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Ren, Lei

Overview:

Dr. Ren's research interests include imaging dose reduction using digital tomosynthesis (DTS), cone-beam CT (CBCT) scatter correction, novel DTS/CBCT image reconstruction methods using prior information and motion modeling, image guided radiation therapy (IGRT), deformable image registration, patient clinical objective QA methods, stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT).       

Positions:

Associate Professor of Radiation Oncology

Radiation Oncology
School of Medicine

Member of the Duke Cancer Institute

Duke Cancer Institute
School of Medicine

Education:

Ph.D. 2009

Ph.D. — Duke University

Medical Physics Faculty, Radiation Oncology, Radiation Oncology

Henry Ford Health System

Grants:

A Limited-angle Intra-fractional Verification (LIVE) System for SBRT Treatments

Administered By
Radiation Oncology
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
December 12, 2014
End Date
November 30, 2018

A synchronized moving grid (SMOG) system to improve CBCT for IGRT and ART

Administered By
Radiation Oncology
AwardedBy
Indiana University
Role
Principal Investigator
Start Date
June 01, 2016
End Date
May 31, 2017

A synchronized moving grid system to improve CBCT for IGRT and ART

Administered By
Radiation Oncology
AwardedBy
Georgia Regents University
Role
Principal Investigator
Start Date
August 27, 2013
End Date
March 28, 2016

Awards:

ASTRO Annual Meeting Basic Science Abstract Award. American Society for Radiation Oncology (ASTRO).

Type
National
Awarded By
American Society for Radiation Oncology (ASTRO)
Date
January 01, 2010

Publications:

Respiratory signal prediction based on adaptive boosting and multi-layer perceptron neural network.

To improve the prediction accuracy of respiratory signals using adaptive boosting and multi-layer perceptron neural network (ADMLP-NN) for gated treatment of moving target in radiation therapy. The respiratory signals acquired using a real-time position management (RPM) device from 138 previous 4DCT scans were retrospectively used in this study. The ADMLP-NN was composed of several artificial neural networks (ANNs) which were used as weaker predictors to compose a stronger predictor. The respiratory signal was initially smoothed using a Savitzky-Golay finite impulse response smoothing filter (S-G filter). Then, several similar multi-layer perceptron neural networks (MLP-NNs) were configured to estimate future respiratory signal position from its previous positions. Finally, an adaptive boosting (Adaboost) decision algorithm was used to set weights for each MLP-NN based on the sample prediction error of each MLP-NN. Two prediction methods, MLP-NN and ADMLP-NN (MLP-NN plus adaptive boosting), were evaluated by calculating correlation coefficient and root-mean-square-error between true and predicted signals. For predicting 500 ms ahead of prediction, average correlation coefficients were improved from 0.83 (MLP-NN method) to 0.89 (ADMLP-NN method). The average of root-mean-square-error (relative unit) for 500 ms ahead of prediction using ADMLP-NN were reduced by 27.9%, compared to those using MLP-NN. The preliminary results demonstrate that the ADMLP-NN respiratory prediction method is more accurate than the MLP-NN method and can improve the respiration prediction accuracy.

Authors
Sun, WZ; Jiang, MY; Ren, L; Dang, J; You, T; Yin, F-F
MLA Citation
Sun, WZ, Jiang, MY, Ren, L, Dang, J, You, T, and Yin, F-F. "Respiratory signal prediction based on adaptive boosting and multi-layer perceptron neural network." Physics in medicine and biology 62.17 (August 2017): 6822-6835.
PMID
28665297
Source
epmc
Published In
Physics in Medicine and Biology
Volume
62
Issue
17
Publish Date
2017
Start Page
6822
End Page
6835
DOI
10.1088/1361-6560/aa7cd4

Reducing scan angle using adaptive prior knowledge for a limited-angle intrafraction verification (LIVE) system for conformal arc radiotherapy.

The purpose of this study is to develop an adaptive prior knowledge guided image estimation technique to reduce the scan angle needed in the limited-angle intrafraction verification (LIVE) system for 4D-CBCT reconstruction. The LIVE system has been previously developed to reconstruct 4D volumetric images on-the-fly during arc treatment for intrafraction target verification and dose calculation. In this study, we developed an adaptive constrained free-form deformation reconstruction technique in LIVE to further reduce the scanning angle needed to reconstruct the 4D-CBCT images for faster intrafraction verification. This technique uses free form deformation with energy minimization to deform prior images to estimate 4D-CBCT based on kV-MV projections acquired in extremely limited angle (orthogonal 3°) during the treatment. Note that the prior images are adaptively updated using the latest CBCT images reconstructed by LIVE during treatment to utilize the continuity of the respiratory motion. The 4D digital extended-cardiac-torso (XCAT) phantom and a CIRS 008A dynamic thoracic phantom were used to evaluate the effectiveness of this technique. The reconstruction accuracy of the technique was evaluated by calculating both the center-of-mass-shift (COMS) and 3D volume-percentage-difference (VPD) of the tumor in reconstructed images and the true on-board images. The performance of the technique was also assessed with varied breathing signals against scanning angle, lesion size, lesion location, projection sampling interval, and scanning direction. In the XCAT study, using orthogonal-view of 3° kV and portal MV projections, this technique achieved an average tumor COMS/VPD of 0.4  ±  0.1 mm/5.5  ±  2.2%, 0.6  ±  0.3 mm/7.2  ±  2.8%, 0.5  ±  0.2 mm/7.1  ±  2.6%, 0.6  ±  0.2 mm/8.3  ±  2.4%, for baseline drift, amplitude variation, phase shift, and patient breathing signal variation, respectively. In the CIRS phantom study, this technique achieved an average tumor COMS/VPD of 0.7  ±  0.1 mm/7.5  ±  1.3% for a 3 cm lesion and 0.6  ±  0.2 mm/11.4  ±  1.5% for a 2 cm lesion in the baseline drift case. The average tumor COMS/VPD were 0.5  ±  0.2 mm/10.8  ±  1.4%, 0.4  ±  0.3 mm/7.3  ±  2.9%, 0.4  ±  0.2 mm/7.4  ±  2.5%, 0.4  ±  0.2 mm/7.3  ±  2.8% for the four real patient breathing signals, respectively. Results demonstrated that the adaptive prior knowledge guided image estimation technique with LIVE system is robust against scanning angle, lesion size, location and scanning direction. It can estimate on-board images accurately with as little as 6 projections in orthogonal-view 3° angle. In conclusion, adaptive prior knowledge guided image reconstruction technique accurately estimates 4D-CBCT images using extremely-limited angle and projections. This technique greatly improves the efficiency and accuracy of LIVE system for ultrafast 4D intrafraction verification of lung SBRT treatments.

Authors
Zhang, Y; Yin, F-F; Zhang, Y; Ren, L
MLA Citation
Zhang, Y, Yin, F-F, Zhang, Y, and Ren, L. "Reducing scan angle using adaptive prior knowledge for a limited-angle intrafraction verification (LIVE) system for conformal arc radiotherapy." Physics in medicine and biology 62.9 (May 2017): 3859-3882.
PMID
28338470
Source
epmc
Published In
Physics in Medicine and Biology
Volume
62
Issue
9
Publish Date
2017
Start Page
3859
End Page
3882
DOI
10.1088/1361-6560/aa6913

Estimating 4D-CBCT from prior information and extremely limited angle projections using structural PCA and weighted free-form deformation for lung radiotherapy.

To investigate the feasibility of using structural-based principal component analysis (PCA) motion-modeling and weighted free-form deformation to estimate on-board 4D-CBCT using prior information and extremely limited angle projections for potential 4D target verification of lung radiotherapy.A technique for lung 4D-CBCT reconstruction has been previously developed using a deformation field map (DFM)-based strategy. In the previous method, each phase of the 4D-CBCT was generated by deforming a prior CT volume. The DFM was solved by a motion model extracted by a global PCA and free-form deformation (GMM-FD) technique, using a data fidelity constraint and deformation energy minimization. In this study, a new structural PCA method was developed to build a structural motion model (SMM) by accounting for potential relative motion pattern changes between different anatomical structures from simulation to treatment. The motion model extracted from planning 4DCT was divided into two structures: tumor and body excluding tumor, and the parameters of both structures were optimized together. Weighted free-form deformation (WFD) was employed afterwards to introduce flexibility in adjusting the weightings of different structures in the data fidelity constraint based on clinical interests. XCAT (computerized patient model) simulation with a 30 mm diameter lesion was simulated with various anatomical and respiratory changes from planning 4D-CT to on-board volume to evaluate the method. The estimation accuracy was evaluated by the volume percent difference (VPD)/center-of-mass-shift (COMS) between lesions in the estimated and "ground-truth" on-board 4D-CBCT. Different on-board projection acquisition scenarios and projection noise levels were simulated to investigate their effects on the estimation accuracy. The method was also evaluated against three lung patients.The SMM-WFD method achieved substantially better accuracy than the GMM-FD method for CBCT estimation using extremely small scan angles or projections. Using orthogonal 15° scanning angles, the VPD/COMS were 3.47 ± 2.94% and 0.23 ± 0.22 mm for SMM-WFD and 25.23 ± 19.01% and 2.58 ± 2.54 mm for GMM-FD among all eight XCAT scenarios. Compared to GMM-FD, SMM-WFD was more robust against reduction of the scanning angles down to orthogonal 10° with VPD/COMS of 6.21 ± 5.61% and 0.39 ± 0.49 mm, and more robust against reduction of projection numbers down to only 8 projections in total for both orthogonal-view 30° and orthogonal-view 15° scan angles. SMM-WFD method was also more robust than the GMM-FD method against increasing levels of noise in the projection images. Additionally, the SMM-WFD technique provided better tumor estimation for all three lung patients compared to the GMM-FD technique.Compared to the GMM-FD technique, the SMM-WFD technique can substantially improve the 4D-CBCT estimation accuracy using extremely small scan angles and low number of projections to provide fast low dose 4D target verification.

Authors
Harris, W; Zhang, Y; Yin, F-F; Ren, L
MLA Citation
Harris, W, Zhang, Y, Yin, F-F, and Ren, L. "Estimating 4D-CBCT from prior information and extremely limited angle projections using structural PCA and weighted free-form deformation for lung radiotherapy." Medical physics 44.3 (March 2017): 1089-1104.
PMID
28079267
Source
epmc
Published In
Medical physics
Volume
44
Issue
3
Publish Date
2017
Start Page
1089
End Page
1104
DOI
10.1002/mp.12102

Clinical Study of Orthogonal-View Phase-Matched Digital Tomosynthesis for Lung Tumor Localization.

Compared to cone-beam computed tomography, digital tomosynthesis imaging has the benefits of shorter scanning time, less imaging dose, and better mechanical clearance for tumor localization in radiation therapy. However, for lung tumors, the localization accuracy of the conventional digital tomosynthesis technique is affected by the lack of depth information and the existence of lung tumor motion. This study investigates the clinical feasibility of using an orthogonal-view phase-matched digital tomosynthesis technique to improve the accuracy of lung tumor localization.The proposed orthogonal-view phase-matched digital tomosynthesis technique benefits from 2 major features: (1) it acquires orthogonal-view projections to improve the depth information in reconstructed digital tomosynthesis images and (2) it applies respiratory phase-matching to incorporate patient motion information into the synthesized reference digital tomosynthesis sets, which helps to improve the localization accuracy of moving lung tumors. A retrospective study enrolling 14 patients was performed to evaluate the accuracy of the orthogonal-view phase-matched digital tomosynthesis technique. Phantom studies were also performed using an anthropomorphic phantom to investigate the feasibility of using intratreatment aggregated kV and beams' eye view cine MV projections for orthogonal-view phase-matched digital tomosynthesis imaging. The localization accuracy of the orthogonal-view phase-matched digital tomosynthesis technique was compared to that of the single-view digital tomosynthesis techniques and the digital tomosynthesis techniques without phase-matching.The orthogonal-view phase-matched digital tomosynthesis technique outperforms the other digital tomosynthesis techniques in tumor localization accuracy for both the patient study and the phantom study. For the patient study, the orthogonal-view phase-matched digital tomosynthesis technique localizes the tumor to an average (± standard deviation) error of 1.8 (0.7) mm for a 30° total scan angle. For the phantom study using aggregated kV-MV projections, the orthogonal-view phase-matched digital tomosynthesis localizes the tumor to an average error within 1 mm for varying magnitudes of scan angles.The pilot clinical study shows that the orthogonal-view phase-matched digital tomosynthesis technique enables fast and accurate localization of moving lung tumors.

Authors
Zhang, Y; Ren, L; Vergalasova, I; Yin, F-F
MLA Citation
Zhang, Y, Ren, L, Vergalasova, I, and Yin, F-F. "Clinical Study of Orthogonal-View Phase-Matched Digital Tomosynthesis for Lung Tumor Localization." Technology in cancer research & treatment (January 2017): 1533034617705716-.
PMID
28449625
Source
epmc
Published In
Technology in cancer research & treatment
Publish Date
2017
Start Page
1533034617705716
DOI
10.1177/1533034617705716

Development of a Computerized 4-D MRI Phantom for Liver Motion Study.

To develop a 4-dimensional computerized magnetic resonance imaging phantom with image textures extracted from real patient scans for liver motion studies.The proposed phantom was developed based on the current version of 4-dimensional extended cardiac-torso computerized phantom and a clinical magnetic resonance scan. Initially, the extended cardiac-torso phantom was voxelized in abdominal-chest region at the end of exhalation phase. Structures/tissues were classified into 4 categories: (1) Seven key textured organs, including liver, gallbladder, spleen, stomach, heart, kidneys, and pancreas, were mapped from a clinical T1-weighted liver magnetic resonance scan using deformable registration. (2) Large textured soft tissue volumes were simulated via an iterative pattern generation method using the same magnetic resonance scan. (3) Lung and intestine structures were generated by assigning uniform intensity with proper noise modeling. (4) Bony structures were generated by assigning the magnetic resonance values. A spherical hypointensity tumor was inserted into the liver. Other respiratory phases of the 4-dimensional phantom were generated using the backward deformation vector fields exported by the extended cardiac-torso program, except that bony structures were generated separately for each phase. A weighted image filtering process was utilized to improve the overall tissue smoothness at each phase.Three 4-dimensional series with different motion amplitudes were generated. The developed motion phantom produced good illustrations of abdominal-chest region with anatomical structures in key organs and texture patterns in large soft tissue volumes. In a standard series, the tumor volume was measured as 13.90 ± 0.11 cm3 in a respiratory cycle and the tumor's maximum center-of-mass shift was 2.95 cm/1.84 cm on superior-inferior/anterior-posterior directions. The organ motion during the respiratory cycle was well rendered. The developed motion phantom has the flexibility of motion pattern variation, organ geometry variation, and tumor modeling variation.A 4-D computerized phantom was developed and could be used to produce image series with synthetic magnetic resonance textures for magnetic resonance imaging research of liver motion.

Authors
Wang, C; Yin, F-F; Segars, WP; Chang, Z; Ren, L
MLA Citation
Wang, C, Yin, F-F, Segars, WP, Chang, Z, and Ren, L. "Development of a Computerized 4-D MRI Phantom for Liver Motion Study." Technology in cancer research & treatment (January 2017): 1533034617723753-.
PMID
28789598
Source
epmc
Published In
Technology in cancer research & treatment
Publish Date
2017
Start Page
1533034617723753
DOI
10.1177/1533034617723753

Sensitivity of 3D Dose Verification to Multileaf Collimator Misalignments in Stereotactic Body Radiation Therapy of Spinal Tumor.

This study aimed to detect the sensitivity of Delt 4 on ordinary field multileaf collimator misalignments, system misalignments, random misalignments, and misalignments caused by gravity of the multileaf collimator in stereotactic body radiation therapy.(1) Two field sizes, including 2.00 cm (X) × 6.00 cm (Y) and 7.00 cm (X) × 6.00 cm (Y), were set. The leaves of X1 and X2 in the multileaf collimator were simultaneously opened. (2) Three cases of stereotactic body radiation therapy of spinal tumor were used. The dose of the planning target volume was 1800 cGy with 3 fractions. The 4 types to be simulated included (1) the leaves of X1 and X2 in the multileaf collimator were simultaneously opened, (2) only X1 of the multileaf collimator and the unilateral leaf were opened, (3) the leaves of X1 and X2 in the multileaf collimator were randomly opened, and (4) gravity effect was simulated. The leaves of X1 and X2 in the multileaf collimator shifted to the same direction. The difference between the corresponding 3-dimensional dose distribution measured by Delt 4 and the dose distribution in the original plan made in the treatment planning system was analyzed with γ index criteria of 3.0 mm/3.0%, 2.5 mm/2.5%, 2.0 mm/2.0%, 2.5 mm/1.5%, and 1.0 mm/1.0%.(1) In the field size of 2.00 cm (X) × 6.00 cm (Y), the γ pass rate of the original was 100% with 2.5 mm/2.5% as the statistical standard. The pass rate decreased to 95.9% and 89.4% when the X1 and X2 directions of the multileaf collimator were opened within 0.3 and 0.5 mm, respectively. In the field size of 7.00 (X) cm × 6.00 (Y) cm with 1.5 mm/1.5% as the statistical standard, the pass rate of the original was 96.5%. After X1 and X2 of the multileaf collimator were opened within 0.3 mm, the pass rate decreased to lower than 95%. The pass rate was higher than 90% within the 3 mm opening. (2) For spinal tumor, the change in the planning target volume V18 under various modes calculated using treatment planning system was within 1%. However, the maximum dose deviation of the spinal cord was high. In the spinal cord with a gravity of -0.25 mm, the maximum dose deviation minimally changed and increased by 6.8% than that of the original. In the largest opening of 1.00 mm, the deviation increased by 47.7% than that of the original. Moreover, the pass rate of the original determined through Delt 4 was 100% with 3 mm/3% as the statistical standard. The pass rate was 97.5% in the 0.25 mm opening and higher than 95% in the 0.5 mm opening A, 0.25 mm opening A, whole gravity series, and 0.20 mm random opening. Moreover, the pass rate was higher than 90% with 2.0 mm/2.0% as the statistical standard in the original and in the 0.25 mm gravity. The difference in the pass rates was not statistically significant among the -0.25 mm gravity, 0.25 mm opening A, 0.20 mm random opening, and original as calculated using SPSS 11.0 software with P > .05.Different analysis standards of Delt 4 were analyzed in different field sizes to improve the detection sensitivity of the multileaf collimator position on the basis of 90% throughout rate. In stereotactic body radiation therapy of spinal tumor, the 2.0 mm/2.0% standard can reveal the dosimetric differences caused by the minor multileaf collimator position compared with the 3.0 mm/3.0% statistical standard. However, some position derivations of the misalignments that caused high dose amount to the spinal cord cannot be detected. However, some misalignments were not detected when a large number of multileaf collimator were administered into the spinal cord.

Authors
Xin-Ye, N; Ren, L; Yan, H; Yin, F-F
MLA Citation
Xin-Ye, N, Ren, L, Yan, H, and Yin, F-F. "Sensitivity of 3D Dose Verification to Multileaf Collimator Misalignments in Stereotactic Body Radiation Therapy of Spinal Tumor." Technology in cancer research & treatment 15.6 (December 2016): NP25-NP34.
PMID
26525748
Source
epmc
Published In
Technology in cancer research & treatment
Volume
15
Issue
6
Publish Date
2016
Start Page
NP25
End Page
NP34
DOI
10.1177/1533034615610251

Development of a Machine Learning Methodology to Estimate Lung Stereotactic Body Radiation Therapy Dosimetric Endpoints Based on Patient-Specific Anatomic Features

Authors
Lafata, K; Cai, J; Ren, L; Wu, Q; Hong, JC; Kelsey, CR; Yin, FF
MLA Citation
Lafata, K, Cai, J, Ren, L, Wu, Q, Hong, JC, Kelsey, CR, and Yin, FF. "Development of a Machine Learning Methodology to Estimate Lung Stereotactic Body Radiation Therapy Dosimetric Endpoints Based on Patient-Specific Anatomic Features." October 1, 2016.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
96
Issue
2
Publish Date
2016
Start Page
E420
End Page
E421

Ultrafast Volumetric Cine Magnetic Resonance Imaging (UVC-MRI) for Real-Time 3-Dimensional Target Localization/Tracking

Authors
Harris, W; Yin, FF; Wang, C; Chang, Z; Cai, J; Zhang, Y; Ren, L
MLA Citation
Harris, W, Yin, FF, Wang, C, Chang, Z, Cai, J, Zhang, Y, and Ren, L. "Ultrafast Volumetric Cine Magnetic Resonance Imaging (UVC-MRI) for Real-Time 3-Dimensional Target Localization/Tracking." October 1, 2016.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
96
Issue
2
Publish Date
2016
Start Page
E626
End Page
E626

Ultrafast Volumetric Cine Magnetic Resonance Imaging (UVC-MRI) for Real-Time 3-Dimensional Target Localization/Tracking

Authors
Harris, W; Yin, FF; Wang, C; Chang, Z; Cai, J; Zhang, Y; Ren, L
MLA Citation
Harris, W, Yin, FF, Wang, C, Chang, Z, Cai, J, Zhang, Y, and Ren, L. "Ultrafast Volumetric Cine Magnetic Resonance Imaging (UVC-MRI) for Real-Time 3-Dimensional Target Localization/Tracking." October 1, 2016.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
96
Issue
2
Publish Date
2016
Start Page
E626
End Page
E626

Development of a Machine Learning Methodology to Estimate Lung Stereotactic Body Radiation Therapy Dosimetric Endpoints Based on Patient-Specific Anatomic Features

Authors
Lafata, K; Cai, J; Ren, L; Wu, Q; Hong, JC; Kelsey, CR; Yin, FF
MLA Citation
Lafata, K, Cai, J, Ren, L, Wu, Q, Hong, JC, Kelsey, CR, and Yin, FF. "Development of a Machine Learning Methodology to Estimate Lung Stereotactic Body Radiation Therapy Dosimetric Endpoints Based on Patient-Specific Anatomic Features." October 1, 2016.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
96
Issue
2
Publish Date
2016
Start Page
E420
End Page
E421

Development of a Machine Learning Methodology to Estimate Lung Stereotactic Body Radiation Therapy Dosimetric Endpoints Based on Patient-Specific Anatomic Features.

Authors
Lafata, K; Cai, J; Ren, L; Wu, Q; Hong, JC; Kelsey, CR; Yin, FF
MLA Citation
Lafata, K, Cai, J, Ren, L, Wu, Q, Hong, JC, Kelsey, CR, and Yin, FF. "Development of a Machine Learning Methodology to Estimate Lung Stereotactic Body Radiation Therapy Dosimetric Endpoints Based on Patient-Specific Anatomic Features." International journal of radiation oncology, biology, physics 96.2S (October 2016): E420-E421.
PMID
27674646
Source
epmc
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
96
Issue
2S
Publish Date
2016
Start Page
E420
End Page
E421
DOI
10.1016/j.ijrobp.2016.06.1687

Ultrafast Volumetric Cine Magnetic Resonance Imaging (UVC-MRI) for Real-Time 3-Dimensional Target Localization/Tracking.

Authors
Harris, W; Yin, FF; Wang, C; Chang, Z; Cai, J; Zhang, Y; Ren, L
MLA Citation
Harris, W, Yin, FF, Wang, C, Chang, Z, Cai, J, Zhang, Y, and Ren, L. "Ultrafast Volumetric Cine Magnetic Resonance Imaging (UVC-MRI) for Real-Time 3-Dimensional Target Localization/Tracking." International journal of radiation oncology, biology, physics 96.2S (October 2016): E626-.
PMID
27675199
Source
epmc
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
96
Issue
2S
Publish Date
2016
Start Page
E626
DOI
10.1016/j.ijrobp.2016.06.2196

Scatter Reduction and Correction for Dual-Source Cone-Beam CT Using Prepatient Grids.

Scatter significantly limits the application of the dual-source cone-beam computed tomography by inducing scatter artifacts and degrading contrast-to-noise ratio, Hounsfield-unit accuracy, and image uniformity. Although our previously developed interleaved acquisition mode addressed the cross scatter between the 2 X-ray sources, it doubles the scanning time and doesn't address the forward scatter issue. This study aims to develop a prepatient grid system to address both forward scatter and cross scatter in the dual-source cone-beam computed tomography.Grids attached to both X-ray sources provide physical scatter reduction during the image acquisition. Image data were measured in the unblocked region, while both forward scatter and cross scatter were measured in the blocked region of the projection for postscan scatter correction. Complementary projections were acquired with grids at complementary locations and were merged to form complete projections for reconstruction. Experiments were conducted with different phantom sizes, grid blocking ratios, image acquisition modes, and reconstruction algorithms to investigate their effects on the scatter reduction and correction. The image quality improvement by the prepatient grids was evaluated both qualitatively through the artifact reduction and quantitatively through contrast-to-noise ratio, Hounsfield-unit accuracy, and uniformity using a CATphan 504 phantom.Scatter artifacts were reduced by scatter reduction and were removed by scatter correction method. Contrast-to-noise ratio, Hounsfield-unit accuracy, and image uniformity were improved substantially. The simultaneous acquisition mode achieved comparable contrast-to-noise ratio as the interleaved and sequential modes after scatter reduction and correction. Higher grid blocking ratio and smaller phantom size led to higher contrast-to-noise ratio for the simultaneous mode. The iterative reconstruction with total variation regularization was more effective than the Feldkamp, Davis, and Kress method in reducing noise caused by the scatter correction to enhance contrast-to-noise ratio.The prepatient grid system is effective in removing the scatter effects in the simultaneous acquisition mode of the dual-source cone-beam computed tomography, which is useful for scanning time reduction or dual energy imaging.

Authors
Ren, L; Chen, Y; Zhang, Y; Giles, W; Jin, J; Yin, F-F
MLA Citation
Ren, L, Chen, Y, Zhang, Y, Giles, W, Jin, J, and Yin, F-F. "Scatter Reduction and Correction for Dual-Source Cone-Beam CT Using Prepatient Grids." Technology in cancer research & treatment 15.3 (June 2016): 416-427.
PMID
26009495
Source
epmc
Published In
Technology in cancer research & treatment
Volume
15
Issue
3
Publish Date
2016
Start Page
416
End Page
427
DOI
10.1177/1533034615587615

A Technique for Generating Volumetric Cine-Magnetic Resonance Imaging.

The purpose of this study was to develop a techique to generate on-board volumetric cine-magnetic resonance imaging (VC-MRI) using patient prior images, motion modeling, and on-board 2-dimensional cine MRI.One phase of a 4-dimensional MRI acquired during patient simulation is used as patient prior images. Three major respiratory deformation patterns of the patient are extracted from 4-dimensional MRI based on principal-component analysis. The on-board VC-MRI at any instant is considered as a deformation of the prior MRI. The deformation field is represented as a linear combination of the 3 major deformation patterns. The coefficients of the deformation patterns are solved by the data fidelity constraint using the acquired on-board single 2-dimensional cine MRI. The method was evaluated using both digital extended-cardiac torso (XCAT) simulation of lung cancer patients and MRI data from 4 real liver cancer patients. The accuracy of the estimated VC-MRI was quantitatively evaluated using volume-percent-difference (VPD), center-of-mass-shift (COMS), and target tracking errors. Effects of acquisition orientation, region-of-interest (ROI) selection, patient breathing pattern change, and noise on the estimation accuracy were also evaluated.Image subtraction of ground-truth with estimated on-board VC-MRI shows fewer differences than image subtraction of ground-truth with prior image. Agreement between normalized profiles in the estimated and ground-truth VC-MRI was achieved with less than 6% error for both XCAT and patient data. Among all XCAT scenarios, the VPD between ground-truth and estimated lesion volumes was, on average, 8.43 ± 1.52% and the COMS was, on average, 0.93 ± 0.58 mm across all time steps for estimation based on the ROI region in the sagittal cine images. Matching to ROI in the sagittal view achieved better accuracy when there was substantial breathing pattern change. The technique was robust against noise levels up to SNR = 20. For patient data, average tracking errors were less than 2 mm in all directions for all patients.Preliminary studies demonstrated the feasibility of generating real-time VC-MRI for on-board localization of moving targets in radiation therapy.

Authors
Harris, W; Ren, L; Cai, J; Zhang, Y; Chang, Z; Yin, F-F
MLA Citation
Harris, W, Ren, L, Cai, J, Zhang, Y, Chang, Z, and Yin, F-F. "A Technique for Generating Volumetric Cine-Magnetic Resonance Imaging." International journal of radiation oncology, biology, physics 95.2 (June 2016): 844-853.
PMID
27131085
Source
epmc
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
95
Issue
2
Publish Date
2016
Start Page
844
End Page
853
DOI
10.1016/j.ijrobp.2016.02.011

SU-D-204-01: A Methodology Based On Machine Learning and Quantum Clustering to Predict Lung SBRT Dosimetric Endpoints From Patient Specific Anatomic Features.

To develop a data-mining methodology based on quantum clustering and machine learning to predict expected dosimetric endpoints for lung SBRT applications based on patient-specific anatomic features.Ninety-three patients who received lung SBRT at our clinic from 2011-2013 were retrospectively identified. Planning information was acquired for each patient, from which various features were extracted using in-house semi-automatic software. Anatomic features included tumor-to-OAR distances, tumor location, total-lung-volume, GTV and ITV. Dosimetric endpoints were adopted from RTOG-0195 recommendations, and consisted of various OAR-specific partial-volume doses and maximum point-doses. First, PCA analysis and unsupervised quantum-clustering was used to explore the feature-space to identify potentially strong classifiers. Secondly, a multi-class logistic regression algorithm was developed and trained to predict dose-volume endpoints based on patient-specific anatomic features. Classes were defined by discretizing the dose-volume data, and the feature-space was zero-mean normalized. Fitting parameters were determined by minimizing a regularized cost function, and optimization was performed via gradient descent. As a pilot study, the model was tested on two esophageal dosimetric planning endpoints (maximum point-dose, dose-to-5cc), and its generalizability was evaluated with leave-one-out cross-validation.Quantum-Clustering demonstrated a strong separation of feature-space at 15Gy across the first-and-second Principle Components of the data when the dosimetric endpoints were retrospectively identified. Maximum point dose prediction to the esophagus demonstrated a cross-validation accuracy of 87%, and the maximum dose to 5cc demonstrated a respective value of 79%. The largest optimized weighting factor was placed on GTV-to-esophagus distance (a factor of 10 greater than the second largest weighting factor), indicating an intuitively strong correlation between this feature and both endpoints.This pilot study shows that it is feasible to predict dose-volume endpoints based on patient-specific anatomic features. The developed methodology can potentially help to identify patients at risk for higher OAR doses, thus improving the efficiency of treatment planning. R01-184173.

Authors
Lafata, K; Ren, L; Wu, Q; Kelsey, C; Hong, J; Cai, J; Yin, F
MLA Citation
Lafata, K, Ren, L, Wu, Q, Kelsey, C, Hong, J, Cai, J, and Yin, F. "SU-D-204-01: A Methodology Based On Machine Learning and Quantum Clustering to Predict Lung SBRT Dosimetric Endpoints From Patient Specific Anatomic Features." Medical physics 43.6 (June 2016): 3332-.
PMID
28047753
Source
epmc
Published In
Medical physics
Volume
43
Issue
6
Publish Date
2016
Start Page
3332
DOI
10.1118/1.4955606

TH-EF-BRA-02: A Novel Markerless 4D CBCT Projection Phase Sorting Technique Using Prior Knowledge and Patient Motion Modeling: A Feasibility Study.

To investigate the feasibility of a novel marker-less motion-modeling based method for automatic 4D-CBCT projection phase sorting.Patient on-board image volume at any instant is considered as a deformation of one phase of the prior planning 4D-CT. The deformation field map(DFM) is represented as a linear combination of three major deformation patterns extracted from the planning 4D-CT using principle-component-analysis(PCA). The PCA coefficients are solved for each single projection based on data fidelity constraint, and are used as motion information for phase sorting. Projections at the valleys of the Z direction coefficient are sorted as phase 0/100% and projection phases in between are linearly interpolated. 4D-digital-extended-cardiac-torso(XCAT) phantoms and 3 patient cases were used for evaluation. XCAT phantoms simulated different patient respiratory and anatomical changes from prior 4D-CT to on-board image volume, including changes of tumor size, locations, motion amplitudes and motion directions. Three patient cases include 2 full-fan slow-rotation and one half-fan normal-rotation case. Manual phase sorting based on visual inspection was used as the gold standard. The average absolute phase difference, and the pass rate (percentage of projections sorted within 10% phase error) were used to evaluate sorting accuracy.The amplitude of PCA coefficient motion curve correlated with the actual motion amplitude. The algorithm was robust against respiratory and anatomical changes from prior to on-board imaging. For all XCAT cases, the average phase errors were lower than 1.43%, and the pass rate was 100%. The patient data set showed average phase error of 2.47%, 1.90% for full fan slow rotation case and 2.78% for half fan normal rotation case, respectively. The corresponding pass rates were 99.4%, 98.5% and 99.5%, respectively.Preliminary results demonstrated the robustness and high accuracy of the marker-less PCA based phase sorting algorithm for different patient scenarios and 4D-CBCT scanning protocols.

Authors
Zhang, L; Zhang, Y; Yin, F; Harris, W; Cai, J; Ren, L
MLA Citation
Zhang, L, Zhang, Y, Yin, F, Harris, W, Cai, J, and Ren, L. "TH-EF-BRA-02: A Novel Markerless 4D CBCT Projection Phase Sorting Technique Using Prior Knowledge and Patient Motion Modeling: A Feasibility Study." Medical physics 43.6 (June 2016): 3897-.
PMID
28047738
Source
epmc
Published In
Medical physics
Volume
43
Issue
6
Publish Date
2016
Start Page
3897
DOI
10.1118/1.4958259

TH-EF-BRA-08: A Novel Technique for Estimating Volumetric Cine MRI (VC-MRI) From Multi-Slice Sparsely Sampled Cine Images Using Motion Modeling and Free Form Deformation.

To develop a technique to estimate on-board VC-MRI using multi-slice sparsely-sampled cine images, patient prior 4D-MRI, motion-modeling and free-form deformation for real-time 3D target verification of lung radiotherapy.A previous method has been developed to generate on-board VC-MRI by deforming prior MRI images based on a motion model(MM) extracted from prior 4D-MRI and a single-slice on-board 2D-cine image. In this study, free-form deformation(FD) was introduced to correct for errors in the MM when large anatomical changes exist. Multiple-slice sparsely-sampled on-board 2D-cine images located within the target are used to improve both the estimation accuracy and temporal resolution of VC-MRI. The on-board 2D-cine MRIs are acquired at 20-30frames/s by sampling only 10% of the k-space on Cartesian grid, with 85% of that taken at the central k-space. The method was evaluated using XCAT(computerized patient model) simulation of lung cancer patients with various anatomical and respirational changes from prior 4D-MRI to onboard volume. The accuracy was evaluated using Volume-Percent-Difference(VPD) and Center-of-Mass-Shift(COMS) of the estimated tumor volume. Effects of region-of-interest(ROI) selection, 2D-cine slice orientation, slice number and slice location on the estimation accuracy were evaluated.VCMRI estimated using 10 sparsely-sampled sagittal 2D-cine MRIs achieved VPD/COMS of 9.07±3.54%/0.45±0.53mm among all scenarios based on estimation with ROI_MM-ROI_FD. The FD optimization improved estimation significantly for scenarios with anatomical changes. Using ROI-FD achieved better estimation than global-FD. Changing the multi-slice orientation to axial, coronal, and axial/sagittal orthogonal reduced the accuracy of VCMRI to VPD/COMS of 19.47±15.74%/1.57±2.54mm, 20.70±9.97%/2.34±0.92mm, and 16.02±13.79%/0.60±0.82mm, respectively. Reducing the number of cines to 8 enhanced temporal resolution of VC-MRI by 25% while maintaining the estimation accuracy. Estimation using slices sampled uniformly through the tumor achieved better accuracy than slices sampled non-uniformly.Preliminary studies showed that it is feasible to generate VC-MRI from multi-slice sparsely-sampled 2D-cine images for real-time 3D-target verification. This work was supported by the National Institutes of Health under Grant No. R01-CA184173 and a research grant from Varian Medical Systems.

Authors
Harris, W; Yin, F; Wang, C; Chang, Z; Cai, J; Zhang, Y; Ren, L
MLA Citation
Harris, W, Yin, F, Wang, C, Chang, Z, Cai, J, Zhang, Y, and Ren, L. "TH-EF-BRA-08: A Novel Technique for Estimating Volumetric Cine MRI (VC-MRI) From Multi-Slice Sparsely Sampled Cine Images Using Motion Modeling and Free Form Deformation." Medical physics 43.6 (June 2016): 3898-3899.
PMID
28048297
Source
epmc
Published In
Medical physics
Volume
43
Issue
6
Publish Date
2016
Start Page
3898
End Page
3899
DOI
10.1118/1.4958265

SU-G-JeP3-01: A Method to Quantify Lung SBRT Target Localization Accuracy Based On Digitally Reconstructed Fluoroscopy.

To develop a methodology based on digitally-reconstructed-fluoroscopy (DRF) to quantitatively assess target localization accuracy of lung SBRT, and to evaluate using both a dynamic digital phantom and a patient dataset.For each treatment field, a 10-phase DRF is generated based on the planning 4DCT. Each frame is pre-processed with a morphological top-hat filter, and corresponding beam apertures are projected to each detector plane. A template-matching algorithm based on cross-correlation is used to detect the tumor location in each frame. Tumor motion relative beam aperture is extracted in the superior-inferior direction based on each frame's impulse response to the template, and the mean tumor position (MTP) is calculated as the average tumor displacement. The DRF template coordinates are then transferred to the corresponding MV-cine dataset, which is retrospectively filtered as above. The treatment MTP is calculated within each field's projection space, relative to the DRF-defined template. The field's localization error is defined as the difference between the DRF-derived-MTP (planning) and the MV-cine-derived-MTP (delivery). A dynamic digital phantom was used to assess the algorithm's ability to detect intra-fractional changes in patient alignment, by simulating different spatial variations in the MV-cine and calculating the corresponding change in MTP. Inter-and-intra-fractional variation, IGRT accuracy, and filtering effects were investigated on a patient dataset.Phantom results demonstrated a high accuracy in detecting both translational and rotational variation. The lowest localization error of the patient dataset was achieved at each fraction's first field (mean=0.38mm), with Fx3 demonstrating a particularly strong correlation between intra-fractional motion-caused localization error and treatment progress. Filtering significantly improved tracking visibility in both the DRF and MV-cine images.We have developed and evaluated a methodology to quantify lung SBRT target localization accuracy based on digitally-reconstructed-fluoroscopy. Our approach may be useful in potentially reducing treatment margins to optimize lung SBRT outcomes. R01-184173.

Authors
Lafata, K; Ren, L; Cai, J; Yin, F
MLA Citation
Lafata, K, Ren, L, Cai, J, and Yin, F. "SU-G-JeP3-01: A Method to Quantify Lung SBRT Target Localization Accuracy Based On Digitally Reconstructed Fluoroscopy." Medical physics 43.6 (June 2016): 3670-.
PMID
28047062
Source
epmc
Published In
Medical physics
Volume
43
Issue
6
Publish Date
2016
Start Page
3670
DOI
10.1118/1.4957066

TU-AB-BRA-09: A Novel Method of Generating Ultrafast Volumetric Cine MRI (VC-MRI) Using Prior 4D-MRI and On-Board Phase-Skipped Encoding Acquisition for Radiotherapy Target Localization.

To develop a technique generating ultrafast on-board VC-MRI using prior 4D-MRI and on-board phase-skipped encoding k-space acquisition for real-time 3D target tracking of liver and lung radiotherapy.The end-of-expiration (EOE) volume in 4D-MRI acquired during the simulation was selected as the prior volume. 3 major respiratory deformation patterns were extracted through the principal component analysis of the deformation field maps (DFMs) generated between EOE and all other phases. The on-board VC-MRI at each instant was considered as a deformation of the prior volume, and the deformation was modeled as a linear combination of the extracted 3 major deformation patterns. To solve the weighting coefficients of the 3 major patterns, a 2D slice was extracted from VC-MRI volume to match with the 2D on-board sampling data, which was generated by 8-fold phase skipped-encoding k-space acquisition (i.e., sample 1 phase-encoding line out of every 8 lines) to achieve an ultrafast 16-24 volumes/s frame rate. The method was evaluated using XCAT digital phantom to simulate lung cancer patients. The 3D volume of end-ofinhalation (EOI) phase at the treatment day was used as ground-truth onboard VC-MRI with simulated changes in 1) breathing amplitude and 2) breathing amplitude/phase change from the simulation day. A liver cancer patient case was evaluated for in-vivo feasibility demonstration.The comparison between ground truth and estimated on-board VC-MRI shows good agreements. In XCAT study with changed breathing amplitude, the volume-percent-difference(VPD) between ground-truth and estimated tumor volumes at EOI was 6.28% and the Center-of-Mass-Shift(COMS) was 0.82mm; with changed breathing amplitude and phase, the VPD was 8.50% and the COMS was 0.54mm. The study of liver patient case also demonstrated a promising in vivo feasibility of the proposed method CONCLUSION: Preliminary results suggest the feasibility to estimate ultrafast VC-MRI for on-board target localization with phase skipped-encoding k-space acquisition. Research grant from NIH R01-184173.

Authors
Wang, C; Yin, F; Harris, W; Cai, J; Chang, Z; Ren, L
MLA Citation
Wang, C, Yin, F, Harris, W, Cai, J, Chang, Z, and Ren, L. "TU-AB-BRA-09: A Novel Method of Generating Ultrafast Volumetric Cine MRI (VC-MRI) Using Prior 4D-MRI and On-Board Phase-Skipped Encoding Acquisition for Radiotherapy Target Localization." Medical physics 43.6 (June 2016): 3735-.
PMID
28046715
Source
epmc
Published In
Medical physics
Volume
43
Issue
6
Publish Date
2016
Start Page
3735
DOI
10.1118/1.4957419

WE-DE-BRA-01: SCIENCE COUNCIL JUNIOR INVESTIGATOR COMPETITION WINNER: Acceleration of a Limited-Angle Intrafraction Verification (LIVE) System Using Adaptive Prior Knowledge Based Image Estimation.

To develop an adaptive prior knowledge based image estimation method to reduce the scan angle needed in the LIVE system to reconstruct 4D-CBCT for intrafraction verification.The LIVE system has been previously proposed to reconstructs 4D volumetric images on-the-fly during arc treatment for intrafraction target verification and dose calculation. This system uses limited-angle beam's eye view (BEV) MV cine images acquired from the treatment beam together with the orthogonally acquired limited-angle kV projections to reconstruct 4D-CBCT images for target verification during treatment. In this study, we developed an adaptive constrained free-form deformation reconstruction technique in LIVE to further reduce the scanning angle needed to reconstruct the CBCT images. This technique uses free form deformation with energy minimization to deform prior images to estimate 4D-CBCT based on projections acquired in limited angle (orthogonal 6°) during the treatment. Note that the prior images are adaptively updated using the latest CBCT images reconstructed by LIVE during treatment to utilize the continuity of patient motion.The 4D digital extended-cardiac-torso (XCAT) phantom was used to evaluate the efficacy of this technique with LIVE system. A lung patient was simulated with different scenario, including baseline drifts, amplitude change and phase shift. Limited-angle orthogonal kV and beam's eye view (BEV) MV projections were generated for each scenario. The CBCT reconstructed by these projections were compared with the ground-truth generated in XCAT.Volume-percentage-difference (VPD) and center-of-mass-shift (COMS) were calculated between the reconstructed and the ground-truth tumors to evaluate the reconstruction accuracy.Using orthogonal-view of 6° kV and BEV- MV projections, the VPD/COMS values were 12.7±4.0%/0.7±0.5 mm, 13.0±5.1%/0.8±0.5 mm, and 11.4±5.4%/0.5±0.3 mm for the three scenarios, respectively.The technique enables LIVE to accurately reconstruct 4D-CBCT images using only orthogonal 6° angle, which greatly improves the efficiency and reduces dose of LIVE for intrafraction verification.

Authors
Zhang, Y; Yin, F; Zhang, Y; Ren, L
MLA Citation
Zhang, Y, Yin, F, Zhang, Y, and Ren, L. "WE-DE-BRA-01: SCIENCE COUNCIL JUNIOR INVESTIGATOR COMPETITION WINNER: Acceleration of a Limited-Angle Intrafraction Verification (LIVE) System Using Adaptive Prior Knowledge Based Image Estimation." Medical physics 43.6 (June 2016): 3812-.
PMID
28048308
Source
epmc
Published In
Medical physics
Volume
43
Issue
6
Publish Date
2016
Start Page
3812
DOI
10.1118/1.4957830

SU-G-JeP4-02: An Investigation of Respiratory Surrogate Motion Data Requirements for Multiple-Step Ahead Prediction.

Respiratory-gated radiotherapy and dynamic tracking employ real-time imaging and surrogate motion-monitoring methods with tumor motion prediction in advance of real-time. This study investigated respiratory motion data length on prediction accuracy of tumor motion.Predictions generated from the algorithm are validated against a one-dimensional surrogate signal of amplitude versus time. Prediction consists of three major components: extracting top-ranked subcomponents from training data matching the last respiratory cycle; calculating weighting factors from best-matched subcomponents; fusing data proceeding best-matched subcomponents with respective weighting factors to form predictions. Predictions for one respiratory cycle (∼3-6seconds) were assessed using 351 patient data from the respiratory management device. Performance was evaluated for correlation coefficient and root mean square error (RMSE) between prediction and final respiratory cycle.Respiratory prediction results fell into two classes, where best predictions for 70 cycles or less performed using relative prediction and greater than 70 cycles are predicted similarly using relative and derivative relative. For 70 respiratory cycles or less, the average correlation between prediction and final respiratory cycle was 0.9999±0.0001, 0.9999±0.0001, 0.9988±0.0003, 0.9985±0.0023, and 0.9981±0.0023 with RMSE values of 0.0091±0.0030, 0.0091±0.0030, 0.0305±0.0051, 0.0299±0.0259, and 0.0299±0.0259 for equal, relative, pattern, derivative equal and derivative relative weighting methods, respectively. Respectively, the total best prediction for each method was 37, 65, 20, 22, and 22. For data with greater than 70 cycles average correlation was 0.9999±0.0001, 0.9999±0.0001, 0.9988±0.0004, 0.9988±0.0020, and 0.9988±0.0020 with RMSE values of 0.0081±0.0031, 0.0082±0.0033, 0.0306±0.0056, 0.0218±0.0222, and 0.0218±0.0222 for equal, relative, pattern, derivative equal and derivative relative weighting methods, respectively. Respectively, the total best prediction for each method was 24, 44, 42, 30, and 45.The prediction algorithms are effective in estimating surrogate motion in advance. These results indicate an advantage in using relative prediction for shorter data and either relative or derivative relative prediction for longer data.

Authors
Zawisza, I; Ren, L; Yin, F
MLA Citation
Zawisza, I, Ren, L, and Yin, F. "SU-G-JeP4-02: An Investigation of Respiratory Surrogate Motion Data Requirements for Multiple-Step Ahead Prediction." Medical physics 43.6 (June 2016): 3681-.
PMID
28048180
Source
epmc
Published In
Medical physics
Volume
43
Issue
6
Publish Date
2016
Start Page
3681
DOI
10.1118/1.4957112

SU-G-JeP3-06: Lower KV Image Dose Are Expected From a Limited-Angle Intra-Fractional Verification (LIVE) System for SBRT Treatments.

In order to track the tumor movement for patient positioning verification during arc treatment delivery or in between 3D/IMRT beams for stereotactic body radiation therapy (SBRT), the limited-angle kV projections acquisition simultaneously during arc treatment delivery or in-between static treatment beams as the gantry moves to the next beam angle was proposed. The purpose of this study is to estimate additional imaging dose resulting from multiple tomosynthesis acquisitions in-between static treatment beams and to compare with that of a conventional kV-CBCT acquisition.kV imaging system integrated into Varian TrueBeam accelerators was modeled using EGSnrc Monte Carlo user code, BEAMnrc and DOSXYZnrc code was used in dose calculations. The simulated realistic kV beams from the Varian TrueBeam OBI 1.5 system were used to calculate dose to patient based on CT images. Organ doses were analyzed using DVHs. The imaging dose to patient resulting from realistic multiple tomosynthesis acquisitions with each 25-30 degree kV source rotation between 6 treatment beam gantry angles was studied.For a typical lung SBRT treatment delivery much lower (20-50%) kV imaging doses from the sum of realistic six tomosynthesis acquisitions with each 25-30 degree x-ray source rotation between six treatment beam gantry angles were observed compared to that from a single CBCT image acquisition.This work indicates that the kV imaging in this proposed Limited-angle Intra-fractional Verification (LIVE) System for SBRT Treatments has a negligible imaging dose increase. It is worth to note that the MV imaging dose caused by MV projection acquisition in-between static beams in LIVE can be minimized by restricting the imaging to the target region and reducing the number of projections acquired. For arc treatments, MV imaging acquisition in LIVE does not add additional imaging dose as the MV images are acquired from treatment beams directly during the treatment.

Authors
Ding, G; Yin, F; Ren, L
MLA Citation
Ding, G, Yin, F, and Ren, L. "SU-G-JeP3-06: Lower KV Image Dose Are Expected From a Limited-Angle Intra-Fractional Verification (LIVE) System for SBRT Treatments." Medical physics 43.6 (June 2016): 3671-.
PMID
28048270
Source
epmc
Published In
Medical physics
Volume
43
Issue
6
Publish Date
2016
Start Page
3671
DOI
10.1118/1.4957071

SU-G-JeP3-04: Estimating 4D CBCT from Prior Information and Extremely Limited Angle Projections Using Structural PCA and Weighted Free-Form Deformation.

To investigate the feasibility of using structure-based principal component analysis (PCA) motion-modeling and weighted free-form deformation to estimate on-board 4D-CBCT using prior information and extremely limited angle projections for potential 4D target verification of lung radiotherapy.A technique for lung 4D-CBCT reconstruction has been previously developed using a deformation field map (DFM)-based strategy. In the previous method, each phase of the 4D-CBCT was generated by deforming a prior CT volume. The DFM was solved by a motion-model extracted by global PCA and a free-form deformation (GMM-FD) technique, using data fidelity constraint and the deformation energy minimization. In this study, a new structural-PCA method was developed to build a structural motion-model (SMM) by accounting for potential relative motion pattern changes between different anatomical structures from simulation to treatment. The motion model extracted from planning 4DCT was divided into two structures: tumor and body excluding tumor, and the parameters of both structures were optimized together. Weighted free-form deformation (WFD) was employed afterwards to introduce flexibility in adjusting the weightings of different structures in the data fidelity constraint based on clinical interests. XCAT (computerized patient model) simulation with a 30 mm diameter lesion was simulated with various anatomical and respirational changes from planning 4D-CT to onboard volume. The estimation accuracy was evaluated by the Volume-Percent-Difference (VPD)/Center-of-Mass-Shift (COMS) between lesions in the estimated and "ground-truth" on board 4D-CBCT.Among 6 different XCAT scenarios corresponding to respirational and anatomical changes from planning CT to on-board using single 30° on-board projections, the VPD/COMS for SMM-WFD was reduced to 10.64±3.04%/1.20±0.45mm from 21.72±9.24%/1.80±0.53mm for GMM-FD. Using 15° orthogonal projections, the VPD/COMS was further reduced to 1.91±0.86%/0.31±0.42mm based on SMM-WFD.Compared to GMM-FD technique, the SMM-WFD technique can substantially improve the 4D-CBCT estimation accuracy using extremely small scan angles to provide ultra-fast 4D verification. This work was supported by the National Institutes of Health under Grant No. R01-CA184173 and a research grant from Varian Medical Systems.

Authors
Harris, W; Yin, F; Zhang, Y; Ren, L
MLA Citation
Harris, W, Yin, F, Zhang, Y, and Ren, L. "SU-G-JeP3-04: Estimating 4D CBCT from Prior Information and Extremely Limited Angle Projections Using Structural PCA and Weighted Free-Form Deformation." Medical physics 43.6 (June 2016): 3671-.
PMID
28047816
Source
epmc
Published In
Medical physics
Volume
43
Issue
6
Publish Date
2016
Start Page
3671
DOI
10.1118/1.4957069

TH-C-BRC-03: Emerging Linac Based SRS/SBRT Technologies with Modulated Arc Delivery.

The delivery techniques for SRS/SBRT have been under rapid developments in recent years, which pose new challenges to medical physicists ranging from planning and quality assurance to imaging and motion management. This educational course will provide a general overview of the latest delivery techniques in SRS/SBRT, and discuss the clinical processes to address the challenges of each technique with special emphasis on dedicated gamma-ray based device, robotic x-band linac-based system and conventional C-arm s-band linac-based SRS systems. (1). Gamma-ray based SRS/SRT: This is the gold standard of intracranial SRS. With the advent of precision imaging guidance and frameless patient positioning capabilities, novel stereoscopic CBCT and automatic dose adaption solution are introduced to the Gamma-ray based SRS for the first time. The first North American system has been approved by the US regulatory for patient treatments in the spring of 2016. (2). Robotic SRS/SBRT system: A number of technological milestones have been developed in the past few years, including variable aperture collimator, sequential optimization technique, and the time reduction technique. Recently, a new robotic model allows the option of a multi-leaf collimator. These technological advances have reduced the treatment time and improved dose conformity significantly and could potentially expand the application of radiosurgery for the treatment of targets not previously suitable for robotic SRS/SBRT or fractionated stereotactic radiotherapy. These technological advances have created new demanding mandates on hardware and patient quality assurance (QA) tasks, as well as the need for updating/educating the physicists in the community on these requirements. (3). Conventional Linac based treatments: Modulated arc therapy (MAT) has gained wide popularities in Linac-based treatments in recent years due to its high delivery efficiency and excellent dose conformities. Recently, MAT has been introduced to deliver highly conformal radiosurgery treatments to multiple targets simultaneously via a single isocenter to replace the conventional multi-iso multi-plan treatments. It becomes important to understand the advantages and limitations of this technique, and the pitfalls for implementing this technique in clinical practice. The planning process of single-iso multi-target MAT will be described, and its plan quality and delivery efficiency will be compared with multi-iso plans. The QA process for verifying such complex plans will be illustrated, and pitfalls in imaging and patient set up will be discussed. Overall, this session will focus on the following areas: 1) Update on the emerging technology in current SRS/SBRT delivery. 2) New developments in treatment planning and Quality Assurance program. 3) Imaging guidance and motion management.1. To understand the SRS/SBRT principles and its clinical applications, and gain knowledge on the emerging technologies in SRS/SBRT. 2. To review planning concepts and useful tips in treatment planning. 3. To learn about the imaging guidance procedures and the quality assurance program in SRS/SBRT. National Institutes of Health, Varian Medical System; L. Ren, The presenter is funded by National Institutes of Health and Varian Medical System.

Authors
Ren, L
MLA Citation
Ren, L. "TH-C-BRC-03: Emerging Linac Based SRS/SBRT Technologies with Modulated Arc Delivery." Medical physics 43.6 (June 2016): 3872-.
PMID
28047808
Source
epmc
Published In
Medical physics
Volume
43
Issue
6
Publish Date
2016
Start Page
3872
DOI
10.1118/1.4958138

SU-F-J-82: A Rapid Direct Method for Inverting Respiratory Deformation Fields.

To enable efficient and consistent registrationbetween source and target images, related bynonlinear but periodic deformation, with particular focus on 4D CTimages.We present a non-iterative method for inverting forward (or backward) deformation fields from a sequence of p CT images in arespiratory cycle. By exploiting the cyclic structure, the direct inversion methodeffectively factors the inverse transformation between any two frames inthe respiratory sequence into no more than p forward (or backward) transformations, which are available in the provided forward (or backward) sequence.The direct method, inspired by a fixed-point iteration method, iscompared to the iterative method with an analytical phantom and a XCATlung phantom. With the analytic phantom, the new method renders the reversed deformation field in no more than p steps with satisfactory accuracy (RMSE is below 1E-10, for example), while the iterative method becomes slow, very slow or divergent under various conditions such as large deformation. The direct method is efficient and with the XCAT phantom as well. However, when interpolations are spatial resolution limited and by low-degree interpolant, the direct method suffers from the introduced perturbation due to the lack of self-correction capability. The direct method can be used as aprediction step, making large deformation small and followed bycorrection by an iterative method.A direct method is presented for inverting periodic motion fields with high efficiency. When interpolation is resolution limited, the method can be used in combination with an iterative method, especially, for the case where the deformation is large and the iterative method may not converge. NIH Grant No: R01-184173.

Authors
Dubey, A; Iliopoulos, AS; Sun, X; Yin, FF; Ren, L
MLA Citation
Dubey, A, Iliopoulos, AS, Sun, X, Yin, FF, and Ren, L. "SU-F-J-82: A Rapid Direct Method for Inverting Respiratory Deformation Fields." Medical physics 43.6 (June 2016): 3425-.
PMID
28047343
Source
epmc
Published In
Medical physics
Volume
43
Issue
6
Publish Date
2016
Start Page
3425
DOI
10.1118/1.4955990

TH-C-BRC-00: Emerging Technologies in SRS/SBRT Delivery.

The delivery techniques for SRS/SBRT have been under rapid developments in recent years, which pose new challenges to medical physicists ranging from planning and quality assurance to imaging and motion management. This educational course will provide a general overview of the latest delivery techniques in SRS/SBRT, and discuss the clinical processes to address the challenges of each technique with special emphasis on dedicated gamma-ray based device, robotic x-band linac-based system and conventional C-arm s-band linac-based SRS systems. (1). Gamma-ray based SRS/SRT: This is the gold standard of intracranial SRS. With the advent of precision imaging guidance and frameless patient positioning capabilities, novel stereoscopic CBCT and automatic dose adaption solution are introduced to the Gamma-ray based SRS for the first time. The first North American system has been approved by the US regulatory for patient treatments in the spring of 2016. (2). Robotic SRS/SBRT system: A number of technological milestones have been developed in the past few years, including variable aperture collimator, sequential optimization technique, and the time reduction technique. Recently, a new robotic model allows the option of a multi-leaf collimator. These technological advances have reduced the treatment time and improved dose conformity significantly and could potentially expand the application of radiosurgery for the treatment of targets not previously suitable for robotic SRS/SBRT or fractionated stereotactic radiotherapy. These technological advances have created new demanding mandates on hardware and patient quality assurance (QA) tasks, as well as the need for updating/educating the physicists in the community on these requirements. (3). Conventional Linac based treatments: Modulated arc therapy (MAT) has gained wide popularities in Linac-based treatments in recent years due to its high delivery efficiency and excellent dose conformities. Recently, MAT has been introduced to deliver highly conformal radiosurgery treatments to multiple targets simultaneously via a single isocenter to replace the conventional multi-iso multi-plan treatments. It becomes important to understand the advantages and limitations of this technique, and the pitfalls for implementing this technique in clinical practice. The planning process of single-iso multi-target MAT will be described, and its plan quality and delivery efficiency will be compared with multi-iso plans. The QA process for verifying such complex plans will be illustrated, and pitfalls in imaging and patient set up will be discussed. Overall, this session will focus on the following areas: 1) Update on the emerging technology in current SRS/SBRT delivery. 2) New developments in treatment planning and Quality Assurance program. 3) Imaging guidance and motion management.1. To understand the SRS/SBRT principles and its clinical applications, and gain knowledge on the emerging technologies in SRS/SBRT. 2. To review planning concepts and useful tips in treatment planning. 3. To learn about the imaging guidance procedures and the quality assurance program in SRS/SBRT. National Institutes of Health, Varian Medical System; L. Ren, The presenter is funded by National Institutes of Health and Varian Medical System.

Authors
Ren, L
MLA Citation
Ren, L. "TH-C-BRC-00: Emerging Technologies in SRS/SBRT Delivery." Medical physics 43.6 (June 2016): 3872-.
PMID
28047049
Source
epmc
Published In
Medical physics
Volume
43
Issue
6
Publish Date
2016
Start Page
3872
DOI
10.1118/1.4958135

SU-F-I-10: Spatially Local Statistics for Adaptive Image Filtering.

To facilitate adaptive image filtering operations, addressing spatial variations in both noise and signal. Such issues are prevalent in cone-beam projections, where physical effects such as X-ray scattering result in spatially variant noise, violating common assumptions of homogeneous noise and challenging conventional filtering approaches to signal extraction and noise suppression.We present a computational mechanism for probing into and quantifying the spatial variance of noise throughout an image. The mechanism builds a pyramid of local statistics at multiple spatial scales; local statistical information at each scale includes (weighted) mean, median, standard deviation, median absolute deviation, as well as histogram or dynamic range after local mean/median shifting. Based on inter-scale differences of local statistics, the spatial scope of distinguishable noise variation is detected in a semi- or un-supervised manner. Additionally, we propose and demonstrate the incorporation of such information in globally parametrized (i.e., non-adaptive) filters, effectively transforming the latter into spatially adaptive filters. The multi-scale mechanism is materialized by efficient algorithms and implemented in parallel CPU/GPU architectures.We demonstrate the impact of local statistics for adaptive image processing and analysis using cone-beam projections of a Catphan phantom, fitted within an annulus to increase X-ray scattering. The effective spatial scope of local statistics calculations is shown to vary throughout the image domain, necessitating multi-scale noise and signal structure analysis. Filtering results with and without spatial filter adaptation are compared visually, illustrating improvements in imaging signal extraction and noise suppression, and in preserving information in low-contrast regions.Local image statistics can be incorporated in filtering operations to equip them with spatial adaptivity to spatial signal/noise variations. An efficient multi-scale computational mechanism is developed to curtail processing latency. Spatially adaptive filtering may impact subsequent processing tasks such as reconstruction and numerical gradient computations for deformable registration. NIH Grant No. R01-184173.

Authors
Iliopoulos, AS; Floros, D; Zhang, Y; Pitsianis, N; Sun, X; Yin, FF; Ren, L
MLA Citation
Iliopoulos, AS, Floros, D, Zhang, Y, Pitsianis, N, Sun, X, Yin, FF, and Ren, L. "SU-F-I-10: Spatially Local Statistics for Adaptive Image Filtering." Medical physics 43.6 (June 2016): 3388-.
PMID
28046905
Source
epmc
Published In
Medical physics
Volume
43
Issue
6
Publish Date
2016
Start Page
3388
DOI
10.1118/1.4955838

SU-F-J-83: Estimation of Deformation Field with Two-Scale Supervoxel Equations.

To circumvent the ill-posedness in the problem to estimate inhomogeneous motion or deformation field without resorting to global regularization conditions.We present a novel method for deformable registration. First, we estimate the deformation field at a coarse resolution level, with super-voxels as the spatial elements, keeping the target/reference image remains at the fine resolution. The resultant system of nonlinear equations are no longer under-determined. Next we establish local systems of 2-scale equations to determine the difference in deformation between the coarser level and the fine level, namely, the relative deformation between each super-voxel and its 8 sub-pixels. The equations are set up as follows. Consider an arbitrarily fixed super-voxel, we refer to it as the pivot voxel to be refined. Partition the other super-voxels as its near neighbors or far neighbors. In the local equations, the deformation at far neighbors are fixed as that obtained at the coarse resolution. The relative deformation at the sub-voxels within the pivot voxel is unknown and to be estimated. The deformation at the near neighbors is allowed to undergo changes, acting as elastic variables bridging the deformation associated with sub-pixels within the pivot voxel and that over the far neighbors. Each local system is not under-determined. The refinement is regularized by the principle of strong near-neighbor influence and weak far-neighbor influence, inspired primarily by the celebrated numerical Fast Multiple Method.We demonstrate the viability and efficacy of the new method using 2D XCAT lung images. We provide comparisons to two other commonly used iterative methods.The proposed method is essentially a self-regularization mechanism, which is adaptive, non-parametric, non-global, in the sense that the solution at the finer resolution is regulated by the deformation structure itself at multiple resolution scale. NIH Grant No: R01-184173.

Authors
Dubey, A; Iliopoulos, AS; Sun, X; Yin, FF; Ren, L
MLA Citation
Dubey, A, Iliopoulos, AS, Sun, X, Yin, FF, and Ren, L. "SU-F-J-83: Estimation of Deformation Field with Two-Scale Supervoxel Equations." Medical physics 43.6 (June 2016): 3425-.
PMID
28046673
Source
epmc
Published In
Medical physics
Volume
43
Issue
6
Publish Date
2016
Start Page
3425
DOI
10.1118/1.4955991

SU-F-J-138: An Extension of PCA-Based Respiratory Deformation Modeling Via Multi-Linear Decomposition.

To address and lift the limited degree of freedom (DoF) of globally bilinear motion components such as those based on principal components analysis (PCA), for encoding and modeling volumetric deformation motion.We provide a systematic approach to obtaining a multi-linear decomposition (MLD) and associated motion model from deformation vector field (DVF) data. We had previously introduced MLD for capturing multi-way relationships between DVF variables, without being restricted by the bilinear component format of PCA-based models. PCA-based modeling is commonly used for encoding patient-specific deformation as per planning 4D-CT images, and aiding on-board motion estimation during radiotherapy. However, the bilinear space-time decomposition inherently limits the DoF of such models by the small number of respiratory phases. While this limit is not reached in model studies using analytical or digital phantoms with low-rank motion, it compromises modeling power in the presence of relative motion, asymmetries and hysteresis, etc, which are often observed in patient data. Specifically, a low-DoF model will spuriously couple incoherent motion components, compromising its adaptability to on-board deformation changes. By the multi-linear format of extracted motion components, MLD-based models can encode higher-DoF deformation structure.We conduct mathematical and experimental comparisons between PCA- and MLD-based models. A set of temporally-sampled analytical trajectories provides a synthetic, high-rank DVF; trajectories correspond to respiratory and cardiac motion factors, including different relative frequencies and spatial variations. Additionally, a digital XCAT phantom is used to simulate a lung lesion deforming incoherently with respect to the body, which adheres to a simple respiratory trend. In both cases, coupling of incoherent motion components due to a low model DoF is clearly demonstrated.Multi-linear decomposition can enable decoupling of distinct motion factors in high-rank DVF measurements. This may improve motion model expressiveness and adaptability to on-board deformation, aiding model-based image reconstruction for target verification. NIH Grant No. R01-184173.

Authors
Iliopoulos, AS; Pitsianis, N; Sun, X; Yin, FF; Ren, L
MLA Citation
Iliopoulos, AS, Pitsianis, N, Sun, X, Yin, FF, and Ren, L. "SU-F-J-138: An Extension of PCA-Based Respiratory Deformation Modeling Via Multi-Linear Decomposition." Medical physics 43.6 (June 2016): 3439-.
PMID
28046228
Source
epmc
Published In
Medical physics
Volume
43
Issue
6
Publish Date
2016
Start Page
3439
DOI
10.1118/1.4956046

Tomosynthesis Applications in Radiation Oncology

Authors
Godfrey, DJ; Ren, L; Wu, Q; Yin, F
MLA Citation
Godfrey, DJ, Ren, L, Wu, Q, and Yin, F. "Tomosynthesis Applications in Radiation Oncology." Tomosynthesis Imaging. Taylor & Francis, April 19, 2016. (Chapter)
Source
manual
Publish Date
2016

An interprojection sensor fusion approach to estimate blocked projection signal in synchronized moving grid-based CBCT system.

A preobject grid can reduce and correct scatter in cone beam computed tomography (CBCT). However, half of the signal in each projection is blocked by the grid. A synchronized moving grid (SMOG) has been proposed to acquire two complimentary projections at each gantry position and merge them into one complete projection. That approach, however, suffers from increased scanning time and the technical difficulty of accurately merging the two projections per gantry angle. Herein, the authors present a new SMOG approach which acquires a single projection per gantry angle, with complimentary grid patterns for any two adjacent projections, and use an interprojection sensor fusion (IPSF) technique to estimate the blocked signal in each projection. The method may have the additional benefit of reduced imaging dose due to the grid blocking half of the incident radiation.The IPSF considers multiple paired observations from two adjacent gantry angles as approximations of the blocked signal and uses a weighted least square regression of these observations to finally determine the blocked signal. The method was first tested with a simulated SMOG on a head phantom. The signal to noise ratio (SNR), which represents the difference of the recovered CBCT image to the original image without the SMOG, was used to evaluate the ability of the IPSF in recovering the missing signal. The IPSF approach was then tested using a Catphan phantom on a prototype SMOG assembly installed in a bench top CBCT system.In the simulated SMOG experiment, the SNRs were increased from 15.1 and 12.7 dB to 35.6 and 28.9 dB comparing with a conventional interpolation method (inpainting method) for a projection and the reconstructed 3D image, respectively, suggesting that IPSF successfully recovered most of blocked signal. In the prototype SMOG experiment, the authors have successfully reconstructed a CBCT image using the IPSF-SMOG approach. The detailed geometric features in the Catphan phantom were mostly recovered according to visual evaluation. The scatter related artifacts, such as cupping artifacts, were almost completely removed.The IPSF-SMOG is promising in reducing scatter artifacts and improving image quality while reducing radiation dose.

Authors
Zhang, H; Ren, L; Kong, V; Giles, W; Zhang, Y; Jin, J-Y
MLA Citation
Zhang, H, Ren, L, Kong, V, Giles, W, Zhang, Y, and Jin, J-Y. "An interprojection sensor fusion approach to estimate blocked projection signal in synchronized moving grid-based CBCT system." Medical physics 43.1 (January 2016): 268-.
PMID
26745920
Source
epmc
Published In
Medical physics
Volume
43
Issue
1
Publish Date
2016
Start Page
268
DOI
10.1118/1.4937934

Phase-matched DTS Imaging for Lung Tumor Localization

Authors
Zhang, Y; Yin, FF; Vergalasova, I; Ren, L
MLA Citation
Zhang, Y, Yin, FF, Vergalasova, I, and Ren, L. "Phase-matched DTS Imaging for Lung Tumor Localization." November 1, 2015.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
93
Issue
3
Publish Date
2015
Start Page
E600
End Page
E600

Dosimetric verification of lung cancer treatment using the CBCTs estimated from limited-angle on-board projections.

Lung cancer treatment is susceptible to treatment errors caused by interfractional anatomical and respirational variations of the patient. On-board treatment dose verification is especially critical for the lung stereotactic body radiation therapy due to its high fractional dose. This study investigates the feasibility of using cone-beam (CB)CT images estimated by a motion modeling and free-form deformation (MM-FD) technique for on-board dose verification.Both digital and physical phantom studies were performed. Various interfractional variations featuring patient motion pattern change, tumor size change, and tumor average position change were simulated from planning CT to on-board images. The doses calculated on the planning CT (planned doses), the on-board CBCT estimated by MM-FD (MM-FD doses), and the on-board CBCT reconstructed by the conventional Feldkamp-Davis-Kress (FDK) algorithm (FDK doses) were compared to the on-board dose calculated on the "gold-standard" on-board images (gold-standard doses). The absolute deviations of minimum dose (ΔDmin), maximum dose (ΔDmax), and mean dose (ΔDmean), and the absolute deviations of prescription dose coverage (ΔV100%) were evaluated for the planning target volume (PTV). In addition, 4D on-board treatment dose accumulations were performed using 4D-CBCT images estimated by MM-FD in the physical phantom study. The accumulated doses were compared to those measured using optically stimulated luminescence (OSL) detectors and radiochromic films.Compared with the planned doses and the FDK doses, the MM-FD doses matched much better with the gold-standard doses. For the digital phantom study, the average (± standard deviation) ΔDmin, ΔDmax, ΔDmean, and ΔV100% (values normalized by the prescription dose or the total PTV) between the planned and the gold-standard PTV doses were 32.9% (±28.6%), 3.0% (±2.9%), 3.8% (±4.0%), and 15.4% (±12.4%), respectively. The corresponding values of FDK PTV doses were 1.6% (±1.9%), 1.2% (±0.6%), 2.2% (±0.8%), and 17.4% (±15.3%), respectively. In contrast, the corresponding values of MM-FD PTV doses were 0.3% (±0.2%), 0.9% (±0.6%), 0.6% (±0.4%), and 1.0% (±0.8%), respectively. Similarly, for the physical phantom study, the average ΔDmin, ΔDmax, ΔDmean, and ΔV100% of planned PTV doses were 38.1% (±30.8%), 3.5% (±5.1%), 3.0% (±2.6%), and 8.8% (±8.0%), respectively. The corresponding values of FDK PTV doses were 5.8% (±4.5%), 1.6% (±1.6%), 2.0% (±0.9%), and 9.3% (±10.5%), respectively. In contrast, the corresponding values of MM-FD PTV doses were 0.4% (±0.8%), 0.8% (±1.0%), 0.5% (±0.4%), and 0.8% (±0.8%), respectively. For the 4D dose accumulation study, the average (± standard deviation) absolute dose deviation (normalized by local doses) between the accumulated doses and the OSL measured doses was 3.3% (±2.7%). The average gamma index (3%/3 mm) between the accumulated doses and the radiochromic film measured doses was 94.5% (±2.5%).MM-FD estimated 4D-CBCT enables accurate on-board dose calculation and accumulation for lung radiation therapy. It can potentially be valuable for treatment quality assessment and adaptive radiation therapy.

Authors
Zhang, Y; Yin, F-F; Ren, L
MLA Citation
Zhang, Y, Yin, F-F, and Ren, L. "Dosimetric verification of lung cancer treatment using the CBCTs estimated from limited-angle on-board projections." Medical physics 42.8 (August 2015): 4783-4795.
PMID
26233206
Source
epmc
Published In
Medical physics
Volume
42
Issue
8
Publish Date
2015
Start Page
4783
End Page
4795
DOI
10.1118/1.4926559

WE-G-BRD-06: Volumetric Cine MRI (VC-MRI) Estimated Based On Prior Knowledge for On-Board Target Localization.

PURPOSE: To develop a technique to generate on-board VC-MRI using patient prior 4D-MRI, motion modeling and on-board 2D-cine MRI for real-time 3D target verification of liver and lung radiotherapy. METHODS: The end-expiration phase images of a 4D-MRI acquired during patient simulation are used as patient prior images. Principal component analysis (PCA) is used to extract 3 major respiratory deformation patterns from the Deformation Field Maps (DFMs) generated between end-expiration phase and all other phases. On-board 2D-cine MRI images are acquired in the axial view. The on-board VC-MRI at any instant is considered as a deformation of the prior MRI at the end-expiration phase. The DFM is represented as a linear combination of the 3 major deformation patterns. The coefficients of the deformation patterns are solved by matching the corresponding 2D slice of the estimated VC-MRI with the acquired single 2D-cine MRI. The method was evaluated using both XCAT (a computerized patient model) simulation of lung cancer patients and MRI data from a real liver cancer patient. The 3D-MRI at every phase except end-expiration phase was used to simulate the ground-truth on-board VC-MRI at different instances, and the center-tumor slice was selected to simulate the on-board 2D-cine images. RESULTS: Image subtraction of ground truth with estimated on-board VC-MRI shows fewer differences than image subtraction of ground truth with prior image. Excellent agreement between profiles was achieved. The normalized cross correlation coefficients between the estimated and ground-truth in the axial, coronal and sagittal views for each time step were >= 0.982, 0.905, 0.961 for XCAT data and >= 0.998, 0.911, 0.9541 for patient data. For XCAT data, the maximum-Volume-Percent-Difference between ground-truth and estimated tumor volumes was 1.6% and the maximum-Center-of-Mass-Shift was 0.9 mm. CONCLUSION: Preliminary studies demonstrated the feasibility to estimate real-time VC-MRI for on-board target localization before or during radiotherapy treatments. National Institutes of Health Grant No. R01-CA184173; Varian Medical System.

Authors
Harris, W; Yin, F; Cai, J; Zhang, Y; Ren, L
MLA Citation
Harris, W, Yin, F, Cai, J, Zhang, Y, and Ren, L. "WE-G-BRD-06: Volumetric Cine MRI (VC-MRI) Estimated Based On Prior Knowledge for On-Board Target Localization." Medical physics 42.6 (June 2015): 3689-.
PMID
26129362
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3689
DOI
10.1118/1.4926062

SU-E-T-341: DVH-Based Comparison of True 3D Measurements to a Delta4 System.

PURPOSE: Delta4 dosimetric software can be used to calculate DVH-based metrics for patient-specific quality assurance from measurements made by a Delta4 QA device. This study investigates the effectiveness of a novel transform method that transposes measurements made with a full-density 3D dosimeter onto patient anatomy, enabling the calculation of DVHs. This allows for DVH comparisons from the transformed dose distribution, which are based on true 3D measurements, to those from the Delta4 system, which are based on semi-3D measurements and interpolation. METHODS: A double-arc VMAT treatment for a head-and-neck case was delivered to a 1kg PRESAGE 3D dosimeter inserted into a polyurethane head phantom. The dosimeter was readout using an in-house optical-CT scanner to gather full-density 3D dosimetric data. The transform method is achieved by multiplication of the measured doses with a "transformation matrix" which accounts for heterogeneities and differences in geometry between the patient and the phantom. The transformation matrix is a voxel-by-voxel division of the patient planned dose by the phantom planned dose, both calculated in the treatment planning system (Eclipse). The transformed distribution was then overlaid on the patient CT data, enabling the calculation of DVHs. The same VMAT treatment was delivered to the Delta4 phantom and DVH data was calculated using its associated software. RESULTS: The transformed dose distribution showed good agreement with calculated patient values, determined by similarity in dose profiles between the two distributions and a 3D gamma index passing rate of 94.87% for 3%/3mm criteria. For every structure contained within the dosimeter volume, the transformed DVHs demonstrated better agreement than the Delta4 DVHs, when compared to the values calculated in the treatment planning system. CONCLUSION: The coupled technique of full-density 3D dose measurements and the presented transform method enables clinical patient-specific quality assurance data that is more accurate than the semi-3D Delta4 system. This work was supported by NIH R01CA100835.

Authors
Crockett, E; Oldham, M; Ren, L
MLA Citation
Crockett, E, Oldham, M, and Ren, L. "SU-E-T-341: DVH-Based Comparison of True 3D Measurements to a Delta4 System." Medical physics 42.6 (June 2015): 3411-.
PMID
26128004
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3411
DOI
10.1118/1.4924702

TH-D-BRD-01: X-Ray Based Real Time Imaging Verification.

UNLABELLED: Radiotherapy of moving targets, such as lung, liver or prostate tumors, is prone to treatment errors due to the uncertainties in the target position. Minimizing such error is critical for radiotherapy treatments, especially hypofractionated SBRT treatments. On-board real time imaging verification and tracking of moving targets has become one of the most exciting areas in radiotherapy. The tremendous developments in this area enable us to improve targeting accuracy and reduce the healthy tissue toxicity, which paves the road to further margin reduction and dose escalation in conventionally fractionated or SBRT treatments.Over the past few years, several real-time imaging techniques have been clinically implemented, including techniques using ionizing radiation, such as x-ray based imaging, and radiation-free techniques such as MRI, imaging based on implanted electromagnetic transponders and optical imaging. The x-ray imaging techniques are widely accessible in clinics, although they have limited soft tissue contrast and contribute to patient exposure. Recently, MRI has gained wide interests in radiotherapy due to its better soft tissue contrast and no radiation dose. Imaging based on electromagnetic transponders and optical imaging have also gained popularity in many clinical scenarios due to their unique capabilities.Based on these imaging techniques, various tracking approaches have been developed. The room mounted orthogonal 2D x-ray system (CyberKnife system) was the first medical device capable to perform real-time target tracking by combining image guidance with robotically targeted radiation delivery. In the Vero system, tumor tracking is achieved by combining image-guidance with a two-dimensional pivot assembly of the linear accelerator. In gantry-based linear accelerators, target motion can be tracked in real time by repositioning the MLC based on the signal from x-ray images or electromagnetic transponders implanted.The rapid development of new imaging and tracking technologies raises new challenges in revolutionizing our treatment procedures. It becomes important to understand the functionality, limitations and clinical impact of each technique so that they can be chosen wisely for different clinical settings. The goal of this educational session is to compare and contrast different imaging and tracking techniques implemented in CyberKnife, Vero, MRI based, and gantry-based radiotherapy machines. The general concepts of real-time imaging and tracking, from imaging the target to adapting the treatment, will be reviewed for each modality. While discussing the technical aspects of the systems including the overall uncertainties and residual imaging and tracking errors, emphasis will be placed on the clinical implementation and workflow. The increased patient dose due to x-ray imaging and quality assurance procedures will be described. Additionally, the impact of tracking on treatment volume and margin reduction will be discussed. The session will close with an outlook at future developments. LEARNING OBJECTIVES: 1.Understand the opportunities and challenges of real time imaging and tumor tracking.2.Understand the advantages and limitations of different imaging and tracking techniques, as well as the clinical implementation of each technique.3.Understand the clinical impact of real time tumor tracking and future directions in this area.Supported by National Institutes of Health, Varian Medical System, Accuray Inc.

Authors
Ren, L
MLA Citation
Ren, L. "TH-D-BRD-01: X-Ray Based Real Time Imaging Verification." Medical physics 42.6 (June 2015): 3738-.
PMID
26129578
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3738
DOI
10.1118/1.4926279

TH-CD-303-06: Deformable Registration-Based Image Estimation Method for 4D CBCT Using Region-Based PCA.

PURPOSE: To investigate the feasibility of using region-based principal component analysis (PCA) for motion modeling to estimate on-board 4D-CBCT using prior information and limited angle projections for potential 4D target verification of lung radiotherapy. METHODS: A technique for lung 4D-CBCT reconstruction has been previously developed using a deformation field map (DFM)-based strategy. In this method, each phase of the 4D-CBCT is generated by deforming a prior CT volume. The DFM is solved by a motion modeling based on global PCA and free-form deformation (MM-FD) technique, using data fidelity constraint and the deformation energy minimization. For this study, a new region-based PCA method was developed to optimize the motion-modeling part of the MM-FD technique in order to estimate target delineation more accurately using fewer on-board projection angles. First, the DFMs are estimated using the region-based PCA divides the motion model extracted from planning 4D-CT into two regions: tumor and everything else. The motion model parameters of both regions are optimized together based on data fidelity constraint with relative weighting added to the tumor PCA model. The 4D digital extended cardiac-torso phantom was used to evaluate the region-based PCA MM-FD technique. A lung patient with a 30 mm diameter lesion was simulated with various anatomical and respirational changes from planning 4D CT to onboard volume. The reconstruction accuracy was evaluated by the Volume-Percent-Difference(VPD)/Center-of-Mass-Shift(COMS) between lesions in the estimated and "ground-truth" on board 4D CBCT. RESULTS: For patient scenarios with various shifts of tumor from planning CT to on-board acquisition with 15 degree orthogonal projections, the average VPD/COMS for the MM-FD technique was 5.04%/0.26 mm and 23.23%/2.4mm for region-based and global PCA MM-FD, respectively. CONCLUSION: The region-based PCA MM-FD technique can potentially further reduces the scan angle needed for onboard 4D CBCT reconstruction for ultra-fast 4D verification. National Institutes of Health Grant No. R01-CA184173 Varian Medical System.

Authors
Harris, W; Zhang, Y; Yin, F; Ren, L
MLA Citation
Harris, W, Zhang, Y, Yin, F, and Ren, L. "TH-CD-303-06: Deformable Registration-Based Image Estimation Method for 4D CBCT Using Region-Based PCA." Medical physics 42.6 (June 2015): 3729-.
PMID
26129540
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3729
DOI
10.1118/1.4926241

TH-AB-303-02: An Investigation of Respiratory Signal Parameters for Multiple-Step Ahead Prediction of Surrogate Motion.

PURPOSE: Target tracking or gating the radiation beam using real-time imaging and surrogate motion monitoring methods are employed for dynamic tracking treatment or respiratory-gated radiotherapy. This method requires tumor motion prediction far enough in advance. This study investigated the effect of various respiratory motion parameters on the prediction accuracy of tumor motion in a newly developed prediction algorithm. METHODS: The algorithm takes a one-dimensional surrogate signal of amplitude versus time, which is further divided into three components: training, input, and analysis components used as a validation against the prediction. The prediction algorithm consists of three major steps: (1)extracting top-ranked subcomponents from training component which best-match the input component; (2)calculating weighting factors from these best-matched subcomponents; (3)fusing the proceeding optimal subcomponents with assigned weighting factors to form prediction. The prediction algorithm was examined using respiratory signals obtained from 30 simulations for prediction algorithm parameter optimization, and 555 phantom and patient data from the respiratory positioning management device. The analysis and input components were calculated for both a full and half respiratory cycle. Performance is assessed on correlation and root mean square error (RMSE) between prediction and analysis component. RESULTS: Average correlation between prediction and analysis component was 0.720±0.390, 0.727±0.383, 0.535±0.454, 0.725±0.397, and 0.725±0.398 for full respiratory cycle prediction and 0.789±0.398, 0.800±0.385, 0.426±0.562, 0.784±0.389, and 0.784±0.389 for half respiratory cycle prediction for equal, relative, pattern, derivative equal and derivative relative weighting methods, respectively. Wilcoxon signed-rank test (p-test) between the full and half respiratory cycle correlations for each algorithm Result in statistically highly significant results (p<0.1%), in favor of a half respiratory cycle prediction in all cases except for Pattern Method. CONCLUSION: The prediction algorithms are effective in estimating surrogate motion multiple-steps in advance. Statistical analysis indicates an advantage in using a half cycle prediction. Relative weighting method shows the best prediction accuracy.

Authors
Zawisza, I; Ren, L; Yin, F
MLA Citation
Zawisza, I, Ren, L, and Yin, F. "TH-AB-303-02: An Investigation of Respiratory Signal Parameters for Multiple-Step Ahead Prediction of Surrogate Motion." Medical physics 42.6 (June 2015): 3711-.
PMID
26129460
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3711
DOI
10.1118/1.4926157

WE-EF-207-04: An Inter-Projection Sensor Fusion (IPSF) Approach to Estimate Missing Projection Signal in Synchronized Moving Grid (SMOG) System.

PURPOSE: A synchronized moving grid (SMOG) has been proposed to reduce scatter and lag artifacts in cone beam computed tomography (CBCT). However, information is missing in each projection because certain areas are blocked by the grid. A previous solution to this issue is acquiring 2 complimentary projections at each position, which increases scanning time. This study reports our first Result using an inter-projection sensor fusion (IPSF) method to estimate missing projection in our prototype SMOG-based CBCT system. METHODS: An in-house SMOG assembling with a 1:1 grid of 3 mm gap has been installed in a CBCT benchtop. The grid moves back and forth in a 3-mm amplitude and up-to 20-Hz frequency. A control program in LabView synchronizes the grid motion with the platform rotation and x-ray firing so that the grid patterns for any two neighboring projections are complimentary. A Catphan was scanned with 360 projections. After scatter correction, the IPSF algorithm was applied to estimate missing signal for each projection using the information from the 2 neighboring projections. Feldkamp-Davis-Kress (FDK) algorithm was applied to reconstruct CBCT images. The CBCTs were compared to those reconstructed using normal projections without applying the SMOG system. RESULTS: The SMOG-IPSF method may reduce image dose by half due to the blocked radiation by the grid. The method almost completely removed scatter related artifacts, such as the cupping artifacts. The evaluation of line pair patterns in the CatPhan suggested that the spatial resolution degradation was minimal. CONCLUSION: The SMOG-IPSF is promising in reducing scatter artifacts and improving image quality while reducing radiation dose.

Authors
Zhang, H; Ren, L; Kong, V; Zhang, Y; Giles, W; Jin, J
MLA Citation
Zhang, H, Ren, L, Kong, V, Zhang, Y, Giles, W, and Jin, J. "WE-EF-207-04: An Inter-Projection Sensor Fusion (IPSF) Approach to Estimate Missing Projection Signal in Synchronized Moving Grid (SMOG) System." Medical physics 42.6 (June 2015): 3681-.
PMID
26129310
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3681
DOI
10.1118/1.4926011

WE-EF-207-08: Improve Cone Beam CT Using a Synchronized Moving Grid, An Inter-Projection Sensor Fusion and a Probability Total Variation Reconstruction.

PURPOSE: To present a cone beam computed tomography (CBCT) system, which uses a synchronized moving grid (SMOG) to reduce and correct scatter, an inter-projection sensor fusion (IPSF) algorithm to estimate the missing information blocked by the grid, and a probability total variation (pTV) algorithm to reconstruct the CBCT image. METHODS: A prototype SMOG-equipped CBCT system was developed, and was used to acquire gridded projections with complimentary grid patterns in two neighboring projections. Scatter was reduced by the grid, and the remaining scatter was corrected by measuring it under the grid. An IPSF algorithm was used to estimate the missing information in a projection from data in its 2 neighboring projections. Feldkamp-Davis-Kress (FDK) algorithm was used to reconstruct the initial CBCT image using projections after IPSF processing for pTV. A probability map was generated depending on the confidence of estimation in IPSF for the regions of missing data and penumbra. pTV was finally used to reconstruct the CBCT image for a Catphan, and was compared to conventional CBCT image without using SMOG, images without using IPSF (SMOG + FDK and SMOG + mask-TV), and image without using pTV (SMOG + IPSF + FDK). RESULTS: The conventional CBCT without using SMOG shows apparent scatter-induced cup artifacts. The approaches with SMOG but without IPSF show severe (SMOG + FDK) or additional (SMOG + TV) artifacts, possibly due to using projections of missing data. The 2 approaches with SMOG + IPSF removes the cup artifacts, and the pTV approach is superior than the FDK by substantially reducing the noise. Using the SMOG also reduces half of the imaging dose. CONCLUSION: The proposed technique is promising in improving CBCT image quality while reducing imaging dose.

Authors
Zhang, H; Ren, L; Kong, V; Zhang, Y; Giles, W; Jin, J
MLA Citation
Zhang, H, Ren, L, Kong, V, Zhang, Y, Giles, W, and Jin, J. "WE-EF-207-08: Improve Cone Beam CT Using a Synchronized Moving Grid, An Inter-Projection Sensor Fusion and a Probability Total Variation Reconstruction." Medical physics 42.6 (June 2015): 3682-.
PMID
26129316
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3682
DOI
10.1118/1.4926015

WE-D-303-05: Dosimetric Accuracy of CBCT Images Estimated by a Motion Modeling and Free-Form Deformation Technique for Radiotherapy of Lung Cancer.

PURPOSE: To investigate the dosimetric accuracy of CBCTs estimated by a motion modeling and free-form deformation(MM-FD) technique for radiotherapy of lung cancer. METHODS: Various inter-fractional variations featuring patient motion pattern change, tumor size change and tumor average position change were simulated from planning-CT to on-board images using both digital and physical motion phantoms. The doses calculated on the planning-CT (planned doses), the on-board CBCT estimated by MM-FD (MM-FD doses) and the on-board CBCT reconstructed by the conventional Feldkamp-Davis-Kress(FDK) algorithm (FDK doses) were compared to the on-board dose calculated on the 'gold-standard' on-board images (gold-standard doses). The absolute deviations of minimum dose (dDmin), maximum dose (dDmax), mean dose (dDmean) and dose coverage (dV100%) of PTV were evaluated. In addition, 4D on-board dose accumulations were performed using the 4D-CBCT images estimated by MM-FD. The accumulated doses were compared to measurements using OSL detectors and radiochromic films. RESULTS: Of all the 50 scenarios simulated, the average(± standard deviation) dDmin, dDmax, dDmean and dV100% (values normalized by the prescription dose or the PTV volume) between the planned and the gold-standard PTV doses were 34.8% (± 29.2%), 3.2% (± 3.8%), 3.5% (± 3.5%) and 13.0% (± 11.4%), respectively. The corresponding values of FDK PTV doses were 3.1% (± 3.7%), 1.4% (± 1.1%), 2.1% (± 0.8%) and 14.5% (± 14.2%), respectively. In contrast, the corresponding values of MM-FD PTV doses were 0.4% (± 0.5%), 0.9% (± 0.7%), 0.6% (± 0.4%) and 0.9% (± 0.8%), respectively.For the 4D dose accumulation study, the average(± standard deviation) absolute dose deviation (normalized by local doses) between the accumulated doses and the OSL measured doses was 3.0% (± 2.4%). The average gamma pass-rate(3%/3mm) between the accumulated doses and the radiochromic film measured doses was 96.1%. CONCLUSION: MM-FD estimated CBCT enables accurate on-board dose calculation and accumulation for lung radiation therapy. The research was funded by the National Institutes of Health Grant No. R01-CA184173 and a grant from Varian Medical Systems.

Authors
Zhang, Y; Yin, F; Ren, L
MLA Citation
Zhang, Y, Yin, F, and Ren, L. "WE-D-303-05: Dosimetric Accuracy of CBCT Images Estimated by a Motion Modeling and Free-Form Deformation Technique for Radiotherapy of Lung Cancer." Medical physics 42.6 (June 2015): 3669-.
PMID
26129239
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3669
DOI
10.1118/1.4925940

WE-D-303-06: Multi-Layer Spectral Analysis for Tensor Structure Encoding of 4D Deformation Field Data.

PURPOSE: Adaptive denoising and encoding of 4D deformation-vector-field (DVF) extracted from 4D planning CT, for modeling patient dominant motion features across coupled trajectory dimensions and respiratory phases. METHODS: We propose a multi-layer spectral analysis method to capture inherent structure in 4D deformation fields such as those obtained from phase-correlated 4D-CT data. We illustrate the method with two particular two-layer schemes. One involves phase analysis of 3D trajectories at the first layer, followed by directional analysis of deformation trajectories within each time-spectral component. In the other scheme, we first analyze dominant features in the joint direction-phase trajectory space at the first layer; at the second layer, we separate the directional and temporal variables and discard residual noise which may be correlated in the joint space. With either scheme, directional and phase-wise coherence are preserved. Essentially, we regard the DVF data as a tensor that spans space (voxels), direction (deformation vectors), and time (respiratory phases). The method can be extended to multiple layers and augmented with prior structure. Dominant components across layers may be extracted automatically according to a prescribed dominance percentile. RESULTS: We have investigated the feasibility and efficacy of the two schemes using a set of DVFs across 10 respiratory phases in a digital XCAT phantom 4D-CT. Dominant multi-layer spectral components are shown to capture a different spectral structure than their single-layer counterparts, attesting to the multi-dimensional nature of motion features. We are proceeding to analyze real patient data where motion patterns and correlations may be more complex and noisy. CONCLUSION: The proposed methodology provides an interpretable, adaptable feature space for motion model extraction and compressive encoding. Noise components may be removed in different spectral regions, while preserving temporal, directional, and spatial motion coherence. The resulting motion models have the potential to improve deformable image reconstruction using motion models. National Institutes of Health Grant No. R01-CA184173.

Authors
Iliopoulos, AS; Zhang, Y; Pitsianis, N; Sun, X; Yin, FF; Ren, L
MLA Citation
Iliopoulos, AS, Zhang, Y, Pitsianis, N, Sun, X, Yin, FF, and Ren, L. "WE-D-303-06: Multi-Layer Spectral Analysis for Tensor Structure Encoding of 4D Deformation Field Data." Medical physics 42.6 (June 2015): 3669-.
PMID
26129241
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3669
DOI
10.1118/1.4925941

WE-AB-303-01: FEATURED PRESENTATION: A Dual-Detector Phase-Matched Digital Tomosynthesis (DTS) Imaging Scheme Using Aggregated KV and MV Projections for Intra-Treatment Lung Tumor Tracking.

PURPOSE: To develop a dual-detector phase-matched DTS technique for continuous and fast intra-treatment lung tumor localization. METHODS: Tumor localization accuracy of limited-angle DTS imaging is affected by low inter-slice resolution. The dual-detector DTS technique aims to overcome this limitation through combining orthogonally acquired beam's eye view MV projections and kV projections for intra-treatment DTS reconstruction and localization. To aggregate the kV and MV projections for reconstruction, the MV projections were linearly converted to synthesize corresponding kV projections. To further address the lung motion induced localization errors, this technique uses respiratory phase-matching to match the motion information between on-board DTS and reference DTS to offset the adverse effects of motion blurriness in tumor localization.A study was performed using the CIRS008A lung phantom to simulate different on-board target variation scenarios for localization. The intra-treatment kV and MV acquisition was achieved through the Varian TrueBeam Developer Mode. Four methods were compared for their localization accuracy: 1. the proposed dual-detector phase-matched DTS technique; 2. the single-detector phase-matched DTS technique; 3. the dual-detector 3D-DTS technique without phase-matching; and 4. the single-detector 3D-DTS technique without phase-matching. RESULTS: For scan angles of 2.5°, 5°, 10°, 20° and 30°, the dual-detector phase-matched DTS technique localized the tumor with average(±standard deviations) errors of 0.4±0.3 mm, 0.5±0.3 mm, 0.6±0.2 mm, 0.9±0.4 mm and 1.0±0.3 mm, respectively. The corresponding values of single-detector phase-matched DTS technique were 4.0±2.5 mm, 2.7±1.1 mm, 1.7±1.2 mm, 2.2±0.9 mm and 1.5±0.8 mm, respectively. The values of dual-detector 3D-DTS technique were 6.2±1.7 mm, 6.3±1.2 mm, 5.3±1.3 mm, 2.0±2.2 mm and 1.5±0.5 mm, respectively. And the values of single-detector 3D-DTS technique were 9.7±8.9 mm, 9.8±8.8 mm, 10.0±9.7 mm, 3.9±2.7 mm and 2.2±1.3 mm, respectively. CONCLUSION: The dual-detector phase-matched DTS technique substantially improves the tumor localization accuracy, which can be applied to real-time intra-treatment lung tumor localization. The research was funded by the National Institutes of Health Grant No. R01-CA184173 and a grant from Varian Medical Systems.

Authors
Zhang, Y; Yin, F; Mao, R; Gao, R; Ren, L
MLA Citation
Zhang, Y, Yin, F, Mao, R, Gao, R, and Ren, L. "WE-AB-303-01: FEATURED PRESENTATION: A Dual-Detector Phase-Matched Digital Tomosynthesis (DTS) Imaging Scheme Using Aggregated KV and MV Projections for Intra-Treatment Lung Tumor Tracking." Medical physics 42.6 (June 2015): 3655-.
PMID
26129166
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3655
DOI
10.1118/1.4925866

WE-AB-303-09: Rapid Projection Computations for On-Board Digital Tomosynthesis in Radiation Therapy.

PURPOSE: To facilitate fast and accurate iterative volumetric image reconstruction from limited-angle on-board projections. METHODS: Intrafraction motion hinders the clinical applicability of modern radiotherapy techniques, such as lung stereotactic body radiation therapy (SBRT). The LIVE system may impact clinical practice by recovering volumetric information via Digital Tomosynthesis (DTS), thus entailing low time and radiation dose for image acquisition during treatment. The DTS is estimated as a deformation of prior CT via iterative registration with on-board images; this shifts the challenge to the computational domain, owing largely to repeated projection computations across iterations. We address this issue by composing efficient digital projection operators from their constituent parts. This allows us to separate the static (projection geometry) and dynamic (volume/image data) parts of projection operations by means of pre-computations, enabling fast on-board processing, while also relaxing constraints on underlying numerical models (e.g. regridding interpolation kernels). Further decoupling the projectors into simpler ones ensures the incurred memory overhead remains low, within the capacity of a single GPU. These operators depend only on the treatment plan and may be reused across iterations and patients. The dynamic processing load is kept to a minimum and maps well to the GPU computational model. RESULTS: We have integrated efficient, pre-computable modules for volumetric ray-casting and FDK-based back-projection with the LIVE processing pipeline. Our results show a 60x acceleration of the DTS computations, compared to the previous version, using a single GPU; presently, reconstruction is attained within a couple of minutes. The present implementation allows for significant flexibility in terms of the numerical and operational projection model; we are investigating the benefit of further optimizations and accurate digital projection sub-kernels. CONCLUSION: Composable projection operators constitute a versatile research tool which can greatly accelerate iterative registration algorithms and may be conducive to the clinical applicability of LIVE. National Institutes of Health Grant No. R01-CA184173; GPU donation by NVIDIA Corporation.

Authors
Iliopoulos, AS; Pitsianis, N; Sun, X; Yin, FF; Ren, L
MLA Citation
Iliopoulos, AS, Pitsianis, N, Sun, X, Yin, FF, and Ren, L. "WE-AB-303-09: Rapid Projection Computations for On-Board Digital Tomosynthesis in Radiation Therapy." Medical physics 42.6 (June 2015): 3658-.
PMID
26129177
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3658
DOI
10.1118/1.4925874

SU-E-T-293: Dosimetric Analysis of Microscopic Disease in SBRT for Lung Cancers.

PURPOSE: To evaluate the dosimetry of microscopic disease (MD) region of lung cancer in stereotactic body radiation therapy (SBRT). METHODS: For simplicity, we assume organ moves along one dimension. The probability distribution function of tumor position was calculated according to the breathing cycle. The dose to the MD region was obtained through accumulating the treatment planning system calculated doses at different positions in a breathing cycle. A phantom experiment was then conducted to validate the calculated results using a motion phantom (The CIRS 'Dynamic' Thorax Phantom). The simulated breathing pattern used a cos4(x) curve with an amplitude of 10mm. A 3-D conformal 7-field plan with 6X energy was created and the dose was calculated in the average intensity projection (AIP) simulation CT images. Both films (EBT2) and optically stimulated luminescence (OSL) detectors were inserted in the target of the phantom to measure the dose during radiation delivery (Varian Truebeam) and results were compared to planning dose parameters. RESULTS: The Gamma analysis (3%/3mm) between measured dose using EBT2 film and calculated dose using AIP was 80.5%, indicating substantial dosimetric differences. While the Gamma analysis (3%/3mm) between measured dose using EBT2 and accumulated dose using 4D-CT was 98.9%, indicating the necessity of dose accumulation using 4D-CT. The measured doses using OSL and theoretically calculated doses using probability distribution function at the corresponding position were comparable. CONCLUSION: Use of static dose calculation in the treatment planning system could substantially underestimate the actually delivered dose in the MD region for a moving target. Funding Supported by NSFC, No.81372436.

Authors
Mao, R; Zhang, Y; Ren, L; Tian, L; Gao, R; Ge, H; Yin, F
MLA Citation
Mao, R, Zhang, Y, Ren, L, Tian, L, Gao, R, Ge, H, and Yin, F. "SU-E-T-293: Dosimetric Analysis of Microscopic Disease in SBRT for Lung Cancers." Medical physics 42.6 (June 2015): 3400-.
PMID
26127955
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3400
DOI
10.1118/1.4924655

SU-E-J-26: A Novel Technique for Markerless Self-Sorted 4D-CBCT Using Patient Motion Modeling: A Feasibility Study.

PURPOSE: To develop an automatic markerless 4D-CBCT projection sorting technique by using a patient respiratory motion model extracted from the planning 4D-CT images. METHODS: Each phase of onboard 4D-CBCT is considered as a deformation of one phase of the prior planning 4D-CT. The deformation field map (DFM) is represented as a linear combination of three major deformation patterns extracted from the planning 4D-CT using principle component analysis (PCA). The coefficients of the PCA deformation patterns are solved by matching the digitally reconstructed radiograph (DRR) of the deformed volume to the onboard projection acquired. The PCA coefficients are solved for each single projection, and are used for phase sorting. Projections at the peaks of the Z direction coefficient are sorted as phase 1 and other projections are assigned into 10 phase bins by dividing phases equally between peaks. The 4D digital extended-cardiac-torso (XCAT) phantom was used to evaluate the proposed technique. Three scenarios were simulated, with different tumor motion amplitude (3cm to 2cm), tumor spatial shift (8mm SI), and tumor body motion phase shift (2 phases) from prior to on-board images. Projections were simulated over 180 degree scan-angle for the 4D-XCAT. The percentage of accurately binned projections across entire dataset was calculated to represent the phase sorting accuracy. RESULTS: With a changed tumor motion amplitude from 3cm to 2cm, markerless phase sorting accuracy was 100%. With a tumor phase shift of 2 phases w.r.t. body motion, the phase sorting accuracy was 100%. With a tumor spatial shift of 8mm in SI direction, phase sorting accuracy was 86.1%. CONCLUSION: The XCAT phantom simulation results demonstrated that it is feasible to use prior knowledge and motion modeling technique to achieve markerless 4D-CBCT phase sorting. National Institutes of Health Grant No. R01-CA184173 Varian Medical System.

Authors
Zhang, L; Zhang, Y; Harris, W; Yin, F; Ren, L
MLA Citation
Zhang, L, Zhang, Y, Harris, W, Yin, F, and Ren, L. "SU-E-J-26: A Novel Technique for Markerless Self-Sorted 4D-CBCT Using Patient Motion Modeling: A Feasibility Study." Medical physics 42.6 (June 2015): 3269-.
PMID
26127420
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3269
DOI
10.1118/1.4924113

SU-E-I-40: Phantom Research On Monochromatic Images Taken by Dual CBCT with Multiple Energy Sets.

PURPOSE: To evaluate the quality of monochromatic images at the same virtual monochromatic energy using dual cone-beam computed tomography (CBCT) with either kV/kV or MV/kV or MV/MV energy sets. METHODS: CT images of Catphan 504 phantom were acquired using four different KV and MV settings: 80kV, 140kV, 4MV, 6MV. Three sets of monochromatic images were calculated: 80kV-140kV, 140kV-4MV and 4MV-6MV. Each set of CBCT images were reconstructed from the same selected virtual monochromatic energy of 1MeV. Contrast-to-Noise Ratios (CNRs) were calculated and compared between each pair of images with different energy sets. RESULTS: Between kV/MV and MV/MV images, the CNRs are comparable for all inserts. However, differences of CNRs were observed between the kV/kV and kV/MV images. Delrin's CNR ratio between kV/kV image and kV/MV image is 1.634. LDPE's (Low-Density Polyethylene) CNR ratio between kV/kV and kV/MV images is 0.509. Polystyrene's CNR ratio between kV/kV image and kV/MV image is 2.219. CONCLUSION: Preliminary results indicated that the CNRs calculated from CBCT images reconstructed from either kV/MV projections or MV/MV projections for the same selected virtual monochromatic energy may be comparable.

Authors
Gao, R; Wang, H; Zhang, Y; Mao, R; Ren, L; Yin, F
MLA Citation
Gao, R, Wang, H, Zhang, Y, Mao, R, Ren, L, and Yin, F. "SU-E-I-40: Phantom Research On Monochromatic Images Taken by Dual CBCT with Multiple Energy Sets." Medical physics 42.6 (June 2015): 3250-.
PMID
26127341
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3250
DOI
10.1118/1.4924037

Dosimetric Analysis of Microscopic Disease in SBRT for Lung Cancers

Authors
Mao, R; Zhang, Y; Ren, L; Tian, L; Gao, R; Ge, H; Yin, F
MLA Citation
Mao, R, Zhang, Y, Ren, L, Tian, L, Gao, R, Ge, H, and Yin, F. "Dosimetric Analysis of Microscopic Disease in SBRT for Lung Cancers." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3400
End Page
3400

Dosimetric Accuracy of CBCT Images Estimated by a Motion Modeling and Free-Form Deformation Technique for Radiotherapy of Lung Cancer

Authors
Zhang, Y; Yin, F; Ren, L
MLA Citation
Zhang, Y, Yin, F, and Ren, L. "Dosimetric Accuracy of CBCT Images Estimated by a Motion Modeling and Free-Form Deformation Technique for Radiotherapy of Lung Cancer." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3669
End Page
3669

Deformable Registration-Based Image Estimation Method for 4D CBCT Using Region-Based PCA

Authors
Harris, W; Zhang, Y; Yin, F; Ren, L
MLA Citation
Harris, W, Zhang, Y, Yin, F, and Ren, L. "Deformable Registration-Based Image Estimation Method for 4D CBCT Using Region-Based PCA." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3729
End Page
3730

Phantom Research On Monochromatic Images Taken by Dual CBCT with Multiple Energy Sets

Authors
Gao, R; Wang, H; Zhang, Y; Mao, R; Ren, L; Yin, F
MLA Citation
Gao, R, Wang, H, Zhang, Y, Mao, R, Ren, L, and Yin, F. "Phantom Research On Monochromatic Images Taken by Dual CBCT with Multiple Energy Sets." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3250
End Page
3250

FEATURED PRESENTATION: A Dual-Detector Phase-Matched Digital Tomosynthesis (DTS) Imaging Scheme Using Aggregated KV and MV Projections for Intra-Treatment Lung Tumor Tracking

Authors
Zhang, Y; Yin, F; Mao, R; Gao, R; Ren, L
MLA Citation
Zhang, Y, Yin, F, Mao, R, Gao, R, and Ren, L. "FEATURED PRESENTATION: A Dual-Detector Phase-Matched Digital Tomosynthesis (DTS) Imaging Scheme Using Aggregated KV and MV Projections for Intra-Treatment Lung Tumor Tracking." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3655
End Page
3656

A Novel Technique for Markerless Self-Sorted 4D-CBCT Using Patient Motion Modeling: A Feasibility Study

Authors
Zhang, L; Zhang, Y; Harris, W; Yin, F; Ren, L
MLA Citation
Zhang, L, Zhang, Y, Harris, W, Yin, F, and Ren, L. "A Novel Technique for Markerless Self-Sorted 4D-CBCT Using Patient Motion Modeling: A Feasibility Study." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3269
End Page
3269

Multi-Layer Spectral Analysis for Tensor Structure Encoding of 4D Deformation Field Data

Authors
Iliopoulos, AS; Zhang, Y; Pitsianis, N; Sun, X; Yin, FF; Ren, L
MLA Citation
Iliopoulos, AS, Zhang, Y, Pitsianis, N, Sun, X, Yin, FF, and Ren, L. "Multi-Layer Spectral Analysis for Tensor Structure Encoding of 4D Deformation Field Data." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3669
End Page
3670

Volumetric Cine MRI (VC-MRI) Estimated Based On Prior Knowledge for On-Board Target Localization

Authors
Harris, W; Yin, F; Cai, J; Zhang, Y; Ren, L
MLA Citation
Harris, W, Yin, F, Cai, J, Zhang, Y, and Ren, L. "Volumetric Cine MRI (VC-MRI) Estimated Based On Prior Knowledge for On-Board Target Localization." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3689
End Page
3689

An Inter-Projection Sensor Fusion (IPSF) Approach to Estimate Missing Projection Signal in Synchronized Moving Grid (SMOG) System

Authors
Zhang, H; Ren, L; Kong, V; Zhang, Y; Giles, W; Jin, J
MLA Citation
Zhang, H, Ren, L, Kong, V, Zhang, Y, Giles, W, and Jin, J. "An Inter-Projection Sensor Fusion (IPSF) Approach to Estimate Missing Projection Signal in Synchronized Moving Grid (SMOG) System." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3681
End Page
3681

Improve Cone Beam CT Using a Synchronized Moving Grid, An Inter-Projection Sensor Fusion and a Probability Total Variation Reconstruction

Authors
Zhang, H; Ren, L; Kong, V; Zhang, Y; Giles, W; Jin, J
MLA Citation
Zhang, H, Ren, L, Kong, V, Zhang, Y, Giles, W, and Jin, J. "Improve Cone Beam CT Using a Synchronized Moving Grid, An Inter-Projection Sensor Fusion and a Probability Total Variation Reconstruction." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3682
End Page
3682

An Investigation of Respiratory Signal Parameters for Multiple-Step Ahead Prediction of Surrogate Motion

Authors
Zawisza, I; Ren, L; Yin, F
MLA Citation
Zawisza, I, Ren, L, and Yin, F. "An Investigation of Respiratory Signal Parameters for Multiple-Step Ahead Prediction of Surrogate Motion." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3711
End Page
3711

Rapid Projection Computations for On-Board Digital Tomosynthesis in Radiation Therapy

Authors
Iliopoulos, AS; Pitsianis, N; Sun, X; Yin, FF; Ren, L
MLA Citation
Iliopoulos, AS, Pitsianis, N, Sun, X, Yin, FF, and Ren, L. "Rapid Projection Computations for On-Board Digital Tomosynthesis in Radiation Therapy." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3658
End Page
3658

DVH-Based Comparison of True 3D Measurements to a Delta4 System

Authors
Crockett, E; Oldham, M; Ren, L
MLA Citation
Crockett, E, Oldham, M, and Ren, L. "DVH-Based Comparison of True 3D Measurements to a Delta4 System." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3411
End Page
3412

Real Time Imaging Verification and Tracking for Moving Targets

Authors
Ren, L; Low, D; Descovich, M; Keall, P
MLA Citation
Ren, L, Low, D, Descovich, M, and Keall, P. "Real Time Imaging Verification and Tracking for Moving Targets." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3738
End Page
3739

Preliminary clinical evaluation of a 4D-CBCT estimation technique using prior information and limited-angle projections

© 2015 Elsevier Ireland Ltd. All rights reserved. Background and purpose A technique has been previously reported to estimate high-quality 4D-CBCT using prior information and limited-angle projections. This study is to investigate its clinical feasibility through both phantom and patient studies. Materials and methods The new technique used to estimate 4D-CBCT is called MMFD-NCC. It is based on the previously reported motion modeling and free-form deformation (MMFD) method, with the introduction of normalized-cross-correlation (NCC) as a new similarity metric. The clinical feasibility of this technique was evaluated by assessing the accuracy of estimated anatomical structures in comparison to those in the 'ground-truth' reference 4D-CBCTs, using data obtained from a physical phantom and three lung cancer patients. Both volume percentage error (VPE) and center-of-mass error (COME) of the estimated tumor volume were used as the evaluation metrics. Results The average VPE/COME of the tumor in the prior image was 257.1%/10.1 mm for the phantom study and 55.6%/3.8 mm for the patient study. Using only orthogonal-view 30° projections, the MMFD-NCC has reduced the corresponding values to 7.7%/1.2 mm and 9.6%/1.1 mm, respectively. Conclusion The MMFD-NCC technique is able to estimate 4D-CBCT images with geometrical accuracy of the tumor within 10% VPE and 2 mm COME, which can be used to improve the localization accuracy of radiotherapy.

Authors
Zhang, Y; Yin, FF; Pan, T; Vergalasova, I; Ren, L
MLA Citation
Zhang, Y, Yin, FF, Pan, T, Vergalasova, I, and Ren, L. "Preliminary clinical evaluation of a 4D-CBCT estimation technique using prior information and limited-angle projections." Radiotherapy and Oncology 115.1 (April 1, 2015): 22-29.
Source
scopus
Published In
Radiotherapy & Oncology
Volume
115
Issue
1
Publish Date
2015
Start Page
22
End Page
29
DOI
10.1016/j.radonc.2015.02.022

Preliminary clinical evaluation of a 4D-CBCT estimation technique using prior information and limited-angle projections.

A technique has been previously reported to estimate high-quality 4D-CBCT using prior information and limited-angle projections. This study is to investigate its clinical feasibility through both phantom and patient studies.The new technique used to estimate 4D-CBCT is called MMFD-NCC. It is based on the previously reported motion modeling and free-form deformation (MMFD) method, with the introduction of normalized-cross-correlation (NCC) as a new similarity metric. The clinical feasibility of this technique was evaluated by assessing the accuracy of estimated anatomical structures in comparison to those in the 'ground-truth' reference 4D-CBCTs, using data obtained from a physical phantom and three lung cancer patients. Both volume percentage error (VPE) and center-of-mass error (COME) of the estimated tumor volume were used as the evaluation metrics.The average VPE/COME of the tumor in the prior image was 257.1%/10.1 mm for the phantom study and 55.6%/3.8 mm for the patient study. Using only orthogonal-view 30° projections, the MMFD-NCC has reduced the corresponding values to 7.7%/1.2 mm and 9.6%/1.1 mm, respectively.The MMFD-NCC technique is able to estimate 4D-CBCT images with geometrical accuracy of the tumor within 10% VPE and 2 mm COME, which can be used to improve the localization accuracy of radiotherapy.

Authors
Zhang, Y; Yin, F-F; Pan, T; Vergalasova, I; Ren, L
MLA Citation
Zhang, Y, Yin, F-F, Pan, T, Vergalasova, I, and Ren, L. "Preliminary clinical evaluation of a 4D-CBCT estimation technique using prior information and limited-angle projections." Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology 115.1 (April 2015): 22-29.
PMID
25818396
Source
epmc
Published In
Radiotherapy & Oncology
Volume
115
Issue
1
Publish Date
2015
Start Page
22
End Page
29
DOI
10.1016/j.radonc.2015.02.022

Dosimetric Evaluation of a Limited-angle Intrafraction Verification (LIVE) System

Authors
Ren, L; Zhang, Y; Yin, F
MLA Citation
Ren, L, Zhang, Y, and Yin, F. "Dosimetric Evaluation of a Limited-angle Intrafraction Verification (LIVE) System." September 1, 2014.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
90
Publish Date
2014
Start Page
S25
End Page
S25

Lung 40-CBCT Reconstruction Using Prior Information and Limited-Angle Projections: Phantom and Patient Studies

Authors
Zhang, Y; Yin, F; Pan, T; Vergalasova, I; Ren, L
MLA Citation
Zhang, Y, Yin, F, Pan, T, Vergalasova, I, and Ren, L. "Lung 40-CBCT Reconstruction Using Prior Information and Limited-Angle Projections: Phantom and Patient Studies." September 1, 2014.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
90
Publish Date
2014
Start Page
S835
End Page
S835

An Inter-Projection Interpolation (IPI) Approach with Geometric Model Restriction to Reduce Image Dose in Cone Beam CT (CBCT).

Cone beam computed tomography (CBCT) imaging is a key step in image guided radiation therapy (IGRT) to improve tumor targeting. The quality and imaging dose of CBCT are two important factors. However, X-ray scatter in the large cone beam field usually induces image artifacts and degrades the image quality for CBCT. A synchronized moving grid (SMOG) approach has recently been proposed to resolve this issue and shows great promise. However, the SMOG technique requires two projections in the same gantry angle to obtain full information due to signal blockage by the grid. This study aims to develop an inter-projection interpolation (IPI) method to estimate the blocked image information. This approach will require only one projection in each gantry angle, thus reducing the scan time and patient dose. IPI is also potentially suitable for sparse-view CBCT reconstruction to reduce the imaging dose. To be compared with other state-of-the-art spatial interpolation (called inpainting) methods in terms of signal-to-noise ratio (SNR) on a Catphan and head phantoms, IPI increases SNR from 15.3dB and 12.7dB to 29.0dB and 28.1dB, respectively. The SNR of IPI on sparse-view CBCT reconstruction can achieve from 28dB to 17dB for undersample projection sets with gantry angle interval varying from 1 to 3 degrees for both phantoms.

Authors
Zhang, H; Kong, F; Ren, L; Jin, J-Y
MLA Citation
Zhang, H, Kong, F, Ren, L, and Jin, J-Y. "An Inter-Projection Interpolation (IPI) Approach with Geometric Model Restriction to Reduce Image Dose in Cone Beam CT (CBCT)." September 2014.
PMID
26005721
Source
epmc
Published In
Computational modeling of objects presented in images : fundamentals, methods, and applications : 4th International Conference, CompIMAGE 2014, Pittsburgh, PA, USA, September 3-5, 2014. CompIMAGE (Conference) (4th : 2014 : Pittsburgh, P..
Volume
8641
Publish Date
2014
Start Page
12
End Page
23
DOI
10.1007/978-3-319-09994-1_2

TH-A-18C-05: Scatter Reduction and Correction for Dual-Source CBCT Using the Synchronized Moving Grid (SMOG) System.

to implement the newly developed synchronized moving grid (SMOG) system on a prototype dual-source CBCT system to evaluate its efficacy for scatter reduction and correction under various settings, including different phantom size, grid ratio and image acquisition modes.A 1D grid was designed for each tube in our dual-source CBCT system. Projections were acquired with the grid at different complementary positions from each scan angle and merged for reconstruction. The scatter signal was measured from the grid blocked area and the scatter distribution was estimated by using a cubic spline interpolated/extrapolated in each projection for scatter correction. The projections without grid were also acquired as the comparing group. Three sets of images were reconstructed from projections: a) without grid, b) with grid but without scatter correction and c) with grid and with scatter correction to evaluate CNR (contrast-to-noise ratio) and CT number linearity enhancement. The efficacy of the SMOG system was evaluated using CAT phantoms with different diameters (15cm, 20cm and 30cm), grids (grid ratios of 1:1 and 2:1) and acquisition modes (simultaneous: two tubes firing at the same time and sequential: only one tube firing in one rotation).That scatter artifacts were substantially reduced with our scatter correction algorithm. CNR, degraded by the cross scatter in dual-source system, were increased by 74%, 32% and 28% for phantom size of 15cm, 20cm and 30cm respectively after using scatter correction with 1:1 grid. And in 20 cm phantom case with simultaneous acquisition, the CT number linearity improved from 0.9969 to 0.9997. Higher grid ratio (more blocked area) resulted in better scatter artifact removal and CNR improvement at the cost of complexity and increased exposure.The SMOG system can effectively reduce the scatter artifacts and enhance CNR and CT number linearity for the dual-source CBCT system. This work was supported by NIH grant R01CA166948.

Authors
Chen, Y; Zhang, Y; Giles, W; Jin, J; Yin, F; Ren, L
MLA Citation
Chen, Y, Zhang, Y, Giles, W, Jin, J, Yin, F, and Ren, L. "TH-A-18C-05: Scatter Reduction and Correction for Dual-Source CBCT Using the Synchronized Moving Grid (SMOG) System." Medical physics 41.6 (June 2014): 541-.
PMID
28037063
Source
epmc
Published In
Medical physics
Volume
41
Issue
6
Publish Date
2014
Start Page
541
DOI
10.1118/1.4889564

SU-E-T-472: A Multi-Dimensional Measurements Comparison to Analyze a 3D Patient Specific QA Tool.

To quantitatively evaluate a 3D patient specific QA tool using 2D film and 3D Presage dosimetry.A brain IMRT case was delivered to Delta4, EBT2 film and Presage plastic dosimeter. The film was inserted in the solid water slabs at 7.5cm depth for measurement. The Presage dosimeter was inserted into a head phantom for 3D dose measurement. Delta4's Anatomy software was used to calculate the corresponding dose to the film in solid water slabs and to Presage in the head phantom. The results from Anatomy were compared to both calculated results from Eclipse and measured dose from film and Presage to evaluate its accuracy. Using RIT software, we compared the "Anatomy" dose to the EBT2 film measurement and the film measurement to ECLIPSE calculation. For 3D analysis, DICOM file of "Anatomy" was extracted and imported to CERR software, which was used to compare the Presage dose to both "Anatomy" calculation and ECLIPSE calculation. Gamma criteria of 3% - 3mm and 5% - 5mm was used for comparison.Gamma passing rates of film vs "Anatomy", "Anatomy" vs ECLIPSE and film vs ECLIPSE were 82.8%, 70.9% and 87.6% respectively when 3% - 3mm criteria is used. When the criteria is changed to 5% - 5mm, the passing rates became 87.8%, 76.3% and 90.8% respectively. For 3D analysis, Anatomy vs ECLIPSE showed gamma passing rate of 86.4% and 93.3% for 3% - 3mm and 5% - 5mm respectively. The rate is 77.0% for Presage vs ECLIPSE analysis. The Anatomy vs ECLIPSE were absolute dose comparison. However, film and Presage analysis were relative comparison CONCLUSION: The results show higher passing rate in 3D than 2D in "Anatomy" software. This could be due to the higher degrees of freedom in 3D than in 2D for gamma analysis.

Authors
Ashmeg, S; Jackson, J; Zhang, Y; Oldham, M; Yin, F; Ren, L
MLA Citation
Ashmeg, S, Jackson, J, Zhang, Y, Oldham, M, Yin, F, and Ren, L. "SU-E-T-472: A Multi-Dimensional Measurements Comparison to Analyze a 3D Patient Specific QA Tool." Medical physics 41.6 (June 2014): 335-.
PMID
28036412
Source
epmc
Published In
Medical physics
Volume
41
Issue
6
Publish Date
2014
Start Page
335
DOI
10.1118/1.4888805

SU-E-I-56: Scan Angle Reduction for a Limited-Angle Intrafraction Verification (LIVE) System.

To develop a novel adaptive reconstruction strategy to further reduce the scanning angle required by the limited-angle intrafraction verification (LIVE) system for intrafraction verification.LIVE acquires limited angle MV projections from the exit fluence of the arc treatment beam or during gantry rotation between static beams. Orthogonal limited-angle kV projections are also acquired simultaneously to provide additional information. LIVE considers the on-board 4D-CBCT images as a deformation of the prior 4D-CT images, and solves the deformation field based on deformation models and data fidelity constraint. LIVE reaches a checkpoint after a limited-angle scan, and reconstructs 4D-CBCT for intrafraction verification at the checkpoint. In adaptive reconstruction strategy, a larger scanning angle of 30° is used for the first checkpoint, and smaller scanning angles of 15° are used for subsequent checkpoints. The onboard images reconstructed at the previous adjacent checkpoint are used as the prior images for reconstruction at the current checkpoint. As the algorithm only needs to reconstruct the small deformation occurred between adjacent checkpoints, projections from a smaller scan angle provide enough information for the reconstruction. XCAT was used to simulate tumor motion baseline drift of 2mm along sup-inf direction at every subsequent checkpoint, which are 15° apart. Adaptive reconstruction strategy was used to reconstruct the images at each checkpoint using orthogonal 15° kV and MV projections.Results showed that LIVE reconstructed the tumor volumes accurately using orthogonal 15° kV-MV projections. Volume percentage differences (VPDs) were within 5% and center of mass shifts (COMS) were within 1mm for reconstruction at all checkpoints.It's feasible to use an adaptive reconstruction strategy to further reduce the scan angle needed by LIVE to allow faster and more frequent intrafraction verification to minimize the treatment errors in lung cancer treatments. Grant from Varian Medical System.

Authors
Ren, L; Zhang, Y; Yin, F
MLA Citation
Ren, L, Zhang, Y, and Yin, F. "SU-E-I-56: Scan Angle Reduction for a Limited-Angle Intrafraction Verification (LIVE) System." Medical physics 41.6 (June 2014): 143-.
PMID
28038284
Source
epmc
Published In
Medical physics
Volume
41
Issue
6
Publish Date
2014
Start Page
143
DOI
10.1118/1.4888006

WE-G-BRF-03: A Quasi-Cine CBCT Reconstruction Technique for Real-Time On- Board Target Tracking of Lung Cancer Treatment.

To develop a quasi-cine CBCT reconstruction technique that uses extremely-small angle (∼3°) projections to generate real-time high-quality lung CBCT images.4D-CBCT is obtained at the beginning and used as prior images. This study uses extremely-small angle (∼3°) on-board projections acquired at a single respiratory phase to reconstruct the CBCT image at this phase. An adaptive constrained free-form deformation (ACFD) method is developed to deform the prior 4D-CBCT volume at the same phase to reconstruct the new CBCT. Quasi-cine CBCT images are obtained by continuously reconstructing CBCT images at subsequent phases every 3° angle (∼0.5s). Note that the prior 4D-CBCT images are dynamically updated using the latest CBCT images. The 4D digital extended-cardiac-torso (XCAT) phantom was used to evaluate the efficacy of ACFD. A lung patient was simulated with a tumor baseline shift of 2mm along superior-inferior (SI) direction after every respiratory cycle for 5 cycles. Limited-angle projections were simulated for each cycle. The 4D-CBCT reconstructed by these projections were compared with the ground-truth generated in XCAT.Volume-percentage-difference (VPD) and center-of-mass-shift (COMS) were calculated between the reconstructed and the ground-truth tumors to evaluate their geometric differences. The ACFD was also compared to a principal-component-analysis based motion-modeling (MM) method.Using orthogonal-view 3° projections, the VPD/COMS values for tumor baseline shifts of 2mm, 4mm, 6mm, 8mm, 10mm were 11.0%/0.3mm, 25.3%/2.7mm, 22.4%/2.9mm, 49.5%/5.4mm, 77.2%/8.1mm for the MM method, and 2.9%/0.7mm, 3.9%/0.8mm, 6.2%/1mm, 7.9%/1.2mm, 10.1%/1.1mm for the ACFD method. Using orthogonal-view 0° projections (1 projection only), the ACFD method yielded VPD/COMS results of 5.0%/0.9mm, 10.5%/1.2mm, 15.1%/1.4mm, 20.9%/1.6mm and 24.8%/1.6mm. Using single-view instead of orthogonal-view projections yielded less accurate results for ACFD.The ACFD method accurately reconstructs snapshot CBCT images using orthogonal-view 3° projections. It has a great potential to provide real-time quasi-cine CBCT images for verification in lung radiation therapy. The research is supported by grant from Varian Medical Systems.

Authors
Zhang, Y; Yin, F; Ren, L
MLA Citation
Zhang, Y, Yin, F, and Ren, L. "WE-G-BRF-03: A Quasi-Cine CBCT Reconstruction Technique for Real-Time On- Board Target Tracking of Lung Cancer Treatment." Medical physics 41.6 (June 2014): 522-.
PMID
28038093
Source
epmc
Published In
Medical physics
Volume
41
Issue
6
Publish Date
2014
Start Page
522
DOI
10.1118/1.4889496

SU-E-I-08: An Inpaint-Based Interpolation Technique to Recover Blocked Information for Cone Beam CT with a Synchronized Moving Grid (SMOG).

Synchronized moving grid (SMOG) is a promising technique to reduce scatter and ghost artifacts in cone beam computed tomography (CBCT). However, the grid blocks part of image information in each projection, and multiple projections at the same gantry angle have to been taken to obtain full information. Because of the continuity of a patient's anatomy in the projection, the blocked information may be estimated by interpolation. This study aims to evaluate an inpainting-based interpolation approach to recover the missing information for CBCT reconstruction.We used a simple region-based inpainting approach to interpolate the missing information. For a pixel to be interpolated, we divided the nearby regions having image information into 6 sub-regions: up-left, up-middle, up-right, down-left, down-middle, and down-right, each with 9 pixels. The average pixel value of each sub-region was calculated. These average values, along with the pixel location, were used to determine the interpolated pixel value. We compared our approach with the Criminisi Exemplar (CE) and total variation (TV) based inpainting techniques. Projection images of Catphan and a head phantom were used for the comparison. The SMOG was simulated by erasing the information (filling with "0") of the areas in each projection corresponding to the grid.For the Catphan, the processing time was 178, 45 and 0.98 minutes for CE, TV and our approach, respectively. The signal to noise ratio (SNR) was 19.4, 18.5 and 26.4 db, correspondingly. For the head phantom, the processing time was 222, 45 and 0.93 minutes for CE, TV and our approach, respectively. The SNR was 24.6, 20.2 and 26.2db correspondingly.We have developed a simple inpainting based interpolation approach, which can recover some of the image information for the SMOG-based CBCT imaging. This study is supported by NIH/NCI grant 1R01CA166948-01.

Authors
Kong, V; Zhang, H; Ren, L; Jin, J
MLA Citation
Kong, V, Zhang, H, Ren, L, and Jin, J. "SU-E-I-08: An Inpaint-Based Interpolation Technique to Recover Blocked Information for Cone Beam CT with a Synchronized Moving Grid (SMOG)." Medical physics 41.6 (June 2014): 131-.
PMID
28038167
Source
epmc
Published In
Medical physics
Volume
41
Issue
6
Publish Date
2014
Start Page
131
DOI
10.1118/1.4887956

SU-D-17A-01: Geometric and Dosimetric Evaluation of a 4D-CBCT Reconstruction Technique Using Prior Knowledge.

To evaluate a 4D-CBCT reconstruction technique both geometrically and dosimetrically METHODS: A prior-knowledge guided 4DC-BCT reconstruction method named the motion-modeling and free-form deformation (MM-FD) has been developed. MM-FD views each phase of the 4D-CBCT as a deformation of a prior CT volume. The deformation field is first solved by principal component analysis based motion modeling, followed by constrained free-form deformation. The 4D digital extended-cardiac- torso (XCAT) phantom was used for comprehensive evaluation. Based on a simulated 4D planning CT of a lung patient, 8 different scenarios were simulated to cover the typical on-board anatomical and respiratory variations: (1) synchronized and (2) unsynchronized motion amplitude change for body and tumor; tumor (3) shrinkage and (4) expansion; tumor average position shift in (5) superior-inferior (SI) direction, (6) anterior-posterior (AP) direction and (7) SI, AP and lateral directions altogether; and (8) tumor phase shift relative to the respiratory cycle of the body. Orthogonal-view 30° projections were simulated based on the eight patient scenarios to reconstruct on-board 4D-CBCTs. For geometric evaluation, the volume-percentage-difference (VPD) was calculated to assess the volumetric differences between the reconstructed and the ground-truth tumor.For dosimetric evaluation, a gated treatment plan was designed for the prior 4D-CT. The dose distributions were calculated on the reconstructed 4D-CBCTs and the ground-truth images for comparison. The MM-FD technique was compared with MM-only and FD-only techniques.The average (±s.d.) VPD values of reconstructed tumors for MM-only, FDonly and MM-FD methods were 59.16%(± 26.66%), 75.98%(± 27.21%) and 5.22%(± 2.12%), respectively. The average min/max/mean dose (normalized to prescription) of the reconstructed tumors by MM-only, FD-only, MM-FD methods and ground-truth tumors were 78.0%/122.2%/108.2%, 13%/117.7%/86%, 58.1%/120.8%/103.6% and 57.6%/118.6%/101.8%,respectively.The MM-FD method provides superior reconstruction accuracy both geometrically and dosimetrically, which can potentially be used for 4D target localization, dose tracking and adaptive radiation therapy. This research is supported by grant from Varian Medical Systems.

Authors
Zhang, Y; Yin, F; Ren, L
MLA Citation
Zhang, Y, Yin, F, and Ren, L. "SU-D-17A-01: Geometric and Dosimetric Evaluation of a 4D-CBCT Reconstruction Technique Using Prior Knowledge." Medical physics 41.6 (June 2014): 116-.
PMID
28037739
Source
epmc
Published In
Medical physics
Volume
41
Issue
6
Publish Date
2014
Start Page
116
DOI
10.1118/1.4887894

SU-D-18A-02: Towards Real-Time On-Board Volumetric Image Reconstruction for Intrafraction Target Verification in Radiation Therapy.

To expedite on-board volumetric image reconstruction from limited-angle kV-MV projections for intrafraction verification.A limited-angle intrafraction verification (LIVE) system has recently been developed for real-time volumetric verification of moving targets, using limited-angle kV-MV projections. Currently, it is challenged by the intensive computational load of the prior-knowledge-based reconstruction method. To accelerate LIVE, we restructure the software pipeline to make it adaptable to model and algorithm parameter changes, while enabling efficient utilization of rapidly advancing, modern computer architectures. In particular, an innovative two-level parallelization scheme has been designed: At the macroscopic level, data and operations are adaptively partitioned, taking into account algorithmic parameters and the processing capacity or constraints of underlying hardware. The control and data flows of the pipeline are scheduled in such a way as to maximize operation concurrency and minimize total processing time. At the microscopic level, the partitioned functions act as independent modules, operating on data partitions in parallel. Each module is pre-parallelized and optimized for multi-core processors (CPUs) and graphics processing units (GPUs).We present results from a parallel prototype, where most of the controls and module parallelization are carried out via Matlab and its Parallel Computing Toolbox. The reconstruction is 5 times faster on a data-set of twice the size, compared to recently reported results, without compromising on algorithmic optimization control.The prototype implementation and its results have served to assess the efficacy of our system concept. While a production implementation will yield much higher processing rates by approaching full-capacity utilization of CPUs and GPUs, some mutual constraints between algorithmic flow and architecture specifics remain. Based on a careful analysis of the prototype performance, it will be feasible to resolve such issues through appropriate algorithmic modifications or special-purpose hardware, thus enabling target verification in seconds with the LIVE system. This work was partially supported by a research grant from Varian Medical Systems.

Authors
Xu, X; Iliopoulos, A; Zhang, Y; Pitsianis, N; Sun, X; Yin, F; Ren, L
MLA Citation
Xu, X, Iliopoulos, A, Zhang, Y, Pitsianis, N, Sun, X, Yin, F, and Ren, L. "SU-D-18A-02: Towards Real-Time On-Board Volumetric Image Reconstruction for Intrafraction Target Verification in Radiation Therapy." Medical physics 41.6 (June 2014): 118-.
PMID
28037621
Source
epmc
Published In
Medical physics
Volume
41
Issue
6
Publish Date
2014
Start Page
118
DOI
10.1118/1.4887902

SU-D-12A-01: An Inter-Projection Interpolation (IPI) Approach for the Synchronized Moving Grid (SMOG) to Reduce Dose in Cone Beam CT.

Synchronized moving grid is a promising technique to reduce scatter and ghost artifacts in cone beam computed tomography (CBCT). However, it requires 2 projections in the same gantry angle to obtain full information due to signal blockage by the grid. We proposed an inter-projection interpolation (IPI) method to estimate blocked signals, which may reduce the scan time and the dose. This study aims to provide a framework to achieve a balance between speed, dose and image quality.The IPI method is based on the hypothesis that an abrupt signal in a projection can be well predicted by the information in the two immediate neighboring projections if the gantry angle step is small. The study was performed on a Catphan and a head phantom. The SMOG was simulated by erasing the information (filling with "0") of the areas in each projection corresponding to the grid. An IPI algorithm was applied on each projection to recover the erased information. FDK algorithm was used to reconstruct CBCT images for the IPI-processed projections, and compared with the original image in term of signal to noise ratio (SNR) measured in the whole reconstruction image range. The effect of gantry angle step was investigated by comparing the CBCT images from projection sets of various gantry intervals, with IPI-predicted projections to fill the missing projection in the interval.The IPI procession time was 1.79s±0.53s for each projection. SNR after IPI was 29.0db and 28.1db for the Catphan and head phantom, respectively, comparing to 15.3db and 22.7db for an inpainting based interpolation technique. SNR was 28.3, 28.3, 21.8, 19.3 and 17.3 db for gantry angle intervals of 1, 1.5, 2, 2.5 and 3 degrees, respectively.IPI is feasible to estimate the missing information, and achieve an reasonable CBCT image quality with reduced dose and scan time. This study is supported by NIH/NCI grant 1R01CA166948-01.

Authors
Zhang, H; Kong, V; Ren, L; Jin, J
MLA Citation
Zhang, H, Kong, V, Ren, L, and Jin, J. "SU-D-12A-01: An Inter-Projection Interpolation (IPI) Approach for the Synchronized Moving Grid (SMOG) to Reduce Dose in Cone Beam CT." Medical physics 41.6 (June 2014): 123-124.
PMID
28037198
Source
epmc
Published In
Medical physics
Volume
41
Issue
6
Publish Date
2014
Start Page
123
End Page
124
DOI
10.1118/1.4887925

SU-E-J-246: A Deformation-Field Map Based Liver 4D CBCT Reconstruction Method Using Gold Nanoparticles as Constraints.

To investigate the feasibility of using nanoparticle markers to validate liver tumor motion together with a deformation field map-based four dimensional (4D) cone-beam computed tomography (CBCT) reconstruction method.A technique for lung 4D-CBCT reconstruction has been previously developed using a deformation field map (DFM)-based strategy. In this method, each phase of the 4D-CBCT is considered as a deformation of a prior CT volume. The DFM is solved by a motion modeling and free-form deformation (MM-FD) technique, using a data fidelity constraint and the deformation energy minimization. For liver imaging, there is low contrast of a liver tumor in on-board projections. A validation of liver tumor motion using implanted gold nanoparticles, along with the MM-FD deformation technique is implemented to reconstruct onboard 4D CBCT liver radiotherapy images. These nanoparticles were placed around the liver tumor to reflect the tumor positions in both CT simulation and on-board image acquisition. When reconstructing each phase of the 4D-CBCT, the migrations of the gold nanoparticles act as a constraint to regularize the deformation field, along with the data fidelity and the energy minimization constraints. In this study, multiple tumor diameters and positions were simulated within the liver for on-board 4D-CBCT imaging. The on-board 4D-CBCT reconstructed by the proposed method was compared with the "ground truth" image.The preliminary data, which uses reconstruction for lung radiotherapy suggests that the advanced reconstruction algorithm including the gold nanoparticle constraint will Resultin volume percentage differences (VPD) between lesions in reconstructed images by MM-FD and "ground truth" on-board images of 11.5% (± 9.4%) and a center of mass shift of 1.3 mm (± 1.3 mm) for liver radiotherapy.The advanced MM-FD technique enforcing the additional constraints from gold nanoparticles, results in improved accuracy for reconstructing on-board 4D-CBCT of liver tumor. Varian medical systems research grant.

Authors
Harris, W; Zhang, Y; Ren, L; Yin, F
MLA Citation
Harris, W, Zhang, Y, Ren, L, and Yin, F. "SU-E-J-246: A Deformation-Field Map Based Liver 4D CBCT Reconstruction Method Using Gold Nanoparticles as Constraints." Medical physics 41.6 (June 2014): 214-.
PMID
28037519
Source
epmc
Published In
Medical physics
Volume
41
Issue
6
Publish Date
2014
Start Page
214
DOI
10.1118/1.4888300

SU-E-T-159: Evaluation of a Patient Specific QA Tool Based On TG119.

To evaluate the accuracy of a 3D patient specific QA tool by analysis of the results produced from associated software in homogenous phantom and heterogonous patient CT.IMRT and VMAT plans of five test suites introduced by TG119 were created in ECLIPSE on a solid water phantom. The ten plans -of increasing complexity- were delivered to Delta4 to give a 3D measurement. The Delta4's "Anatomy" software uses the measured dose to back-calculate the energy fluence of the delivered beams, which is used for dose calculation in a patient CT using a pencilbeam algorithm. The effect of the modulated beams' complexity on the accuracy of the "Anatomy" calculation was evaluated. Both measured and Anatomy doses were compared to ECLIPSE calculation using 3% - 3mm gamma criteria.We also tested the effect of heterogeneity by analyzing the results of "Anatomy" calculation on a Brain VMAT and a 3D conformal lung cases.In homogenous phantom, the gamma passing rates were found to be as low as 74.75% for a complex plan with high modulation. The mean passing rates were 91.47% ± 6.35% for "Anatomy" calculation and 99.46% ± 0.62% for Delta4 measurements.As for the heterogeneous cases, the rates were 96.54%±3.67% and 83.87%±9.42% for Brain VMAT and 3D lung respectively. This increased error in the lung case could be due to the use of the pencil beam algorithm as opposed to the AAA used by ECLIPSE.Also, gamma analysis showed high discrepancy along the beam edge in the "Anatomy" calculated results. This suggests a poor beam modeling in the penumbra region.The results show various sources of errors in "Anatomy" calculations. These include beam modeling in the penumbra region, complexity of a modulated beam (shown in homogenous phantom and brain cases) and dose calculation algorithms (3D conformal lung case).

Authors
Ashmeg, S; Zhang, Y; O' Daniel, J; Yin, F; Ren, L
MLA Citation
Ashmeg, S, Zhang, Y, O' Daniel, J, Yin, F, and Ren, L. "SU-E-T-159: Evaluation of a Patient Specific QA Tool Based On TG119." Medical physics 41.6 (June 2014): 259-.
PMID
28037103
Source
epmc
Published In
Medical physics
Volume
41
Issue
6
Publish Date
2014
Start Page
259
DOI
10.1118/1.4888488

A limited-angle intrafraction verification (LIVE) system for radiation therapy.

Currently, no 3D or 4D volumetric x-ray imaging techniques are available for intrafraction verification of target position during actual treatment delivery or in-between treatment beams, which is critical for stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) treatments. This study aims to develop a limited-angle intrafraction verification (LIVE) system to use prior information, deformation models, and limited angle kV-MV projections to verify target position intrafractionally.The LIVE system acquires limited-angle kV projections simultaneously during arc treatment delivery or in-between static 3D/IMRT treatment beams as the gantry moves from one beam to the next. Orthogonal limited-angle MV projections are acquired from the beam's eye view (BEV) exit fluence of arc treatment beam or in-between static beams to provide additional anatomical information. MV projections are converted to kV projections using a linear conversion function. Patient prior planning CT at one phase is used as the prior information, and the on-board patient volume is considered as a deformation of the prior images. The deformation field is solved using the data fidelity constraint, a breathing motion model extracted from the planning 4D-CT based on principal component analysis (PCA) and a free-form deformation (FD) model. LIVE was evaluated using a 4D digital extended cardiac torso phantom (XCAT) and a CIRS 008A dynamic thoracic phantom. In the XCAT study, patient breathing pattern and tumor size changes were simulated from CT to treatment position. In the CIRS phantom study, the artificial target in the lung region experienced both size change and position shift from CT to treatment position. Varian Truebeam research mode was used to acquire kV and MV projections simultaneously during the delivery of a dynamic conformal arc plan. The reconstruction accuracy was evaluated by calculating the 3D volume percentage difference (VPD) and the center of mass (COM) difference of the tumor in the true on-board images and reconstructed images.In both simulation and phantom studies, LIVE achieved substantially better reconstruction accuracy than reconstruction using PCA or FD deformation model alone. In the XCAT study, the average VPD and COM differences among different patient scenarios for LIVE system using orthogonal 30° scan angles were 4.3% and 0.3 mm when using kV+BEV MV. Reducing scan angle to 15° increased the average VPD and COM differences to 15.1% and 1.7 mm. In the CIRS phantom study, the VPD and COM differences for the LIVE system using orthogonal 30° scan angles were 6.4% and 1.4 mm. Reducing scan angle to 15° increased the VPD and COM differences to 51.9% and 3.8 mm.The LIVE system has the potential to substantially improve intrafraction target localization accuracy by providing volumetric verification of tumor position simultaneously during arc treatment delivery or in-between static treatment beams. With this improvement, LIVE opens up a new avenue for margin reduction and dose escalation in both fractionated treatments and SRS and SBRT treatments.

Authors
Ren, L; Zhang, Y; Yin, F-F
MLA Citation
Ren, L, Zhang, Y, and Yin, F-F. "A limited-angle intrafraction verification (LIVE) system for radiation therapy." Medical physics 41.2 (February 2014): 020701-.
PMID
24506590
Source
epmc
Published In
Medical physics
Volume
41
Issue
2
Publish Date
2014
Start Page
020701
DOI
10.1118/1.4861820

A technique for estimating 4D-CBCT using prior knowledge and limited-angle projections.

PURPOSE: To develop a technique to estimate onboard 4D-CBCT using prior information and limited-angle projections for potential 4D target verification of lung radiotherapy. METHODS: Each phase of onboard 4D-CBCT is considered as a deformation from one selected phase (prior volume) of the planning 4D-CT. The deformation field maps (DFMs) are solved using a motion modeling and free-form deformation (MM-FD) technique. In the MM-FD technique, the DFMs are estimated using a motion model which is extracted from planning 4D-CT based on principal component analysis (PCA). The motion model parameters are optimized by matching the digitally reconstructed radiographs of the deformed volumes to the limited-angle onboard projections (data fidelity constraint). Afterward, the estimated DFMs are fine-tuned using a FD model based on data fidelity constraint and deformation energy minimization. The 4D digital extended-cardiac-torso phantom was used to evaluate the MM-FD technique. A lung patient with a 30 mm diameter lesion was simulated with various anatomical and respirational changes from planning 4D-CT to onboard volume, including changes of respiration amplitude, lesion size and lesion average-position, and phase shift between lesion and body respiratory cycle. The lesions were contoured in both the estimated and "ground-truth" onboard 4D-CBCT for comparison. 3D volume percentage-difference (VPD) and center-of-mass shift (COMS) were calculated to evaluate the estimation accuracy of three techniques: MM-FD, MM-only, and FD-only. Different onboard projection acquisition scenarios and projection noise levels were simulated to investigate their effects on the estimation accuracy. RESULTS: For all simulated patient and projection acquisition scenarios, the mean VPD (±S.D.)∕COMS (±S.D.) between lesions in prior images and "ground-truth" onboard images were 136.11% (±42.76%)∕15.5 mm (±3.9 mm). Using orthogonal-view 15°-each scan angle, the mean VPD∕COMS between the lesion in estimated and "ground-truth" onboard images for MM-only, FD-only, and MM-FD techniques were 60.10% (±27.17%)∕4.9 mm (±3.0 mm), 96.07% (±31.48%)∕12.1 mm (±3.9 mm) and 11.45% (±9.37%)∕1.3 mm (±1.3 mm), respectively. For orthogonal-view 30°-each scan angle, the corresponding results were 59.16% (±26.66%)∕4.9 mm (±3.0 mm), 75.98% (±27.21%)∕9.9 mm (±4.0 mm), and 5.22% (±2.12%)∕0.5 mm (±0.4 mm). For single-view scan angles of 3°, 30°, and 60°, the results for MM-FD technique were 32.77% (±17.87%)∕3.2 mm (±2.2 mm), 24.57% (±18.18%)∕2.9 mm (±2.0 mm), and 10.48% (±9.50%)∕1.1 mm (±1.3 mm), respectively. For projection angular-sampling-intervals of 0.6°, 1.2°, and 2.5° with the orthogonal-view 30°-each scan angle, the MM-FD technique generated similar VPD (maximum deviation 2.91%) and COMS (maximum deviation 0.6 mm), while sparser sampling yielded larger VPD∕COMS. With equal number of projections, the estimation results using scattered 360° scan angle were slightly better than those using orthogonal-view 30°-each scan angle. The estimation accuracy of MM-FD technique declined as noise level increased. CONCLUSIONS: The MM-FD technique substantially improves the estimation accuracy for onboard 4D-CBCT using prior planning 4D-CT and limited-angle projections, compared to the MM-only and FD-only techniques. It can potentially be used for the inter/intrafractional 4D-localization verification.

Authors
Zhang, Y; Yin, F-F; Segars, WP; Ren, L
MLA Citation
Zhang, Y, Yin, F-F, Segars, WP, and Ren, L. "A technique for estimating 4D-CBCT using prior knowledge and limited-angle projections." Med Phys 40.12 (December 2013): 121701-.
PMID
24320487
Source
pubmed
Volume
40
Issue
12
Publish Date
2013
Start Page
121701
DOI
10.1118/1.4825097

Breathing Irregularity-Induced Uncertainties in Patient Positioning of Lung SBRT: An Investigation Based on a Digital Human Phantom

Authors
Turner, K; Zhang, Y; Vergalasova, I; Ren, L; Segars, P; Yin, F; Cai, J
MLA Citation
Turner, K, Zhang, Y, Vergalasova, I, Ren, L, Segars, P, Yin, F, and Cai, J. "Breathing Irregularity-Induced Uncertainties in Patient Positioning of Lung SBRT: An Investigation Based on a Digital Human Phantom." October 1, 2013.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
87
Issue
2
Publish Date
2013
Start Page
S681
End Page
S681

A Simulation Study of Treatment Verification Using On-Board Multipinhole SPECT

Authors
Yan, S; Bowsher, J; Giles, W; Ren, L; Yin, F
MLA Citation
Yan, S, Bowsher, J, Giles, W, Ren, L, and Yin, F. "A Simulation Study of Treatment Verification Using On-Board Multipinhole SPECT." October 1, 2013.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
87
Issue
2
Publish Date
2013
Start Page
S707
End Page
S707

A Limited-Angle Intrafractional Verification (LIVE) System for Intrafractional Positioning Verification of Lung SBRT Treatment

Authors
Ren, L; Zhang, Y; Yin, F
MLA Citation
Ren, L, Zhang, Y, and Yin, F. "A Limited-Angle Intrafractional Verification (LIVE) System for Intrafractional Positioning Verification of Lung SBRT Treatment." October 1, 2013.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
87
Issue
2
Publish Date
2013
Start Page
S145
End Page
S146

Respiration-phase-matched digital tomosynthesis imaging for moving target verification: a feasibility study.

PURPOSE: To develop a respiration-phase-matched digital tomosynthesis (DTS) technique to monitor moving targets, and to evaluate its accuracy for various imaging parameters and anatomical characteristics. METHODS: Previously developed 3D-DTS techniques, registering onboard DTS (OB-DTS, reconstructed from onboard projections) to reference DTS (R-DTS, reconstructed from DRRs of 3D reference CT), are inadequate to monitor moving targets. The authors' proposed respiration-phase-matched DTS technique registers OB-DTS to R-DTS reconstructed from DRRs generated by the same phase images of 4D reference CT as the corresponding onboard projections. To evaluate the improved accuracy of the author's technique, the authors performed thoracic phantom studies using (1) simulation with the 4D digital extended-cardiac-torso (XCAT) phantom, and (2) experiments with an anthropomorphic motion phantom. The studies were performed for various: respiratory cycle (RC), scan angle, and fraction of RC contained therein. Also, the authors assessed the accuracy of their technique relative to target size/location, and respiration inconsistencies from the R-DTS to OB-DTS. RESULTS: In both simulation and experimental studies, the respiration-phase-matched DTS technique is significantly more accurate in determining moving target positions. For 324 different scenarios simulated by XCAT, the respiration-phase-matched DTS technique localizes the 3D target position to errors of 1.07 ± 0.57 mm (mean ± S.D.), as compared to (a) 2.58 ± 1.37 and (b) 7.37 ± 4.18 mm, for 3D-DTS using 3D reference CT of (a) average intensity projection and (b) free-breathing CT. For 60 scenarios evaluated through experimental study, the uncertainties corresponding to those above are 1.24 ± 0.87, 2.42 ± 1.80, and 5.77 ± 6.45 mm, respectively. For a given scan angle, the accuracy of respiration-phase-matched DTS technique is less dependent on RC and the fraction of RC included in the scan. Increasing scan angle improves its accuracy. For different target locations, the targets near the chest wall or in the middle of lung provide higher registration accuracy compared to those near the mediastinum and diaphragm. Larger targets provide higher registration accuracy than small targets. Different respiratory cycle inconsistencies from R-DTS to OB-DTS minimally affect the registration accuracy. Increasing the respiratory amplitude inconsistencies will decrease the accuracy. CONCLUSIONS: The respiration-phase-matched DTS is more accurate and robust in determining moving target positions than 3D-DTS. It has potential application in pretreatment setup, post-treatment analysis, and intrafractional target verification.

Authors
Zhang, Y; Ren, L; Ling, CC; Yin, F-F
MLA Citation
Zhang, Y, Ren, L, Ling, CC, and Yin, F-F. "Respiration-phase-matched digital tomosynthesis imaging for moving target verification: a feasibility study." Med Phys 40.7 (July 2013): 071723-.
PMID
23822427
Source
pubmed
Volume
40
Issue
7
Publish Date
2013
Start Page
071723
DOI
10.1118/1.4810921

SU-E-T-196: Pretreatment Patient Clinical Objective IMRT Quality Assurance Using a 3D Diode Array.

To evaluate the accuracy and sensitivity of a patient clinical objective IMRT QA tool using a 3D diode array.A 3D QA device (Delta4, Scandidos Inc.) with 2 orthogonal diode array planes was used for IMRT QA. The diode spacing is 5mm in central 6cmx6cm region and 1cm in the peripheral 20cmx20cm region. 3D volumetric dose is interpolated from the measured planar dose. The Delta4 Anatomy software (Anatomy) calculates the entrance energy fluence for each beam, which is then applied to the patient anatomy to calculate dose to the patient using a pencil-beam dose calculation algorithm. The accuracy of Anatomy was evaluated in both solid water phantom using open fields and in patient anatomy using a prostate IMRT plan. The dose calculated by Eclipse was used as the gold standard. The sensitivity of the Anatomy was also evaluated by introducing leaf positioning errors in the delivery of a spine SBRT plan.Excellent agreement between Anatomy and Eclipse was achieved for the solid water phantom with open fields. Discrepancy was observed for the PTV DVH calculated in patient anatomy using the prostate IMRT plan. This is mainly due to sharp dose fall-off outside PTV and phantom setup errors during QA. Good agreement between Anatomy and Eclipse was achieved for bladder and rectum DVH. For spine case with introduced 1cm single leaf positioning error, the traditional gamma analysis using Delta4 still showed 95% pass rate using 3%, 3mm criteria. However, Anatomy showed 40% increase of cord max dose due to this error, which was consistent with Eclipse.Patient clinical objective QA using Delta4 Anatomy can potentially provide valuable information about the clinical significance of the QA results. It can potentially catch clinically significant delivery errors that would otherwise be missed in the traditional QA process using gamma analysis. Funding from Scandidos Inc.

Authors
Ren, L; Zhang, Y; Yang, Y; Adamson, J; Yin, F
MLA Citation
Ren, L, Zhang, Y, Yang, Y, Adamson, J, and Yin, F. "SU-E-T-196: Pretreatment Patient Clinical Objective IMRT Quality Assurance Using a 3D Diode Array." Medical physics 40.6Part13 (June 2013): 249-.
PMID
28519276
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part13
Publish Date
2013
Start Page
249
DOI
10.1118/1.4814631

WE-G-141-07: Feasibility of Using a Grid to Detect and Correct the Geometric Variations in Flat-Panel Based Cone Beam CT.

To study the feasibility of using a grid, shown previously to mitigate the scatter problem, to detect and correct geometric variations in flat-panel-based cone beam CT (CBCT) imaging.The study was performed on the CBCT system of a Varian Trilogy linac. The grid was located before the imaging object and attached to the bowtie-filter with a source-to-grid distance (SGD) of 40-50 cm. We first studied the correlations in geometric variation between the grid, bowtie-filter, source and imager. The grid position was represented by BBs in a plastic-plate replacing the grid. The bowtie-filter position was determined by a BB placed on its surface. The source and imager geometries were derived from the projections of 16 BBs in an IsoCal phantom using an in-house-developed computer program. Multiple scans were performed with different SGD in a 2-month period. Correlations were analyzed and used to predict the geometric variations of the bowtie-filter, source and imager from the grid variation obtained using a grid in a CatPhan scan.The grid and bowtie-filter showed exactly same variations (up to 5 mm) in Y-direction during a 360° rotation, with a sine-like pattern superimposed by 1-2 mm random vibrations. The variation patterns were also sine-like curves in the X-direction. However, they were smooth and repeatable, with differences in phase and amplitude between the two, and the amplitude varying with SGD. The source and imager showed similar and repeatable 0.3-0.5 mm sine-like variation patterns. Based on these results, a model was developed to predict and correct the geometric variations in a CBCT scan with the grid.The preliminary results suggest that it is able to predict geometric variations of the CBCT system. Future study is underway to verify whether correction of these variations will improve the spatial resolution and mitigate the bowtie-filter variation-induced crescent artifact. The study is supported by NIH Grant Number 5 R01 CA166948-02.

Authors
Zou, G; Ren, L; Kim, J; Jaffray, D; Chetty, I; Jin, J
MLA Citation
Zou, G, Ren, L, Kim, J, Jaffray, D, Chetty, I, and Jin, J. "WE-G-141-07: Feasibility of Using a Grid to Detect and Correct the Geometric Variations in Flat-Panel Based Cone Beam CT." Medical physics 40.6Part31 (June 2013): 509-.
PMID
28519714
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part31
Publish Date
2013
Start Page
509
DOI
10.1118/1.4815658

MO-F-WAB-11: Investigation of CBCT-Based Patient Positioning Accuracy in Lung SBRT: Correlation with Breathing Irregularity.

To evaluate breathing irregularity induced error in CBCT-based patient positioning in lung SBRT and correlate the error with a measure of breathing variability.The 4D extended cardiac-torso (XCAT) digital phantom was used to generate 10-phase 4DCT and CBCT images using in-house developed simulation programs. Images were generated for various respiratory profiles (one regular sinusoidal and 10 irregular) and tumor sizes (1 cm, 2 cm, 3 cm). Maximum intensity projection (MIP) and average intensity projection (AIP) images were generated from 4DCT images. Image registrations between CBCT and AIP were performed for each respiratory profile and tumor size by four clinicians (two physicians and two physicists) based on target volume matching. Error of registration was determined as the difference between manual CBCT-to-AIP registration and known registration between the two. Breathing irregularities of the respiratory profiles were measured and correlated to errors of registration.Inter-observer variation of registration was 0.15 mm, 0.34 mm, and 0.69 mm, in the medial-lateral (ML), anterior-posterior (AP), and superior-inferior (SI) direction, respectively. For the regular profile, negligible errors of registration were found in all directions (median<0.5 mm). For the irregular profiles and all tumor sizes, small errors (median=0.5 mm) were found in the ML and AP directions, while non-trivial errors were seen in the SI direction (median (+/- SD): 2.10 (+/- 2.27) mm). No significant difference in mean error of registration was found for different tumor sizes (p>0.6). Maximum error of registration in the ML, AP, and SI direction was 1.2 mm, 2.6 mm, and 8.4 mm, respectively. Mild correlations (R2 range: 0.37 to 0.47) were observed between error of registration error and breathing irregularity for all tumor sizes.Irregular breathing can induce error in CBCT-based image registration in lung SBRT. This error increases as the breathing irregularity increases.

Authors
Turner, K; Zhang, Y; Vergalasova, I; Ren, L; Segars, P; Kelsey, C; Yoo, D; Yin, F; Cai, J
MLA Citation
Turner, K, Zhang, Y, Vergalasova, I, Ren, L, Segars, P, Kelsey, C, Yoo, D, Yin, F, and Cai, J. "MO-F-WAB-11: Investigation of CBCT-Based Patient Positioning Accuracy in Lung SBRT: Correlation with Breathing Irregularity." Medical physics 40.6Part24 (June 2013): 412-.
PMID
28518416
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part24
Publish Date
2013
Start Page
412
DOI
10.1118/1.4815300

SU-E-T-560: A Method to Determine Optimal Dynamic MLC Parameters for Varian Truebeam with Millennium MLC and HDMLC.

Correct MLC modeling is essential to the accurate IMRT delivery. Most TPSs use simplified models with parameters of leaf transmission (LT) and dynamic leaf gap (DLG). The common way to determine them is through extrapolation from measurements. In this study, we propose a new technique to determine these parameters with EPID and ion chambers using specially designed fluence pattern.The fluence has symmetric twin peaks separated by 10cm and each has a width of 2cm. The DMLC files were generated based on initial values of LT and DLG from measurements. Plans were delivered to EPID and analyzed in portal dosimetry software. The FWHM of each peak was evaluated. The optimal DLG value was determined by iteratively adjusting its value and repeating calculation to match the FWHM between calculation and measurement. To determine LT, an ion chamber was placed at the central axis where dose is primarily from MLC leakage. Both Millennium MLC (MMLC) and HDMLC in Varian Truebeam were investigated for photon energies of 6X, 10X, 15X. QAs of realistic IMRT plans were performed and compared.The MMLC has measured LT values from 1.3%-1.5%, and corresponding optimal values 1.6-1.9%, an increase of 20% on average. The DLGs extrapolated from measurement are 0.8-0.9 mm, and optimal at 1.2-1.6 mm, a 60% increase. For HDMLC, the LTs are similar. However, the DLGs are much smaller, with extrapolations at 0.15-0.21 mm, and optimal at 0.4-0.7 mm. The portal dosimetry QA for 6X plan with MMLC reduces pixels failing γ (criteria: 3%/1mm) from 9% to 3% with optimal parameters. Similarly, QA for 15X plan with HDMLC reduces from 21% to 6%.We have developed a method to determine optimal MLC parameters that minimize TPS modeling errors. This ensures that patient specific QA reflects the true discrepancies in treatment plan or machine delivery.

Authors
Wu, Q; Chang, Z; Adamson, J; Ren, L; Yin, F
MLA Citation
Wu, Q, Chang, Z, Adamson, J, Ren, L, and Yin, F. "SU-E-T-560: A Method to Determine Optimal Dynamic MLC Parameters for Varian Truebeam with Millennium MLC and HDMLC." Medical physics 40.6Part19 (June 2013): 334-.
PMID
28524505
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part19
Publish Date
2013
Start Page
334
DOI
10.1118/1.4814989

WE-A-134-04: Comprehensive Evaluation of a Respiration-Phase-Matched Digital Tomosynthesis (DTS) Imaging Technique for Monitoring Moving Targets.

To develop a respiration-phase-matched DTS technique to monitor moving targets, and to evaluate its accuracy for various imaging parameters and anatomical characteristics Methods: Conventional methods, registering on-board DTS(OB-DTS, reconstructed from on-board projections) to reference DTS(R-DTS, reconstructed from DRRs of 3D-planning-CT), are inadequate to monitor moving targets. Our proposed technique registers OB-DTS to R-DTS reconstructed from DRRs generated by the same phase images of 4D-planning-CT as the corresponding on-board projections. To evaluate the improved accuracy of our technique, we performed thoracic phantom studies using (1)simulation with the 4D Digital Extended-cardiac-torso(XCAT) phantom, and (2)experiments with an anthropomorphic motion phantom. The studies were performed for various: respiratory-cycle(RC), scan angle and fraction of RC contained therein. Also, we assessed the accuracy of our technique relative to target size/location, and respiration changes from the planning-CT scan to on-board volume.In both simulation and experimental studies the respiration-phase-matched DTS technique is significantly more accurate in determining moving target positions. For 324 different scenarios simulated by XCAT, the respiration-phase-matched DTS technique localizes the 3D target position to within 1.07±0.57mm(mean±S.D.), as compared to (a)2.58±1.37mm and (b)7.37±4.18mm, for traditional DTS using 3D-planning-CT of (a)average-intensity-projection(AIP) and (b)free-breathing-CT(FB-CT). For the 60 scenarios evaluated through experimental study, the uncertainties corresponding to those above are 1.24±0.87mm, 2.42±1.80mm, and 5.77±6.45mm, respectively. For a given scan angle, the accuracy of respiration-phase-matched DTS technique is less dependent on RC and the fraction of RC included in the scan. Increasing scan angle improves its accuracy. Its accuracy is also minimally dependent on different tumor size/location combinations, or different respiratory cycle changes from planning-CT to on-board volume. Increasing the respiratory amplitude change will decrease its accuracy.The respiration-phase-matched DTS is more accurate and robust in determining moving target positions than traditional DTS. It has potential application in pre-treatment setup, post-treatment analysis and intra-fractional target verification. Research partially supported by grant from Varian Medical Systems.

Authors
Zhang, Y; Ren, L; Ling, C; Yin, F
MLA Citation
Zhang, Y, Ren, L, Ling, C, and Yin, F. "WE-A-134-04: Comprehensive Evaluation of a Respiration-Phase-Matched Digital Tomosynthesis (DTS) Imaging Technique for Monitoring Moving Targets." Medical physics 40.6Part28 (June 2013): 469-470.
PMID
28519947
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part28
Publish Date
2013
Start Page
469
End Page
470
DOI
10.1118/1.4815510

TU-G-141-03: An On-Board 4D-CBCT Reconstruction Technique Using Limited-Angle Projections Based On Motion Modeling and Free-Form Deformation (MM-FD).

To develop an on-board 4D-CBCT(OB-4D-CBCT) reconstruction technique using prior information and limited-angle projections for 4D inter/intra-fractional target verificationMethods: The OB-4D-CBCT at each phase is considered as a deformation of planning 4D-CT at one selected phase (prior image). The MM-FD technique solves the deformation field maps(DFMs) with a two-step approach: 1. MM: a principal component analysis-based method is applied to the planning 4D-CT to extract a motion model. Coarse estimation of DFMs are obtained by optimizing motion model parameters to meet data-fidelity constraint for limited-angle on-board projections. 2. FD: the coarse DFMs are further fine-tuned by free-form deformation based on data-fidelity constraint and deformation-energy minimization, using constrained-optimization algorithm ASD-POCS. OB-4D-CBCT is then reconstructed by deforming prior volume based on final DFMs. The 4D Digital Extended-cardiac-torso(XCAT) Phantom was used to evaluate MM-FD. A lung patient with 3-cm diameter lesion was simulated to have various anatomical and respirational changes from 4D-CT to OB-4D-CBCT including respiration amplitude change, lesion size change, lesion average-position change, and phase shift between lesion and body respiratory cycle. The lesions were contoured in both the reconstructed and 'ground-truth' OB-4D-CBCT for comparison. 3D volume percentage-difference (VD) and center-of-mass shifts(COMS) were calculated for evaluation. The MM-FD technique was compared with MM-only and FD-only techniques.For all patient scenarios, the mean original VD/COMS between prior volume and true OB-4D-CBCT were 137.65%/15.5mm. Using orthogonal-15-degree scan angle, the mean VD/COMS between reconstructed and true OB-4D-CBCT for MM-only, FD-only and MM-FD techniques were 64.67%/4.9mm, 98.80%/12.1mm and 20.90%/1.3mm, respectively. For orthogonal-30-degree scan angle, the corresponding results were 63.87%/4.9mm, 79.92%/9.9mm and 15.23%/0.5mm. For single-view 30-and 60-degree projections, the mean VD/COMS for MM-FD technique were 32.67%/2.9mm and 19.67%/1.1mm, respectively.The MM-FD technique substantially improves the reconstruction accuracy for OB-4D-CBCT using limited-angle projections. It can potentially improve the inter/intra-fractional 4D-localization accuracy for lung SBRT. Research partially supported by grant from Varian Medical Systems.

Authors
Zhang, Y; Segars, P; Yin, F; Ren, L
MLA Citation
Zhang, Y, Segars, P, Yin, F, and Ren, L. "TU-G-141-03: An On-Board 4D-CBCT Reconstruction Technique Using Limited-Angle Projections Based On Motion Modeling and Free-Form Deformation (MM-FD)." Medical physics 40.6Part27 (June 2013): 456-.
PMID
28518822
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part27
Publish Date
2013
Start Page
456
DOI
10.1118/1.4815463

Phase/Amplitude-matched Digital Tomosynthesis (DTS) Imaging for Moving Target Localization.

Authors
Ren, L; Zhang, Y; Yin, F
MLA Citation
Ren, L, Zhang, Y, and Yin, F. "Phase/Amplitude-matched Digital Tomosynthesis (DTS) Imaging for Moving Target Localization." Practical radiation oncology 3.2 Suppl 1 (April 2013): S20-S21.
PMID
24674507
Source
epmc
Published In
Practical Radiation Oncology
Volume
3
Issue
2 Suppl 1
Publish Date
2013
Start Page
S20
End Page
S21
DOI
10.1016/j.prro.2013.01.070

Evaluation of multiple image-based modalities for image-guided radiation therapy (IGRT) of prostate carcinoma: a prospective study.

PURPOSE: Setup errors and prostate intrafraction motion are main sources of localization uncertainty in prostate cancer radiation therapy. This study evaluates four different imaging modalities 3D ultrasound (US), kV planar images, cone-beam computed tomography (CBCT), and implanted electromagnetic transponders (Calypso/Varian) to assess inter- and intrafraction localization errors during intensity-modulated radiation therapy based treatment of prostate cancer. METHODS: Twenty-seven prostate cancer patients were enrolled in a prospective IRB-approved study and treated to a total dose of 75.6 Gy (1.8 Gy/fraction). Overall, 1100 fractions were evaluated. For each fraction, treatment targets were localized using US, kV planar images, and CBCT in a sequence defined to determine setup offsets relative to the patient skin tattoos, intermodality differences, and residual errors for each patient and patient cohort. Planning margins, following van Herk's formalism, were estimated based on error distributions. Calypso-based localization was not available for the first eight patients, therefore centroid positions of implanted gold-seed markers imaged prior to and immediately following treatment were used as a motion surrogate during treatment. For the remaining 19 patients, Calypso transponders were used to assess prostate intrafraction motion. RESULTS: The means (μ), and standard deviations (SD) of the systematic (Σ) and random errors (σ) of interfraction prostate shifts (relative to initial skin tattoo positioning), as evaluated using CBCT, kV, and US, averaged over all patients and fractions, were: [μ CBCT = (-1.2, 0.2, 1.1) mm, Σ CBCT = (3.0, 1.4, 2.4) mm, σ CBCT = (3.2, 2.2, 2.5) mm], [μkV = (-2.9, -0.4, 0.5) mm, Σ kV = (3.4, 3.1, 2.6) mm, σ kV = (2.9, 2.0, 2.4) mm], and [μ US = (-3.6, -1.4, 0.0) mm, Σ US = (3.3, 3.5, 2.8) mm, σ US = (4.1, 3.8, 3.6) mm], in the anterior-posterior (A/P), superior-inferior (S/I), and the left-right (L/R) directions, respectively. In the treatment protocol, adjustment of couch was guided by US images. Residual setup errors as assessed by kV images were found to be: μ residual = (-0.4, 0.2, 0.2) mm, Σ residual = (1.0, 1.0,0.7) mm, and σ residual = (2.5, 2.3, 1.8) mm. Intrafraction prostate motion, evaluated using electromagnetic transponders, was: μ intrafxn = (0.0, 0.0, 0.0) mm, Σ intrafxn = (1.3, 1.5, 0.6) mm, and σ intrafxn = (2.6, 2.4, 1.4) mm. Shifts between pre- and post-treatment kV images were: μ kV(post-pre) = (-0.3, 0.8, -0.2), Σ kV(post-pre) = (2.4, 2.7, 2.1) mm, and σ kV(post-pre) = (2.7, 3.2, 3.1) mm. Relative to skin tattoos, planning margins for setup error were within 10-11 mm for all image-based modalities. The use of image guidance was shown to reduce these margins to less than 5 mm. Margins to compensate for both residual setup (interfraction) errors as well as intrafraction motion were 6.6, 6.8, and 3.9 mm in the A/P, S/I, and L/R directions, respectively. CONCLUSIONS: Analysis of interfraction setup errors, performed with US, CBCT, planar kV images, and electromagnetic transponders, from a large dataset revealed intermodality shifts were comparable (within 3-4 mm). Interfraction planning margins, relative to setup based on skin marks, were generally within the 10 mm prostate-to-planning target volume margin used in our clinic. With image guidance, interfraction residual planning margins were reduced to approximately less than 4 mm. These findings are potentially important for dose escalation studies using smaller margins to better protect normal tissues.

Authors
Mayyas, E; Chetty, IJ; Chetvertkov, M; Wen, N; Neicu, T; Nurushev, T; Ren, L; Lu, M; Stricker, H; Pradhan, D; Movsas, B; Elshaikh, MA
MLA Citation
Mayyas, E, Chetty, IJ, Chetvertkov, M, Wen, N, Neicu, T, Nurushev, T, Ren, L, Lu, M, Stricker, H, Pradhan, D, Movsas, B, and Elshaikh, MA. "Evaluation of multiple image-based modalities for image-guided radiation therapy (IGRT) of prostate carcinoma: a prospective study." Med Phys 40.4 (April 2013): 041707-.
PMID
23556877
Source
pubmed
Volume
40
Issue
4
Publish Date
2013
Start Page
041707
DOI
10.1118/1.4794502

Can Standard Radiation Therapy Quality Assurance (QA) Detect Potential Delivery Errors?

Authors
Ren, L; O'Daniel, J; Adamson, J; Yan, H; Yin, F
MLA Citation
Ren, L, O'Daniel, J, Adamson, J, Yan, H, and Yin, F. "Can Standard Radiation Therapy Quality Assurance (QA) Detect Potential Delivery Errors?." November 1, 2012.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
84
Issue
3
Publish Date
2012
Start Page
S779
End Page
S779

Commissioning and dosimetric characteristics of TrueBeam system: composite data of three TrueBeam machines.

PURPOSE: A TrueBeam linear accelerator (TB-LINAC) is designed to deliver traditionally flattened and flattening-filter-free (FFF) beams. Although it has been widely adopted in many clinics for patient treatment, limited information is available related to commissioning of this type of machine. In this work, commissioning data of three units were measured, and multiunit comparison was presented to provide valuable insights and reliable evaluations on the characteristics of the new treatment system. METHODS: The TB-LINAC is equipped with newly designed waveguide, carousel assembly, monitoring control, and integrated imaging systems. Each machine in this study has 4, 6, 8, 10, 15 MV flattened photon beams, and 6 MV and 10 MV FFF photon beams as well as 6, 9, 12, 16, 20, and 22 MeV electron beams. Dosimetric characteristics of the three new TB-LINAC treatment units are systematically measured for commissioning. High-resolution diode detectors and ion chambers were used to measure dosimetric data for a range of field sizes from 10 × 10 to 400 × 400 mm(2). The composite dosimetric data of the three units are presented in this work. The commissioning of intensity modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), image-guided radiation therapy, and gating systems are also illustrated. Critical considerations of P(ion) of FFF photon beams and small field dosimetric measurements were investigated. RESULTS: The authors found all PDDs and profiles matched well among the three machines. Beam data were quantitatively compared and combined through average to yield composite beam data. The discrepancies among the machines were quantified using standard deviation (SD). The mean SD of the PDDs among the three units is 0.12%, and the mean SD of the profiles is 0.40% for 10 MV FFF open fields. The variations of P(ion) of the chamber CC13 is 1.2 ± 0.1% under 6 MV FFF and 2.0 ± 0.5% under 10 MV FFF from dmax to the 18 cm-off-axis point at 35 cm depth under 40 × 40 cm(2). The mean penumbra of crossplane flattened photon beams at collimator angle of 0° is measured from 5.88 ± 0.09 to 5.99 ± 0.13 mm from 4 to 15 MV at 10 cm depth of 100 × 100 mm(2). The mean penumbra of crossplane beams at collimator angle of 0° is measured as 3.70 ± 0.21 and 4.83 ± 0.04 mm for 6 MV FFF and 10 MV FFF, respectively, at 10 cm depth with a field size of 5 × 5 cm(2). The end-to-end test procedures of both IMRT and VMAT were performed for various energy modes. The mean ion chamber measurements of three units showed less than 2% between measurement and calculation; the mean MultiCube ICA measurements demonstrated over 90% pixels passing gamma analysis (3%, 3 mm, 5% threshold). The imaging dosimetric data of KV planar imaging and CBCT demonstrated improved consistency with vendor specifications and dose reduction for certain imaging protocols. The gated output verification showed a discrepancy of 0.05% or less between gating radiation delivery and nongating radiation delivery. CONCLUSIONS: The commissioning data indicated good consistency among the three TB-LINAC units. The commissioning data provided us valuable insights and reliable evaluations on the characteristics of the new treatment system. The systematically measured data might be useful for future reference.

Authors
Chang, Z; Wu, Q; Adamson, J; Ren, L; Bowsher, J; Yan, H; Thomas, A; Yin, F-F
MLA Citation
Chang, Z, Wu, Q, Adamson, J, Ren, L, Bowsher, J, Yan, H, Thomas, A, and Yin, F-F. "Commissioning and dosimetric characteristics of TrueBeam system: composite data of three TrueBeam machines." Med Phys 39.11 (November 2012): 6981-7018.
PMID
23127092
Source
pubmed
Published In
Medical physics
Volume
39
Issue
11
Publish Date
2012
Start Page
6981
End Page
7018
DOI
10.1118/1.4762682

Implementation of dual-energy technique for virtual monochromatic and linearly mixed CBCTs.

PURPOSE: To implement dual-energy imaging technique for virtual monochromatic (VM) and linearly mixed (LM) cone beam CTs (CBCTs) and to demonstrate their potential applications in metal artifact reduction and contrast enhancement in image-guided radiation therapy (IGRT). METHODS: A bench-top CBCT system was used to acquire 80 kVp and 150 kVp projections, with an additional 0.8 mm tin filtration. To implement the VM technique, these projections were first decomposed into acrylic and aluminum basis material projections to synthesize VM projections, which were then used to reconstruct VM CBCTs. The effect of VM CBCT on the metal artifact reduction was evaluated with an in-house titanium-BB phantom. The optimal VM energy to maximize contrast-to-noise ratio (CNR) for iodine contrast and minimize beam hardening in VM CBCT was determined using a water phantom containing two iodine concentrations. The LM technique was implemented by linearly combining the low-energy (80 kVp) and high-energy (150 kVp) CBCTs. The dose partitioning between low-energy and high-energy CBCTs was varied (20%, 40%, 60%, and 80% for low-energy) while keeping total dose approximately equal to single-energy CBCTs, measured using an ion chamber. Noise levels and CNRs for four tissue types were investigated for dual-energy LM CBCTs in comparison with single-energy CBCTs at 80, 100, 125, and 150 kVp. RESULTS: The VM technique showed substantial reduction of metal artifacts at 100 keV with a 40% reduction in the background standard deviation compared to a 125 kVp single-energy scan of equal dose. The VM energy to maximize CNR for both iodine concentrations and minimize beam hardening in the metal-free object was 50 keV and 60 keV, respectively. The difference of average noise levels measured in the phantom background was 1.2% between dual-energy LM CBCTs and equivalent-dose single-energy CBCTs. CNR values in the LM CBCTs of any dose partitioning are better than those of 150 kVp single-energy CBCTs. The average CNR for four tissue types with 80% dose fraction at low-energy showed 9.0% and 4.1% improvement relative to 100 kVp and 125 kVp single-energy CBCTs, respectively. CNRs for low-contrast objects improved as dose partitioning was more heavily weighted toward low-energy (80 kVp) for LM CBCTs. CONCLUSIONS: Dual-energy CBCT imaging techniques were implemented to synthesize VM CBCT and LM CBCTs. VM CBCT was effective at achieving metal artifact reduction. Depending on the dose-partitioning scheme, LM CBCT demonstrated the potential to improve CNR for low contrast objects compared to single-energy CBCT acquired with equivalent dose.

Authors
Li, H; Giles, W; Ren, L; Bowsher, J; Yin, F-F
MLA Citation
Li, H, Giles, W, Ren, L, Bowsher, J, and Yin, F-F. "Implementation of dual-energy technique for virtual monochromatic and linearly mixed CBCTs." Med Phys 39.10 (October 2012): 6056-6064.
PMID
23039644
Source
pubmed
Published In
Medical physics
Volume
39
Issue
10
Publish Date
2012
Start Page
6056
End Page
6064
DOI
10.1118/1.4752212

Feasibility study of a synchronized-moving-grid (SMOG) system to improve image quality in cone-beam computed tomography (CBCT).

PURPOSE: To evaluate the feasibility of a synchronized moving grid (SMOG) system to remove scatter artifacts, improve the contrast-to-noise ratio (CNR), and reduce image lag artifacts in cone-beam CT (CBCT). METHODS: The SMOG system proposed here uses a rapidly oscillating, synchronized moving grid attached to the kV source. Multiple partial projections are taken at different grid positions to form a complete projection in each gantry position, before the gantry moves to the next position during a scan. The grid has a low transmission factor, and it is used for both scatter reduction and scatter measurement for postscan scatter correction. Experimental studies using a static grid and an enlarged CATphan phantom were performed to evaluate the potential CNR enhancement for different SMOG exposure numbers (1, 2, and 4). Simulation studies were performed to evaluate the image lag correction for different exposure numbers (2, 3, and 4) and grid interspace widths in SMOG using the data from an anthropomorphic pelvis phantom scan. Imaging dose of SMOG was also estimated by measuring the imaging dose in a CIRS CT dose phantom using a static grid. RESULTS: SMOG can enhance the CNR by 16% and 13% when increasing exposure number from 1 to 2 and from 2 to 4, respectively. This enhancement was more dramatic for larger phantoms and smaller initial exposure numbers. Simulation results indicated that SMOG could reduce the lag to less than 4.3% for 2-exposure mode and to less than 0.8% for 3-exposure mode when the grid interspace width was 1.4 cm. Increasing the number of exposures in SMOG dramatically reduced the residual lag in the image. Reducing the grid interspace width somewhat reduced the residual lag. Skin line artifacts were removed entirely in SMOG. Point dose measurement showed that imaging dose of SMOG at isocenter was similar as that of a conventional CBCT. CONCLUSIONS: Compared to our previously developed static-grid dual-rotation method, the proposed SMOG technique has the advantages of enhancing the CNR, correcting the image lag, and reducing the delivery time. Once implemented, SMOG has the potential to remove scatter and image lag artifacts, and significantly enhance CNR for CBCT using the same scanning time as conventional CBCT.

Authors
Ren, L; Yin, F-F; Chetty, IJ; Jaffray, DA; Jin, J-Y
MLA Citation
Ren, L, Yin, F-F, Chetty, IJ, Jaffray, DA, and Jin, J-Y. "Feasibility study of a synchronized-moving-grid (SMOG) system to improve image quality in cone-beam computed tomography (CBCT)." Med Phys 39.8 (August 2012): 5099-5110.
PMID
22894435
Source
pubmed
Published In
Medical physics
Volume
39
Issue
8
Publish Date
2012
Start Page
5099
End Page
5110
DOI
10.1118/1.4736826

Imaging system QA of a medical accelerator, Novalis Tx, for IGRT per TG 142: our 1 year experience.

American Association of Physicists in Medicine (AAPM) task group (TG) 142 has recently published a report to update recommendations of the AAPM TG 40 report and add new recommendations concerning medical accelerators in the era of image-guided radiation therapy (IGRT). The recommendations of AAPM TG 142 on IGRT are timely. In our institute, we established a comprehensive imaging QA program on a medical accelerator based on AAPM TG 142 and implemented it successfully. In this paper, we share our one-year experience and performance evaluation of an OBI capable linear accelerator, Novalis Tx, per TG 142 guidelines.

Authors
Chang, Z; Bowsher, J; Cai, J; Yoo, S; Wang, Z; Adamson, J; Ren, L; Yin, F-F
MLA Citation
Chang, Z, Bowsher, J, Cai, J, Yoo, S, Wang, Z, Adamson, J, Ren, L, and Yin, F-F. "Imaging system QA of a medical accelerator, Novalis Tx, for IGRT per TG 142: our 1 year experience. (Published online)" J Appl Clin Med Phys 13.4 (July 5, 2012): 3754-.
PMID
22766946
Source
pubmed
Published In
Journal of applied clinical medical physics / American College of Medical Physics
Volume
13
Issue
4
Publish Date
2012
Start Page
3754

SU-E-T-104: Commissioning and Dosimetric Characteristics of TrueBeam System: Composite Data of Three TrueBeam Machines.

A TrueBeam linear accelerator (TB-LINAC) is designed to deliver standard flattened and flattening-filter-free (FFF) beams. In our institute, three TB-LINAC units are installed. In this work, composite data of the three units and multi-unit comparison are presented.Each TB-LINAC can deliver photon beams from 4MV to 15MV, electron beams from 6MeV to 22MeV, and 6MV-FFF and 10MV-FFF. Dosimetric characteristics are systematically measured for commissioning including percent depth dose (PDD), beam profile, relative scatter factor, dynamic leaf shift, output factor and MLC leakage. Critic considerations of Pion of FFF photon beams and dosimetric penumbra are investigated.All measured PDDs and profiles of photon and electron matched well across the three machines. Beam data were quantitatively compared and combined through average to yield composite beam data. The discrepancies among the machines were quantified using standard deviation (SD). For example, the mean SD of the PDDs among the three units is 0.12%, and the mean SD of the profiles is 0.40% for 10MV-FFF open fields. The variations of Pion of the chamber CC13 is 1.2±0.1% under 6MV-FFF and 2.0±0.5% from dmax to the 18cm-off-axis point at 35cm depth under 40×40cm2 . The measured relative output factors range from 0.866 to 1.141 with the mean discrepancy of 0.06±0.04% among the three units. The measured wedge factors range from 0.863 to 1.254 with the mean overall discrepancy of 0.04±0.04%. The mean MLC transmission and dynamic leaf shift were measured from 1.0% to 1.5% and from 0.77mm to 0.96 mm from 4MV to 15MV. The mean penumbra of various photon beams are measured from 5.88±0.09mm to 5.99±0.13mm from 4MV to 15MV at 10cm depth of 10×10 cm2 .Dosimetric data demonstrated that the three units could and had been matched well. The systematically measured data might be useful for future reference.

Authors
Chang, Z; Wu, Q; Adamson, J; Ren, L; Bowsher, J; Yan, H; Thomas, A; Yin, F
MLA Citation
Chang, Z, Wu, Q, Adamson, J, Ren, L, Bowsher, J, Yan, H, Thomas, A, and Yin, F. "SU-E-T-104: Commissioning and Dosimetric Characteristics of TrueBeam System: Composite Data of Three TrueBeam Machines." Medical physics 39.6Part11 (June 2012): 3726-.
PMID
28517167
Source
epmc
Published In
Medical physics
Volume
39
Issue
6Part11
Publish Date
2012
Start Page
3726
DOI
10.1118/1.4735162

SU-E-T-645: Treatment of Multiple Brain Metastases Using Stereotactic Radiosurgery with Single-Isocenter Volumetric Modulated Arc Therapy: Comparison with Conventional Dynamic Conformal Arc and Static Beam Stereotactic Radiosurgery.

To investigate the treatment of multiple brain metastases using stereotactic radiosurgery with single-isocenter volumetric modulated arc therapy (VMAT) compared with conventional multi-isocenter dynamic conformal arc therapy (DCAT) and three-dimensional conformal radiation therapy (3D-CRT).Seventeen patients with 2 to 5 brain metastatic lesions were studied. The number of patients with 5, 4, 3, and 2 lesions were 4, 5, 4, and 4, respectively. For patients treated with DCAT/3D-CRT plans, VMAT plans were retrospectively generated, and vice versa. Single-isocenter set up was employed in VMAT plans while the number of isocenters was proportional to the number of lesions in DCAT/3D-CRT plans. The DCAT/3D-CRT and VMAT plans were generated using iPlan® RT Dose Version 4.1.1 (BrainLAB, Germany) and Eclipse™ Version 8.6 (Varian, USA) treatment planning system, respectively. All plans were designed to be delivered on Novalis Tx™ system (Varian, USA and BrainLAB, Germany), in which the accelerator equipped with a high definition multileaf collimator (HDMLC).Conformity index for VMAT plans were equivalent to or better than that for DCAT/3D-CRT plans. While VMAT and DCAT/3D-CRT plans were similar in target coverage, quality of coverage for VMAT plans was better. However, the volume receiving 5Gy was 46% larger for VMAT plans. In addition, the distance from individual lesion to the VMAT isocenter has no impact on VMAT plans. Compared with DCAT/3D-CRT plans, the mean monitor units (MU) decreased by 42% and the estimated treatment time decreased by 49% for VMAT plans.This work suggests that single-isocenter VMAT is promising for stereotactic radiosurgery in the treatment of multiple brain metastases. Single-isocenter VMAT is able to achieve comparable conformity, target coverage and quality of coverage with significantly superior delivery efficiency.

Authors
Huang, C; Ren, L; Kirkpatrick, J; Wang, Z
MLA Citation
Huang, C, Ren, L, Kirkpatrick, J, and Wang, Z. "SU-E-T-645: Treatment of Multiple Brain Metastases Using Stereotactic Radiosurgery with Single-Isocenter Volumetric Modulated Arc Therapy: Comparison with Conventional Dynamic Conformal Arc and Static Beam Stereotactic Radiosurgery." Medical physics 39.6Part20 (June 2012): 3854-.
PMID
28517544
Source
epmc
Published In
Medical physics
Volume
39
Issue
6Part20
Publish Date
2012
Start Page
3854
DOI
10.1118/1.4735734

SU-E-T-74: Assessing Effects of Ion Collection Efficiency in Flattening Filter-Free (FFF) Beams on Three TrueBeam Machines

Authors
Chang, Z; Wu, Q; Adamson, J; Ren, L; Bowsher, J; Yan, H; Thomas, A; Yin, F
MLA Citation
Chang, Z, Wu, Q, Adamson, J, Ren, L, Bowsher, J, Yan, H, Thomas, A, and Yin, F. "SU-E-T-74: Assessing Effects of Ion Collection Efficiency in Flattening Filter-Free (FFF) Beams on Three TrueBeam Machines." June 2012.
Source
crossref
Published In
Medical physics
Volume
39
Issue
6Part10
Publish Date
2012
Start Page
3719
End Page
3719
DOI
10.1118/1.4735130

TH-E-218-01: Dual-Energy CBCT Imaging for Metal Artifact Reduction and Contrast Enhancement

Authors
Li, H; Giles, W; Ren, L; Bowsher, J; Yin, F
MLA Citation
Li, H, Giles, W, Ren, L, Bowsher, J, and Yin, F. "TH-E-218-01: Dual-Energy CBCT Imaging for Metal Artifact Reduction and Contrast Enhancement." June 2012.
Source
crossref
Published In
Medical physics
Volume
39
Issue
6Part31
Publish Date
2012
Start Page
4017
End Page
4017
DOI
10.1118/1.4736387

TU-A-BRA-09: Phase-Matched Digital Tomosynthesis (DTS) Imaging for Simultaneous Target Verification during Volumetric Modulated Arc Therapy (VMAT) Treatment

Authors
Zhang, Y; Ren, L; Vergalasova, I; Cai, J; Yin, F
MLA Citation
Zhang, Y, Ren, L, Vergalasova, I, Cai, J, and Yin, F. "TU-A-BRA-09: Phase-Matched Digital Tomosynthesis (DTS) Imaging for Simultaneous Target Verification during Volumetric Modulated Arc Therapy (VMAT) Treatment." June 2012.
Source
crossref
Published In
Medical physics
Volume
39
Issue
6Part22
Publish Date
2012
Start Page
3889
End Page
3890
DOI
10.1118/1.4735877

SU-E-T-70: A Protocol for Comprehensive Acceptance/Commissioning of Complex 3D QA Devices

Authors
O'Daniel, J; Ren, L; Yan, H; Yin, F
MLA Citation
O'Daniel, J, Ren, L, Yan, H, and Yin, F. "SU-E-T-70: A Protocol for Comprehensive Acceptance/Commissioning of Complex 3D QA Devices." June 2012.
Source
crossref
Published In
Medical physics
Volume
39
Issue
6Part10
Publish Date
2012
Start Page
3718
End Page
3718
DOI
10.1118/1.4735126

TU-A-213CD-11: A Synchronized Moving Grid (SMOG) to Detect and Correct Imaging Lag in Cone Beam Computed Tomography (CBCT): A Simulation Study

Authors
Jin, J; Ren, L; Kim, J; Kim, S; Movsas, B; Jaffrey, D; Chetty, I
MLA Citation
Jin, J, Ren, L, Kim, J, Kim, S, Movsas, B, Jaffrey, D, and Chetty, I. "TU-A-213CD-11: A Synchronized Moving Grid (SMOG) to Detect and Correct Imaging Lag in Cone Beam Computed Tomography (CBCT): A Simulation Study." June 2012.
Source
crossref
Published In
Medical physics
Volume
39
Issue
6Part23
Publish Date
2012
Start Page
3893
End Page
3893
DOI
10.1118/1.4735890

TU-A-213CD-02: Contrast-To-Noise Ratio (CNR) Enhancement and Lag Correction in Cone Beam CT (CBCT) Using a Synchronized-MOving-Grid (SMOG) System

Authors
Ren, L; Jin, J; Yin, F
MLA Citation
Ren, L, Jin, J, and Yin, F. "TU-A-213CD-02: Contrast-To-Noise Ratio (CNR) Enhancement and Lag Correction in Cone Beam CT (CBCT) Using a Synchronized-MOving-Grid (SMOG) System." June 2012.
Source
crossref
Published In
Medical physics
Volume
39
Issue
6Part22
Publish Date
2012
Start Page
3890
End Page
3890
DOI
10.1118/1.4735881

Phase-Matched Digital Tomosynthesis (DTS) Imaging for Simultaneous Target Verification During Volumetric Modulated Arc Therapy (VMAT) Treatment

Authors
Zhang, Y; Ren, L; Vergalasova, I; Cai, J; Yin, F
MLA Citation
Zhang, Y, Ren, L, Vergalasova, I, Cai, J, and Yin, F. "Phase-Matched Digital Tomosynthesis (DTS) Imaging for Simultaneous Target Verification During Volumetric Modulated Arc Therapy (VMAT) Treatment." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3889
End Page
3890

Assessing Effects of Ion Collection Efficiency in Flattening Filter-Free (FFF) Beams On Three TrueBeam Machines

Authors
Chang, Z; Wu, Q; Adamson, J; Ren, L; Bowsher, J; Yan, H; Thomas, A; Yin, F
MLA Citation
Chang, Z, Wu, Q, Adamson, J, Ren, L, Bowsher, J, Yan, H, Thomas, A, and Yin, F. "Assessing Effects of Ion Collection Efficiency in Flattening Filter-Free (FFF) Beams On Three TrueBeam Machines." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3719
End Page
3719

Commissioning and Dosimetric Characteristics of TrueBeam System: Composite Data of Three TrueBeam Machines

Authors
Chang, Z; Wu, Q; Adamson, J; Ren, L; Bowsher, J; Yan, H; Thomas, A; Yin, F
MLA Citation
Chang, Z, Wu, Q, Adamson, J, Ren, L, Bowsher, J, Yan, H, Thomas, A, and Yin, F. "Commissioning and Dosimetric Characteristics of TrueBeam System: Composite Data of Three TrueBeam Machines." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3726
End Page
3726

A Synchronized Moving Grid (SMOG) to Detect and Correct Imaging Lag in Cone Beam Computed Tomography (CBCT): A Simulation Study

Authors
Jin, J; Ren, L; Kim, J; Kim, S; Movsas, B; Jaffrey, D; Chetty, I
MLA Citation
Jin, J, Ren, L, Kim, J, Kim, S, Movsas, B, Jaffrey, D, and Chetty, I. "A Synchronized Moving Grid (SMOG) to Detect and Correct Imaging Lag in Cone Beam Computed Tomography (CBCT): A Simulation Study." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3893
End Page
3893

Treatment of Multiple Brain Metastases Using Stereotactic Radiosurgery with Single-Isocenter Volumetric Modulated Arc Therapy: Comparison with Conventional Dynamic Conformal Arc and Static Beam Stereotactic Radiosurgery

Authors
Huang, C; Ren, L; Kirkpatrick, J; Wang, Z
MLA Citation
Huang, C, Ren, L, Kirkpatrick, J, and Wang, Z. "Treatment of Multiple Brain Metastases Using Stereotactic Radiosurgery with Single-Isocenter Volumetric Modulated Arc Therapy: Comparison with Conventional Dynamic Conformal Arc and Static Beam Stereotactic Radiosurgery." June 2012.
Website
http://hdl.handle.net/10161/5478
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3854
End Page
3854

Dual-Energy CBCT Imaging for Metal Artifact Reduction and Contrast Enhancement

Authors
Li, H; Giles, W; Ren, L; Bowsher, J; Yin, F
MLA Citation
Li, H, Giles, W, Ren, L, Bowsher, J, and Yin, F. "Dual-Energy CBCT Imaging for Metal Artifact Reduction and Contrast Enhancement." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
4017
End Page
4017

Contrast-To-Noise Ratio (CNR) Enhancement and Lag Correction in Cone Beam CT (CBCT) Using a Synchronized-MOving-Grid (SMOG) System

Authors
Ren, L; Jin, J; Yin, F
MLA Citation
Ren, L, Jin, J, and Yin, F. "Contrast-To-Noise Ratio (CNR) Enhancement and Lag Correction in Cone Beam CT (CBCT) Using a Synchronized-MOving-Grid (SMOG) System." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3890
End Page
3891

A Protocol for Comprehensive Acceptance/Commissioning of Complex 3D QA Devices

Authors
O'Daniel, J; Ren, L; Yan, H; Yin, F
MLA Citation
O'Daniel, J, Ren, L, Yan, H, and Yin, F. "A Protocol for Comprehensive Acceptance/Commissioning of Complex 3D QA Devices." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3718
End Page
3718

Clinical commissioning and use of the Novalis Tx linear accelerator for SRS and SBRT.

The purpose of this study was to perform comprehensive measurements and testing of a Novalis Tx linear accelerator, and to develop technical guidelines for com-missioning from the time of acceptance testing to the first clinical treatment. The Novalis Tx (NTX) linear accelerator is equipped with, among other features, a high-definition MLC (HD120 MLC) with 2.5 mm central leaves, a 6D robotic couch, an optical guidance positioning system, as well as X-ray-based image guidance tools to provide high accuracy radiation delivery for stereotactic radiosurgery and stereotactic body radiation therapy procedures. We have performed extensive tests for each of the components, and analyzed the clinical data collected in our clinic. We present technical guidelines in this report focusing on methods for: (1) efficient and accurate beam data collection for commissioning treatment planning systems, including small field output measurements conducted using a wide range of detectors; (2) commissioning tests for the HD120 MLC; (3) data collection for the baseline characteristics of the on-board imager (OBI) and ExacTrac X-ray (ETX) image guidance systems in conjunction with the 6D robotic couch; and (4) end-to-end testing of the entire clinical process. Established from our clinical experience thus far, recommendations are provided for accurate and efficient use of the OBI and ETX localization systems for intra- and extracranial treatment sites. Four results are presented. (1) Basic beam data measurements: Our measurements confirmed the necessity of using small detectors for small fields. Total scatter factors varied significantly (30% to approximately 62%) for small field measurements among detectors. Unshielded stereotactic field diode (SFD) overestimated dose by ~ 2% for large field sizes. Ion chambers with active diameters of 6 mm suffered from significant volume averaging. The sharpest profile penumbra was observed for the SFD because of its small active diameter (0.6 mm). (2) MLC commissioning: Winston Lutz test, light/radiation field congruence, and Picket Fence tests were performed and were within criteria established by the relevant task group reports. The measured mean MLC transmission and dynamic leaf gap of 6 MV SRS beam were 1.17% and 0.36 mm, respectively. (3) Baseline characteristics of OBI and ETX: The isocenter localization errors in the left/right, posterior/anterior, and superior/inferior directions were, respectively, -0.2 ± 0.2 mm, -0.8 ± 0.2 mm, and -0.8 ± 0.4 mm for ETX, and 0.5 ± 0.7 mm, 0.6 ± 0.5 mm, and 0.0 ± 0.5 mm for OBI cone-beam computed tomography. The registration angular discrepancy was 0.1 ± 0.2°, and the maximum robotic couch error was 0.2°. (4) End-to-end tests: The measured isocenter dose differences from the planned values were 0.8% and 0.4%, measured respectively by an ion chamber and film. The gamma pass rate, measured by EBT2 film, was 95% (3% DD and 1 mm DTA). Through a systematic series of quantitative commissioning experiments and end-to-end tests and our initial clinical experience, described in this report, we demonstrate that the NTX is a robust system, with the image guidance and MLC requirements to treat a wide variety of sites - in particular for highly accurate delivery of SRS and SBRT-based treatments.

Authors
Kim, J; Wen, N; Jin, J-Y; Walls, N; Kim, S; Li, H; Ren, L; Huang, Y; Doemer, A; Faber, K; Kunkel, T; Balawi, A; Garbarino, K; Levin, K; Patel, S; Ajlouni, M; Miller, B; Nurushev, T; Huntzinger, C; Schulz, R; Chetty, IJ; Movsas, B; Ryu, S
MLA Citation
Kim, J, Wen, N, Jin, J-Y, Walls, N, Kim, S, Li, H, Ren, L, Huang, Y, Doemer, A, Faber, K, Kunkel, T, Balawi, A, Garbarino, K, Levin, K, Patel, S, Ajlouni, M, Miller, B, Nurushev, T, Huntzinger, C, Schulz, R, Chetty, IJ, Movsas, B, and Ryu, S. "Clinical commissioning and use of the Novalis Tx linear accelerator for SRS and SBRT. (Published online)" J Appl Clin Med Phys 13.3 (May 10, 2012): 3729-.
PMID
22584170
Source
pubmed
Published In
Journal of applied clinical medical physics / American College of Medical Physics
Volume
13
Issue
3
Publish Date
2012
Start Page
3729

Development and clinical evaluation of a three-dimensional cone-beam computed tomography estimation method using a deformation field map.

PURPOSE: To develop a three-dimensional (3D) cone-beam computed tomography (CBCT) estimation method using a deformation field map, and to evaluate and optimize the efficiency and accuracy of the method for use in the clinical setting. METHODS AND MATERIALS: We propose a method to estimate patient CBCT images using prior information and a deformation model. Patients' previous CBCT data are used as the prior information, and the new CBCT volume to be estimated is considered as a deformation of the prior image volume. The deformation field map is solved by minimizing deformation energy and maintaining new projection data fidelity using a nonlinear conjugate gradient method. This method was implemented in 3D form using hardware acceleration and multi-resolution scheme, and it was evaluated for different scan angles, projection numbers, and scan directions using liver, lung, and prostate cancer patient data. The accuracy of the estimation was evaluated by comparing the organ volume difference and the similarity between estimated CBCT and the CBCT reconstructed from fully sampled projections. RESULTS: Results showed that scan direction and number of projections do not have significant effects on the CBCT estimation accuracy. The total scan angle is the dominant factor affecting the accuracy of the CBCT estimation algorithm. Larger scan angles yield better estimation accuracy than smaller scan angles. Lung cancer patient data showed that the estimation error of the 3D lung tumor volume was reduced from 13.3% to 4.3% when the scan angle was increased from 60° to 360° using 57 projections. CONCLUSIONS: The proposed estimation method is applicable for 3D DTS, 3D CBCT, four-dimensional CBCT, and four-dimensional DTS image estimation. This method has the potential for significantly reducing the imaging dose and improving the image quality by removing the organ distortion artifacts and streak artifacts shown in images reconstructed by the conventional Feldkamp-Davis-Kress (FDK) algorithm.

Authors
Ren, L; Chetty, IJ; Zhang, J; Jin, J-Y; Wu, QJ; Yan, H; Brizel, DM; Lee, WR; Movsas, B; Yin, F-F
MLA Citation
Ren, L, Chetty, IJ, Zhang, J, Jin, J-Y, Wu, QJ, Yan, H, Brizel, DM, Lee, WR, Movsas, B, and Yin, F-F. "Development and clinical evaluation of a three-dimensional cone-beam computed tomography estimation method using a deformation field map." Int J Radiat Oncol Biol Phys 82.5 (April 1, 2012): 1584-1593.
PMID
21477945
Source
pubmed
Published In
International Journal of Radiation: Oncology - Biology - Physics
Volume
82
Issue
5
Publish Date
2012
Start Page
1584
End Page
1593
DOI
10.1016/j.ijrobp.2011.02.002

On-Board Digital Tomosynthesis: An Emerging New Technology for IGRT

Authors
Wu, QJ; Godfrey, DJ; Ren, L; Yoo, S; Yin, F
MLA Citation
Wu, QJ, Godfrey, DJ, Ren, L, Yoo, S, and Yin, F. "On-Board Digital Tomosynthesis: An Emerging New Technology for IGRT." Image-Guided Radiation Therapy. Ed. D Bourland. CRC Press, February 22, 2012. (Chapter)
Source
manual
Publish Date
2012

Imaging system QA of a medical accelerator, Novalis Tx, for IGRT per TG 142: Our 1 year experience

American Association of Physicists in Medicine (AAPM) task group (TG) 142 has recently published a report to update recommendations of the AAPM TG 40 report and add new recommendations concerning medical accelerators in the era of image-guided radiation therapy (IGRT). The recommendations of AAPM TG 142 on IGRT are timely. In our institute, we established a comprehensive imaging QA program on a medical accelerator based on AAPM TG 142 and implemented it successfully. In this paper, we share our one-year experience and performance evaluation of an OBI capable linear accelerator, Novalis Tx, per TG 142 guidelines.

Authors
Chang, Z; Bowsher, J; Cai, J; Yoo, S; Wang, Z; Adamson, J; Ren, L; Yin, F-F
MLA Citation
Chang, Z, Bowsher, J, Cai, J, Yoo, S, Wang, Z, Adamson, J, Ren, L, and Yin, F-F. "Imaging system QA of a medical accelerator, Novalis Tx, for IGRT per TG 142: Our 1 year experience." Journal of Applied Clinical Medical Physics 13.4 (2012): 113-140.
Source
scival
Published In
Journal of applied clinical medical physics / American College of Medical Physics
Volume
13
Issue
4
Publish Date
2012
Start Page
113
End Page
140

Clinical commissioning and use of the Novalis Tx linear accelerator for SRS and SBRT

The purpose of this study was to perform comprehensive measurements and testing of a Novalis Tx linear accelerator, and to develop technical guidelines for commissioning from the time of acceptance testing to the first clinical treatment. The Novalis Tx (NTX) linear accelerator is equipped with, among other features, a high-definition MLC (HD120 MLC) with 2.5 mm central leaves, a 6D robotic couch, an optical guidance positioning system, as well as X-ray-based image guidance tools to provide high accuracy radiation delivery for stereotactic radiosurgery and stereotactic body radiation therapy procedures. We have performed extensive tests for each of the components, and analyzed the clinical data collected in our clinic. We present technical guidelines in this report focusing on methods for: (1) efficient and accurate beam data collection for commissioning treatment planning systems, including small field output measurements conducted using a wide range of detectors; (2) commissioning tests for the HD120 MLC; (3) data collection for the baseline characteristics of the on-board imager (OBI) and ExacTrac X-ray (ETX) image guidance systems in conjunction with the 6D robotic couch; and (4) end-to-end testing of the entire clinical process. Established from our clinical experience thus far, recommendations are provided for accurate and efficient use of the OBI and ETX localization systems for intra- and extracranial treatment sites. Four results are presented. (1) Basic beam data measurements: Our measurements confirmed the necessity of using small detectors for small fields. Total scatter factors varied significantly (30% to approximately 62%) for small field measurements among detectors. Unshielded stereotactic field diode (SFD) overestimated dose by ~ 2% for large field sizes. Ion chambers with active diameters of 6 mm suffered from significant volume averaging. The sharpest profile penumbra was observed for the SFD because of its small active diameter (0.6 mm). (2) MLC commissioning: Winston Lutz test, light/radiation field congruence, and Picket Fence tests were performed and were within criteria established by the relevant task group reports. The measured mean MLC transmission and dynamic leaf gap of 6 MV SRS beam were 1.17% and 0.36 mm, respectively. (3) Baseline characteristics of OBI and ETX: The isocenter localization errors in the left/right, posterior/anterior, and superior/inferior directions were, respectively, -0.2 ± 0.2 mm, -0.8 ± 0.2 mm, and -0.8 ± 0.4 mm for ETX, and 0.5 ± 0.7 mm, 0.6 ± 0.5 mm, and 0.0 ± 0.5 mm for OBI cone-beam computed tomography. The registration angular discrepancy was 0.1 ± 0.2°, and the maximum robotic couch error was 0.2°. (4) End-to-end tests: The measured isocenter dose differences from the planned values were 0.8% and 0.4%, measured respectively by an ion chamber and film. The gamma pass rate, measured by EBT2 film, was 95% (3% DD and 1 mm DTA). Through a systematic series of quantitative commissioning experiments and end-to-end tests and our initial clinical experience, described in this report, we demonstrate that the NTX is a robust system, with the image guidance and MLC requirements to treat a wide variety of sites - in particular for highly accurate delivery of SRS and SBRT-based treatments.

Authors
Kim, J; Wen, N; Jin, J-Y; Walls, N; Kim, S; Li, H; Ren, L; Huang, Y; Doemer, A; Faber, K; Kunkel, T; Balawi, A; Garbarino, K; Levin, K; Patel, S; Ajlouni, M; Miller, B; Nurushev, T; Huntzinger, C; Schulz, R; Chetty, IJ; Movsas, B; Ryu, S
MLA Citation
Kim, J, Wen, N, Jin, J-Y, Walls, N, Kim, S, Li, H, Ren, L, Huang, Y, Doemer, A, Faber, K, Kunkel, T, Balawi, A, Garbarino, K, Levin, K, Patel, S, Ajlouni, M, Miller, B, Nurushev, T, Huntzinger, C, Schulz, R, Chetty, IJ, Movsas, B, and Ryu, S. "Clinical commissioning and use of the Novalis Tx linear accelerator for SRS and SBRT." Journal of Applied Clinical Medical Physics 13.3 (2012): 124-151.
Source
scival
Published In
Journal of applied clinical medical physics / American College of Medical Physics
Volume
13
Issue
3
Publish Date
2012
Start Page
124
End Page
151

MO-D-BRC-01: Dosimetric Evaluation of a Novel Cone-Beam CT (CBCT) Estimation Method Using Prior Information for Lung Cancer Patient Treatment

Authors
Ren, L; Jin, J; Movsas, B; Yin, F; Chetty, I
MLA Citation
Ren, L, Jin, J, Movsas, B, Yin, F, and Chetty, I. "MO-D-BRC-01: Dosimetric Evaluation of a Novel Cone-Beam CT (CBCT) Estimation Method Using Prior Information for Lung Cancer Patient Treatment." June 2011.
Source
crossref
Published In
Medical physics
Volume
38
Issue
6Part26
Publish Date
2011
Start Page
3712
End Page
3712
DOI
10.1118/1.3612965

SU-E-J-21: Verification of a Monte Carlo Model of CBCT Flat Panel Detector Using BEAMnrc/EGSnrc Code

Authors
Kim, S; Ren, L; Jin, J; Kim, J; Movsas, B; Chetty, I
MLA Citation
Kim, S, Ren, L, Jin, J, Kim, J, Movsas, B, and Chetty, I. "SU-E-J-21: Verification of a Monte Carlo Model of CBCT Flat Panel Detector Using BEAMnrc/EGSnrc Code." June 2011.
Source
crossref
Published In
Medical physics
Volume
38
Issue
6Part7
Publish Date
2011
Start Page
3446
End Page
3446
DOI
10.1118/1.3611789

MO-D-BRC-06: A Multi-Exposure Approach to Improve Image Quality for Linac-Based Cone Beam Computed Tomography (CBCT)

Authors
Jin, J; Ren, L; Kim, J; Kim, S; Movsas, B; Chetty, I
MLA Citation
Jin, J, Ren, L, Kim, J, Kim, S, Movsas, B, and Chetty, I. "MO-D-BRC-06: A Multi-Exposure Approach to Improve Image Quality for Linac-Based Cone Beam Computed Tomography (CBCT)." June 2011.
Source
crossref
Published In
Medical physics
Volume
38
Issue
6Part26
Publish Date
2011
Start Page
3713
End Page
3713
DOI
10.1118/1.3612970

Advances in treatment techniques: arc-based and other intensity modulated therapies.

Treatment planning and radiation delivery techniques have advanced significantly during the past 2 decades. The development of the multileaf collimator has changed the scope of radiotherapy. The dynamic conformal arc technique emerged from traditional cone-based conformal arc therapies, which aim to improve target dose uniformity and reduce normal tissue doses. With dynamic conformal arc, the multileaf collimator aperture is shaped dynamically to conform to the target. With the advent of intensity-modulated radiotherapy (IMRT), the concept of arc therapy in combination with IMRT has enabled better-quality dose distributions and more efficient delivery. Helical tomotherapy has been developed to treat targets sequentially by modulating the beam intensity in each "slice" of the patient. Helical tomotherapy offers improved dose distributions for complicated treatments, such as whole-body radiation. Intensity-modulated arc therapy has been studied to modulate fluences in a cone beam rather than fan beam geometry to improve delivery efficiency. This article reviews arc-based IMRT, intensity-modulated arc therapy, and helical tomotherapy techniques. We compare the dosimetric results reported in the literature for each technique in various treatment sites. We also review the application of these techniques in specialized clinical procedures including total marrow irradiation, simultaneous treatment of multiple brain metastases, dose painting, simultaneous integrated boost, and stereotactic radiosurgery.

Authors
Jin, J-Y; Wen, N; Ren, L; Glide-Hurst, C; Chetty, IJ
MLA Citation
Jin, J-Y, Wen, N, Ren, L, Glide-Hurst, C, and Chetty, IJ. "Advances in treatment techniques: arc-based and other intensity modulated therapies." Cancer J 17.3 (May 2011): 166-176. (Review)
PMID
21610470
Source
pubmed
Published In
Cancer Journal
Volume
17
Issue
3
Publish Date
2011
Start Page
166
End Page
176
DOI
10.1097/PPO.0b013e31821f8318

A TCP model incorporating setup uncertainty and tumor cell density variation in microscopic extension to guide treatment planning.

PURPOSE: Tumor control probability (TCP) models have been proposed to evaluate and guide treatment planning. However, they are usually based on the dose volume histograms (DVHs) of the planning target volume (PTV) and may not properly reflect the substantial variation in tumor burden from the gross tumor volume (GTV) to the microscopic extension (ME) and to the margin of PTV. In this study, the authors propose a TCP model that can account for the effects of setup uncertainties and tumor cell density decay in the ME region. METHODS: The proposed TCP model is based on the total surviving clonogenic tumor cells (CTCs) after irradiation of a known dose distribution to a region with a CTC distribution. The CTC density was considered to be homogeneous within the GTV, while decreasing exponentially in the ME region. The effect of random setup uncertainty was modeled by convolving the dose distribution with a Gaussian probability density function, represented by a standard deviation, sigma. The effect of systematic setup uncertainty was modeled by summing each calculated TCP for all potential offsets in a Gaussian probability, represented by sigma. The model was then applied to simplified cases to demonstrate the concept. TCP dose responses were calculated for various GTV volumes, DVH shapes, CTC density decay coefficients, probabilities of lymph node metastasis, and random and systematic errors. The slopes of the dose falloff to cover the CTC density decay in the ME region and the margins to compensate setup errors were also analyzed in generalized cases. RESULTS: The sigmoid TCP dose response curve shifted to the right substantially for a larger GTV, while modestly for cold spots in DVH. A dose distribution with a uniform dose within the GTV, and a linear dose falloff in the ME region, tended to cause a minimal TCP deterioration if a proper dose falloff slope was used. When the dose falloff slope was less steep than a critical slope represented by kT, the D50, which is the prescription dose at TCP=50%, and gamma50, which is the TCP slope at TCP=50%, varied little with different dose falloff slopes. However, both D50 and gamma50 deteriorated fast when the slopes were steeper than kT. The random setup error tended to shift the TCP curve to the right, while the systematic error tended to compress the curve downward. For combined random and systematic errors, we demonstrated that based on the model, a margin of mean square root of (0.75 sigma)2 + (1.15 sigma)2 added to the GTV was found to cause a TCP change corresponding to 2% drop at TCP=90%, or 0.5 Gy shift in D50. CONCLUSIONS: This study conceptually demonstrated that a TCP model incorporating the effects of tumor cell density variation and setup uncertainty may be used to guide radiation treatment planning.

Authors
Jin, J-Y; Kong, F-M; Liu, D; Ren, L; Li, H; Zhong, H; Movsas, B; Chetty, IJ
MLA Citation
Jin, J-Y, Kong, F-M, Liu, D, Ren, L, Li, H, Zhong, H, Movsas, B, and Chetty, IJ. "A TCP model incorporating setup uncertainty and tumor cell density variation in microscopic extension to guide treatment planning." Med Phys 38.1 (January 2011): 439-448.
PMID
21361212
Source
pubmed
Published In
Medical physics
Volume
38
Issue
1
Publish Date
2011
Start Page
439
End Page
448
DOI
10.1118/1.3531543

Dosimetric Evaluation and Optimization of a Novel CBCT Estimation Method for Adaptive Radiation Therapy (ART)

Authors
Ren, L; Jin, J; Movsas, B; Yin, F; Chetty, I
MLA Citation
Ren, L, Jin, J, Movsas, B, Yin, F, and Chetty, I. "Dosimetric Evaluation and Optimization of a Novel CBCT Estimation Method for Adaptive Radiation Therapy (ART)." 2011.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
81
Issue
2
Publish Date
2011
Start Page
S821
End Page
S821

Combining scatter reduction and correction to improve image quality in cone-beam computed tomography (CBCT).

PURPOSE: The authors propose a combined scatter reduction and correction method to improve image quality in cone-beam computed tomography (CBCT). Although using a beam-block approach similar to previous techniques to measure the scatter, this method differs in that the authors utilize partially blocked projection data obtained during scatter measurement for CBCT image reconstruction. This study aims to evaluate the feasibility of the proposed approach. METHODS: A 1D grid, composed of lead septa, was placed between the radiation source and the imaging object for scatter measurement. Image data were collected from the grid interspace regions while the scatter distribution was measured in the blocked regions under the grid. Scatter correction was performed by subtracting the measured scatter from the imaging data. Image information in the penumbral regions of the grid was derived. Three imaging modes were developed to reconstruct full CBCT images from partial projection data. The single-rotation half-fan mode uses interpolation to fill the missing data. The dual-rotation half-fan mode uses two rotations, with the grid offset by half a grid cycle, to acquire two complementary sets of projections, which are then merged to form complete projections for reconstruction. The single-rotation full-fan mode was designed for imaging a small object or a region of interest. Full-fan projection images were acquired over a 360 degrees scan angle with the grid shifting a distance during the scan. An enlarged Catphan phantom was used to evaluate potential improvement in image quality with the proposed technique. An anthropomorphic pelvis phantom was used to validate the feasibility of reconstructing a complete set of CBCT images from the partially blocked projections using three imaging modes. Rigid-body image registration was performed between the CBCT images from the single-rotation half-fan mode and the simulation CT and the results were compared to that for the CBCT images from dual-rotation mode and conventional CBCT images. RESULTS: The proposed technique reduced the streak artifact index from 58% to 1% in comparison with the conventional CBCT. It also improved CT number linearity from 0.880 to 0.998 and the contrast-to-noise ratio (CNR) from 4.29 to 6.42. Complete sets of CBCT images with overall improved image quality were achieved for all three image modes. The longitudinal resolution was slightly compromised for the single-rotation half-fan mode. High resolution was retained for the dual-rotation half-fan and single-rotation full-fan modes in the longitudinal direction. The registration error for the CBCT images from the single-rotation half-fan mode was 0.8 +/- 0.3 mm in the longitudinal direction and negligible in the other directions. CONCLUSIONS: The proposed method provides combined scatter correction and direct scatter reduction. Scatter correction may eliminate scatter artifacts, while direct scatter reduction may improve the CNR to compensate the CNR degradation due to scatter correction. Complete sets of CBCT images are reconstructed in all three imaging modes. The single-rotation mode can be used for rigid-body patient alignment despite degradation in longitudinal resolution. The dual-rotation mode may be used to improve CBCT image quality for soft tissue delineation in adaptive radiation therapy.

Authors
Jin, J-Y; Ren, L; Liu, Q; Kim, J; Wen, N; Guan, H; Movsas, B; Chetty, IJ
MLA Citation
Jin, J-Y, Ren, L, Liu, Q, Kim, J, Wen, N, Guan, H, Movsas, B, and Chetty, IJ. "Combining scatter reduction and correction to improve image quality in cone-beam computed tomography (CBCT)." Med Phys 37.11 (November 2010): 5634-5644.
PMID
21158275
Source
pubmed
Published In
Medical physics
Volume
37
Issue
11
Publish Date
2010
Start Page
5634
End Page
5644
DOI
10.1118/1.3497272

SU-DD-A4-03: Cone Beam Computed Tomography Reconstruction on Graphics Processing Units: Flat3D Texture Techniques

Authors
Kim, J; Ren, L; Jin, J; Zhong, H; Chetty, IJ
MLA Citation
Kim, J, Ren, L, Jin, J, Zhong, H, and Chetty, IJ. "SU-DD-A4-03: Cone Beam Computed Tomography Reconstruction on Graphics Processing Units: Flat3D Texture Techniques." June 2010.
Source
crossref
Published In
Medical physics
Volume
37
Issue
6Part6
Publish Date
2010
Start Page
3092
End Page
3092
DOI
10.1118/1.3468001

TU-C-204B-01: Reduce Patient Dose and Improve Image Quality in CBCT for Image Guided Radiotherapy

Authors
Jin, J; Ren, L; Kim, J; Movsas, B; Chetty, I
MLA Citation
Jin, J, Ren, L, Kim, J, Movsas, B, and Chetty, I. "TU-C-204B-01: Reduce Patient Dose and Improve Image Quality in CBCT for Image Guided Radiotherapy." June 2010.
Source
crossref
Published In
Medical physics
Volume
37
Issue
6Part13
Publish Date
2010
Start Page
3384
End Page
3384
DOI
10.1118/1.3469224

TU-C-204B-07: A Comparative Study for Daily Localization with 3D Ultrasound, Cone Beam CT, Implanted Prostate Fiducial Markers and Calypso 4D Localization System for Patients Undergoing IGRT for Prostate Cancer

Authors
Neicu, T; Ren, L; Chetty, I; Pradhan, D; Stricker, H; Movsas, B; Elshaikh, M
MLA Citation
Neicu, T, Ren, L, Chetty, I, Pradhan, D, Stricker, H, Movsas, B, and Elshaikh, M. "TU-C-204B-07: A Comparative Study for Daily Localization with 3D Ultrasound, Cone Beam CT, Implanted Prostate Fiducial Markers and Calypso 4D Localization System for Patients Undergoing IGRT for Prostate Cancer." June 2010.
Source
crossref
Published In
Medical physics
Volume
37
Issue
6Part13
Publish Date
2010
Start Page
3385
End Page
3386
DOI
10.1118/1.3469230

SU-GG-J-30: A Novel Scatter Reduction and Correction Method to Improve Cone-Beam CT (CBCT) Image Quality

Authors
Ren, L; Kim, J; Liu, Q; Movsas, B; Chetty, I; Jin, J
MLA Citation
Ren, L, Kim, J, Liu, Q, Movsas, B, Chetty, I, and Jin, J. "SU-GG-J-30: A Novel Scatter Reduction and Correction Method to Improve Cone-Beam CT (CBCT) Image Quality." June 2010.
Source
crossref
Published In
Medical physics
Volume
37
Issue
6Part9
Publish Date
2010
Start Page
3151
End Page
3151
DOI
10.1118/1.3468254

SU-FF-J-09: Limited-Angle Imaging for Target Positioning Using Orthogonal Conebeam X-Ray Systems

Authors
Bowsher, J; Giles, W; Roper, J; Ren, L; Yin, F
MLA Citation
Bowsher, J, Giles, W, Roper, J, Ren, L, and Yin, F. "SU-FF-J-09: Limited-Angle Imaging for Target Positioning Using Orthogonal Conebeam X-Ray Systems." June 2009.
Source
crossref
Published In
Medical physics
Volume
36
Issue
6Part5
Publish Date
2009
Start Page
2476
End Page
2477
DOI
10.1118/1.3181301

TH-A-211A-01: Digital Tomosynthesis for Target Localization

Authors
Yin, F; Wu, Q; Godfrey, D; Ren, L; Yoo, S; Maurer, J; Yan, H
MLA Citation
Yin, F, Wu, Q, Godfrey, D, Ren, L, Yoo, S, Maurer, J, and Yan, H. "TH-A-211A-01: Digital Tomosynthesis for Target Localization." June 2009.
Source
crossref
Published In
Medical physics
Volume
36
Issue
6Part26
Publish Date
2009
Start Page
2790
End Page
2791
DOI
10.1118/1.3182588

Clinical evaluation of positioning verification using digital tomosynthesis and bony anatomy and soft tissues for prostate image-guided radiotherapy.

PURPOSE: To evaluate on-board digital tomosynthesis (DTS) for patient positioning vs. two-dimensional (2D) radiography and three-dimensional cone beam (CBCT). METHODS AND MATERIALS: A total of 92 image sessions from 9 prostate cancer patients were analyzed. An on-board image set was registered to a corresponding reference image set. Four pairs of image sets were used: digitally reconstructed radiographs vs. on-board orthogonal paired radiographs for the 2D method, coronal-reference DTS vs. on-board coronal DTS for the coronal-DTS method, sagittal-reference DTS vs. on-board sagittal DTS for the sagittal-DTS method, and planning CT vs. CBCT for the CBCT method. The registration results were compared. RESULTS: The systematic errors in all methods were <1 mm/1 degrees . When registering the bony anatomy, the mean vector difference was 0.21 +/- 0.11 cm between 2D and CBCT, 0.11 +/- 0.08 cm between CBCT and coronal DTS, and 0.14 +/- 0.07 cm between CBCT and sagittal DTS. The correlation between CBCT to DTS was stronger (coefficient = 0.92-0.95) than the correlation between 2D and CBCT or DTS (coefficient = 0.81-0.83). When registering the soft tissue, the mean vector difference was 0.18 +/- 0.11 cm between CBCT and coronal DTS and 0.29 +/- 0.17 cm between CBCT and sagittal DTS. The correlation coefficient of CBCT to sagittal DTS and to coronal DTS was 0.84 and 0.92, respectively. CONCLUSION: DTS could provide equivalent results to CBCT when the bony anatomy is used as landmarks for prostate image-guided radiotherapy. For soft tissue-based positioning verification, coronal DTS produced equivalent results to CBCT, but sagittal DTS alone was insufficient. DTS could allow for comparable soft tissue-based target localization with faster scanning time and a lower imaging dose compared with CBCT.

Authors
Yoo, S; Wu, QJ; Godfrey, D; Yan, H; Ren, L; Das, S; Lee, WR; Yin, F-F
MLA Citation
Yoo, S, Wu, QJ, Godfrey, D, Yan, H, Ren, L, Das, S, Lee, WR, and Yin, F-F. "Clinical evaluation of positioning verification using digital tomosynthesis and bony anatomy and soft tissues for prostate image-guided radiotherapy." Int J Radiat Oncol Biol Phys 73.1 (January 1, 2009): 296-305.
PMID
19100923
Source
pubmed
Published In
International Journal of Radiation: Oncology - Biology - Physics
Volume
73
Issue
1
Publish Date
2009
Start Page
296
End Page
305
DOI
10.1016/j.ijrobp.2008.09.006

Development and Clinical Evaluation of a Novel 3D Digital Tomosynthesis (DTS) Reconstruction Method using a Deformation Field Map

Authors
Ren, L; Zhang, J; Thongphiew, D; Wu, Q; Yan, H; Brizel, DM; Lee, WR; Willett, CG; Yin, F
MLA Citation
Ren, L, Zhang, J, Thongphiew, D, Wu, Q, Yan, H, Brizel, DM, Lee, WR, Willett, CG, and Yin, F. "Development and Clinical Evaluation of a Novel 3D Digital Tomosynthesis (DTS) Reconstruction Method using a Deformation Field Map." 2009.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
75
Issue
3
Publish Date
2009
Start Page
S96
End Page
S96

A novel digital tomosynthesis (DTS) reconstruction method using a deformation field map.

We developed a novel digital tomosynthesis (DTS) reconstruction method using a deformation field map to optimally estimate volumetric information in DTS images. The deformation field map is solved by using prior information, a deformation model, and new projection data. Patients' previous cone-beam CT (CBCT) or planning CT data are used as the prior information, and the new patient volume to be reconstructed is considered as a deformation of the prior patient volume. The deformation field is solved by minimizing bending energy and maintaining new projection data fidelity using a nonlinear conjugate gradient method. The new patient DTS volume is then obtained by deforming the prior patient CBCT or CT volume according to the solution to the deformation field. This method is novel because it is the first method to combine deformable registration with limited angle image reconstruction. The method was tested in 2D cases using simulated projections of a Shepp-Logan phantom, liver, and head-and-neck patient data. The accuracy of the reconstruction was evaluated by comparing both organ volume and pixel value differences between DTS and CBCT images. In the Shepp-Logan phantom study, the reconstructed pixel signal-to-noise ratio (PSNR) for the 60° DTS image reached 34.3dB. In the liver patient study, the relative error of the liver volume reconstructed using 60° projections was 3.4%. The reconstructed PSNR for the 60° DTS image reached 23.5dB. In the head-and-neck patient study, the new method using 60° projections was able to reconstruct the 8.1° rotation of the bony structure with 0.0° error. The reconstructed PSNR for the 60° DTS image reached 24.2dB. In summary, the new reconstruction method can optimally estimate the volumetric information in DTS images using 60° projections. Preliminary validation of the algorithm showed that it is both technically and clinically feasible for image guidance in radiation therapy.

Authors
Ren, L; Zhang, J; Thongphiew, D; Godfrey, DJ; Wu, QJ; Zhou, S-M; Yin, F-F
MLA Citation
Ren, L, Zhang, J, Thongphiew, D, Godfrey, DJ, Wu, QJ, Zhou, S-M, and Yin, F-F. "A novel digital tomosynthesis (DTS) reconstruction method using a deformation field map." Medical physics 35.7Part1 (July 2008): 3110-3115. (Letter)
PMID
28513030
Source
epmc
Published In
Medical physics
Volume
35
Issue
7Part1
Publish Date
2008
Start Page
3110
End Page
3115
DOI
10.1118/1.2940725

A novel digital tomosynthesis (DTS) reconstruction method using a deformation field map.

We developed a novel digital tomosynthesis (DTS) reconstruction method using a deformation field map to optimally estimate volumetric information in DTS images. The deformation field map is solved by using prior information, a deformation model, and new projection data. Patients' previous cone-beam CT (CBCT) or planning CT data are used as the prior information, and the new patient volume to be reconstructed is considered as a deformation of the prior patient volume. The deformation field is solved by minimizing bending energy and maintaining new projection data fidelity using a nonlinear conjugate gradient method. The new patient DTS volume is then obtained by deforming the prior patient CBCT or CT volume according to the solution to the deformation field. This method is novel because it is the first method to combine deformable registration with limited angle image reconstruction. The method was tested in 2D cases using simulated projections of a Shepp-Logan phantom, liver, and head-and-neck patient data. The accuracy of the reconstruction was evaluated by comparing both organ volume and pixel value differences between DTS and CBCT images. In the Shepp-Logan phantom study, the reconstructed pixel signal-to-noise ratio (PSNR) for the 60 degrees DTS image reached 34.3 dB. In the liver patient study, the relative error of the liver volume reconstructed using 60 degrees projections was 3.4%. The reconstructed PSNR for the 60 degrees DTS image reached 23.5 dB. In the head-and-neck patient study, the new method using 60 degrees projections was able to reconstruct the 8.1 degrees rotation of the bony structure with 0.0 degrees error. The reconstructed PSNR for the 60 degrees DTS image reached 24.2 dB. In summary, the new reconstruction method can optimally estimate the volumetric information in DTS images using 60 degrees projections. Preliminary validation of the algorithm showed that it is both technically and clinically feasible for image guidance in radiation therapy.

Authors
Ren, L; Zhang, J; Thongphiew, D; Godfrey, DJ; Wu, QJ; Zhou, S-M; Yin, F-F
MLA Citation
Ren, L, Zhang, J, Thongphiew, D, Godfrey, DJ, Wu, QJ, Zhou, S-M, and Yin, F-F. "A novel digital tomosynthesis (DTS) reconstruction method using a deformation field map." Med Phys 35.7 (July 2008): 3110-3115. (Letter)
PMID
18697536
Source
pubmed
Published In
Medical physics
Volume
35
Issue
7
Publish Date
2008
Start Page
3110
End Page
3115
DOI
10.1118/1.2940725

SU-GG-I-52: Conversion of On-Board Digital TomoSynthesis (DTS) to HU Values

Authors
Yoo, S; Wu, Q; Godfrey, D; Ren, L; Yin, F
MLA Citation
Yoo, S, Wu, Q, Godfrey, D, Ren, L, and Yin, F. "SU-GG-I-52: Conversion of On-Board Digital TomoSynthesis (DTS) to HU Values." June 2008.
Source
crossref
Published In
Medical physics
Volume
35
Issue
6Part3
Publish Date
2008
Start Page
2654
End Page
2654
DOI
10.1118/1.2961450

SU-GG-J-119: Localization Accuracy of Target Verification System Using Digitial Tomosynthesis (DTS)

Authors
Yan, H; Ren, L; Godfrey, D; Yoo, S; Yin, F
MLA Citation
Yan, H, Ren, L, Godfrey, D, Yoo, S, and Yin, F. "SU-GG-J-119: Localization Accuracy of Target Verification System Using Digitial Tomosynthesis (DTS)." June 2008.
Source
crossref
Published In
Medical physics
Volume
35
Issue
6Part7
Publish Date
2008
Start Page
2706
End Page
2706
DOI
10.1118/1.2961668

SU-GG-I-53: The Impact of Scan Angles On the Visibility of Anatomy in On-Board Digital Tomosynthesis (DTS) Images for Head and Neck Cancer Patients: A Single-Observer Study

Authors
Ma, J; Wu, Q; Godfrey, D; Yan, H; Ren, L; Yin, F
MLA Citation
Ma, J, Wu, Q, Godfrey, D, Yan, H, Ren, L, and Yin, F. "SU-GG-I-53: The Impact of Scan Angles On the Visibility of Anatomy in On-Board Digital Tomosynthesis (DTS) Images for Head and Neck Cancer Patients: A Single-Observer Study." June 2008.
Source
crossref
Published In
Medical physics
Volume
35
Issue
6Part3
Publish Date
2008
Start Page
2654
End Page
2654
DOI
10.1118/1.2961451

TH-D-351-02: A Novel Digital Tomosynthesis (DTS) Reconstruction Method Using Prior Information and a Deformation Model

Authors
Ren, L; Zhang, J; Thongphiew, D; Godfrey, D; Zhou, S; Yin, F
MLA Citation
Ren, L, Zhang, J, Thongphiew, D, Godfrey, D, Zhou, S, and Yin, F. "TH-D-351-02: A Novel Digital Tomosynthesis (DTS) Reconstruction Method Using Prior Information and a Deformation Model." June 2008.
Source
crossref
Published In
Medical physics
Volume
35
Issue
6Part27
Publish Date
2008
Start Page
2989
End Page
2989
DOI
10.1118/1.2962923

Automatic registration between reference and on-board digital tomosynthesis images for positioning verification.

The authors developed a hybrid multiresolution rigid-body registration technique to automatically register reference digital tomosynthesis (DTS) images with on-board DTS images to guide patient positioning in radiation therapy. This hybrid registration technique uses a faster but less accurate static method to achieve an initial registration, followed by a slower but more accurate adaptive method to fine tune the registration. A multiresolution scheme is employed in the registration to further improve the registration accuracy, robustness, and efficiency. Normalized mutual information is selected as the criterion for the similarity measure and the downhill simplex method is used as the search engine. This technique was tested using image data both from an anthropomorphic chest phantom and from eight head-and-neck cancer patients. The effects of the scan angle and the region-of-interest (ROI) size on the registration accuracy and robustness were investigated. The necessity of using the adaptive registration method in the hybrid technique was validated by comparing the results of the static method and the hybrid method. With a 44 degrees scan angle and a large ROI covering the entire DTS volume, the average of the registration capture ranges in single-axis simulations was between -31 and +34 deg for rotations and between -89 and +78 mm for translations in the phantom study, and between -38 and +38 deg for rotations and between -58 and +65 mm for translations in the patient study. Decreasing the DTS scan angle from 44 degrees to 22 degrees mainly degraded the registration accuracy and robustness for the out-of-plane rotations. Decreasing the ROI size from the entire DTS volume to the volume surrounding the spinal cord reduced the capture ranges to between -23 and +18 deg for rotations and between -33 and +43 mm for translations in the phantom study, and between -18 and +25 deg for rotations and between -35 and +39 mm for translations in the patient study. Results also showed that the hybrid registration technique had much larger capture ranges than the static method alone in registering the out-of-plane rotations.

Authors
Ren, L; Godfrey, DJ; Yan, H; Wu, QJ; Yin, F-F
MLA Citation
Ren, L, Godfrey, DJ, Yan, H, Wu, QJ, and Yin, F-F. "Automatic registration between reference and on-board digital tomosynthesis images for positioning verification." Med Phys 35.2 (February 2008): 664-672.
PMID
18383688
Source
pubmed
Published In
Medical physics
Volume
35
Issue
2
Publish Date
2008
Start Page
664
End Page
672
DOI
10.1118/1.2831903

Evaluation of Image Enhancement Method on Target Registration Using Cone Beam CT in Radiation Therapy.

An intensity based six-degree image registration algorithm between cone-beam CT (CBCT) and planning CT has been developed for image-guided radiation therapy (IGRT). CT images of an anthropomorphic chest phantom were acquired using conventional CT scanner and corresponding CBCT was reconstructed based on projection images acquired by an on-board imager (OBI). Both sets of images were initially registered to each other using attached fudicial markers to achieve a golden standard registration. Starting from this point, an offset was applied to one set of images, and the matching result was found by a gray-value based registration method. Finally, The registration error was evaluated by comparing the detected shifts with the known shift. Three window-level (WL) combinations commonly used for image enhancement were examined to investigate the effect of anatomical information of Bony only (B), Bone+Tissue (BT), and Bone+Tissue+Air (BTA) on the accuracy and robustness of gray-value based registration algorithm. Extensive tests were performed in searching for the attraction range of registration algorithm. The widest attraction range was achieved with the WL combination of BTA. The average attraction ranges of this combination were 73.3 mm and 81.6 degree in the translation and rotation dimensions, respectively, and the average registration errors were 0.15 mm and 0.32 degree. The WL combination of BT shows the secondary largest attraction ranges. The WL combination of B shows limited convergence property and its attraction range was the smallest among the three examined combinations (on average 33.3 mm and 25.0 degree). If two sets of 3D images in original size (512 × 512) were used, registration could be accomplished within 10~20 minutes by current algorithm, which is only acceptable for off-line reviewing purpose. As the size of image set reduced by a factor of 2~4, the registration time would be 2~4 minutes which is feasible for on-line target localization.

Authors
Yan, H; Lei, R; Wu, J; Di, F; Yin, F-F
MLA Citation
Yan, H, Lei, R, Wu, J, Di, F, and Yin, F-F. "Evaluation of Image Enhancement Method on Target Registration Using Cone Beam CT in Radiation Therapy." Clinical medicine. Oncology 2 (January 2008): 289-299.
PMID
21892290
Source
epmc
Published In
Clinical Medicine: Oncology
Volume
2
Publish Date
2008
Start Page
289
End Page
299

Limited-angle DTS imaging using CT bone information

Authors
Bowsher, JE; Ren, L; Yin, F
MLA Citation
Bowsher, JE, Ren, L, and Yin, F. "Limited-angle DTS imaging using CT bone information." 2008.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
72
Issue
1
Publish Date
2008
Start Page
S654
End Page
S654
DOI
10.1016/j.ijrobp.2008.06.335

A novel digital tomosynthesis (DTS) reconstruction method using prior information and a deformation model

Authors
Ren, L; Zhang, J; Thongphiew, D; Wu, Q; Godfrey, DJ; Zhou, S; Yin, F
MLA Citation
Ren, L, Zhang, J, Thongphiew, D, Wu, Q, Godfrey, DJ, Zhou, S, and Yin, F. "A novel digital tomosynthesis (DTS) reconstruction method using prior information and a deformation model." 2008.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
72
Issue
1
Publish Date
2008
Start Page
S109
End Page
S109
DOI
10.1016/j.ijrobp.2008.06.1014

Accelerating reconstruction of reference digital tomosynthesis using graphics hardware.

The successful implementation of digital tomosynthesis (DTS) for on-board image guided radiation therapy (IGRT) requires fast DTS image reconstruction. Both target and reference DTS image sets are required to support an image registration application for IGRT. Target images are usually DTS image sets reconstructed from on-board projections, which can be accomplished quickly using the conventional filtered backprojection algorithm. Reference images are DTS image sets reconstructed from digitally reconstructed radiographs (DRRs) previously generated from conventional planning CT data. Generating a set of DRRs from planning CT is relatively slow using the conventional ray-casting algorithm. In order to facilitate DTS reconstruction within a clinically acceptable period of time, we implemented a high performance DRR reconstruction algorithm on a graphics processing unit of commercial PC graphics hardware. The performance of this new algorithm was evaluated and compared with that which is achieved using the conventional software-based ray-casting algorithm. DTS images were reconstructed from DRRs previously generated by both hardware and software algorithms. On average, the DRR reconstruction efficiency using the hardware method is improved by a factor of 67 over the software method. The image quality of the DRRs was comparable to those generated using the software-based ray-casting algorithm. Accelerated DRR reconstruction significantly reduces the overall time required to produce a set of reference DTS images from planning CT and makes this technique clinically practical for target localization for radiation therapy.

Authors
Yan, H; Ren, L; Godfrey, DJ; Yin, F-F
MLA Citation
Yan, H, Ren, L, Godfrey, DJ, and Yin, F-F. "Accelerating reconstruction of reference digital tomosynthesis using graphics hardware." Med Phys 34.10 (October 2007): 3768-3776.
PMID
17985622
Source
pubmed
Published In
Medical physics
Volume
34
Issue
10
Publish Date
2007
Start Page
3768
End Page
3776
DOI
10.1118/1.2779945

Evaluation of three types of reference image data for external beam radiotherapy target localization using digital tomosynthesis (DTS).

Digital tomosynthesis (DTS) is a fast, low-dose three-dimensional (3D) imaging approach which yields slice images with excellent in-plane resolution, though low plane-to-plane resolution. A stack of DTS slices can be reconstructed from a single limited-angle scan, with typical scan angles ranging from 10 degrees to 40 degrees and acquisition times of less than 10 s. The resulting DTS slices show soft tissue contrast approaching that of full cone-beam CT. External beam radiotherapy target localization using DTS requires the registration of on-board DTS images with corresponding reference image data. This study evaluates three types of reference volume: original reference CT, exact reference DTS (RDTS), and a more computationally efficient approximate reference DTS (RDTSapprox), as well as three different DTS scan angles (22 degrees, 44 degrees, and 65 degrees) for the DTS target localization task. Three-dimensional mutual information (MI) shared between reference and onboard DTS volumes was computed in a region surrounding the spine of a chest phantom, as translations spanning +/-5 mm and rotations spanning +/-5 degrees were simulated along each dimension in the reference volumes. The locations of the MI maxima were used as surrogates for registration accuracy, and the width of the MI peaks were used to characterize the registration robustness. The results show that conventional treatment planning CT volumes are inadequate reference volumes for direct registration with on-board DTS data. The efficient RDTSapprox method also appears insufficient for MI-based registration without further refinement of the technique, though it may be suitable for manual registration performed by a human observer. The exact RDTS volumes, on the other hand, delivered a 3D DTS localization accuracy of 0.5 mm and 0.50 along each axis, using only a single 44 degrees coronal on-board DTS scan of the chest phantom.

Authors
Godfrey, DJ; Ren, L; Yan, H; Wu, Q; Yoo, S; Oldham, M; Yin, FF
MLA Citation
Godfrey, DJ, Ren, L, Yan, H, Wu, Q, Yoo, S, Oldham, M, and Yin, FF. "Evaluation of three types of reference image data for external beam radiotherapy target localization using digital tomosynthesis (DTS)." Med Phys 34.8 (August 2007): 3374-3384.
PMID
17879800
Source
pubmed
Published In
Medical physics
Volume
34
Issue
8
Publish Date
2007
Start Page
3374
End Page
3384
DOI
10.1118/1.2756941

A hybrid multiresolution method for automatic registration between reference and on board digital tomosynthesis

Authors
Ren, L; Yan, H; Godfrey, D; Yin, F
MLA Citation
Ren, L, Yan, H, Godfrey, D, and Yin, F. "A hybrid multiresolution method for automatic registration between reference and on board digital tomosynthesis." June 2007.
Source
wos-lite
Published In
Medical physics
Volume
34
Issue
6
Publish Date
2007
Start Page
2380
End Page
2380
DOI
10.1118/1.2760559

Development of clinical application platform using digital tomosynthesis for target localization

Authors
Yan, H; Ren, L; Godfrey, D; Yin, F
MLA Citation
Yan, H, Ren, L, Godfrey, D, and Yin, F. "Development of clinical application platform using digital tomosynthesis for target localization." June 2007.
Source
wos-lite
Published In
Medical physics
Volume
34
Issue
6
Publish Date
2007
Start Page
2346
End Page
2347
DOI
10.1118/1.2760416

Automatic registration between reference and on-board digital tomosynthesis for target localization of head and neck treatment

Authors
Ren, L; Yan, H; Godfrey, D; Yin, F
MLA Citation
Ren, L, Yan, H, Godfrey, D, and Yin, F. "Automatic registration between reference and on-board digital tomosynthesis for target localization of head and neck treatment." 2007.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
69
Issue
3
Publish Date
2007
Start Page
S682
End Page
S682
DOI
10.1016/j.ijrobp.2007.07.2045

Clinical evaluation of digital tomosynthesis in positioning verification based on bony anatomy and soft-tissue for prostate IMRT treatment

Authors
Yoo, S; Wu, Q; Godfrey, D; Yan, H; Ren, L; Yin, F
MLA Citation
Yoo, S, Wu, Q, Godfrey, D, Yan, H, Ren, L, and Yin, F. "Clinical evaluation of digital tomosynthesis in positioning verification based on bony anatomy and soft-tissue for prostate IMRT treatment." 2007.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
69
Issue
3
Publish Date
2007
Start Page
S640
End Page
S641
DOI
10.1016/j.ijrobp.2007.07.1978

Implementation of digital tomosynthesis for on-board target localization of radiotherapy

Authors
Yan, H; Godfrey, D; Ren, L; Marks, L; Kasibhalta, M; Wu, J; Willet, C; Yin, F
MLA Citation
Yan, H, Godfrey, D, Ren, L, Marks, L, Kasibhalta, M, Wu, J, Willet, C, and Yin, F. "Implementation of digital tomosynthesis for on-board target localization of radiotherapy." 2007.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
69
Issue
3
Publish Date
2007
Start Page
S633
End Page
S634
DOI
10.1016/j.ijrobp.2007.07.1968

TH-C-ValB-04: Evaluation of the Quality of 3D-3D Mutual Information (MI) Shared Between Reference and On-Board DTS Images

Authors
Godfrey, D; Ren, L; Yan, H; Oldham, M; Yin, F
MLA Citation
Godfrey, D, Ren, L, Yan, H, Oldham, M, and Yin, F. "TH-C-ValB-04: Evaluation of the Quality of 3D-3D Mutual Information (MI) Shared Between Reference and On-Board DTS Images." June 2006.
Source
crossref
Published In
Medical physics
Volume
33
Issue
6Part21
Publish Date
2006
Start Page
2268
End Page
2268
DOI
10.1118/1.2241855

Evaluation of the quality of 3D-3D mutual information (MI) shared between reference and on-board DTS images

Authors
Godfrey, D; Ren, L; Yan, H; Oldham, M; Yin, F
MLA Citation
Godfrey, D, Ren, L, Yan, H, Oldham, M, and Yin, F. "Evaluation of the quality of 3D-3D mutual information (MI) shared between reference and on-board DTS images." June 2006.
Source
wos-lite
Published In
Medical physics
Volume
33
Issue
6
Publish Date
2006
Start Page
2268
End Page
2268
DOI
10.1118/1.2241856

Automatic comparison between reference and on board digital tomosynthesis for target localization

Authors
Ren, L; Godfrey, D; Wu, J; Yan, H; Yin, F
MLA Citation
Ren, L, Godfrey, D, Wu, J, Yan, H, and Yin, F. "Automatic comparison between reference and on board digital tomosynthesis for target localization." June 2006.
Source
wos-lite
Published In
Medical physics
Volume
33
Issue
6
Publish Date
2006
Start Page
1982
End Page
1982
DOI
10.1118/1.2240119
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