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Intensity Modulated Radiation Therapy Using Static Ports of Tomotherapy: Comparison With the Helical Tomotherapy Mode
S854
International Journal of Radiation Oncology Biology Physics
a clinical case, CTV coverage and the spinal cord dose in the DTT and the motion encompassing plans were nearly equal while the mean-lung-dose in the DTT plan was 15% lower. For all five DTT cases, D95 of the CTV calculated from any phase composite doses were close to the one calculated from 10 phase composite dose within 2%. Meanwhile, V15 of the liver from 2 phase composite dose were about 30% higher than the one from 10 phase composite dose when a tumor was near the liver even though the compute time was reduced by 80%. Conclusion: This study has demonstrated that our proposed 4D dose calculation method has acceptable accuracy for DTT irradiation using Vero4DRT. Furthermore, it may be preferable to accumulate dose distribution at more than 4 phases for the DTT irradiation. Author Disclosure: Y. Ishihara: None. A. Sawada: None. Y. Miyabe: None. N. Mukumoto: None. M. Nakamura: None. N. Ueki: None. Y. Matsuo: None. T. Mizowaki: None. M. Kokubo: None. M. Hiraoka: E. Research Grant; Funding Program for World-Leading Innovative R&D.
yet, thoracic wall and lung tumors should be a good indication of TD. In the prostate plans, TD plans took longer treatment time than TH and could not reduce the rectum doses. Thus, prostate cancer should be treated with TH. Author Disclosure: T. Murai: None. Y. Shibamoto: None. R. Murata: None. Y. Manabe: None. S. Ayakawa: None. C. Sugie: None.
3686 Intensity Modulated Radiation Therapy Using Static Ports of Tomotherapy: Comparison With the Helical Tomotherapy Mode T. Murai,1 Y. Shibamoto,1 R. Murata,2 Y. Manabe,2 S. Ayakawa,3 and C. Sugie1; 1Department of Radiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan, 2Department of Radiation Oncology, Suzuka General Hospital, Suzuka, Japan, 3 Department of Radiology, Nagoya Daini Red Cross Hospital, Nagoya, Japan Purpose/Objective(s): With the new HD version of tomotherapy, irradiation can be delivered using static ports of the TomoDirect (TD) mode. The purpose of this study was to evaluate characteristics of TD plans compared to the conventional TomoHelical (TH) plans. Materials/Methods: TH and TD plans were compared in 45 patients with prostate cancer, thoracic wall metastasis or lung tumor. The mean target dose (Dmean) was used for a prescription dose in both plans. A minimum coverage of 95% of the target (D95), conformity index (CI), uniformity index (UI), dose distribution in organs at risk and treatment time were evaluated. In the prostate plans, the prostate and seminal vesicles were contoured as the clinical target volume and 74.8 Gy in 34 fractions was prescribed. Five static ports were used for TD. Dose constraints were: 1) rectum: V58.5Gy < 18%, V38.5Gy < 35%, maximum dose (Dmax) < 75.1 Gy and 2) bladder: V60Gy < 20%, V40Gy < 35%. In the thoracic wall plans, 39 Gy in 13 fractions was prescribed. For TD, 2 or 3 static ports were used depending on the tumor location. The skin was contoured as a 35 mm layer under the body surface, and even when the PTV included the skin surface, it was spared to avoid skin toxicity. Spinal cord, lung and liver doses were reduced as much as possible. In the lung plans, 59.4 Gy in 27 fractions was prescribed to Dmean in both plans. Four static ports were used for TD. Dose constraints were: 1) lung: mean lung dose (MLD) < 17 Gy, V10Gy < 40%, V20Gy < 30% and 2) spinal cord + 5 mm margin: Dmax < 50 Gy. Results: In the prostate plans for 18 patients, D95, CI and UI were almost equal. However, the V10, 20, 30, 40, 50 and 60 Gy of the rectum in TD plans were significantly higher than those in TH. Treatment time in TD plans was longer than that in TH (221 19 [SE] vs. 202 3 sec, p Z 0.001). In the thoracic wall plans, although CI in TH was better than that in TD (2.2 0.1 vs. 4.6 0.6, p Z 0.004), D95 in TD was better than that in TH (97 0.5% vs. 96 1.1%, p Z 0.04). The V5Gy of the lung or liver in TH was higher than that in TD (44.3 8.1% vs. 18.7 6.0%, p Z 0.02). In the lung plans, D95, UI and MLD did not differ significantly between the two modes, but CI in TH was better than that in TD (2.3 0.1 vs. 3.2 0.3, p Z 0.009). The V5Gy of the lung was larger than that in TD (42.7 3.4% vs. 29.9 2.3%, p Z 0.005). Treatment time did not differ significantly between TH and TD in the thoracic wall and lung plans. Conclusions: TD and TH plans achieved comparable target dose coverage for the three types of tumors. In the thoracic wall and lung planning, the TH plan delivered lower dose to the larger lung volume than the TD plan. Since the safety of low-dose radiation to the lung has not been established
3687 A Novel Semi-automated Multimodality Segmentation Tool for Radiation Therapy Treatment Planning in Sarcoma Patients D. Markel, I. El Naqa, C. Freeman, and M. Vallieres; McGill University Health Centre, Montreal, QC, Canada Purpose/Objective(s): Automated segmentation has the potential to reduce radiation therapy treatment planning times and improve contouring reproducibility. This may especially be the case when the boundary between tumor and normal tissue is unclear on diagnostic images. The presence of edema adjacent to the tumor in patients with soft tissue sarcoma (STS) can complicate treatment planning: underestimating the tumor volume increases the risk of failure while overestimating (beyond necessary margins) will lead to unnecessary normal tissue exposure. Presented is a novel active contour algorithm using the information theoretic Jensen-Re´nyi (JR) Divergence that has improved noise robustness and only uses a single tuning parameter. The tool can integrate information from multiple imaging modalities (CT/MR) to further improve STS segmentation accuracy and differentiation between tumor and surrounding uninvolved normal tissue. Materials/Methods: T2 fat suppression weighted images of 5 histologically proven STS were acquired on a 1.5T MR scanner. The images had an in-plane resolution of 0.98 mm and slice thickness of 3.27 mm. Contours differentiating tumor from edema were generated using the novel active contour tool and compared to those obtained using a thresholding and region growing technique available on a commercial treatment planning program. The ground truth was defined by manual contours of the tumor mass excluding edema as defined by an expert radiation oncologist. Performance was evaluated using concordance index and classification error. Concordance index is defined as the ratio of the intersection of the segmentation with the ground truth over the union. The classification error is defined as the sum of the volume of falsely classified tumor and falsely classified background divided by the volume of the ground truth as a percentage. Results: The commercially available tools were found to be useful but produced inconsistent results that in many cases would require a large amount of manual intervention to become acceptable. The JR tool was able to perform with the lowest mean classification error (41%) versus 57% and 62.3% for the thresholding and region grow tools respectively. The JR tool also showed the highest mean concordance index (0.59) versus 0.51 and 0.50 for the threshold and region grow tools. Conclusion: The JR active contour tool better differentiates between tumor and edema compared to commercial methods using only a single user defined parameter. The tool has the potential to reduce treatment planning time in STS and aid in complex scenarios that require expert human interpretation of images from multiple modalities and/or contaminated with noise. Author Disclosure: D. Markel: None. I. El Naqa: E. Research Grant; NSERC. C. Freeman: None. M. Vallieres: None.
3688 Locally Drug Enhanced Brachytherapy: A Comparison of 2 Approaches Based on Biologically Effective Dose R. Cormack,1 P. Nguyen,1 A.V. D’Amico,1 S. Sridhar,2 and G.M. Makrigiorgos1; 1Dana-Farber Cancer Institute and Brigham and Women’s Hospital, Boston, MA, 2Northeastern University, Boston, MA Purpose/Objective(s): Permanent prostate brachytherapy may be enhanced by delivering radiosensitizer to the target during the implant process. Nanoparticles released from a substrate can deliver drug over an
International Journal of Radiation Oncology Biology Physics
a clinical case, CTV coverage and the spinal cord dose in the DTT and the motion encompassing plans were nearly equal while the mean-lung-dose in the DTT plan was 15% lower. For all five DTT cases, D95 of the CTV calculated from any phase composite doses were close to the one calculated from 10 phase composite dose within 2%. Meanwhile, V15 of the liver from 2 phase composite dose were about 30% higher than the one from 10 phase composite dose when a tumor was near the liver even though the compute time was reduced by 80%. Conclusion: This study has demonstrated that our proposed 4D dose calculation method has acceptable accuracy for DTT irradiation using Vero4DRT. Furthermore, it may be preferable to accumulate dose distribution at more than 4 phases for the DTT irradiation. Author Disclosure: Y. Ishihara: None. A. Sawada: None. Y. Miyabe: None. N. Mukumoto: None. M. Nakamura: None. N. Ueki: None. Y. Matsuo: None. T. Mizowaki: None. M. Kokubo: None. M. Hiraoka: E. Research Grant; Funding Program for World-Leading Innovative R&D.
yet, thoracic wall and lung tumors should be a good indication of TD. In the prostate plans, TD plans took longer treatment time than TH and could not reduce the rectum doses. Thus, prostate cancer should be treated with TH. Author Disclosure: T. Murai: None. Y. Shibamoto: None. R. Murata: None. Y. Manabe: None. S. Ayakawa: None. C. Sugie: None.
3686 Intensity Modulated Radiation Therapy Using Static Ports of Tomotherapy: Comparison With the Helical Tomotherapy Mode T. Murai,1 Y. Shibamoto,1 R. Murata,2 Y. Manabe,2 S. Ayakawa,3 and C. Sugie1; 1Department of Radiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan, 2Department of Radiation Oncology, Suzuka General Hospital, Suzuka, Japan, 3 Department of Radiology, Nagoya Daini Red Cross Hospital, Nagoya, Japan Purpose/Objective(s): With the new HD version of tomotherapy, irradiation can be delivered using static ports of the TomoDirect (TD) mode. The purpose of this study was to evaluate characteristics of TD plans compared to the conventional TomoHelical (TH) plans. Materials/Methods: TH and TD plans were compared in 45 patients with prostate cancer, thoracic wall metastasis or lung tumor. The mean target dose (Dmean) was used for a prescription dose in both plans. A minimum coverage of 95% of the target (D95), conformity index (CI), uniformity index (UI), dose distribution in organs at risk and treatment time were evaluated. In the prostate plans, the prostate and seminal vesicles were contoured as the clinical target volume and 74.8 Gy in 34 fractions was prescribed. Five static ports were used for TD. Dose constraints were: 1) rectum: V58.5Gy < 18%, V38.5Gy < 35%, maximum dose (Dmax) < 75.1 Gy and 2) bladder: V60Gy < 20%, V40Gy < 35%. In the thoracic wall plans, 39 Gy in 13 fractions was prescribed. For TD, 2 or 3 static ports were used depending on the tumor location. The skin was contoured as a 35 mm layer under the body surface, and even when the PTV included the skin surface, it was spared to avoid skin toxicity. Spinal cord, lung and liver doses were reduced as much as possible. In the lung plans, 59.4 Gy in 27 fractions was prescribed to Dmean in both plans. Four static ports were used for TD. Dose constraints were: 1) lung: mean lung dose (MLD) < 17 Gy, V10Gy < 40%, V20Gy < 30% and 2) spinal cord + 5 mm margin: Dmax < 50 Gy. Results: In the prostate plans for 18 patients, D95, CI and UI were almost equal. However, the V10, 20, 30, 40, 50 and 60 Gy of the rectum in TD plans were significantly higher than those in TH. Treatment time in TD plans was longer than that in TH (221 19 [SE] vs. 202 3 sec, p Z 0.001). In the thoracic wall plans, although CI in TH was better than that in TD (2.2 0.1 vs. 4.6 0.6, p Z 0.004), D95 in TD was better than that in TH (97 0.5% vs. 96 1.1%, p Z 0.04). The V5Gy of the lung or liver in TH was higher than that in TD (44.3 8.1% vs. 18.7 6.0%, p Z 0.02). In the lung plans, D95, UI and MLD did not differ significantly between the two modes, but CI in TH was better than that in TD (2.3 0.1 vs. 3.2 0.3, p Z 0.009). The V5Gy of the lung was larger than that in TD (42.7 3.4% vs. 29.9 2.3%, p Z 0.005). Treatment time did not differ significantly between TH and TD in the thoracic wall and lung plans. Conclusions: TD and TH plans achieved comparable target dose coverage for the three types of tumors. In the thoracic wall and lung planning, the TH plan delivered lower dose to the larger lung volume than the TD plan. Since the safety of low-dose radiation to the lung has not been established
3687 A Novel Semi-automated Multimodality Segmentation Tool for Radiation Therapy Treatment Planning in Sarcoma Patients D. Markel, I. El Naqa, C. Freeman, and M. Vallieres; McGill University Health Centre, Montreal, QC, Canada Purpose/Objective(s): Automated segmentation has the potential to reduce radiation therapy treatment planning times and improve contouring reproducibility. This may especially be the case when the boundary between tumor and normal tissue is unclear on diagnostic images. The presence of edema adjacent to the tumor in patients with soft tissue sarcoma (STS) can complicate treatment planning: underestimating the tumor volume increases the risk of failure while overestimating (beyond necessary margins) will lead to unnecessary normal tissue exposure. Presented is a novel active contour algorithm using the information theoretic Jensen-Re´nyi (JR) Divergence that has improved noise robustness and only uses a single tuning parameter. The tool can integrate information from multiple imaging modalities (CT/MR) to further improve STS segmentation accuracy and differentiation between tumor and surrounding uninvolved normal tissue. Materials/Methods: T2 fat suppression weighted images of 5 histologically proven STS were acquired on a 1.5T MR scanner. The images had an in-plane resolution of 0.98 mm and slice thickness of 3.27 mm. Contours differentiating tumor from edema were generated using the novel active contour tool and compared to those obtained using a thresholding and region growing technique available on a commercial treatment planning program. The ground truth was defined by manual contours of the tumor mass excluding edema as defined by an expert radiation oncologist. Performance was evaluated using concordance index and classification error. Concordance index is defined as the ratio of the intersection of the segmentation with the ground truth over the union. The classification error is defined as the sum of the volume of falsely classified tumor and falsely classified background divided by the volume of the ground truth as a percentage. Results: The commercially available tools were found to be useful but produced inconsistent results that in many cases would require a large amount of manual intervention to become acceptable. The JR tool was able to perform with the lowest mean classification error (41%) versus 57% and 62.3% for the thresholding and region grow tools respectively. The JR tool also showed the highest mean concordance index (0.59) versus 0.51 and 0.50 for the threshold and region grow tools. Conclusion: The JR active contour tool better differentiates between tumor and edema compared to commercial methods using only a single user defined parameter. The tool has the potential to reduce treatment planning time in STS and aid in complex scenarios that require expert human interpretation of images from multiple modalities and/or contaminated with noise. Author Disclosure: D. Markel: None. I. El Naqa: E. Research Grant; NSERC. C. Freeman: None. M. Vallieres: None.
3688 Locally Drug Enhanced Brachytherapy: A Comparison of 2 Approaches Based on Biologically Effective Dose R. Cormack,1 P. Nguyen,1 A.V. D’Amico,1 S. Sridhar,2 and G.M. Makrigiorgos1; 1Dana-Farber Cancer Institute and Brigham and Women’s Hospital, Boston, MA, 2Northeastern University, Boston, MA Purpose/Objective(s): Permanent prostate brachytherapy may be enhanced by delivering radiosensitizer to the target during the implant process. Nanoparticles released from a substrate can deliver drug over an