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Evaluating the Commissioning and QA of Intensity Modulated Arc Therapy using a Benchmark IMRT Planning Suite
Proceedings of the 51st Annual ASTRO Meeting
3207
Evaluating the Commissioning and QA of Intensity Modulated Arc Therapy using a Benchmark IMRT Planning Suite
R. McMahon1, Y. Xiao2, G. Ezzell3, J. Wu1, F. Yin1 Duke University Medical Center, Durham, NC, 2Thomas Jefferson University, Philadelphia, PA, 3Mayo Clinic Scottsdale, Phoenix, AZ 1
Purpose/Objective(s): Volumetric Intensity Modulated Arc Therapy (IMAT) is often implemented using a planning and delivery system that has already been commissioned for static beam IMRT. This study is designed to provide benchmark data for commissioning IMAT on these dual-purpose systems. The primary aim of this phase of the study was to assess whether an existing test suite could be used for evaluating IMAT commissioning and QA, with an emphasis on comparisons to traditional IMRT delivery techniques. Materials/Methods: This study used an IMRT commissioning and QA benchmarking system developed through the efforts of AAPM Task Group 119. This system consists of a suite of four IMRT planning geometries with dose-volume constraints (prostate, head & neck, spine, and cylindrical target with multiple prescriptions (‘multitarget’)). This test suite had previously been evaluated by nine institutions using traditional IMRT delivery systems. Here it was evaluated for Varian RapidArc and IMRT delivery using the Eclipse planning system and a Novalis NTx Linac. IMRT and IMAT plans were generated for each case. Target coverage and OAR sparing were compared to the multi-institutional IMRT results. Coverage and homogeneity were specified by the following DVH regions: D99-D10 (multitarget), D95-D5 (prostate), D99-D90 & D90-D20 (head & neck), and D95-D10 (spine). OAR sparing was specified by D10 & D30 (rectum & bladder), D10 & max dose (cord), and D50 (parotids). Point dose and planar film measurements were taken in high dose, low gradient regions. Film response was normalized to a chamber reading and analyzed with a 3%-3mm gamma analysis. Results: For all IMRT and IMAT plans, target coverage and dose homogeneity were comparable to (within 1 standard deviation) or better than the multi-institutional IMRT average. For all IMRT plans, OAR sparing was also comparable to or better than the average. OAR sparing in the single-arc IMAT plans, other than parotid D50, was also comparable to or better than the average. Phantom characteristics and measurement geometries were found to be compatible with IMAT delivery. Averaged over all plans, the error measured with ion chamber in high dose regions was -0.7 +/- 1.2% (IMRT) and -1.8 +/- 1.7% (IMAT). Maximum errors were 2.1% for IMRT and 4.6% for IMAT. Average gamma pass rates for the composite plan film analysis were 95.9 +/- 3.1% for IMRT and 95.5 +/- 5.4% for IMAT. Conclusions: An existing IMRT commissioning and QA test suite was found to be compatible with IMAT. The IMRT plans met all 23 planning goals and constraints, while the IMAT plans met 22 of 23. The methods developed in this study will facilitate a multi-institutional comparison of IMRT and IMAT commissioning and QA. Author Disclosure: R. McMahon, None; Y. Xiao, None; G. Ezzell, None; J. Wu, None; F. Yin, None.
3208
Evaluation of Dynamic Volume Scanning on a 320-slice CT for Routine Assessment of Respiratory-induced Lung Tumor Motion
C. Coolens, J. Publicover, A. Owrangi, H. Keller Princess Margaret Hospital, Toronto, ON, Canada Purpose/Objective(s): A novel volumetric CT scanner (Aquilion One, Toshiba) has been installed at the Princess Margaret Hospital for implementation into routine CT simulation. This 320-slice technology offers great advantages for dynamic imaging in terms of speed and coverage as conventional 4D CT studies are limited in cradio-caudal extent during dynamic acquisition and rely on respiratory correlation between couch positions. The aim of this work is to evaluate the dynamic volume capabilities in the presence of simulated respiratory motion. Materials/Methods: The volume mode of the Aquilion One scanner uses a wide-area detector that allows capturing at isocenter a 16 cm field-of-view in a single rotation of 0.35sec. This generates a volume data set with isotropic voxel size of 0.5mm. The dynamic (or cine) volume scan mode can therefore provide ‘true’ 4D data that can at all times cover the entire range of motion of lung or upper GI tumors. The accuracy and sensitivity of this dynamic scanning mode to typical respiration motion speeds and amplitudes was tested by scanning different-shape objects whilst moving on a computer-controlled platform. A sinusoidal motion pattern was applied along the longitudinal axis with amplitudes between 0.5 and 4cm and breathing cycles between 3 and 6 sec. The position at exhale was chosen to set-up the phantom to CT isocenter and dynamic volume scans consequently acquired at 120 kVp, 200mA for a total of 10 breathing cycles. Volumes were extracted at the same 10 phase points within the breathing cycle for all motion scenarios, threshold to the same window and level and then used for subsequent quantification of volume definition and image registration. Results: An acrylic phantom containing a cylindrical rod (38cc) was scanned as well as one containing a 30 mm cube, a 20 mm sphere and a 10 mm sphere. Volume definition, relative to stationary acquisition of cylindrical and spherical inserts was within 1% and 3.5% with the phantom moving at a rate of 1 and 2cm/sec respectively. This compares to 5.5 and 46% respectively with conventional 4DCT. The latter situation represents a worst case scenario of high acceleration between inhale and exhale. Conclusions: This study is the first to quantify the accuracy of dynamic volume scanning on a 320-slice CT scanner for assessment of respiratory motion of lung tumors. Initial experience indicates that using the fastest full rotation time of 0.35sec, very good volume definition was obtained even at a simulated sinusoidal motion of up to 2cm/sec. This allows further optimization of the scan time sequence. Future work will benchmark this technique with conventional 4DCT scanning for clinical situations. Author Disclosure: C. Coolens, None; J. Publicover, None; A. Owrangi, None; H. Keller, None.
3209
Simultaneous Integrated Boost in the Treatment of Breast Cancer: A Dosimetric Comparison of Helical Tomotherapy (HT) and Three-dimensional Conformal Radiotherapy (3D CRT)
T. Hijal, P. Castro-Pena, N. Fournier-Bidoz, Y. Kirova, S. Zefkili, M. Bollet, R. Dendale, F. Campana, A. Fourquet Institut Curie, Paris, France Purpose/Objective(s): To evaluate the dosimetric characteristics of HT and 3D CRT, with respect to target volumes and organs at risk (OARs), in breast cancer patients undergoing whole breast radiation with simultaneous integrated boost of the tumor bed.
S725
3207
Evaluating the Commissioning and QA of Intensity Modulated Arc Therapy using a Benchmark IMRT Planning Suite
R. McMahon1, Y. Xiao2, G. Ezzell3, J. Wu1, F. Yin1 Duke University Medical Center, Durham, NC, 2Thomas Jefferson University, Philadelphia, PA, 3Mayo Clinic Scottsdale, Phoenix, AZ 1
Purpose/Objective(s): Volumetric Intensity Modulated Arc Therapy (IMAT) is often implemented using a planning and delivery system that has already been commissioned for static beam IMRT. This study is designed to provide benchmark data for commissioning IMAT on these dual-purpose systems. The primary aim of this phase of the study was to assess whether an existing test suite could be used for evaluating IMAT commissioning and QA, with an emphasis on comparisons to traditional IMRT delivery techniques. Materials/Methods: This study used an IMRT commissioning and QA benchmarking system developed through the efforts of AAPM Task Group 119. This system consists of a suite of four IMRT planning geometries with dose-volume constraints (prostate, head & neck, spine, and cylindrical target with multiple prescriptions (‘multitarget’)). This test suite had previously been evaluated by nine institutions using traditional IMRT delivery systems. Here it was evaluated for Varian RapidArc and IMRT delivery using the Eclipse planning system and a Novalis NTx Linac. IMRT and IMAT plans were generated for each case. Target coverage and OAR sparing were compared to the multi-institutional IMRT results. Coverage and homogeneity were specified by the following DVH regions: D99-D10 (multitarget), D95-D5 (prostate), D99-D90 & D90-D20 (head & neck), and D95-D10 (spine). OAR sparing was specified by D10 & D30 (rectum & bladder), D10 & max dose (cord), and D50 (parotids). Point dose and planar film measurements were taken in high dose, low gradient regions. Film response was normalized to a chamber reading and analyzed with a 3%-3mm gamma analysis. Results: For all IMRT and IMAT plans, target coverage and dose homogeneity were comparable to (within 1 standard deviation) or better than the multi-institutional IMRT average. For all IMRT plans, OAR sparing was also comparable to or better than the average. OAR sparing in the single-arc IMAT plans, other than parotid D50, was also comparable to or better than the average. Phantom characteristics and measurement geometries were found to be compatible with IMAT delivery. Averaged over all plans, the error measured with ion chamber in high dose regions was -0.7 +/- 1.2% (IMRT) and -1.8 +/- 1.7% (IMAT). Maximum errors were 2.1% for IMRT and 4.6% for IMAT. Average gamma pass rates for the composite plan film analysis were 95.9 +/- 3.1% for IMRT and 95.5 +/- 5.4% for IMAT. Conclusions: An existing IMRT commissioning and QA test suite was found to be compatible with IMAT. The IMRT plans met all 23 planning goals and constraints, while the IMAT plans met 22 of 23. The methods developed in this study will facilitate a multi-institutional comparison of IMRT and IMAT commissioning and QA. Author Disclosure: R. McMahon, None; Y. Xiao, None; G. Ezzell, None; J. Wu, None; F. Yin, None.
3208
Evaluation of Dynamic Volume Scanning on a 320-slice CT for Routine Assessment of Respiratory-induced Lung Tumor Motion
C. Coolens, J. Publicover, A. Owrangi, H. Keller Princess Margaret Hospital, Toronto, ON, Canada Purpose/Objective(s): A novel volumetric CT scanner (Aquilion One, Toshiba) has been installed at the Princess Margaret Hospital for implementation into routine CT simulation. This 320-slice technology offers great advantages for dynamic imaging in terms of speed and coverage as conventional 4D CT studies are limited in cradio-caudal extent during dynamic acquisition and rely on respiratory correlation between couch positions. The aim of this work is to evaluate the dynamic volume capabilities in the presence of simulated respiratory motion. Materials/Methods: The volume mode of the Aquilion One scanner uses a wide-area detector that allows capturing at isocenter a 16 cm field-of-view in a single rotation of 0.35sec. This generates a volume data set with isotropic voxel size of 0.5mm. The dynamic (or cine) volume scan mode can therefore provide ‘true’ 4D data that can at all times cover the entire range of motion of lung or upper GI tumors. The accuracy and sensitivity of this dynamic scanning mode to typical respiration motion speeds and amplitudes was tested by scanning different-shape objects whilst moving on a computer-controlled platform. A sinusoidal motion pattern was applied along the longitudinal axis with amplitudes between 0.5 and 4cm and breathing cycles between 3 and 6 sec. The position at exhale was chosen to set-up the phantom to CT isocenter and dynamic volume scans consequently acquired at 120 kVp, 200mA for a total of 10 breathing cycles. Volumes were extracted at the same 10 phase points within the breathing cycle for all motion scenarios, threshold to the same window and level and then used for subsequent quantification of volume definition and image registration. Results: An acrylic phantom containing a cylindrical rod (38cc) was scanned as well as one containing a 30 mm cube, a 20 mm sphere and a 10 mm sphere. Volume definition, relative to stationary acquisition of cylindrical and spherical inserts was within 1% and 3.5% with the phantom moving at a rate of 1 and 2cm/sec respectively. This compares to 5.5 and 46% respectively with conventional 4DCT. The latter situation represents a worst case scenario of high acceleration between inhale and exhale. Conclusions: This study is the first to quantify the accuracy of dynamic volume scanning on a 320-slice CT scanner for assessment of respiratory motion of lung tumors. Initial experience indicates that using the fastest full rotation time of 0.35sec, very good volume definition was obtained even at a simulated sinusoidal motion of up to 2cm/sec. This allows further optimization of the scan time sequence. Future work will benchmark this technique with conventional 4DCT scanning for clinical situations. Author Disclosure: C. Coolens, None; J. Publicover, None; A. Owrangi, None; H. Keller, None.
3209
Simultaneous Integrated Boost in the Treatment of Breast Cancer: A Dosimetric Comparison of Helical Tomotherapy (HT) and Three-dimensional Conformal Radiotherapy (3D CRT)
T. Hijal, P. Castro-Pena, N. Fournier-Bidoz, Y. Kirova, S. Zefkili, M. Bollet, R. Dendale, F. Campana, A. Fourquet Institut Curie, Paris, France Purpose/Objective(s): To evaluate the dosimetric characteristics of HT and 3D CRT, with respect to target volumes and organs at risk (OARs), in breast cancer patients undergoing whole breast radiation with simultaneous integrated boost of the tumor bed.
S725