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Tomoaxial: A New Opportunity for Treating Small Targets using Tomotherapy Machine
I. J. Radiation Oncology d Biology d Physics
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Volume 75, Number 3, Supplement, 2009
approach, which is used to calculate real-time dose. The computation is then repeated with variations to the repeat daily 4DCT dataset. Treatment plan for these lung tumors has been generated using 5-7 beams with the BrainLAB treatment planning system and verified using the CIRS phantom. Results: The computed dose delivered on the lung was inversely proportional to the lung motion. The simulation framework uses the extracted dose beams as 3D matrices and simulates the dose accumulation. The patient-specific lung motion estimated using optical flow techniques show variations in the regional motion of the lung. Patient-specific dynamic doses show variations between the planned and the actual delivered dose. The GPU based modeling of the dose delivered via conformal external beam was highest when the lung anatomy’s motion was the smallest and the changes in the dose delivered varied from one patient to another. An increased risk of side effects from dose delivery during a radiation therapy treatment is estimated to be significant when the lung motion is not accounted. Conclusions: A patient-specific model was developed to simulate lung motion and real-time dose accumulation in patients during radiation delivery. Author Disclosure: A.P. Santhanam, None; Y. Min, None; H. Neelakkantan, None; A. Shah, None; P. Kupelian, None.
3214
Tomoaxial: A New Opportunity for Treating Small Targets using Tomotherapy Machine
W. Lu, Y. Chen, M. Chen, D. Henderson, Q. Chen, E. Schnarr, K. Ruchala, G. Olivera TomoTherapy Inc., Madison, WI Purpose/Objective(s): Helical TomoTherapy (HT) is regarded as gold standard IMRT for many treatment sites due to its precise image guidance, full range of intensity modulation, and 360o radiation delivery. In this work, we investigated the feasibility of using the TomoTherapy system with a fixed couch position and customized jaw width (TomoAxial) for treating small targets. TomoAxial treatments have the potential to improve longitudinal penumbra and reduce the delivery time. Materials/Methods: We modified the TomoTherapy planning system for TomoAxial treatment planning. In TomoAxial treatment planning, the couch position is fixed at the center of the tumor and the field width is custom-selected so that 90% of the longitudinal beam profile, considering the beam divergence, covers the whole tumor region. We studied 3 synthetic cases and 5 clinical cases. The synthetic cases have ball-shaped targets with diameters of 1, 2, and 4 cm respectively. The clinical cases include both intracranial and extracranial cases, with total tumor length from 0.6cm to 4.5cm. Using the same prescription and constraints, we optimized and compared plans for three delivery modes, TomoAxial, HT with field width 1cm (HT1) and HT with field width 2.5cm (HT2.5). Both 3D dose distribution and DVHs were used for plan evaluation. We calculated the uniformity indices (UI) and radiation delivery time for each mode based on its optimized plan. Results: For synthetic ball-target cases, the uniformity indices (UI=D5/D95) for TomoAxial treatments are 1.09, 1.07, 1.10 for target diameter of 1, 2, and 4 cm respectively. The corresponding UIs for HT1 are 1.03, 1.02, 1.06 and for HT2.5 are 1.03, 1.02, 1.07 respectively. For clinical cases with tumor size up to 4.5 cm longitudinally, TomoAxial plans have comparable plan quality to HT1 but the delivery time of TomoAxial treatments is only 14%-35% that of HT1. While compared with HT2.5, TomoAxial treatments have better plan quality with delivery time only 32% -54% that of HT2.5. Conclusions: For those synthetic and clinical cases with longitudinal target extension up to 4 cm studied, TomoAxial plans with custom field width have comparable or superior plan quality to helical plans and TomoAxial plans have significantly reduced delivery time. TomoAxial treatments show a new opportunity for treating small targets using the current TomoTherapy machine. Author Disclosure: W. Lu, TomoTherapy Inc., A. Employment; Y. Chen, TomoTherapy Inc., A. Employment; M. Chen, TomoTherapy Inc., A. Employment; D. Henderson, TomoTherapy Inc, A. Employment; Q. Chen, TomoTherapy Inc, A. Employment; E. Schnarr, TomoTherapy Inc., A. Employment; K. Ruchala, TomoTherapy Inc., A. Employment; G. Olivera, TomoTherapy Inc., A. Employment.
3215
Comparison of Plan Quality Provided by Volumetric Modulated Arc Therapy and Helical Tomotherapy
H. Yampolsky1,2, B. Martyn3,2, D. Squire3, T. Hartwick3, M. Botnick1,3, L. Botnick1,3, C. Rose1,3 1 Valley Radiotherapy Associates, Manhattan Beach, CA, 2The Center For Radiation Therapy, Beverly Hills, CA, 3Vantage Oncology, Manhattan Beach, CA
Purpose/Objective(s): To compare treatment plans deliverable by volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) for various disease sites. Materials/Methods: Single arc (VMAT1), double arc (VMAT2), and HT plans were created for 8 CT data sets for the following representative cases: prostate, prostate bed, anal cancer, oropharynx cancer with bilateral neck disease, unilateral neck case, pituitary tumor, parasagittal meningioma, and GE junction. Dose volume histogram analysis of the target coverage (PTV) and organs at risk was performed. All plans were normalized for 100% of the prescription dose to cover at least 95% of the PTV. Multiple noncoplanar arcs were used for brain cases. Results: Prostate PTV 77.4 Gy Conformity index (CI): HT 1.3 VMAT1 1.23 VMAT2 1.19 Bladder V70Gy: HT 8.3% VMAT1 8.4% VMAT2 8.4% Rectum V70Gy: HT 7.9% VMAT1 7.6%VMAT2 7.2% Bladder Max Gy: HT 81.5 VMAT 82.9 VMAT2 80.7 Rectum Max Gy: HT 83.8 VMAT1 84 VMAT2 80.8; Prostate Bed and Lymph Nodes: PTV 45Gy PTVmax%: HT 106 VMAT1 113 VMAT2 107 CI: HT 1.3 VMAT1 1.2 VMAT2 1.1 Small Bowel%.45Gy: HT 2 VMAT1 3 VMAT2 1.6 Bladder Mean Gy HT 28.3 VMAT1 31.2 VMAT2 28.7 Rectum Mean Gy HT 25.9 VMAT1 26.3 VMAT2 26.1; Anal PTV 50.Gy PTVmax% HT 105.3 VMAT1 108.6 CI HT 1.28 VMAT1 1.08 Bladder mean Gy HT 28.5 VMAT1 32.2 Genitalia mean Gy HT 6.7, VMAT1 5.6 Small Bowel% .45Gy HT 1.75 VMAT1 3.7 Small bowel mean Gy HT 22 VMAT1 19.5; Oropharynx PTV 70Gy CI HT 1.13, VMAT1 1.7, VMAT2 1.13, PTVmax% HT 108 VMAT1 113 VMAT 108, Dysphagia structure Mean Gy HT 42.2 VMAT1 51.8 VMAT2 40.5 Vocal Folds mean Gy HT 30.1 VMAT1 47 VMAT2 30.1, Combined Parotid Mean HT 26.5 VMAT1 37.6 VMAT2 28.9, Oral
S728
Volume 75, Number 3, Supplement, 2009
approach, which is used to calculate real-time dose. The computation is then repeated with variations to the repeat daily 4DCT dataset. Treatment plan for these lung tumors has been generated using 5-7 beams with the BrainLAB treatment planning system and verified using the CIRS phantom. Results: The computed dose delivered on the lung was inversely proportional to the lung motion. The simulation framework uses the extracted dose beams as 3D matrices and simulates the dose accumulation. The patient-specific lung motion estimated using optical flow techniques show variations in the regional motion of the lung. Patient-specific dynamic doses show variations between the planned and the actual delivered dose. The GPU based modeling of the dose delivered via conformal external beam was highest when the lung anatomy’s motion was the smallest and the changes in the dose delivered varied from one patient to another. An increased risk of side effects from dose delivery during a radiation therapy treatment is estimated to be significant when the lung motion is not accounted. Conclusions: A patient-specific model was developed to simulate lung motion and real-time dose accumulation in patients during radiation delivery. Author Disclosure: A.P. Santhanam, None; Y. Min, None; H. Neelakkantan, None; A. Shah, None; P. Kupelian, None.
3214
Tomoaxial: A New Opportunity for Treating Small Targets using Tomotherapy Machine
W. Lu, Y. Chen, M. Chen, D. Henderson, Q. Chen, E. Schnarr, K. Ruchala, G. Olivera TomoTherapy Inc., Madison, WI Purpose/Objective(s): Helical TomoTherapy (HT) is regarded as gold standard IMRT for many treatment sites due to its precise image guidance, full range of intensity modulation, and 360o radiation delivery. In this work, we investigated the feasibility of using the TomoTherapy system with a fixed couch position and customized jaw width (TomoAxial) for treating small targets. TomoAxial treatments have the potential to improve longitudinal penumbra and reduce the delivery time. Materials/Methods: We modified the TomoTherapy planning system for TomoAxial treatment planning. In TomoAxial treatment planning, the couch position is fixed at the center of the tumor and the field width is custom-selected so that 90% of the longitudinal beam profile, considering the beam divergence, covers the whole tumor region. We studied 3 synthetic cases and 5 clinical cases. The synthetic cases have ball-shaped targets with diameters of 1, 2, and 4 cm respectively. The clinical cases include both intracranial and extracranial cases, with total tumor length from 0.6cm to 4.5cm. Using the same prescription and constraints, we optimized and compared plans for three delivery modes, TomoAxial, HT with field width 1cm (HT1) and HT with field width 2.5cm (HT2.5). Both 3D dose distribution and DVHs were used for plan evaluation. We calculated the uniformity indices (UI) and radiation delivery time for each mode based on its optimized plan. Results: For synthetic ball-target cases, the uniformity indices (UI=D5/D95) for TomoAxial treatments are 1.09, 1.07, 1.10 for target diameter of 1, 2, and 4 cm respectively. The corresponding UIs for HT1 are 1.03, 1.02, 1.06 and for HT2.5 are 1.03, 1.02, 1.07 respectively. For clinical cases with tumor size up to 4.5 cm longitudinally, TomoAxial plans have comparable plan quality to HT1 but the delivery time of TomoAxial treatments is only 14%-35% that of HT1. While compared with HT2.5, TomoAxial treatments have better plan quality with delivery time only 32% -54% that of HT2.5. Conclusions: For those synthetic and clinical cases with longitudinal target extension up to 4 cm studied, TomoAxial plans with custom field width have comparable or superior plan quality to helical plans and TomoAxial plans have significantly reduced delivery time. TomoAxial treatments show a new opportunity for treating small targets using the current TomoTherapy machine. Author Disclosure: W. Lu, TomoTherapy Inc., A. Employment; Y. Chen, TomoTherapy Inc., A. Employment; M. Chen, TomoTherapy Inc., A. Employment; D. Henderson, TomoTherapy Inc, A. Employment; Q. Chen, TomoTherapy Inc, A. Employment; E. Schnarr, TomoTherapy Inc., A. Employment; K. Ruchala, TomoTherapy Inc., A. Employment; G. Olivera, TomoTherapy Inc., A. Employment.
3215
Comparison of Plan Quality Provided by Volumetric Modulated Arc Therapy and Helical Tomotherapy
H. Yampolsky1,2, B. Martyn3,2, D. Squire3, T. Hartwick3, M. Botnick1,3, L. Botnick1,3, C. Rose1,3 1 Valley Radiotherapy Associates, Manhattan Beach, CA, 2The Center For Radiation Therapy, Beverly Hills, CA, 3Vantage Oncology, Manhattan Beach, CA
Purpose/Objective(s): To compare treatment plans deliverable by volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) for various disease sites. Materials/Methods: Single arc (VMAT1), double arc (VMAT2), and HT plans were created for 8 CT data sets for the following representative cases: prostate, prostate bed, anal cancer, oropharynx cancer with bilateral neck disease, unilateral neck case, pituitary tumor, parasagittal meningioma, and GE junction. Dose volume histogram analysis of the target coverage (PTV) and organs at risk was performed. All plans were normalized for 100% of the prescription dose to cover at least 95% of the PTV. Multiple noncoplanar arcs were used for brain cases. Results: Prostate PTV 77.4 Gy Conformity index (CI): HT 1.3 VMAT1 1.23 VMAT2 1.19 Bladder V70Gy: HT 8.3% VMAT1 8.4% VMAT2 8.4% Rectum V70Gy: HT 7.9% VMAT1 7.6%VMAT2 7.2% Bladder Max Gy: HT 81.5 VMAT 82.9 VMAT2 80.7 Rectum Max Gy: HT 83.8 VMAT1 84 VMAT2 80.8; Prostate Bed and Lymph Nodes: PTV 45Gy PTVmax%: HT 106 VMAT1 113 VMAT2 107 CI: HT 1.3 VMAT1 1.2 VMAT2 1.1 Small Bowel%.45Gy: HT 2 VMAT1 3 VMAT2 1.6 Bladder Mean Gy HT 28.3 VMAT1 31.2 VMAT2 28.7 Rectum Mean Gy HT 25.9 VMAT1 26.3 VMAT2 26.1; Anal PTV 50.Gy PTVmax% HT 105.3 VMAT1 108.6 CI HT 1.28 VMAT1 1.08 Bladder mean Gy HT 28.5 VMAT1 32.2 Genitalia mean Gy HT 6.7, VMAT1 5.6 Small Bowel% .45Gy HT 1.75 VMAT1 3.7 Small bowel mean Gy HT 22 VMAT1 19.5; Oropharynx PTV 70Gy CI HT 1.13, VMAT1 1.7, VMAT2 1.13, PTVmax% HT 108 VMAT1 113 VMAT 108, Dysphagia structure Mean Gy HT 42.2 VMAT1 51.8 VMAT2 40.5 Vocal Folds mean Gy HT 30.1 VMAT1 47 VMAT2 30.1, Combined Parotid Mean HT 26.5 VMAT1 37.6 VMAT2 28.9, Oral