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A Monoscopic X-ray Image-Based Position Monitoring System for Liver Stereotactic Body Radiation Therapy
Poster Viewing E637
Volume 96 Number 2S Supplement 2016 Oncology, Asan Medical Center, Seoul, South Korea, 6CQURE Healthcare, Seoul, South Korea, 7Department of Radiation Oncology, College of Medicine, Cheil General Hospital & Women’s Healthcare Center, Seoul, South Korea, 8SoonChunHyang University Hospital, Daejeon, Korea, Republic of Korea, 9Department of Radiation Oncology, Korea University Medical Center Ansan Hospital, Ansan, Korea, Republic of Korea, 10 Department of Radiation Oncology, Korea University Medical Center Guro Hospital, Seoul, South Korea Purpose/Objective(s): We have assessed the correlation of acute gastrointestinal (GI) and genitourinary (GU) toxicity with planning index including dosimetrical and biological indices in prostate cancer treated with helical tomotherapy using Smart RT program. Materials/Methods: A total of 60 prostate cancer patients treated with helical tomotherapy between 2008 and 2014 were retrospectively reviewed. A dose of 77 Gy was administered in 35 daily fractions of 2.2 Gy. Acute and late toxicities were graded on the RTOG/EORTC scales. Plan results were analyzed by using a house-developed plan evaluation program: Smart RT. The program uses dose-volume histogram, statistics, and dosimetrical indices, including prescription isodose to target volume ratio (PITV), conformity index (CI), homogeneity index (HI), target coverage index (TCI), modified dose homogeneity index (MHI), conformation number (CN), critical organ scoring index (COSI), and quality factor (QF). Furthermore, biological indices like biological equivalent dose (BED), generalized equivalent uniform dose (gEUD), tumor control probabilities (TCP), and normal tissue complication probabilities (NTCP) were included to predict clinical outcome. Results: A total of 20 patients developed to grade 2 GU toxicity, which was 24.3% of all patients, and 13 patients developed as grade 2 GI toxicity (15.9%). When comparing patients with grade 2 or higher GI and GU toxicity with others, PTV reduced from 49.55 cm3 to 70.08 cm3, and PITV increased from 0.981 to 0.996 (pZ0.066). Furthermore, MHI was increased from 0.952 to 0.973 (pZ0.038). Overall plan indices of COSI and QF have no correlation with acute toxicity. Conclusion: Our study showed that in the prospective cohort of prostate cancer patients undergoing helical tomotherapy, the dosimetrical index of treatment plans like target coverage index and modulated homogeneity index was associated with the probability of developing acute GI and GU toxicity using the Smart RT program. Author Disclosure: S. Lee: None. K. Kim: None. Y. Cao: None. J. Shim: None. K. Chang: None. J. Ko: None. S. Choi: None. S. Lee: None. C. Min: None. W. Yoon: None. D. Yang: None. Y. Park: None. C. Kim: None.
3562 A Monoscopic X-ray Image-Based Position Monitoring System for Liver Stereotactic Body Radiation Therapy S. Arumugam,1,2 M.T. Lee,3 M. Sidhom,4 A. Xing,5 and L. Holloway6; 1 Liverpool and MacArthur Cancer Therapy Centres and Ingham Institute, New South Wales, Australia, 2University of New South Wales, Sydney, Australia, 3Cancer Therapy Centre, Liverpool Hospital, Liverpool BC 1871, Australia, 4Liverpool Hospital, New South Wales, Australia, 5 University of New South Wales, Sydney, New South Wales, Australia., Sydney, Australia, 6Institute of Medical Physics, School of Physics, University of Sydney, Sydney, Australia Purpose/Objective(s): Accurate positioning of the target volume is paramount for stereotactic body radiation therapy (SBRT). In this work we present an in-house developed position monitoring system for 3-dimensional (3D) position monitoring of liver SBRT. Materials/Methods: A software tool, SeedTracker, was developed inhouse to enable the online position verification of tumors by monitoring the position of radiopaque markers implanted in or in the vicinity of a tumor. The SeedTracker system estimates the 3-dimensional (3D) position of the target volume using monoscopic x-ray images acquired using an x-ray volume imaging system during treatment by following 4 main steps: (1) autosegmenting the seeds in cone beam computed tomographic (CBCT) projection images acquired for the initial patient position on the treatment day; (2) calculating the amplitude binned 3D position of seeds
and plan isocenter; (3) autosegmenting the seed positions in the planar projection images acquired during the treatment; and (4) estimating the 3D position of seeds and isocenter based on the seed positions in the projection image and 3D position information learned from CBCT projections. The performance of SeedTracker software was evaluated using retrospective analysis of CBCT images of 2 liver metastasis patients implanted with radiopaque markers in the vicinity of the tumor. For the evaluation of SeedTracker, the 3D CBCT projection images acquired for patient position verification were used for 3D position learning of the SeedTracker system. The 4D CBCT projection images acquired during the same treatment session were processed in SeedTracker to estimate the 3D position of the seeds and isocenter at different phases of the breathing cycle. The SeedTracker estimated 3D positions were compared with the seed and isocenter positions in x-ray volume imaging reconstructed 4D CBCT image datasets. Results: The SeedTracker system successfully autosegmented the seeds in the projection images acquired at gantry angles ranging from 0to 360. The system showed an autoseed segmentation true positive rate (TPR) of 96%. The 3D seed and plan isocenter positions estimated by SeedTracker agreed with the x-ray volume imaging 4D reconstructed data with a mean (s) difference of 0.2(1.8) mm. Conclusion: The developed software has been shown to estimate the 3D position of the seeds and isocenter based on the seed positions in monoscopic x-ray images and 3D positions learned from the CBCT projection data. This has the potential application of monitoring target position during treatment delivery in linear acceleratorebased liver SBRT. Author Disclosure: S. Arumugam: None. M.T. Lee: None. M. Sidhom: None. A. Xing: None. L. Holloway: None.
3563 Impact of Expiratory Tumor Motion Patterns on Dose-Volume Histogram in Treatment Phase Selection of Respiratory Gating Radiation Therapy for Lung Cancer N. Imano,1 I. Nishibuchi,2 T. Kimura,2 T. Nakashima,3 T. Okumura,3 Y. Murakami,2 and Y. Nagata2; 1Hiroshima Prefectural Hospital, Hiroshima, Japan, 2Department of Radiation Oncology, Hiroshima University Hospital, Hiroshima, Japan, 3Division of Radiation Therapy, Department of Clinical Practice and Support, Hiroshima University Hospital, Hiroshima, Japan Purpose/Objective(s): In respiratory-gated radiation therapy (RGRT), the respiratory cycle is divided into 10 phases (0%-90%), and 3 endeexpiratory phases (commonly defined as 40%-60%) are usually selected as the irradiation phase. We previously reported tumor motion in expiratory phases was varied among tumors with large respiratory motion. The purposes of this study are to evaluate the difference of the dose-volume histogram (DVH) in the lung when number of irradiation phases is increased and to examine the impact on the DVH focusing on expiratory tumor motion patterns. Materials/Methods: We evaluated 40 lung tumor lesions with respiratory motion of >1 cm. The internal target volume (ITV) in 3 endeexpiratory phases (ITV40-60) and in 5 expiratory phases (ITV30-70) were created for each case, and 5 mm was added to each ITV as the planning target volume (PTV) margin. Three-dimensional conformal radiation therapy plans (60 Gy/30 fr) for both ITV40e60 (plan 1) and ITV30e70 (plan 2) were made using anterior-posterior and oblique 4 static beams. Then, the difference of the DVH between each plan was analyzed by calculating increasing rate from plan1 to plan2 in lung volume irradiated more than 5 Gy and 20 Gy (V5 and V20) and mean lung dose (MLD). To examine the influence of expiratory tumor motion on the lung DVH, an ITV reflecting tumor volume of each existence probability (time adjusted internal target volume of expiration phase, TTVe) was used. To create TTVe, the probability of tumor existence within ITV30e70 was calculated. Thereafter, the percentage of each TTVe on ITV30e70 was calculated (TTVe%). For example, TTVe40 represents an area in which the probability of tumor existence exceeds 40% within ITV30e70, and the ratio of TTVe40 to ITV30e70 was defined as TTVe40%. We calculated TTVe60%, 80%, and 100% values in the same way. This value becomes small as expiratory
Volume 96 Number 2S Supplement 2016 Oncology, Asan Medical Center, Seoul, South Korea, 6CQURE Healthcare, Seoul, South Korea, 7Department of Radiation Oncology, College of Medicine, Cheil General Hospital & Women’s Healthcare Center, Seoul, South Korea, 8SoonChunHyang University Hospital, Daejeon, Korea, Republic of Korea, 9Department of Radiation Oncology, Korea University Medical Center Ansan Hospital, Ansan, Korea, Republic of Korea, 10 Department of Radiation Oncology, Korea University Medical Center Guro Hospital, Seoul, South Korea Purpose/Objective(s): We have assessed the correlation of acute gastrointestinal (GI) and genitourinary (GU) toxicity with planning index including dosimetrical and biological indices in prostate cancer treated with helical tomotherapy using Smart RT program. Materials/Methods: A total of 60 prostate cancer patients treated with helical tomotherapy between 2008 and 2014 were retrospectively reviewed. A dose of 77 Gy was administered in 35 daily fractions of 2.2 Gy. Acute and late toxicities were graded on the RTOG/EORTC scales. Plan results were analyzed by using a house-developed plan evaluation program: Smart RT. The program uses dose-volume histogram, statistics, and dosimetrical indices, including prescription isodose to target volume ratio (PITV), conformity index (CI), homogeneity index (HI), target coverage index (TCI), modified dose homogeneity index (MHI), conformation number (CN), critical organ scoring index (COSI), and quality factor (QF). Furthermore, biological indices like biological equivalent dose (BED), generalized equivalent uniform dose (gEUD), tumor control probabilities (TCP), and normal tissue complication probabilities (NTCP) were included to predict clinical outcome. Results: A total of 20 patients developed to grade 2 GU toxicity, which was 24.3% of all patients, and 13 patients developed as grade 2 GI toxicity (15.9%). When comparing patients with grade 2 or higher GI and GU toxicity with others, PTV reduced from 49.55 cm3 to 70.08 cm3, and PITV increased from 0.981 to 0.996 (pZ0.066). Furthermore, MHI was increased from 0.952 to 0.973 (pZ0.038). Overall plan indices of COSI and QF have no correlation with acute toxicity. Conclusion: Our study showed that in the prospective cohort of prostate cancer patients undergoing helical tomotherapy, the dosimetrical index of treatment plans like target coverage index and modulated homogeneity index was associated with the probability of developing acute GI and GU toxicity using the Smart RT program. Author Disclosure: S. Lee: None. K. Kim: None. Y. Cao: None. J. Shim: None. K. Chang: None. J. Ko: None. S. Choi: None. S. Lee: None. C. Min: None. W. Yoon: None. D. Yang: None. Y. Park: None. C. Kim: None.
3562 A Monoscopic X-ray Image-Based Position Monitoring System for Liver Stereotactic Body Radiation Therapy S. Arumugam,1,2 M.T. Lee,3 M. Sidhom,4 A. Xing,5 and L. Holloway6; 1 Liverpool and MacArthur Cancer Therapy Centres and Ingham Institute, New South Wales, Australia, 2University of New South Wales, Sydney, Australia, 3Cancer Therapy Centre, Liverpool Hospital, Liverpool BC 1871, Australia, 4Liverpool Hospital, New South Wales, Australia, 5 University of New South Wales, Sydney, New South Wales, Australia., Sydney, Australia, 6Institute of Medical Physics, School of Physics, University of Sydney, Sydney, Australia Purpose/Objective(s): Accurate positioning of the target volume is paramount for stereotactic body radiation therapy (SBRT). In this work we present an in-house developed position monitoring system for 3-dimensional (3D) position monitoring of liver SBRT. Materials/Methods: A software tool, SeedTracker, was developed inhouse to enable the online position verification of tumors by monitoring the position of radiopaque markers implanted in or in the vicinity of a tumor. The SeedTracker system estimates the 3-dimensional (3D) position of the target volume using monoscopic x-ray images acquired using an x-ray volume imaging system during treatment by following 4 main steps: (1) autosegmenting the seeds in cone beam computed tomographic (CBCT) projection images acquired for the initial patient position on the treatment day; (2) calculating the amplitude binned 3D position of seeds
and plan isocenter; (3) autosegmenting the seed positions in the planar projection images acquired during the treatment; and (4) estimating the 3D position of seeds and isocenter based on the seed positions in the projection image and 3D position information learned from CBCT projections. The performance of SeedTracker software was evaluated using retrospective analysis of CBCT images of 2 liver metastasis patients implanted with radiopaque markers in the vicinity of the tumor. For the evaluation of SeedTracker, the 3D CBCT projection images acquired for patient position verification were used for 3D position learning of the SeedTracker system. The 4D CBCT projection images acquired during the same treatment session were processed in SeedTracker to estimate the 3D position of the seeds and isocenter at different phases of the breathing cycle. The SeedTracker estimated 3D positions were compared with the seed and isocenter positions in x-ray volume imaging reconstructed 4D CBCT image datasets. Results: The SeedTracker system successfully autosegmented the seeds in the projection images acquired at gantry angles ranging from 0to 360. The system showed an autoseed segmentation true positive rate (TPR) of 96%. The 3D seed and plan isocenter positions estimated by SeedTracker agreed with the x-ray volume imaging 4D reconstructed data with a mean (s) difference of 0.2(1.8) mm. Conclusion: The developed software has been shown to estimate the 3D position of the seeds and isocenter based on the seed positions in monoscopic x-ray images and 3D positions learned from the CBCT projection data. This has the potential application of monitoring target position during treatment delivery in linear acceleratorebased liver SBRT. Author Disclosure: S. Arumugam: None. M.T. Lee: None. M. Sidhom: None. A. Xing: None. L. Holloway: None.
3563 Impact of Expiratory Tumor Motion Patterns on Dose-Volume Histogram in Treatment Phase Selection of Respiratory Gating Radiation Therapy for Lung Cancer N. Imano,1 I. Nishibuchi,2 T. Kimura,2 T. Nakashima,3 T. Okumura,3 Y. Murakami,2 and Y. Nagata2; 1Hiroshima Prefectural Hospital, Hiroshima, Japan, 2Department of Radiation Oncology, Hiroshima University Hospital, Hiroshima, Japan, 3Division of Radiation Therapy, Department of Clinical Practice and Support, Hiroshima University Hospital, Hiroshima, Japan Purpose/Objective(s): In respiratory-gated radiation therapy (RGRT), the respiratory cycle is divided into 10 phases (0%-90%), and 3 endeexpiratory phases (commonly defined as 40%-60%) are usually selected as the irradiation phase. We previously reported tumor motion in expiratory phases was varied among tumors with large respiratory motion. The purposes of this study are to evaluate the difference of the dose-volume histogram (DVH) in the lung when number of irradiation phases is increased and to examine the impact on the DVH focusing on expiratory tumor motion patterns. Materials/Methods: We evaluated 40 lung tumor lesions with respiratory motion of >1 cm. The internal target volume (ITV) in 3 endeexpiratory phases (ITV40-60) and in 5 expiratory phases (ITV30-70) were created for each case, and 5 mm was added to each ITV as the planning target volume (PTV) margin. Three-dimensional conformal radiation therapy plans (60 Gy/30 fr) for both ITV40e60 (plan 1) and ITV30e70 (plan 2) were made using anterior-posterior and oblique 4 static beams. Then, the difference of the DVH between each plan was analyzed by calculating increasing rate from plan1 to plan2 in lung volume irradiated more than 5 Gy and 20 Gy (V5 and V20) and mean lung dose (MLD). To examine the influence of expiratory tumor motion on the lung DVH, an ITV reflecting tumor volume of each existence probability (time adjusted internal target volume of expiration phase, TTVe) was used. To create TTVe, the probability of tumor existence within ITV30e70 was calculated. Thereafter, the percentage of each TTVe on ITV30e70 was calculated (TTVe%). For example, TTVe40 represents an area in which the probability of tumor existence exceeds 40% within ITV30e70, and the ratio of TTVe40 to ITV30e70 was defined as TTVe40%. We calculated TTVe60%, 80%, and 100% values in the same way. This value becomes small as expiratory