasound system input, measurement device properties, focal configuration, and temporal properties, the therapeutic potential metric can most efficiently and accurately be defined by maximizing the ratio of the spatial peak intensity at the focus to the heating at the transducer face. The ratio of spatial average intensity or temperature at the focus to surface temperature can be used as alternative or additional metrics. The ID, phased array was determined to have the highest therapeutic potential for focal depths near 3.75 cm. © 2007 IEEE.

Authors
Frinkley, K; Rosenzweig, S; Nightingale, K
MLA Citation
Frinkley, K, Rosenzweig, S, and Nightingale, K. "Therapeutic potential metric for diagnostic transducers." 2007.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Publish Date
2007
Start Page
116
End Page
119
DOI
10.1109/ULTSYM.2007.42

Transcending the traditional: Using Tablet PCs to enhance engineering and computer science instruction

Authors
Huettel, LG; Forbes, J; Franzoni, L; Malkin, R; Nadeau, J; Nightingale, K; Ybarra, GA; IEEE,
MLA Citation
Huettel, LG, Forbes, J, Franzoni, L, Malkin, R, Nadeau, J, Nightingale, K, Ybarra, GA, and IEEE, . "Transcending the traditional: Using Tablet PCs to enhance engineering and computer science instruction." 2007.
Source
wos-lite
Published In
Proceedings - Frontiers in Education Conference
Publish Date
2007
Start Page
1724
End Page
1729

Dynamic mechanical response of elastic spherical inclusions to impulsive acoustic radiation force excitation.

Acoustic radiation force impulse imaging has been used clinically to study the dynamic response of lesions relative to their background material to focused, impulsive acoustic radiation force excitations through the generation of dynamic displacement field images. Dynamic displacement data are typically displayed as a set of parametric images, including displacement immediately after excitation, maximum displacement, time to peak displacement, and recovery time from peak displacement. To date, however, no definitive trends have been established between these parametric images and the tissues' mechanical properties. This work demonstrates that displacement magnitude, time to peak displacement, and recovery time are all inversely related to the Young's modulus in homogeneous elastic media. Experimentally, pulse repetition frequency during displacement tracking limits stiffness resolution using the time to peak displacement parameter. The excitation pulse duration also impacts the time to peak parameter, with longer pulses reducing the inertial effects present during impulsive excitations. Material density affects tissue dynamics, but is not expected to play a significant role in biological tissues. The presence of an elastic spherical inclusion in the imaged medium significantly alters the tissue dynamics in response to impulsive, focused acoustic radiation force excitations. Times to peak displacement for excitations within and outside an elastic inclusion are still indicative of local material stiffness; however, recovery times are altered due to the reflection and transmission of shear waves at the inclusion boundaries. These shear wave interactions cause stiffer inclusions to appear to be displaced longer than the more compliant background material. The magnitude of shear waves reflected at elastic lesion boundaries is dependent on the stiffness contrast between the inclusion and the background material, and the stiffness and size of the inclusion dictate when shear wave reflections within the lesion will interfere with one another. Jitter and bias associated with the ultrasonic displacement tracking also impact the estimation of a tissue's dynamic response to acoustic radiation force excitation.

Authors
Palmeri, ML; McAleavey, SA; Fong, KL; Trahey, GE; Nightingale, KR
MLA Citation
Palmeri, ML, McAleavey, SA, Fong, KL, Trahey, GE, and Nightingale, KR. "Dynamic mechanical response of elastic spherical inclusions to impulsive acoustic radiation force excitation." IEEE Trans Ultrason Ferroelectr Freq Control 53.11 (November 2006): 2065-2079.
PMID
17091842
Source
pubmed
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
53
Issue
11
Publish Date
2006
Start Page
2065
End Page
2079

Ultrasonic tracking of acoustic radiation force-induced displacements in homogeneous media.

The use of ultrasonic methods to track the tissue deformation generated by acoustic radiation force is subject to jitter and displacement underestimation errors, with displacement underestimation being primarily caused by lateral and elevation shearing within the point spread function (PSF) of the ultrasonic beam. Models have been developed using finite element methods and Field II, a linear acoustic field simulation package, to study the impact of focal configuration, tracking frequency, and material properties on the accuracy of ultrasonically tracking the tissue deformation generated by acoustic radiation force excitations. These models demonstrate that lateral and elevation shearing underneath the PSF of the tracking beam leads to displacement underestimation in the focal zone. Displacement underestimation can be reduced by using tracking beams that are narrower than the spatial extent of the displacement fields. Displacement underestimation and jitter decrease with time after excitation as shear wave propagation away from the region of excitation reduces shearing in the lateral and elevation dimensions. The use of higher tracking frequencies in broadband transducers, along with 2D focusing in the elevation dimension, will reduce jitter and improve displacement tracking accuracy. Relative displacement underestimation remains constant as a function of applied force, whereas jitter increases with applied force. Underdeveloped speckle (SNR < 1.91) leads to greater levels of jitter and peak displacement underestimation. Axial shearing is minimal over the tracking kernel lengths used in acoustic radiation force impulse imaging and thus does not impact displacement tracking.

Authors
Palmeri, ML; McAleavey, SA; Trahey, GE; Nightingale, KR
MLA Citation
Palmeri, ML, McAleavey, SA, Trahey, GE, and Nightingale, KR. "Ultrasonic tracking of acoustic radiation force-induced displacements in homogeneous media." IEEE Trans Ultrason Ferroelectr Freq Control 53.7 (July 2006): 1300-1313.
PMID
16889337
Source
pubmed
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
53
Issue
7
Publish Date
2006
Start Page
1300
End Page
1313

Streaming detection for evaluation of indeterminate sonographic breast masses: a pilot study.

OBJECTIVE: Streaming detection is a novel sonography technique that uses ultrasonic energy to induce movement in cyst fluid that is detected on Doppler sonography. This pilot study evaluates the utility of streaming detection for differentiating cysts from solid masses in breast lesions that are indeterminate on sonography. SUBJECTS AND METHODS: Thirty-nine lesions-11 simple cysts and seven solid masses (control group) and 21 masses with indeterminate findings for the diagnosis of a cyst versus a solid lesion (study group)-in 34 patients were evaluated using streaming detection. All lesions underwent cyst aspiration or biopsy (n = 35) or were diagnosed simple cysts (n = 4) on sonography. Lesion size and depth were recorded. Streaming detection software was placed on conventional sonography units. Acoustic pulses were focused on the lesion, and if fluid movement was generated, it was seen on the spectral Doppler display as velocity away from the transducer. Lesions were then aspirated or underwent biopsy, and the viscosity of the aspirated fluid was recorded. The sensitivity and specificity of the technique and the effect of cyst size, cyst depth, and fluid viscosity in diagnosing fluid-filled cysts were assessed. RESULTS: Overall, 31 cysts and eight solid masses (seven benign, one carcinoma) were diagnosed in the study and control groups. Aspiration of indeterminate lesions resulted in 20 cysts and one solid mass. Lesions ranged in size from 4 to 47 mm and in depth from 4 to 29 mm. In the control group, streaming detection correctly showed nine of the 11 simple cysts (sensitivity, 82%; positive predictive value, 100%), and acoustic streaming was absent in all seven solid masses (specificity, 100%; negative predictive value, 78%). Of the indeterminate lesions, streaming detection allowed correct identification of 10 of 20 cysts (sensitivity, 50%; positive predictive value, 100%). Acoustic streaming was not detected in the one solid study group lesion. Neither cyst size or depth nor fluid viscosity had a significant effect on the ability to detect fluid. CONCLUSION: The streaming detection technique improved differentiation of cysts from solid masses in indeterminate lesions and has potential for reducing the number of recommended cyst aspirations for the diagnosis of indeterminate breast masses.

Authors
Soo, MS; Ghate, SV; Baker, JA; Rosen, EL; Walsh, R; Warwick, BN; Ramachandran, AR; Nightingale, KR
MLA Citation
Soo, MS, Ghate, SV, Baker, JA, Rosen, EL, Walsh, R, Warwick, BN, Ramachandran, AR, and Nightingale, KR. "Streaming detection for evaluation of indeterminate sonographic breast masses: a pilot study." AJR Am J Roentgenol 186.5 (May 2006): 1335-1341.
PMID
16632728
Source
pubmed
Published In
AJR. American journal of roentgenology
Volume
186
Issue
5
Publish Date
2006
Start Page
1335
End Page
1341
DOI
10.2214/AJR.05.0005

Characterizing acoustic attenuation of homogeneous media using focused impulsive acoustic radiation force.

A new method to characterize a material's attenuation using acoustic radiation force is proposed. Comparison of displacement magnitudes generated in a homogeneous material by acoustic radiation force excitations can be used to estimate the material's attenuation when the excitations are applied over a range of focal depths while maintaining a constant lateral focal configuration. Acoustic attenuations are related to the inverse of the excitation focal depth that yields the greatest focal zone displacement for this protocol. Experimental studies in calibrated tissue-mimicking phantoms are presented to demonstrate the feasibility of this method. Attenuations ranging from 0.3-1.5 dB/cm/MHz were characterized over excitation focal depths ranging from 5-30 mm, with an accuracy of 0.1 +/- 0.15 dB/cm/MHz. As currently implemented, this method is limited to characterizing materials that have homogeneous material properties and acoustic attenuations. This method for characterizing acoustic attenuation can be performed using conventional diagnostic scanners without any additional hardware and could also be performed concurrently with acoustic radiation force-based imaging modalities to generate images of mechanical properties and attenuation that are spatially co-registered with B-mode images.

Authors
Palmeri, ML; Frinkley, KD; Oldenburg, KG; Nightingale, KR
MLA Citation
Palmeri, ML, Frinkley, KD, Oldenburg, KG, and Nightingale, KR. "Characterizing acoustic attenuation of homogeneous media using focused impulsive acoustic radiation force." Ultrason Imaging 28.2 (April 2006): 114-128.
PMID
17094691
Source
pubmed
Published In
Ultrasonic Imaging
Volume
28
Issue
2
Publish Date
2006
Start Page
114
End Page
128
DOI
10.1177/016173460602800204

Undergraduate biomedical imaging education

A review of the current imaging curricula in biomedical engineering undergraduate programs and the best practice that should guide the development of biomedical engineering curricula, is presented. Students can either gets exposure to imaging courses, either by taking all required BME courses or by selecting different tracks in the BME programs. Biomedical engineering imaging (BMI) should be taught as a stand alone introductory imaging course. BME faculty with expertise in imaging should teach BMI, and it should be complemented by guest lectures by imaging faculty, clinical imaging users, and industries' representatives.

Authors
Paschal, CB; Nightingale, KR; Ropella, KM
MLA Citation
Paschal, CB, Nightingale, KR, and Ropella, KM. "Undergraduate biomedical imaging education." Annals of Biomedical Engineering 34.2 (2006): 232-238.
PMID
16450191
Source
scival
Published In
Annals of Biomedical Engineering
Volume
34
Issue
2
Publish Date
2006
Start Page
232
End Page
238
DOI
10.1007/s10439-005-9031-2

Analysis of contrast in images generated with transient acoustic radiation force

Several mechanical imaging methods are under investigation that use focused ultrasound (US) as a source of mechanical excitation. Images are then generated of the tissue response to this localized excitation. One such method, acoustic radiation force impulse (ARFI) imaging, utilizes a single US transducer on a commercial US system to transmit brief, high-energy, focused acoustic pulses to generate radiation force in tissue and correlation-based US methods to detect the resulting tissue displacements. Local displacements reflect relative mechanical properties of tissue. The resolution of these images is comparable with that of conventional B-mode imaging. The response of tissue to focused radiation force excitation is complex and depends upon tissue geometry, forcing function geometry (i.e., region of excitation, or ROE) and tissue mechanical and acoustic properties. Finite element method (FEM) simulations using an experimentally validated model and phantom experiments have been performed using varying systems, system configurations and tissue-mimicking phantoms to determine their impact on image quality. Image quality is assessed by lesion contrast. Due to the dynamic nature of ARFI excitation, lesion contrast is temporally-dependent. Contrast of spherical inclusions is highest immediately after force cessation, decreases with time postforce and then reverses, due to shear wave interaction with internal boundaries, differences in shear modulus between lesions and background and inertial effects. In images generated immediately after force cessation, contrast does not vary with applied force, increases with lesion stiffness and increases as the ROE size decreases relative to the size of the structure being imaged. These studies indicate that improved contrast in radiation force-generated images will be achieved as ROE size decreases; however, frame rate and thermal considerations present trade-offs with small ROE size. © 2006 World Federation for Ultrasound in Medicine & Biology.

Authors
Nightingale, K; Palmeri, M; Trahey, G
MLA Citation
Nightingale, K, Palmeri, M, and Trahey, G. "Analysis of contrast in images generated with transient acoustic radiation force." Ultrasound in Medicine and Biology 32.1 (2006): 61-72.
PMID
16364798
Source
scival
Published In
Ultrasound in Medicine & Biology
Volume
32
Issue
1
Publish Date
2006
Start Page
61
End Page
72
DOI
10.1016/j.ultrasmedbio.2005.08.008

Shear wave velocity estimation using acoustic radiation force impulsive excitation in liver In Vivo

Acoustic radiation force can be used to mechanically excite tissue in remote, focused locations, and the tissue response can be monitored using ultrasonic correlation based methods. The speed with which the resulting shear waves propagate away from the focal region can be estimated and used to quantify the material shear modulus, as originally proposed by Sarvazyan et. al. [1]. This imaging approach has been implemented by Bercoff et. al. [2], using a highly parallel custom ultrasound system, and Helmholtz reconstructions. We have developed a system that is implemented on a commercial scanner using 4:1 parallel processing, and a new algorithm for estimating shear wave speed, which does not require 2nd order temporal and spatial differentiation of displacement data. The method is robust and generates consistent measurements over multiple acquisitions. The goal of our work is to develop this system for the purpose of staging liver fibrosis. The method was used to measure elastic moduli of liver in vivo in healthy human volunteers, and in a rat model, and the moduli obtained with this method are consistent with those reported in the literature. © 2006 IEEE.

Authors
Nightingale, KR; Zhai, L; Dahl, JJ; Frinkley, KD; Palmeri, ML
MLA Citation
Nightingale, KR, Zhai, L, Dahl, JJ, Frinkley, KD, and Palmeri, ML. "Shear wave velocity estimation using acoustic radiation force impulsive excitation in liver In Vivo." Proceedings - IEEE Ultrasonics Symposium 1 (2006): 1156-1160.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
1
Publish Date
2006
Start Page
1156
End Page
1160
DOI
10.1109/ULTSYM.2006.298

Characterizing acoustic attenuation using focused impulsive acoustic radiation force

A new method to characterize a material's attenuation using acoustic radiation force is proposed. Comparison of displacement magnitudes generated in a homogeneous material by acoustic radiation force excitations can be used to estimate the material's attenuation when the excitations are applied over a range of focal depths while maintaining a constant lateral focal configuration. Acoustic attenuations are related to the inverse of the excitation focal depth that yields the greatest focal zone displacement for this protocol. Experimental studies in calibrated tissue-mimicking phantoms are presented to demonstrate the feasibility of this method. Attenuations ranging from 0.3 - 1.5 dB/cm/MHz were characterized over excitation focal depths ranging from 5 - 30 mm, with an accuracy of 0.1 ± 0.15 dB/cm/MHz. As currently implemented, this method is limited to characterizing materials that have homogeneous material properties and acoustic attenuations. This method for characterizing acoustic attenuation can be performed using conventional diagnostic scanners without any additional hardware and could also be performed concurrently with acoustic radiation force-based imaging modalities to generate images of mechanical properties and attenuation that are spatially co-registered with B-mode images. © 2006 IEEE.

Authors
Palmeri, M; Frinkley, K; Oldenburg, K; Nightingale, K
MLA Citation
Palmeri, M, Frinkley, K, Oldenburg, K, and Nightingale, K. "Characterizing acoustic attenuation using focused impulsive acoustic radiation force." 2006.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
1
Publish Date
2006
Start Page
1680
End Page
1685
DOI
10.1109/ULTSYM.2006.422

A finite-element method model of soft tissue response to impulsive acoustic radiation force.

Several groups are studying acoustic radiation force and its ability to image the mechanical properties of tissue. Acoustic radiation force impulse (ARFI) imaging is one modality using standard diagnostic ultrasound scanners to generate localized, impulsive, acoustic radiation forces in tissue. The dynamic response of tissue is measured via conventional ultrasonic speckle-tracking methods and provides information about the mechanical properties of tissue. A finite-element method (FEM) model has been developed that simulates the dynamic response of tissues, with and without spherical inclusions, to an impulsive acoustic radiation force excitation from a linear array transducer. These FEM models were validated with calibrated phantoms. Shear wave speed, and therefore elasticity, dictates tissue relaxation following ARFI excitation, but Poisson's ratio and density do not significantly alter tissue relaxation rates. Increased acoustic attenuation in tissue increases the relative amount of tissue displacement in the near field compared with the focal depth, but relaxation rates are not altered. Applications of this model include improving image quality, and distilling material and structural information from tissue's dynamic response to ARFI excitation. Future work on these models includes incorporation of viscous material properties and modeling the ultrasonic tracking of displaced scatterers.

Authors
Palmeri, ML; Sharma, AC; Bouchard, RR; Nightingale, RW; Nightingale, KR
MLA Citation
Palmeri, ML, Sharma, AC, Bouchard, RR, Nightingale, RW, and Nightingale, KR. "A finite-element method model of soft tissue response to impulsive acoustic radiation force." IEEE Trans Ultrason Ferroelectr Freq Control 52.10 (October 2005): 1699-1712.
PMID
16382621
Source
pubmed
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
52
Issue
10
Publish Date
2005
Start Page
1699
End Page
1712

Acoustic radiation force impulse imaging of the abdomen: demonstration of feasibility and utility.

The feasibility of utilizing acoustic radiation force impulse (ARFI) imaging to assess the mechanical properties of abdominal tissues was investigated. The thermal safety of the technique was also evaluated through the use of finite element method models. ARFI imaging was shown to be capable of imaging abdominal tissues at clinically realistic depths. Correspondence between anatomical structures in B-mode and ARFI images was observed. ARFI images showed similar tumor contrast when compared with B-mode images of ex vivo abdominal cancers. Finite element method models and in vitro measurements confirmed the thermal safety of ARFI imaging at depth. ARFI imaging is inexpensive, safe and convenient and is a promising modality for use in abdominal imaging.

Authors
Fahey, BJ; Nightingale, KR; Nelson, RC; Palmeri, ML; Trahey, GE
MLA Citation
Fahey, BJ, Nightingale, KR, Nelson, RC, Palmeri, ML, and Trahey, GE. "Acoustic radiation force impulse imaging of the abdomen: demonstration of feasibility and utility." Ultrasound Med Biol 31.9 (September 2005): 1185-1198.
PMID
16176786
Source
pubmed
Published In
Ultrasound in Medicine & Biology
Volume
31
Issue
9
Publish Date
2005
Start Page
1185
End Page
1198
DOI
10.1016/j.ultrasmedbio.2005.05.004

Acoustic radiation force impulse imaging of myocardial radiofrequency ablation: initial in vivo results.

Acoustic radiation force impulse (ARFI) imaging techniques were used to monitor radiofrequency (RF) ablation of ovine cardiac tissue in vivo. Additionally, ARFI M-mode imaging methods were used to interrogate both healthy and ablated regions of myocardial tissue. Although induced cardiac lesions were not visualized well in conventional B-mode images, ARFI images of ablation procedures allowed determination of lesion location, shape, and relative size through time. The ARFI M-mode images were capable of distinguishing differences in behavior through the cardiac cycle between healthy and damaged tissue regions. As conventional sonography is often used to guide ablation catheters, ARFI imaging, which requires no additional equipment, may be a convenient modality for monitoring lesion formation in vivo.

Authors
Fahey, BJ; Nightingale, KR; McAleavey, SA; Palmeri, ML; Wolf, PD; Trahey, GE
MLA Citation
Fahey, BJ, Nightingale, KR, McAleavey, SA, Palmeri, ML, Wolf, PD, and Trahey, GE. "Acoustic radiation force impulse imaging of myocardial radiofrequency ablation: initial in vivo results." IEEE Trans Ultrason Ferroelectr Freq Control 52.4 (April 2005): 631-641.
PMID
16060512
Source
pubmed
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
52
Issue
4
Publish Date
2005
Start Page
631
End Page
641

Acoustic radiation force impulse (ARFI) imaging of the gastrointestinal tract.

The evaluation of lesions in the gastrointestinal (GI) tract using ultrasound can suffer from poor contrast between healthy and diseased tissue. Acoustic Radiation Force Impulse (ARFI) imaging provides information about the mechanical properties of tissue using brief, high-intensity, focused ultrasound to generate radiation force and ultrasonic correlation-based methods to track the resulting tissue displacement. Using conventional linear arrays, ARFI imaging has shown improved contrast over B-mode images when applied to solid masses in the breast and liver. The purpose of this work is to (1) investigate the potential for ARFI imaging to provide improvements over conventional B-mode imaging of GI lesions and (2) demonstrate that ARFI imaging can be performed with an endocavity probe. ARFI images of an adenocarcinoma of the gastroesophageal (GE) junction, status-post chemotherapy and radiation treatment, demonstrate better contrast between healthy and fibrotic/malignant tissue than standard B-mode images. ARFI images of healthy gastric, esophageal, and colonic tissue specimens differentiate normal anatomic tissue layers (i.e., mucosal, muscularis and adventitial layers), as confirmed by histologic evaluation. ARFI imaging of ex vivo colon and small bowel tumors portray interesting contrast and structure that are not as well defined in B-mode images. An endocavity probe created ARFI images to a depth of over 2 cm in tissue-mimicking phantoms, with maximum displacements of 4 microm. These findings support the clinical feasibility of endocavity ARFI imaging to guide diagnosis and staging of disease processes in the GI tract.

Authors
Palmeri, ML; Frinkley, KD; Zhai, L; Gottfried, M; Bentley, RC; Ludwig, K; Nightingale, KR
MLA Citation
Palmeri, ML, Frinkley, KD, Zhai, L, Gottfried, M, Bentley, RC, Ludwig, K, and Nightingale, KR. "Acoustic radiation force impulse (ARFI) imaging of the gastrointestinal tract." Ultrason Imaging 27.2 (April 2005): 75-88.
PMID
16231837
Source
pubmed
Published In
Ultrasonic Imaging
Volume
27
Issue
2
Publish Date
2005
Start Page
75
End Page
88
DOI
10.1177/016173460502700202

Real-time Acoustic Radiation Force Impulse imaging

Acoustic Radiation Force Impulse (ARFI) imaging uses short duration acoustic pulses to generate and subsequently determine localized displacements in tissue. Time delay estimators, such as normalized cross correlation and phase shift estimation, form the computational basis for ARFI imaging. This paper considers these algorithms and the effects of noise, interpolation, and quadrature demodulation on the accuracy of the time delay estimates. These results are used to implement a real-time ARFI imaging system and in an ex vivo liver ablation study.

Authors
Pinton, GF; McAleavey, SA; Dahl, JJ; Nightingale, KR; Trahey, GE
MLA Citation
Pinton, GF, McAleavey, SA, Dahl, JJ, Nightingale, KR, and Trahey, GE. "Real-time Acoustic Radiation Force Impulse imaging." 2005.
Source
scival
Published In
Proceedings of SPIE
Volume
5750
Publish Date
2005
Start Page
226
End Page
235
DOI
10.1117/12.595846

Ultrasonic imaging of the mechanical properties of tissues using localized, transient acoustic radiation FORCE

Acoustic Radiation Force Impulse (ARFI) imaging utilizes brief, high energy, focused acoustic pulses to generate radiation force in tissue, and ultrasonic correlation-based methods to detect the resulting tissue displacements in order to image the relative mechanical properties of tissue. The magnitude and spatial extent of the applied force is dependent upon the transmit beam parameters and the tissue attenuation. Forcing volumes are on the order of 5 mm3, pulse durations are less than 1 msec, and tissue displacements are typically several microns. Displacement is quantified using interpolation and cross correlation methods. Noise reduction is accomplished by adaptively filtering the temporal response, and median filters are applied to the resulting images. Images of tissue displacement reflect local tissue stiffness, with softer tissues (e.g. fat) displacing farther than stiffer tissues (e.g. muscle). Parametric images of maximum displacement, time to peak displacement, and recovery time provide information about tissue material properties and structure. In both in vivo and ex vivo data, structures shown in matched B-mode images are in good agreement with those shown in ARFI images, with comparable resolution. Potential clinical applications under investigation include: soft tissue lesion characterization, assessment of focal atherosclerosis, and imaging of thermal lesion formation during tissue ablation procedures. Results from on-going studies are presented. © 2005 IEEE.

Authors
Nightingale, K; Palmeri, M; Frinkley, K; Sharma, A; Zhai, L; Trahey, G
MLA Citation
Nightingale, K, Palmeri, M, Frinkley, K, Sharma, A, Zhai, L, and Trahey, G. "Ultrasonic imaging of the mechanical properties of tissues using localized, transient acoustic radiation FORCE." 2005.
Source
scival
Published In
IEEE International Conference on Acoustics Speech and Signal Processing
Volume
V
Publish Date
2005
Start Page
V981
End Page
V984
DOI
10.1109/ICASSP.2005.1416470

A combined indenter/ARFI imaging system

The goal of this project is to develop an integrated indenter-ARFI (acoustic radiation force impulse imaging) system. The system is capable of acquiring matched datasets from ex vivo tissue samples, which will be used to evaluate excised colorectal tumors and blood vessels with atherosclerosis. This system will facilitate correlation of ARFI images of tissue samples with independently characterized material properties. We hypothesize that for a fixed indenter stress, the measured tissue displacements will be correlated with the ARFI generated displacements, which are inversely proportional to the stiffness of the tissue. A 100 Bloom gelatin phantom with a 300 Bloom surface lesion was used to test the system. Four indenter tips with different sizes were used to scan across the lesion phantom. Smaller tip diameters provide improved lesion edge definition for a given lateral sampling; for a given indenter tip, closer lateral sampling also improves lesion edge definition. For ARFI imaging, displacements were calculated at 0.35ms after ARFI excitation. To compare the results from the two systems, ARFI data was averaged axially along a 2 mm window starting at the sample surface, and compared with the indenter displacements at a given stress. Good agreement is observed between the ratio of displacements inside and outside of the stiff inclusion, for both the phantom and ex vivo colon cancer samples. © 2005 IEEE.

Authors
Zhai, L; Palmeri, M; Nightingale, R; Gottfried, M; Ludwig, K; Nightingale, K
MLA Citation
Zhai, L, Palmeri, M, Nightingale, R, Gottfried, M, Ludwig, K, and Nightingale, K. "A combined indenter/ARFI imaging system." Proceedings - IEEE Ultrasonics Symposium 1 (2005): 609-612.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
1
Publish Date
2005
Start Page
609
End Page
612
DOI
10.1109/ULTSYM.2005.1602926

Controlled spatio-temporal heating patterns using a commercial, diagnostic ultrasound system

Thermal ultrasound therapy is being investigated as a non-invasive surgical tool with applications in soft tissue tumor and cardiac ablation; as a method for hemostasis; and in the control of thermally-activated drug delivery vehicles. The success of localized ultrasonic thermal therapy depends on image guidance, typically done with a separate imaging transducer, but alignment of these transducers is challenging. A system capable of both functions would be ideal. However, the inherent tradeoff between image quality and power output presents a challenge for dualfunction probe design. A Siemens Antares scanner and CH62 transducer (fc=4.4 MHz) were employed to investigate the feasibility of using a modified, commercial diagnostic ultrasound system to combine B-mode, Doppler guidance, ARFI imaging, and therapeutic thermal applications. Custom pulse sequences were designed to transmit high intensity pulses down a single line of flight using different pulse lengths, amplitudes, PRFs, and F/#s for therapeutic purposes. These sequences were delivered to ex vivo porcine muscle through a waterpath to the focal point, where a type T thermocouple was positioned at the water/muscle interface. Transducer surface heating was monitored in separate experiments for these sequences by centering a thermocouple on the surface of the transducer. The porcine measurements were compared with analytic solutions to the bio-heat transfer equation and FEM models. Transmit parameters were evaluated to determine the optimal sequencing approach for different thermal therapies. Temperature rises of 28.6 ± 1.2°C for ∼50 ms were regularly achieved on the surface of the porcine muscle with damage to the transducer only after several repetitions. Temperature measurements at the focus were made for increasing durations of insonification and were consistent with the bio-heat transfer equation solution (neglecting perfusion). These temperature rises suggest the feasibility of using this system for creating HIFU lesions and aiding in drug therapy treatments. However, these experiments do not incorporate perfusion effects or, more significantly, attenuation of intervening tissue which will be encountered for most in vivo applications and will therefore require increased acoustic output. Thus, passive cooling modifications are being explored to decrease transducer heating while maintaining good image quality. © 2005 IEEE.

Authors
Frinkley, K; Palmeri, M; Nightingale, K
MLA Citation
Frinkley, K, Palmeri, M, and Nightingale, K. "Controlled spatio-temporal heating patterns using a commercial, diagnostic ultrasound system." 2005.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
2
Publish Date
2005
Start Page
1130
End Page
1134
DOI
10.1109/ULTSYM.2005.1603049

Image processing and data acquisition optimization for Acoustic Radiation Force Impulse imaging of in vivo breast masses

Acoustic Radiation Force Impulse (ARFI) imaging utilizes brief, high-energy acoustic pulses to excite tissue and ultrasonic correlation based tracking methods to monitor the resulting tissue displacement, which reflects the relative mechanical properties of tissue (i.e.. suffer tissue displaces less). ARFI image contrast is optimized utilizing tightly focused radiation force excitations at multiple axial and lateral locations throughout a 2D field of view. In an ongoing, IRB approved, clinical study, suspicious breast lesions are interrogated in vivo via multi-focal-zone ARFI prior to undergoing core biopsy. A Siemens SONOLINE Antares (TM) scanner and VF10-5 probe were configured to acquire ARFI data from multiple focal-zones and lateral locations. Data was acquired in real-time, and processed off-line. Processing included: filtering, parametric data analysis, normalization and combination of the multiple focal-zone data, and automatic edge detection. ARFI sequences were designed with varying pushing pulse frequencies and intensities. Contrast to noise ratio was evaluated in a tissue mimicking phantom for lesions at different depths using the different pushing pulse sequences. For shallower lesions (depth=10mm), CNR was higher than for deeper lesions, and did not vary appreciably for the different push sequences. For deeper lesions (depth=20mm), CNR increased with increasing push pulse intensity and decreasing push pulse frequency. With the pushing pulse transmit intensity calibrated (in a homogeneous phantom) to achieve uniform displacement at all axial depths, in vivo results yielded poor SNR at depth and did not achieve overall uniform displacement. In vivo, image quality improved with increasing push pulse intensity. To date, 27 masses have been interrogated using multi-focal-zone ARFI and overall good structural agreement exists between B-mode and ARFI images. Normalization and blending facilitate image generation from ARFI interrogation using different intensities at different focal depths.

Authors
Sharma, A; Trahey, G; Frinkley, K; Soo, MS; Palmeri, M; Nightingale, K
MLA Citation
Sharma, A, Trahey, G, Frinkley, K, Soo, MS, Palmeri, M, and Nightingale, K. "Image processing and data acquisition optimization for Acoustic Radiation Force Impulse imaging of in vivo breast masses." 2005.
Source
scival
Published In
Proceedings of SPIE
Volume
5750
Publish Date
2005
Start Page
205
End Page
215
DOI
10.1117/12.593473

Streaming detection for evaluation of indeterminate sono-graphic breast masses - A pilot study

Authors
Soo, MS; Baker, JA; Ghate, SV; Walsh, R; Warwick, B; Nightingale, K
MLA Citation
Soo, MS, Baker, JA, Ghate, SV, Walsh, R, Warwick, B, and Nightingale, K. "Streaming detection for evaluation of indeterminate sono-graphic breast masses - A pilot study." 2005.
Source
wos-lite
Published In
AJR. American journal of roentgenology
Volume
184
Issue
4
Publish Date
2005
Start Page
27
End Page
27

Acoustic radiation force impulse imaging of the mechanical properties of arteries: in vivo and ex vivo results.

We present results of a pilot study of ex vivo and in vivo acoustic radiation force impulse (ARFI) imaging demonstrating measurements of the mechanical properties of the carotid and popliteal arteries. The results were obtained on a modified commercial scanner, providing coregistered B-mode and color Doppler images. 2D and 1D through time images are formed from the measurements of tissues' response to very brief and localized applications of radiation force. The images show good correlation with B-mode and, in ex vivo studies, pathology-based characterizations of vessel geometry and plaque stiffness. In vivo measurements of arterial response during both systole and diastole are presented. We address implementation issues and discuss potential applications of this new vascular imaging method.

Authors
Trahey, GE; Palmeri, ML; Bentley, RC; Nightingale, KR
MLA Citation
Trahey, GE, Palmeri, ML, Bentley, RC, and Nightingale, KR. "Acoustic radiation force impulse imaging of the mechanical properties of arteries: in vivo and ex vivo results." Ultrasound Med Biol 30.9 (September 2004): 1163-1171.
PMID
15550320
Source
pubmed
Published In
Ultrasound in Medicine & Biology
Volume
30
Issue
9
Publish Date
2004
Start Page
1163
End Page
1171
DOI
10.1016/j.ultrasmedbio.2004.07.022

On the thermal effects associated with radiation force imaging of soft tissue.

Several laboratories are investigating the use of acoustic radiation force to image the mechanical properties of tissue. Acoustic Radiation Force Impulse (ARFI) imaging is one approach that uses brief, high-intensity, focused ultrasound pulses to generate radiation force in tissue. This radiation force generates tissue displacements that are tracked using conventional correlation-based ultrasound methods. The tissue response provides a mechanism to discern mechanical properties of the tissue. The acoustic energy that is absorbed by tissue generates radiation force and tissue heating. A finite element methods model of acoustic heating has been developed that models the thermal response of different tissues during short duration radiation force application. The beam sequences and focal configurations used during ARFI imaging are modeled herein; the results of these thermal models can be extended to the heating due to absorption associated with other radiation force-based imaging modalities. ARFI-induced thermal diffusivity patterns are functions of the transducer f-number, the tissue absorption, and the temporal and spatial spacing of adjacent ARFI interrogations. Cooling time constants are on the order of several seconds. Tissue displacement due to thermal expansion is negligible for ARFI imaging. Changes in sound speed due to temperature changes can be appreciable. These thermal models demonstrate that ARFI imaging of soft tissue is safe, although thermal response must be monitored when ARFI beam sequences are being developed.

Authors
Palmeri, ML; Nightingale, KR
MLA Citation
Palmeri, ML, and Nightingale, KR. "On the thermal effects associated with radiation force imaging of soft tissue." IEEE Trans Ultrason Ferroelectr Freq Control 51.5 (May 2004): 551-565.
PMID
15217233
Source
pubmed
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
51
Issue
5
Publish Date
2004
Start Page
551
End Page
565

Experimental studies of the thermal effects associated with radiation force imaging of soft tissue.

Many groups are studying acoustic radiation force-based imaging modalities to determine the mechanical properties of tissue. Acoustic Radiation Force Impulse (ARFI) imaging is one of these modalities that uses standard diagnostic ultrasound scanners to generate localized, impulsive, acoustic radiation force in tissue. This radiation force generates tissue displacements that are tracked using conventional correlation-based ultrasound methods. The dynamic response of tissue to this impulsive radiation force provides information about the mechanical properties of the tissue. The generation of micron-scale displacements using acoustic radiation force in tissue requires the use of high-intensity acoustic beams, and the soft tissue heating associated with these high-intensity beams must be evaluated to ensure safety when performing ARFI imaging in vivo. Experimental studies using thermocouples have validated Finite Element Method (FEM) models that simulate the heating of soft tissue during ARFI imaging. Spatial maps of heating measured with the thermocouples are in good agreement with FEM model predictions, with cooling time constants measured and modeled to be on the order of several seconds. Transducer heating during ARFI imaging has been measured to be less than 1 degrees C for current clinical implementations. These validated FEM models can now be used to simulate soft tissue heating associated with different transducers, beam spacing, focal configurations and thermal material properties. These experiments confirm that ARFI imaging of soft tissue is safe, although thermal response must be monitored when developing ARFI beam sequences for specific tissue types and organsystems.

Authors
Palmeri, ML; Frinkley, KD; Nightingale, KR
MLA Citation
Palmeri, ML, Frinkley, KD, and Nightingale, KR. "Experimental studies of the thermal effects associated with radiation force imaging of soft tissue." Ultrason Imaging 26.2 (April 2004): 100-114.
PMID
15344414
Source
pubmed
Published In
Ultrasonic Imaging
Volume
26
Issue
2
Publish Date
2004
Start Page
100
End Page
114
DOI
10.1177/016173460402600203

Acoustic radiation force impulse imaging of thermally- and chemically-induced lesions in soft tissues: preliminary ex vivo results.

The ability of acoustic radiation force impulse (ARFI) imaging to visualize thermally- and chemically-induced lesions in soft tissues was investigated. Lesions were induced in freshly excised bovine liver samples. Chemical lesions were induced via the injection of formaldehyde and thermal lesions were created using a radiofrequency (RF) ablation system. Although conventional sonography was unable to visualize induced lesions, ARFI imaging was capable of monitoring lesion size and boundaries. Agreement was observed between lesion size in ARFI images and in results from pathology. The fact that ARFI imaging requires no additional equipment aside from that needed for conventional ultrasonic imaging makes it a promising modality for monitoring lesion development in situations where sonography is already involved as a guiding mechanism, such as in procedures requiring precise catheter placement.

Authors
Fahey, BJ; Nightingale, KR; Stutz, DL; Trahey, GE
MLA Citation
Fahey, BJ, Nightingale, KR, Stutz, DL, and Trahey, GE. "Acoustic radiation force impulse imaging of thermally- and chemically-induced lesions in soft tissues: preliminary ex vivo results." Ultrasound Med Biol 30.3 (March 2004): 321-328.
PMID
15063514
Source
pubmed
Published In
Ultrasound in Medicine & Biology
Volume
30
Issue
3
Publish Date
2004
Start Page
321
End Page
328
DOI
10.1016/j.ultrasmedbio.2003.11.012

Acoustic Radiation Force Impulse (ARFI) imaging of the gastrointestinal tract

Currently, the evaluation of lesions in the gastrointestinal (GI) tract using ultrasound suffers from poor contrast between healthy and diseased tissue. Acoustic Radiation Force Impulse (ARFI) imaging provides information about the mechanical properties of tissue using brief, high-intensity, focused ultrasound to generate radiation force, and conventional, ultrasonic, correlation-based methods to track tissue displacement. Using conventional linear arrays, ARFI imaging has shown improved contrast over B-mode images when applied to solid masses in the breast and liver. The purpose of this work is to (1) demonstrate that ARFI imaging can be performed with an endocavity probe, and (2) demonstrate that ARFI imaging can provide improvements over conventional B-mode imaging of GI lesions. An EC94, 6.2 MHz, endocavity probe was modified to perform ARFI imaging in tissue-mimicking phantoms using a Siemens SONOLINE Antares scanner. ARFI imaging was performed on fresh, surgically-excised, GI lesions using a 75L40, 7.2 MHz, linear array on a modified Siemens SONOLINE Elegra™ scanner. The endocavity probe created ARFI images to a depth of over 2 cm in tissue-mimicking phantoms, with maximum displacements of 5 μm. The endocavity probe did not heat appreciably during ARFI imaging, demonstrating that the probe's small size will not limit in vivo ARFI imaging. ARFI images of an adenocarcinoma of the gastroesophageal (GE) junction, status-post chemotherapy and radiation treatment, demonstrate better contrast between healthy and fibrotic/malignant tissue than standard B-mode images. ARFI images of healthy gastric, esophageal, and colonic tissue specimens differentiate normal anatomic tissue planes (i.e., mucosal, muscularis, and adventitial layers), as confirmed by histologic evaluation. ARFI imaging of an ex vivo colon cancer portrays interesting contrast and structure not present in B-mode images. These findings support the clinical feasibility of endoscopic ARFI imaging to guide diagnosis and staging of disease processes in the GI tract. © 2004 IEEE.

Authors
Palmeri, M; Frinkley, K; Zhai, L; Bentley, R; Ludwig, K; Gottfried, M; Nightingale, K
MLA Citation
Palmeri, M, Frinkley, K, Zhai, L, Bentley, R, Ludwig, K, Gottfried, M, and Nightingale, K. "Acoustic Radiation Force Impulse (ARFI) imaging of the gastrointestinal tract." 2004.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
1
Publish Date
2004
Start Page
744
End Page
747

On the thermal effects associated with radiation force imaging of soft tissue

Several laboratories are investigating the use of acoustic radiation force to image the mechanical properties of tissue. Acoustic Radiation Force Impulse (ARFI) imaging is one approach that uses brief, high-intensity, focused ultrasound pulses to generate radiation force in tissue. This radiation force generates tissue displacements that are tracked using conventional correlation-based ultrasound methods. The tissue response provides a mechanism to discern mechanical properties of the tissue. The acoustic energy that is absorbed by tissue generates radiation force and tissue heating. A finite element methods model of acoustic heating has been developed that models the thermal response of different tissues during short duration radiation force application. The beam sequences and focal configurations used during ARFI imaging are modeled herein; the results of these thermal models can be extended to the heating due to absorption associated with other radiation force-based imaging modalities. ARFI-induced thermal diffusivity patterns are functions of the transducer f-number, the tissue absorption, and the temporal and spatial spacing of adjacent ARFI interrogations. Cooling time constants are on the order of several seconds. Tissue displacement due to thermal expansion is negligible for ARFI imaging. Changes in sound speed due to temperature changes can be appreciable. These thermal models demonstrate that ARFI imaging of soft tissue is safe, although thermal response must be monitored when ARFI beam sequences are being developed.

Authors
Palmeri, ML; Nightingale, KR
MLA Citation
Palmeri, ML, and Nightingale, KR. "On the thermal effects associated with radiation force imaging of soft tissue." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 51.5 (2004): 551-565.
Source
scival
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
51
Issue
5
Publish Date
2004
Start Page
551
End Page
565
DOI
10.1109/TUFFC.2004.1302764

Acoustic radiation force impulse imaging of in vivo breast masses

ARFI datasets were acquired in real time to identify differentiable features between benign and malignant breast masses in ARFI images. A modified Siemens SONOLINE Antares scanner and a VF10-5 probe were programmed to implement ARFI imaging in a multi-focal zone configuration. It was observed that the cysts and fibroadenomas, in general, exhibit less contrast IN ARFI images than in matched B-mode images. The results led to identification of some differentiating features between malingant and benign breast masses.

Authors
Sharma, AC; Soo, MS; Trahey, GE; Nightingale, KR
MLA Citation
Sharma, AC, Soo, MS, Trahey, GE, and Nightingale, KR. "Acoustic radiation force impulse imaging of in vivo breast masses." 2004.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
1
Publish Date
2004
Start Page
728
End Page
731

Imaging tissue mechanical properties using impulsive acoustic radiation force

Acoustic Radiation Force Impulse (ARFI) imaging utilizes brief, high energy, focused acoustic pulses to generate radiation force in tissue, and conventional diagnostic ultrasound methods to detect the resulting tissue displacements in order to image the relative mechanical properties of tissue. Parametric images of maximum displacement, the time the tissue takes to reach its peak displacement, and tissue recovery time provide information about tissue material properties and structure. FEM simulations have been developed and validated of tissue mechanical and thermal response to ARFI excitation. Potential clinical applications under investigation include: soft tissue lesion characterization, assessment of diffuse and focal atherosclerosis, and imaging of thermal lesion formation during tissue ablation procedures. In both in vivo and ex vivo data, structures shown in matched B-mode images are in good agreement with those shown in ARFI displacement images. In ex vivo tissue ablation studies (HIFU and RF-ablation), thermal lesion size correlates well with matched pathology images. In in vivo breast studies, palpable breast masses exhibit smaller displacements (i.e. they are stiffer) than surrounding tissues. Some malignant masses appear larger in ARFI displacement images than in matched B-mode images, consistent with a desmoplastic reaction; however, this is not the case for all malignant breast masses that have been studied. Benign fibroadenomas, in general, exhibit less contrast than malignant masses in ARFI displacement images. Results from ongoing studies will be presented. © 2004 IEEE.

Authors
Nightingale, K; Soo, MS; Palmeri, M; Congdon, A; Frinkley, K; Trahey, G
MLA Citation
Nightingale, K, Soo, MS, Palmeri, M, Congdon, A, Frinkley, K, and Trahey, G. "Imaging tissue mechanical properties using impulsive acoustic radiation force." 2004 2nd IEEE International Symposium on Biomedical Imaging: Macro to Nano 1 (2004): 41-44.
Source
scival
Published In
2004 2nd IEEE International Symposium on Biomedical Imaging: Macro to Nano
Volume
1
Publish Date
2004
Start Page
41
End Page
44

BSS-based filtering of physiological and ARFI-induced tissue and blood motion.

Blind source separation (BSS) for adaptive filtering is presented in application to imaging both physiological and acoustic radiation force impulse (ARFI)-induced tissue and blood motion in the common carotid artery. The collected raw radiofrequency (RF) data includes vessel wall motion, blood flow and ARFI-induced motion. In the context of these complex motion patterns, the same BSS adaptive filtering method was employed for three diverse applications: 1. clutter filtering ensembles prior to blood velocity estimation, 2. extracting small axial velocity components from noisy velocity measurements given large flow angles and 3. reducing noise in measured ARFI-induced tissue displacement profiles to enhance differentiation of local tissue structures. The filter separated physiological vessel wall motion from axial blood flow and ARFI-induced motion; successful filter performance is demonstrated in velocity estimates, color flow images and ARFI displacement profiles. The results demonstrate the breadth of applications for BSS adaptive filtering in the clinical imaging environment.

Authors
Gallippi, CM; Nightingale, KR; Trahey, GE
MLA Citation
Gallippi, CM, Nightingale, KR, and Trahey, GE. "BSS-based filtering of physiological and ARFI-induced tissue and blood motion." Ultrasound Med Biol 29.11 (November 2003): 1583-1592.
PMID
14654154
Source
pubmed
Published In
Ultrasound in Medicine & Biology
Volume
29
Issue
11
Publish Date
2003
Start Page
1583
End Page
1592

Estimates of echo correlation and measurement bias in acoustic radiation force impulse imaging.

Acoustic radiation force impulse (ARFI) imaging is a novel imaging modality in which pulses from a diagnostic ultrasound scanner are used to displace tissue and track its motion. The region displaced has lateral and elevational dimensions of similar scale to the ultrasound beams used to track the motion. Therefore, there is a range of tissue displacements present within the tracking beam, leading to decorrelation of the echo signal. Expressions are derived for the expected value of the displacement estimate and the cross-correlation at the expected displacement. Numerical simulations confirm the analytical model.

Authors
McAleavey, SA; Nightingale, KR; Trahey, GE
MLA Citation
McAleavey, SA, Nightingale, KR, and Trahey, GE. "Estimates of echo correlation and measurement bias in acoustic radiation force impulse imaging." IEEE Trans Ultrason Ferroelectr Freq Control 50.6 (June 2003): 631-641.
PMID
12839175
Source
pubmed
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
50
Issue
6
Publish Date
2003
Start Page
631
End Page
641

Image reconstruction with acoustic radiation force induced shear waves

Acoustic radiation force may be used to induce localized displacements within tissue. This phenomenon is used in Acoustic Radiation Force Impulse Imaging (ARFI), where short bursts of ultrasound deliver an impulsive force to a small region. The application of this transient force launches shear waves which propagate normally to the ultrasound beam axis. Measurement of the displacements induced by the propagating shear wave allow reconstruction of the local shear modulus, by wave tracking and inversion techniques. Here we present in vitro, ex vivo and in vivo measurements and images of shear modulus. Data were obtained with a single transducer, a conventional ultrasound scanner and specialized pulse sequences. Young's modulus values of 4kPa, 13kPa and 14kPa were observed for fat, breast fibroadenoma, and skin. Shear modulus anisotropy in beef muscle was observed.

Authors
McAleavey, SA; Nightingale, KR; Stutz, DL; Hsu, SJ; Trahey, GE
MLA Citation
McAleavey, SA, Nightingale, KR, Stutz, DL, Hsu, SJ, and Trahey, GE. "Image reconstruction with acoustic radiation force induced shear waves." 2003.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
5035
Publish Date
2003
Start Page
223
End Page
234
DOI
10.1117/12.480275

Arterial stiffness measurements with acoustic radiation force impulse imaging

We have developed a new method of imaging the mechanical properties of tissues based on very brief (< 1msec) and localized applications of acoustic radiation force and the ultrasonic measurement of local tissues' responses to that force. Initial results with this technique demonstrate its ability to image mechanical properties of the medial and adventitial layers within ex vivo and in vivo arteries, and to distinguish hard and soft atherosclerotic plaques from normal vessel wall. We have labeled this method Acoustic Radiation Force Impulse (ARFI) imaging. We describe studies to utilize this technique in the characterization of diffuse and focal atherosclerosis. We describe phantom trials and finite element simulations which explore the fundamental resolution and contrast achievable with this method. We describe in vivo and ex vivo trials in the popliteal, femoral and brachial arteries to assess the relationship between the mechanical properties of healthy and diseased arteries provided by this method and those obtained by alternative methods.

Authors
Trahey, GE; Dahl, JJ; McAleavey, SA; Gallippi, CM; Nightingale, KR
MLA Citation
Trahey, GE, Dahl, JJ, McAleavey, SA, Gallippi, CM, and Nightingale, KR. "Arterial stiffness measurements with acoustic radiation force impulse imaging." 2003.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
5035
Publish Date
2003
Start Page
235
End Page
241
DOI
10.1117/12.479966

Shear wave anisotropy imaging

Shear Wave Anisotropy Imaging is a novel method that images local variations in tissue shear wave velocity. A commercial ultrasound scanner is used to generate and track propagating shear waves. Radiation force from a brief high-energy pulse generates shear waves. The pulses are steered in order to launch the waves at oblique angles. The Helmholtz equation is used to extract the shear propagation velocity. Depending on the direction of shear wave propagation, the velocity changes and images are formed from the ratio and directions of the maximum and minimum shear wave speeds. The beam sequence and data acquisition are real time processes, however, data analysis and anisotropy imaging are performed off-line. We describe simulation and experimental studies of this method in phantoms. Finite element methods were employed to test the feasibility and calibration of the method. A homogeneous phantom was imaged and isotropy was observed. Simulation results of an anisotropic medium provided an estimate of anisotropy consistent with expectations. Shear wave speed images were made for each sample in all three planes and inspected for shear speed variations between propagation angles. Shear wave speeds in the homogeneous phantom were quite uniform with an average level of anisotropy of 1.15, indicating little organization within the sample. Upon a ninety degree rotation of the transducer, the average level of anisotropy was 1.14.

Authors
Hsu, SJ; Palermi, ML; Nightingale, KR; McAleavey, SA; Dahl, JD; Trahey, GE
MLA Citation
Hsu, SJ, Palermi, ML, Nightingale, KR, McAleavey, SA, Dahl, JD, and Trahey, GE. "Shear wave anisotropy imaging." 2003.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
2
Publish Date
2003
Start Page
1090
End Page
1093

Shear wave anisotropy imaging

Shear Wave Anisotropy Imaging is a novel method that images local variations in tissue shear wave velocity. A commercial ultrasound scanner is used to generate and track propagating shear waves. Radiation force from a brief high-energy pulse generates shear waves. The pulses are steered in order to launch the waves at oblique angles. The Helmholtz equation is used to extract the shear propagation velocity. Depending on the direction of shear wave propagation, the velocity changes and images are formed from the ratio and directions of the maximum and minimum shear wave speeds. The beam sequence and data acquisition are real time processes, however, data analysis and anisotropy imaging are performed off-line. We describe simulation and experimental studies of this method in phantoms. Finite element methods were employed to test the feasibility and calibration of the method. A homogeneous phantom was imaged and isotropy was observed. Simulation results of an anisotropic medium provided an estimate of anisotropy consistent with expectations. Shear wave speed images were made for each sample in all three planes and inspected for shear speed variations between propagation angles. Shear wave speeds in the homogeneous phantom were quite uniform with an average level of anisotropy of 1.15, indicating little organization within the sample. Upon a ninety degree rotation of the transducer, the average level of anisotropy was 1.14.

Authors
Hsu, SJ; Palermi, ML; Nightingale, KR; McAleavey, SA; Dahl, JD; Trahey, GE
MLA Citation
Hsu, SJ, Palermi, ML, Nightingale, KR, McAleavey, SA, Dahl, JD, and Trahey, GE. "Shear wave anisotropy imaging." 2003.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
1
Publish Date
2003
Start Page
921
End Page
924

Shear-wave generation using acoustic radiation force: In vivo and ex vivo results

Acoustic radiation force impulse (ARFI) imaging involves the mechanical excitation of tissue using localized, impulsive radiation force. This results in shear-wave propagation away from the region of excitation. Using a single diagnostic transducer on a modified commercial ultrasound (US) scanner with conventional beam-forming architecture, repeated excitations with multiple look directions facilitate imaging shear-wave propagation. Direct inversion methods are then applied to estimate the associated Young's modulus. Shear-wave images are generated in tissue-mimicking phantoms, ex vivo human breast tissue and in vivo in the human abdomen. Mean Young's modulus values of between 3.8 and 5.6 kPa, 11.7 kPa and 14.0 kPa were estimated for fat, fibroadenoma and skin, respectively. Reasonable agreement is demonstrated between structures in matched B-mode and reconstructed modulus images. Although the relatively small magnitude of the displacement data presents some challenges, the reconstructions suggest the clinical feasibility of radiation force induced shear-wave imaging. © 2003 World Federation for Ultrasound in Medicine & Biology.

Authors
Nightingale, K; McAleavey, S; Trahey, G
MLA Citation
Nightingale, K, McAleavey, S, and Trahey, G. "Shear-wave generation using acoustic radiation force: In vivo and ex vivo results." Ultrasound in Medicine and Biology 29.12 (2003): 1715-1723.
PMID
14698339
Source
scival
Published In
Ultrasound in Medicine and Biology
Volume
29
Issue
12
Publish Date
2003
Start Page
1715
End Page
1723
DOI
10.1016/j.ultrasmedbio.2003.08.008

Acoustic radiation force impulse imaging: A parametric analysis of factors affecting image quality

Acoustic Radiation Force Impulse (ARFI) imaging utilizes brief, high energy, focused acoustic pulses to generate radiation force in tissue, and conventional diagnostic ultrasound methods to detect the resulting tissue displacements in order to image the mechanical properties of tissue. The goal of this work was to perform a parametric analysis of the effect of system parameters and target characteristics on image quality. METHODS: FEM simulations and phantom experiments have been performed using varying system configurations and tissue properties to determine their impact on ARFI image quality. Phantom experimental results were utilized to validate the FEM models. RESULTS: Matched simulation and FEM experiments support the validity of the FEM model. Due to the dynamic nature of ARFI excitation, lesion contrast is temporally dependent. Contrast efficiencies (CE) were computed immediately after force cessation, prior to appreciable wave propagation. CE does not vary with applied force, increases with lesion stiffness, and increases as the forcing volume size decreases with respect to the size of the structure being imaged. CONCLUSIONS: The response of tissue to ARFI excitation is complex and depends upon tissue geometry, forcing function geometry, and tissue mechanical and acoustic properties. These studies indicate that improved contrast in ARFI images will be achieved as forcing volume size decreases relative to the structure being imaged. Frame rate and thermal considerations present tradeoffs with small load volume sizes for ARFI imaging.

Authors
Nightingale, K; Palmeri, M; Bouchard, R; Trahey, G
MLA Citation
Nightingale, K, Palmeri, M, Bouchard, R, and Trahey, G. "Acoustic radiation force impulse imaging: A parametric analysis of factors affecting image quality." Proceedings of the IEEE Ultrasonics Symposium 1 (2003): 548-553.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
1
Publish Date
2003
Start Page
548
End Page
553

Blind source separation-based adaptive filtering of physiological and ARFI-induced tissue, blood, and cyst fluid motion, in-vivo

In the context of complex tissue motion patterns including physiological and Acoustic Radiation Force Impulse (ARFI) -induced tissue, blood, and cyst fluid motion, the same adaptive blind source separation (BSS)-based filtering method is effective for four diverse applications: 1) clutter filtering prior to blood velocity estimation, 2) extracting axial velocity components from noisy velocity measurements given large flow angles, 3) reducing noise in measured ARFI displacement profiles, and 4) complex phase clutter filtering to measure ARFI-induced cyst streaming. RF data was collected using ARFI imaging beam sequences from the carotid arteries of healthy volunteers and from female subjects (recruited under IRB guidance), each presenting one breast lesion. Biopsy determined that one lesion was a fluid-filled cyst and the other was a malignant mass. In the examined arteries, velocity profiles are parabolic in shape, with nearly zero axial velocity beyond the vessel lumen following BSS clutter filtering and BSS extraction of small axial velocity components. The method maintains peak displacement (1.81 to 21.5μ m) and time to 63% recovery (1.38 to 2.20 ms) parameters after BSS noise reduction in ARFI displacement profiles. Colorflow images generated after BSS complex phase clutter rejection reveal ARFI-induced streaming in the fluid-filled cyst but no streaming in the malignant lesion. Successful filtering for four diverse purposes illustrates the breadth of applications for BSS adaptive filtering in the clinical imaging environment.

Authors
Gallippi, CM; Nightingale, KR; Trahey, GE
MLA Citation
Gallippi, CM, Nightingale, KR, and Trahey, GE. "Blind source separation-based adaptive filtering of physiological and ARFI-induced tissue, blood, and cyst fluid motion, in-vivo." 2003.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
1
Publish Date
2003
Start Page
841
End Page
846

ARFI imaging of the cardiovascular system

We present results of a pilot study of ex vivo and in vivo acoustic radiation force impulse (ARFI) imaging demonstrating measurements of the mechanical properties of the medial and adventitial layers in the carotid, and popliteal arteries. The data was obtained on a commercial scanner, providing co-registered B-mode and Color Doppler images. A real-time ARFI imaging system capable of achieving frame rates of 0.75 Hz was developed. The 2-D and 1-D images of the tissue's response to brief and localized applications of radiation force show good correlation with B-mode and pathology based characterization of vessel geometry and plaque stiffness. Measurements of arterial response during both systole and diastole are presented. We address implementation issues and discuss the potential applications of this new vascular imaging method.

Authors
Pinton, GF; Palmeri, ML; McAleavey, SA; Nightingale, KR; Trahey, GE
MLA Citation
Pinton, GF, Palmeri, ML, McAleavey, SA, Nightingale, KR, and Trahey, GE. "ARFI imaging of the cardiovascular system." Proceedings of the IEEE Ultrasonics Symposium 1 (2003): 228-231.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
1
Publish Date
2003
Start Page
228
End Page
231

Thermal effects associated with acoustic radiation force impulse imaging

Acoustic Radiation Force Impulse (ARFI) imaging uses brief, high-intensity, focused ultrasound pulses to generate radiation force in tissue. The absorption of acoustic energy also generates tissue heating. The purpose of this work is to study the maximum acoustic intensities that can safely be used in ARFI imaging, and to characterize the effects of tissue heating on ARFI displacement tracking. FEM models are implemented to determine the temperature increases associated with ARFI imaging for different transducer configurations and tissue properties. Model validation is accomplished with experimental measurements of heating using thermocouples in gelatin-based tissue-mimicking phantoms and porcine muscle. ARFI imaging typically employs in situ intensities of up to 1000 W/cm 2 that are applied over a period of less than 1 ms. FEM temperature increases of 0.2°C are demonstrated for a single ARFI interrogation for an absorption of 0.5 dB/cm/MHz, with cooling time constants on the order of several seconds. Tissue heating associated with two-dimensional ARFI imaging is a function of the spatial overlap of adjacent heated tissue volumes, with FEM temperature increases not exceeding 0.4°C in current ARFI configurations. Real-time two-dimensional ARFI imaging temperature increases reach steady-state values of less than 2.0°C after 1 minute at 1 frame per second. Tissue displacement due to thermal expansion is negligible for ARFI imaging, however changes in sound speed due to temperature changes may be appreciable. Experimental studies demonstrate that temperature increases of 0.15°C are associated with a single ARFI interrogation for an absorption of 0.5 dB/cm/MHz, with cooling time constants on the order of seconds. Tissue temperature increases do not exceed 1.5°C for two-dimensional ARFI imaging. ARFI-induced thermal diffusivity patterns are shown to be functions of the transducer f-number, the tissue absorption, and the temporal and spatial spacing of adjacent ARFI imaging locations. Good agreement is observed between FEM and experimental data. We conclude that ARFI imaging is safe in soft tissue, although thermal response must be monitored when developing ARFI beam sequences.

Authors
Palmeri, ML; Nightingale, KR
MLA Citation
Palmeri, ML, and Nightingale, KR. "Thermal effects associated with acoustic radiation force impulse imaging." 2003.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
1
Publish Date
2003
Start Page
232
End Page
237

ARFI imaging of thermal lesions in ex vivo and in vivo soft tissues

The ability of ARFI imaging to monitor the ablation of soft tissues both ex vivo and in vivo was investigated. Thermal lesions were induced both in freshly excised bovine liver samples and in myocardial tissue of live sheep. While conventional sonography was unable to visualize induced lesions, ARFI imaging was capable of monitoring lesion size and boundaries. Good agreement was observed between lesion size in ARFI images and in results from pathology. The fact that ARFI imaging requires no additional equipment aside from that needed for conventional ultrasonic imaging makes it a promising modality for monitoring ablation procedures in vivo, especially in situations where sonography is already involved as a guiding mechanism, such as in many procedures requiring precise catheter placement.

Authors
Fahey, BJ; Nightingale, KR; Wolf, PD; Trahey, GE
MLA Citation
Fahey, BJ, Nightingale, KR, Wolf, PD, and Trahey, GE. "ARFI imaging of thermal lesions in ex vivo and in vivo soft tissues." 2003.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
1
Publish Date
2003
Start Page
562
End Page
567

Observations of tissue response to acoustic radiation force: opportunities for imaging.

Acoustic Radiation Force Impulse (ARFI) imaging is a method for characterizing local variations in tissue mechanical properties. In this method, a single ultrasonic transducer array is used to both apply temporally short localized radiation forces within tissue and to track the resulting displacements through time. In an ongoing study of the response of tissue to temporally short radiation force excitation, ARFI datasets have been obtained of ex vivo tissues under various focal configurations. The goal of this paper is to report observations of the response of tissue to radiation force and discuss the implications of these results in the construction of clinical imaging devices.

Authors
Nightingale, K; Bentley, R; Trahey, G
MLA Citation
Nightingale, K, Bentley, R, and Trahey, G. "Observations of tissue response to acoustic radiation force: opportunities for imaging." Ultrason Imaging 24.3 (July 2002): 129-138.
PMID
12503770
Source
pubmed
Published In
Ultrasonic Imaging
Volume
24
Issue
3
Publish Date
2002
Start Page
129
End Page
138
DOI
10.1177/016173460202400301

Acoustic radiation force impulse imaging: EX vivo and in vivo demonstration of transient shear wave propagation

© 2002 IEEE.Acoustic Radiation Force Impulse (ARFI) imaging utilizes brief, high energy, focused acoustic pulses to generate radiation force in remote locations in tissue, and conventional diagnostic ultrasound methods to detect the resulting tissue displacements in order to provide information about the mechanical properties of tissue. Tissue displacement magnitude is inversely related to local tissue stiffness, and the temporal response of the tissue is related to its viscosity. In addition, ARFI imaging allows visualization of the transient shear waves generated by the impulsive radiation force, whose propagation velocity and attenuation reflect the local tissue properties. ARFI imaging is implemented on a modified Siemens Elegra scanner with a 7.5 MHz linear array transducer using radiation force application times ranging from 03 to 1 msec. Good correlation is observed between the matched pathology, B-mode, and ARFI images of ex vivo breast and cervical tissues. ARFI image representation of tissue stiffness is consistent with manual palpation. In addition, localized radiation force induced shear wave propagation is visualized by ARFI imaging in phantoms, ex vivo breast tissue, and in vivo abdominal tissue. Shear wave speeds ranging from 1 to 5 m/s are observed in abdominal tissue in vivo. These results suggest that ARFI imaging holds clinical promise.

Authors
Nightingale, K; Stutz, D; Bentley, R; Trahey, G
MLA Citation
Nightingale, K, Stutz, D, Bentley, R, and Trahey, G. "Acoustic radiation force impulse imaging: EX vivo and in vivo demonstration of transient shear wave propagation." January 1, 2002.
Source
scopus
Published In
Proceedings / IEEE International Symposium on Biomedical Imaging: from nano to macro. IEEE International Symposium on Biomedical Imaging
Volume
2002-January
Publish Date
2002
Start Page
525
End Page
528
DOI
10.1109/ISBI.2002.1029310

Acoustic radiation force impulse imaging: Remote palpation of the mechanical properties of tissue

An overview is given of the Acoustic Radiation Force Impulse (ARFI) imaging. It discusses the derivation of radiation force, the response of tissue to radiation force, and the potential for this imaging method to evaluate the mechanical properties of tissue. It is found that In vivo ARFI images of breast, abdomen, and carotid vessels demonstrate no speckle, good contrast between tissue structures, and resolution comparable to B-mode images.

Authors
Nightingale, K; Soo, MS; Nightingale, R; Bentley, R; Stutz, D; Palmeri, M; Dahl, J; Trahey, G
MLA Citation
Nightingale, K, Soo, MS, Nightingale, R, Bentley, R, Stutz, D, Palmeri, M, Dahl, J, and Trahey, G. "Acoustic radiation force impulse imaging: Remote palpation of the mechanical properties of tissue." Proceedings of the IEEE Ultrasonics Symposium 2 (2002): 1821-1830.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
2
Publish Date
2002
Start Page
1821
End Page
1830

Acoustic radiation force impulse imaging of in vivo vastus medialis muscle under varying isometric load

Acoustic Radiation Force Impulse (ARFI) imaging is a method for characterizing local variations in tissue mechanical properties. In this method, a single ultrasonic transducer array is used to both apply temporally short localized radiation forces within tissue and to track the resulting displacements through time. Images of tissue displacement immediately after force cessation, maximum tissue displacement, the time it takes for the tissue to reach its maximum displacement, and the recovery time constant of the tissue are generated from the ARFI data sets. The information in each of these images demonstrates good agreement with matched B-mode images. The study presented here was designed to evaluate the relationship between changes in these ARFI parameters with known tissue mechanical properties in vivo. Utilizing a modified Siemens Elegra scanner with a 75L40 transducer array, ARFI images of vastus medialis muscle were generated in three of the authors under four levels of activation (0, 5.7, 14.5, and 23.3 N-m). Four ARFI datasets were acquired for each loading condition. The observed trends were that displacement magnitude, the time it took for the tissue to reach its maximum displacement, and recovery time constant decreased with increasing load (i.e., increasing muscle stiffness). Significant differences were observed between load levels and subjects for all parameters (p<0.01). The results indicate that ARFI imaging may be capable of quantifying tissue stiffness in real-time measurements, although further investigation is required.

Authors
Nightingale, K; Nightingale, R; Stutz, D; Trahey, G
MLA Citation
Nightingale, K, Nightingale, R, Stutz, D, and Trahey, G. "Acoustic radiation force impulse imaging of in vivo vastus medialis muscle under varying isometric load." Ultrasonic Imaging 24.2 (2002): 100-108.
PMID
12199416
Source
scival
Published In
Ultrasonic Imaging
Volume
24
Issue
2
Publish Date
2002
Start Page
100
End Page
108

Acoustic radiation force impulse imaging: In vivo demonstration of clinical feasibility

The clinical viability of a method of acoustic remote palpation, capable of imaging local variations in the mechanical properties of soft tissue using acoustic radiation force impulse (ARFI) imaging, is investigated in vivo. In this method, focused ultrasound (US) is used to apply localized radiation force to small volumes of tissue (2 mm3) for short durations (less than 1 ms) and the resulting tissue displacements are mapped using ultrasonic correlation-based methods. The tissue displacements are inversely proportional to the stiffness of the tissue and, thus, a stiffer region of tissue exhibits smaller displacements than a more compliant region. Due to the short duration of the force application, this method provides information about the mechanical impulse response of the tissue, which reflects variations in tissue viscoelastic characteristics. In this paper, experimental results are presented demonstrating that displacements on the order of 10 μm can be generated and detected in soft tissues in vivo using a single transducer on a modified diagnostic US scanner. Differences in the magnitude of displacement and the transient response of tissue are correlated with tissue structures in matched B-mode images. The results comprise the first in vivo ARFI images, and support the clinical feasibility of a radiation force-based remote palpation imaging system. © 2002 World Federation for Ultrasound in Medicine & Biology.

Authors
Nightingale, K; Soo, MS; Nightingale, R; Trahey, G
MLA Citation
Nightingale, K, Soo, MS, Nightingale, R, and Trahey, G. "Acoustic radiation force impulse imaging: In vivo demonstration of clinical feasibility." Ultrasound in Medicine and Biology 28.2 (2002): 227-235.
PMID
11937286
Source
scival
Published In
Ultrasound in Medicine & Biology
Volume
28
Issue
2
Publish Date
2002
Start Page
227
End Page
235
DOI
10.1016/S0301-5629(01)00499-9

On the feasibility of remote palpation using acoustic radiation force.

A method of acoustic remote palpation, capable of imaging local variations in the mechanical properties of tissue, is under investigation. In this method, focused ultrasound is used to apply localized (on the order of 2 mm3) radiation force within tissue. and the resulting tissue displacements are mapped using ultrasonic correlation based methods. The tissue displacements are inversely proportional to the stiffness of the tissue, and thus a stiffer region of tissue exhibits smaller displacements than a more compliant region. In this paper, the feasibility of remote palpation is demonstrated experimentally using breast tissue phantoms with spherical lesion inclusions, and in vitro liver samples. A single diagnostic transducer and modified ultrasonic imaging system are used to perform remote palpation. The displacement images are directly correlated to local variations in tissue stiffness with higher contrast than the corresponding B-mode images. Relationships between acoustic beam parameters, lesion characteristics and radiation force induced tissue displacement patterns are investigated and discussed. The results show promise for the clinical implementation of remote palpation.

Authors
Nightingale, KR; Palmeri, ML; Nightingale, RW; Trahey, GE
MLA Citation
Nightingale, KR, Palmeri, ML, Nightingale, RW, and Trahey, GE. "On the feasibility of remote palpation using acoustic radiation force." J Acoust Soc Am 110.1 (July 2001): 625-634.
PMID
11508987
Source
pubmed
Published In
The Journal of the Acoustical Society of America
Volume
110
Issue
1
Publish Date
2001
Start Page
625
End Page
634

Investigation of real-time remote palpation imaging

We are investigating a novel ultrasonic method for remote palpation, which provides images of local variations in tissue stiffness. Acoustic radiation force is applied to small volumes of tissue, and the resulting displacement patterns are imaged using ultrasonic correlation based techniques. Tissue displacements are inversely proportional to tissue stiffness, thus a stiffer region of tissue exhibits smaller displacements than a more compliant region. This method also provides information about tissue recovery after force cessation. We will present in vivo experimental results demonstrating the feasibility of this method. Using intensities ranging from 120 to 300 W/cm2, peak displacements of up to 50 microns were observed after 1.4 milliseconds of force application. The tissue moved to its peak displacement within 3 milliseconds of force application, and the time constants for tissue recovery varied with tissue type. Tissue displacements appeared to be correlated with tissue structure in matched B-mode images. To our knowledge, these results represent the first in vivo soft tissue images generated using radiation force. These findings support the feasibility of Remote Palpation imaging. We will discuss the technical, safety, and clinical challenges of implementing a real-time Remote Palpation imaging system on a commercial diagnostic scanner.

Authors
Nightingale, KR; Soo, MS; Nightingale, RW; Trahey, GE
MLA Citation
Nightingale, KR, Soo, MS, Nightingale, RW, and Trahey, GE. "Investigation of real-time remote palpation imaging." Proceedings of SPIE - The International Society for Optical Engineering 4325 (2001): 113-119.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
4325
Publish Date
2001
Start Page
113
End Page
119
DOI
10.1117/12.428187

In vivo demonstration of acoustic radiation force impulse (ARFI) imaging in the thyroid, abdomen, and breast

Acoustic Radiation Force Impulse (ARFI) imaging is proposed as a method for characterizing local variations in tissue mechanical response. In this method, a single ultrasonic transducer array is used to both apply localized radiation forces within tissue and to track the resulting displacements. Tissue displacement is inversely proportional to tissue stiffness, and the temporal response of tissue to radiation force varies with tissue type. We have previously presented results generated using radiation force applied in a single pushing location in vivo, and using multiple pushing locations in tissue phantoms where the data was acquired over several minutes. In this paper, data are presented that were acquired using multiple applications of radiation force to interrogate an extended region of interest in a real-time data acquisition implementation, using beam sequences similar to those used for Color Doppler. In vivo ARFI images of the thyroid, abdomen, and breast are presented. Peak displacements of 5, 10, and 8 microns were observed in the these tissues, respectively. In all cases, the ARFI images and matched B-mode images show highly correlated structural information, and comparable resolution. Images of the thyroid exhibit remarkable uniformity in displacement with no speckle. The results suggest considerable clinical potential for ARFI imaging.

Authors
Nightingale, K; Soo, MS; Nightingale, R; Bentley, R; Trahey, G
MLA Citation
Nightingale, K, Soo, MS, Nightingale, R, Bentley, R, and Trahey, G. "In vivo demonstration of acoustic radiation force impulse (ARFI) imaging in the thyroid, abdomen, and breast." Proceedings of the IEEE Ultrasonics Symposium 2 (2001): 1633-1638.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
2
Publish Date
2001
Start Page
1633
End Page
1638

Evaluation of the mechanical properties of active skeletal muscle using acoustic radiation force impulse imaging

Acoustic Radiation Force Impulse (ARFI) imaging is a method for characterizing local variations in tissue mechanical response. In this method, a single ultrasonic transducer array is used to both apply temporally short localized radiation forces within tissue and to track the resulting displacements. Tissue displacement is inversely related to tissue stiffness, and the temporal response of tissue to radiation force varies with tissue type. Utilizing a modified Siemens Elegra scanner with a 75L40 transducer array, ARFI images of bicep muscle were generated in the three authors for four levels of activation (0, 2, 4, and 8 kg). Four ARFI datasets were acquired for each loading condition. Data was acquired in real-time, and processed off-line. Statistically significant differences between the unloaded and loaded cases were found in each of the parameters studied (displacement magnitude, recovery velocity magnitude, and time to peak displacement, p < 0.005). Significant differences were also found between subjects (p>0.01). These results suggest that ARFI imaging has potential for quantifying variations in tissue stiffness in real-time measurements.

Authors
Nightingale, K; Nightingale, R; Trahey, G
MLA Citation
Nightingale, K, Nightingale, R, and Trahey, G. "Evaluation of the mechanical properties of active skeletal muscle using acoustic radiation force impulse imaging." Proceedings of the IEEE Ultrasonics Symposium 2 (2001): 1627-1631.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
2
Publish Date
2001
Start Page
1627
End Page
1631

A finite element model of remote palpation of breast lesions using radiation force: factors affecting tissue displacement.

The early detection of breast cancer reduces patient mortality. The most common method of breast cancer detection is palpation. However, lesions that lie deep within the breast are difficult to palpate when they are small. Thus, a method of remote palpation, which may allow the detection of small lesions lying deep within the breast, is currently under investigation. In this method, acoustic radiation force is used to apply localized forces within tissue (to tissue volumes on the order of 2 mm3) and the resulting tissue displacements are mapped using ultrasonic correlation based methods. A volume of tissue that is stiffer than the surrounding medium (i.e., a lesion) distributes the force throughout the tissue beneath it, resulting in larger regions of displacement, and smaller maximum displacements. The resulting displacement maps may be used to image tissue stiffness. A finite-element-model (FEM) of acoustic remote palpation is presented in this paper. Using this model, a parametric analysis of the affect of varying tissue and acoustic beam characteristics on radiation force induced tissue displacements is performed. The results are used to evaluate the potential of acoustic remote palpation to provide useful diagnostic information in a clinical setting. The potential for using a single diagnostic transducer to both generate radiation force and track the resulting displacements is investigated.

Authors
Nightingale, KR; Nightingale, RW; Palmeri, ML; Trahey, GE
MLA Citation
Nightingale, KR, Nightingale, RW, Palmeri, ML, and Trahey, GE. "A finite element model of remote palpation of breast lesions using radiation force: factors affecting tissue displacement." Ultrason Imaging 22.1 (January 2000): 35-54.
PMID
10823496
Source
pubmed
Published In
Ultrasonic Imaging
Volume
22
Issue
1
Publish Date
2000
Start Page
35
End Page
54
DOI
10.1177/016173460002200103

A finite element model for simulating acoustic streaming in cystic breast lesions with experimental validation.

Streaming detection is an ultrasonic technique that can be used to distinguish fluid-filled lesions, or cysts, from solid lesions. With this technique, high intensity ultrasound pulses are used to induce acoustic streaming in cyst fluid, and this motion is detected using Doppler flow estimation methods. Results from a pilot clinical study were recently published in which acoustic streaming was successfully induced and detected in 14 of 15 simple breast cysts and four of 14 sonographically indeterminate breast lesions in vivo. In the study, the detected velocities were found to vary considerably among cysts and for different pulsing regimes. A finite element model of streaming detection is presented. This model is utilized to investigate methods of increasing induced acoustic streaming velocity while minimizing patient exposure to high intensity ultrasound during streaming detection. Parameters studied include intensity, frequency, acoustic beam shape, cyst-diameter, cyst fluid protein concentration, and cyst fluid viscosity. The model, which provides both transient and steady-state solutions, is shown to predict trends in streaming velocity accurately. Experimental results from studies investigating the potential for nonlinear streaming enhancement in cysts are also provided.

Authors
Nightingale, KR; Trahey, GE
MLA Citation
Nightingale, KR, and Trahey, GE. "A finite element model for simulating acoustic streaming in cystic breast lesions with experimental validation." IEEE Trans Ultrason Ferroelectr Freq Control 47.1 (2000): 201-214.
PMID
18238532
Source
pubmed
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
47
Issue
1
Publish Date
2000
Start Page
201
End Page
214
DOI
10.1109/58.818763

Acoustic remote palpation: Initial in vivo results

An ultrasonic method for remote palpation of tissue is under investigation. In this method, a single ultrasonic transducer array is used to both apply localized radiation forces within tissue and to track the resulting displacements. The magnitude of the tissue displacement is inversely proportional to the local stiffness of the tissue. There are many possible clinical applications for this method, including detecting and characterizing soft tissue lesions, and detecting atherosclerosis. We have previously presented results from studies investigating the application of a single radiation force location in the presence and absence of a lesion in tissue-mimicking phantoms. In this paper, results are presented from in vivo experiments using a single pushing location, and phantom experiments in which multiple pushing locations are used to interrogate a two-dimensional Field of View (FOV). Displacements on the order of 10 to 30 microns are observed in vivo after 10 milliseconds of force application, and the resulting displacement images exhibit structural information about the tissue. Remote Palpation images generated using multiple pushing locations display local variations in tissue stiffness at high resolution. These results suggest considerable clinical potential for Remote Palpation imaging, and the potential for real-time implementation on commercial diagnostic scanners.

Authors
Nightingale, K; Palmeri, M; Nightingale, R; Trahey, G
MLA Citation
Nightingale, K, Palmeri, M, Nightingale, R, and Trahey, G. "Acoustic remote palpation: Initial in vivo results." 2000.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
2
Publish Date
2000
Start Page
1553
End Page
1558

The use of acoustic streaming in breast lesion diagnosis: a clinical study.

Results from a clinical study are presented, in which ultrasonically-induced acoustic streaming was successfully used to differentiate fluid-filled lesions (cysts) from solid lesions in the breast. In this study, high-intensity ultrasound pulses from a modified commercial scanner were used to induce acoustic streaming in cyst fluid, and this motion was detected using Doppler methods. Acoustic streaming was generated and detected in 14 of 15 simple cysts, and 4 of 14 sonographically indeterminate breast lesions. This lesion differentiation method appears to be particularly suited for diagnosis of small, possibly newer, cysts that appear indeterminate on conventional sonography due to their size. The results indicate that this method would be a useful adjunct to conventional sonography for the purpose of breast lesion classification.

Authors
Nightingale, KR; Kornguth, PJ; Trahey, GE
MLA Citation
Nightingale, KR, Kornguth, PJ, and Trahey, GE. "The use of acoustic streaming in breast lesion diagnosis: a clinical study." Ultrasound Med Biol 25.1 (January 1999): 75-87.
PMID
10048804
Source
pubmed
Published In
Ultrasound in Medicine & Biology
Volume
25
Issue
1
Publish Date
1999
Start Page
75
End Page
87

Finite element analysis of radiation force induced tissue motion with experimental validation

An ultrasonic radiation force-based method for remote palpation of tissue is investigated. The use of radiation force to image tissue stiffness has been proposed by several researchers. In this paper, the potential for using a diagnostic ultrasound system to both apply radiation force and track the resulting tissue displacements is investigated using Finite Element Methods (FEM), and the results are compared with experimental results. Remote palpation is accomplished by interspersing high intensity pushing beams with low intensity tracking beams. This generates localized radiation forces which can be applied throughout the tissue, with the resulting displacement patterns determined using correlation techniques. An area that is stiffer than the surrounding medium distributes the force, resulting in larger regions of displacement, and smaller maximum displacements. The resulting displacement maps provide information as to the location and size of regions of increased stiffness. We have developed an FEM model that predicts displacements resulting from acoustic radiation force fields generated by diagnostic transducers in various complex media. We perform a parametric analysis of varying tissue and acoustic beam characteristics on radiation force induced tissue displacements. Displacements are on the order of microns, with considerable differences in displacement patterns in the presence and absence of a lesion (or stiff inclusion). Initial experimental results are presented that support the findings in the model.

Authors
Nightingale, K; Nightingale, R; Palmeri, M; Trahey, G
MLA Citation
Nightingale, K, Nightingale, R, Palmeri, M, and Trahey, G. "Finite element analysis of radiation force induced tissue motion with experimental validation." 1999.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
2
Publish Date
1999
Start Page
1319
End Page
1323

Speckle decorrelation due to two-dimensional flow gradients.

The performance of ultrasonic velocity estimation methods is degraded by speckle decorrelation, the change in received echoes over time. Because ultrasonic speckle is formed by the complex sum of echoes from subresolution scatterers, it is sensitive to the relative motion of those scatterers. Velocity gradients in flowing blood result in relative scatterer motion and can be a significant source of speckle decorrelation. Computer simulations were performed to evaluate speckle decorrelation due to two-dimensional flow gradients. Results indicate that decorrelation due to flow gradients is sensitive to the angle of flow and has a maximum at a beam-vessel angle of 0 degrees , i.e., purely axial flow. A quantitative summary of the major factors causing speckle decorrelation indicates that flow gradients are the most significant contributors under the conditions modeled.

Authors
Friemel, BH; Bohs, LN; Nightingale, KR; Trahey, GE
MLA Citation
Friemel, BH, Bohs, LN, Nightingale, KR, and Trahey, GE. "Speckle decorrelation due to two-dimensional flow gradients." IEEE Trans Ultrason Ferroelectr Freq Control 45.2 (1998): 317-327.
PMID
18244183
Source
pubmed
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
45
Issue
2
Publish Date
1998
Start Page
317
End Page
327
DOI
10.1109/58.660142

A preliminary evaluation of the effects of primary and secondary radiation forces on acoustic contrast agents

Primary and secondary radiation forces result from pressure gradients in the incident and scattered ultrasonic fields. These forces and their dependence on experimental parameters are described, and the theory for primary radiation force is extended to consider a pulsed traveling wave. Both primary and secondary radiation forces are shown to have a significant effect on the flow of microbubbles through a small vessel during insonation. The primary radiation force produces displacement of microspheres across a 100 micron vessel radius for a small transmitted acoustic pressure. The displacement produced by primary radiation force is shown to display the expected linear dependence on the pulse repetition frequency and a nonlinear dependence on transmitted pressure. The secondary radiation force produces a reversible attraction and aggregation of microspheres with a significant attraction over a distance of approximately 100 microns. The magnitude of the secondary radiation force is proportional to the inverse of the squared separation distance, and thus two aggregates accelerate as they approach one another. We show that this force is sufficient to produce aggregates that remain intact for a physiologically appropriate shear rate. Brief interruption of acoustic transmission allows an immediate disruption of the aggregate. © 1997 IEEE.

Authors
Dayton, PA; Morgan, KE; Klibanov, AL; Brandenburger, G; Nightingale, KR; Ferrara, KW
MLA Citation
Dayton, PA, Morgan, KE, Klibanov, AL, Brandenburger, G, Nightingale, KR, and Ferrara, KW. "A preliminary evaluation of the effects of primary and secondary radiation forces on acoustic contrast agents." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 44.6 (1997): 1264-1277.
Source
scival
Published In
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume
44
Issue
6
Publish Date
1997
Start Page
1264
End Page
1277
DOI
10.1109/58.656630

Utilization of acoustic streaming to classify breast lesions in vivo

Results from a clinical study in which Streaming Detection was used to successfully differentiate fluid-filled lesions (cysts) from solid lesions in the breast are presented. Streaming Detection is an ultrasonic technique in which high intensity ultrasound pulses are used to induce acoustic streaming in cyst fluid, and this motion is detected using flow estimation methods. In fourteen of fifteen simple cysts acoustic streaming was generated and detected. Evidence of nonlinear enhancement of acoustic streaming was observed in several cysts. Streaming Detection was also performed on fourteen sonographically indeterminate breast lesions. Acoustic streaming was generated and detected in four of these lesions, each of which were relatively small (average size of 0.4×0.5 cm). It seems that Streaming Detection is particularly suited for diagnosis of small, possibly newer cysts which may appear indeterminate on conventional sonography due to their small size. These results indicate that Streaming Detection would be a useful adjunct to conventional sonography for the purpose of breast lesion classification.

Authors
Nightingale, K; Kornguth, P; Breit, S; Liu, S; Trahey, G
MLA Citation
Nightingale, K, Kornguth, P, Breit, S, Liu, S, and Trahey, G. "Utilization of acoustic streaming to classify breast lesions in vivo." 1997.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
2
Publish Date
1997
Start Page
1419
End Page
1422

Streaming detection: improvements in sensitivity

Streaming Detection is a new ultrasonic technique proposed to distinguish fluid-filled lesions, or cysts, from solid lesions in the breast. In this technique, high intensity ultrasound pulses are used to induce acoustic streaming in cyst fluid, and this motion is detected using flow estimation methods. Results from a pilot clinical study were presented previously in which acoustic streaming was successfully induced and detected in six of seven known cystic lesions in vivo. However, the detected velocities were fairly slow (less than 4 cm/sec), and in some cases the velocities were only detected intermittently. We have conducted finite element simulations and phantom experiments with the goal of increasing the induced acoustic streaming velocity while minimizing patient exposure. Parameters that have been studied include: intensity, transmit aperture size and cyst diameter. We have also investigated the use of clutter filters with optimal slow flow detection capabilities. Results from these studies are presented along with their implications for future implementation of Streaming Detection.

Authors
Nightingale, KR; Kornguth, PJ; Trahey, GE
MLA Citation
Nightingale, KR, Kornguth, PJ, and Trahey, GE. "Streaming detection: improvements in sensitivity." 1996.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
2
Publish Date
1996
Start Page
1261
End Page
1264

Three-dimensional flow images by reconstruction from two-dimensional vector velocity maps.

A method for constructing three-dimensional images of flow is described. The technique involves the acquisition of numerous closely spaced planes, each comprised of a map of the two-dimensional velocities measured in that plane. Each such vector velocity map is formed by tracking the motion of small regions of ultrasonic speckle between two ultrasonic acquisitions separated by a short time interval. In contrast to current Doppler velocity methods, this technique measures both the axial and lateral components of flow and is not subject to aliasing. The resulting series of two-dimensional vector velocity maps is then combined into a three-dimensional data set, which can be manipulated with appropriate software to yield quantitative three-dimensional displays of the flow within the interrogated volume. In this article we present such images obtained from measurements of in vitro laminar flow in a vessel, as well as a free jet phantom. The results allow comprehensive visualization of the three-dimensional flow characteristics, indicating promise for more complete and quantitative clinical assessment of blood flow.

Authors
Bohs, LN; Friemel, BH; Kisslo, J; Harfe, DT; Nightingale, KR; Trahey, GE
MLA Citation
Bohs, LN, Friemel, BH, Kisslo, J, Harfe, DT, Nightingale, KR, and Trahey, GE. "Three-dimensional flow images by reconstruction from two-dimensional vector velocity maps." J Am Soc Echocardiogr 8.6 (November 1995): 915-923.
PMID
8611292
Source
pubmed
Published In
Journal of the American Society of Echocardiography
Volume
8
Issue
6
Publish Date
1995
Start Page
915
End Page
923

A novel ultrasonic technique for differentiating cysts from solid lesions: preliminary results in the breast.

The feasibility of a new ultrasonic technique to distinguish cysts from solid lesions is explored. High intensity pulses are used to induce acoustic streaming in cyst fluid, and this motion is detected using Doppler techniques. Acoustic streaming cannot be generated in solid lesions, therefore, its detection would indicate a cyst. In six of seven breast cysts motion was clearly generated and detected in vivo. Ultrasonic pulses with intensities up to 4.4 W cm-2 (I(spta) in water) were focused on the cysts for 10 s. Lesion diameters ranged from 0.6 to 2.5 cm; induced flow velocities were less than 4.0 cm s-1.

Authors
Nightingale, KR; Kornguth, PJ; Walker, WF; McDermott, BA; Trahey, GE
MLA Citation
Nightingale, KR, Kornguth, PJ, Walker, WF, McDermott, BA, and Trahey, GE. "A novel ultrasonic technique for differentiating cysts from solid lesions: preliminary results in the breast." Ultrasound Med Biol 21.6 (1995): 745-751.
PMID
8571462
Source
pubmed
Published In
Ultrasound in Medicine & Biology
Volume
21
Issue
6
Publish Date
1995
Start Page
745
End Page
751

Ensemble tracking: a new method for 2D vector velocity measurement

We described a new method, called ensemble tracking, for quantifying two dimensional velocities. Compared to previous two-dimensional speckle tracking techniques, ensemble tracking measures motion over smaller translations, thereby reducing errors due to speckle decorrelation. The technique involves acquisition of an ensemble of 2D line sets along a single line of sight using parallel receive processing. This ensemble may be thought of as a sequence of 2D 'snapshots' of the same spatial region at different time instants. A kernel region in each snapshot is tracked within slightly larger search regions in subsequent snapshots, providing velocity estimates at multiple time lags. Interpolation is employed to provide velocity estimates for sub-pixel translations that occur in the short time intervals between parallel acquisitions. We present the results of initial computer simulations indicating the ability to track such sub-pixel translations, and discuss directions for further research in this area.

Authors
Bohs, LN; Geiman, BJ; Nightingale, KR; Choi, CD; Friemel, BH; Trahey, GE
MLA Citation
Bohs, LN, Geiman, BJ, Nightingale, KR, Choi, CD, Friemel, BH, and Trahey, GE. "Ensemble tracking: a new method for 2D vector velocity measurement." Proceedings of the IEEE Ultrasonics Symposium 2 (1995): 1485-1488.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
2
Publish Date
1995
Start Page
1485
End Page
1488

Generation and detection of acoustic streaming to differentiate between solid and cystic breast lesions

Results from both a pilot clinical study and phantom studies performed to evaluate a new ultrasonic technique to distinguish cysts from solid lesions are presented. High intensity pulses are used to induce acoustic streaming in cyst fluid, and this motion is detected using existing flow detection techniques. Since acoustic streaming cannot be generated in solid lesions, its detection would indicate a cyst. In six of seven breast cysts streaming was generated and detected in vivo. In phantom studies, a direct relationship between streaming velocity and cyst size and an indirect relationship between streaming velocity and cyst fluid viscosity were demonstrated.

Authors
Nightingale, KR; Kornguth, PJ; Walker, WF; Glasgow, SC; Jett, EA; Trahey, GE
MLA Citation
Nightingale, KR, Kornguth, PJ, Walker, WF, Glasgow, SC, Jett, EA, and Trahey, GE. "Generation and detection of acoustic streaming to differentiate between solid and cystic breast lesions." Proceedings of the IEEE Ultrasonics Symposium 3 (1994): 1653-1656.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
3
Publish Date
1994
Start Page
1653
End Page
1656

Three-dimensional flow visualization via reconstruction from successive two-dimensional vector velocity maps

A translation system has been assembled to assist in high speed acquisition of parallel planes of ultrasonic data from phantoms and human tissue. Using a previously developed system that measures two-dimensional velocities in real time by tracking speckle patterns, evenly spaced two-dimensional vector maps of flow in a free turbulent jet phantom were obtained. These vector maps were then combined using visualization software to produce three-dimensional representations of the flow. Results indicate that three-dimensional flow characteristics may be examined from the reconstructed images.

Authors
Alsberg, E; Trahey, GE; Bohs, LN; Friemel, BH; Nightingale, KR; Walker, WF
MLA Citation
Alsberg, E, Trahey, GE, Bohs, LN, Friemel, BH, Nightingale, KR, and Walker, WF. "Three-dimensional flow visualization via reconstruction from successive two-dimensional vector velocity maps." 1994.
Source
scival
Published In
Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
Volume
16
Issue
pt 1
Publish Date
1994
Start Page
598
End Page
599

3-DIMENSIONAL FLOW VISUALIZATION VIA RECONSTRUCTION FROM SUCCESSIVE 2-DIMENSIONAL VECTOR VELOCITY MAPS

Authors
ALSBERG, E; TRAHEY, GE; BOHS, LN; FRIEMEL, BH; NIGHTINGALE, KR; WALKER, WF
MLA Citation
ALSBERG, E, TRAHEY, GE, BOHS, LN, FRIEMEL, BH, NIGHTINGALE, KR, and WALKER, WF. "3-DIMENSIONAL FLOW VISUALIZATION VIA RECONSTRUCTION FROM SUCCESSIVE 2-DIMENSIONAL VECTOR VELOCITY MAPS." PROCEEDINGS OF THE 16TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY - ENGINEERING ADVANCES: NEW OPPORTUNITIES FOR BIOMEDICAL ENGINEERS, PTS 1&2 (1994): 598-599.
Source
wos-lite
Published In
PROCEEDINGS OF THE 16TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY - ENGINEERING ADVANCES: NEW OPPORTUNITIES FOR BIOMEDICAL ENGINEERS, PTS 1&2
Publish Date
1994
Start Page
598
End Page
599
DOI
10.1109/IEMBS.1994.411884

Wall filtering challenges in two-dimensional vector velocity estimation

To formulate a clinically viable methodology for tracking blood flow in two dimensions using ultrasound, one must address some challenges posed by the physical limitations of the imaging modality. At the frequencies of interest in medical diagnostic imaging, the echoes from blood are much smaller (often 40-60 dB) than those from the surrounding vessel walls. A blood velocity estimation technique must isolate the blood echo from that of the wall, and that is most often accomplished through the use of wall filters. The conventional application of wall filters to two-dimensional velocity estimation is aggravated, however, by the fact that the azimuthal spatial frequency content of conventional two-dimensional ultrasound scans is typically 5-10 times smaller than the axial spatial frequency content. In this paper, we pose the problem of isolating the blood signal within the composite blood/wall/noise signal received by the imaging system and estimate the effectiveness of wall filters to eliminate stationary echoes from both the axial and azimuthal components of motion.

Authors
Friemel, BH; Nightingale, KR; Bohs, LN; Trahey, GE
MLA Citation
Friemel, BH, Nightingale, KR, Bohs, LN, and Trahey, GE. "Wall filtering challenges in two-dimensional vector velocity estimation." 1993.
Source
scival
Published In
Proceedings of the IEEE Ultrasonics Symposium
Volume
2
Publish Date
1993
Start Page
1031
End Page
1034
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Research Areas:

  • Acoustics
  • Active learning
  • Biomechanics
  • Blood
  • Blood-Brain Barrier
  • Catheter Ablation
  • Computer Simulation
  • Contrast Media
  • Diagnostic Imaging
  • Elasticity
  • Elasticity Imaging Techniques
  • Equipment Design
  • Fatty Liver
  • Finite Element Analysis
  • Image Processing, Computer-Assisted
  • Imaging, Three-Dimensional
  • Liver
  • Liver Cirrhosis, Experimental
  • Muscle, Skeletal
  • Palpation
  • Phantoms, Imaging
  • Prostate
  • Skin
  • Transducers
  • Ultrasonic Therapy
  • Ultrasonics
  • Ultrasonography
  • Ultrasonography, Interventional
  • Ultrasonography, Mammary
  • Urine
  • Viscosity
  • Water