The purpose of this study was to grasp current potential problems of dose error in intensity-modulated proton therapy (IMPT) plans. We were interested in dose differences of the Varian Eclipse treatment planning syste...The purpose of this study was to grasp current potential problems of dose error in intensity-modulated proton therapy (IMPT) plans. We were interested in dose differences of the Varian Eclipse treatment planning system (TPS) and the fast dose calculation method (FDC) for single-field optimization (SFO) and multi-field optimization (MFO) IMPT plans. In addition, because some authors have reported dosimetric benefit of a proton arc therapy with ultimate multi-fields in recent years, we wanted to evaluate how the number of fields and beam angles affect the differences for IMPT plans. Therefore, for one brain cancer patient with a large heterogeneity, SFO and MFO IMPT plans with various multi-angle beams were planned by the TPS. Dose distributions for each IMPT plan were calculated by both the TPS’s conventional pencil beam algorithm and the FDC. The dosimetric parameters were compared between the two algorithms. The TPS overestimated 400 - 500 cGy (RBE) for minimum dose to the CTV relative to the dose calculated by the FDC. These differences indicate clinically relevant effect on clinical results. In addition, we observed that the maximum difference in dose calculated between the TPS and the FDC was about 900 cGy (RBE) for the right optic nerve, and this quantity also has a possibility to have a clinical effect. The major difference was not seen in calculations for SFO IMPT planning and those for MFO IMPT planning. Differences between the TPS and the FDC in SFO and MFO IMPT plans depend strongly on beam arrangement and the presence of a heterogeneous body. We advocate use of a Monte Carlo method in proton treatment planning to deliver the most precise proton dose in IMPT.展开更多
IMPT plans with various multi-angle beams were planned by the Varian Eclipse treatment planning system for one case of brain cancer. Dose distributions for each plan, along with the associated linear energy transfer d...IMPT plans with various multi-angle beams were planned by the Varian Eclipse treatment planning system for one case of brain cancer. Dose distributions for each plan, along with the associated linear energy transfer distributions, were recomputed using an in-house fast Monte Carlo dose calculator with a FRBE of 1.1 or with a previously published VRBE model. We then compared dosimetric parameters obtained by the VRBE with those obtained by the FRBE. Biological doses obtained by the VRBE for the clinical target volume in all plans were 1% - 2% larger than those obtained by the FRBE. The minimum dose obtained by the VRBE for the right optic nerve in the MFO IMPT with 4 fields was 70% larger than that obtained by the FRBE, but the difference was only 18.1 cGy (RBE). The difference in maximum dose for the right optic nerve in the MFO IMPT with 5 fields was less than 10.4%, but the difference was 131.8 cGy (RBE). The mean difference in maximum dose was less than 2% for all other organs at risk. We found that biological dose with the FRBE had any dose errors in IMPT with various multi-angle beams.展开更多
Objective:To determine under what conditions and criteria comparisons between calculations made with the current clinical treatment planning system(Syngo)and an in-house built TPS(TIMPS)would allow skipping of in-beam...Objective:To determine under what conditions and criteria comparisons between calculations made with the current clinical treatment planning system(Syngo)and an in-house built TPS(TIMPS)would allow skipping of in-beam portal-specific measurements.Methods:Measurements were made with an array of 24 ion chambers in a water phantom for 227 proton and 313 carbon ion portals with and without a range shifter(RS).These measurements were compared with calculations performed with Syngo and TIMPS using metrics of average dose difference and Gamma index.Results:For proton portals without RS,if a Gamma comparison between TIMPS and Syngo passed using criteria of 90%of tested points being within 3%and 3 mm,then 74%of measurements would agree with both TIMPS and Syngo.For proton portals with RS,more than 80%of measurements would agree with both calculations using the same criteria.For carbon ion portals without RS,if a Gamma evaluation between TIMPS and Syngo passed with criteria of 90%of tested points being within 2%and 2 mm,85%of measurements would agree with both cal-culations.For carbon ion portals with RS,if a Gamma evaluation between TIMPS and Syngo passed with criteria of 90%of tested points being within 3%and 3 mm,60%of measurements would agree with both calculations.Conclusions:Both the pencil beam algorithm in Syngo and the FDC algorithm in TIMPS can provide accurate dose calculations in water for most clinical portals.For about 75%of portals,physicists can perform comparisons of calculations instead of phantom measurements to verify Syngo calculations thereby saving a large amount of beam time.There are some portals,however,such as for low-energy protons without RS and high-energy carbon ions,where agreement between the two calculations and measurements are not yet satisfactory to allow the elimination of all measurements.展开更多
Objective:To verify the accuracy of an independent dose calculation method,as incorporated into an in-house developed treatment planning system(TPS),for performing quality assurance of dose distributions delivered to ...Objective:To verify the accuracy of an independent dose calculation method,as incorporated into an in-house developed treatment planning system(TPS),for performing quality assurance of dose distributions delivered to a water phantom planned by a clinical TPS.Methods:A Monte Carlo based track repeating algorithm was incorporated into an in-house treatment planning system for proton and carbon ion beams.Calculations were performed in a flat water phantom for both a traditional pencil beam algorithm and a new Monte Carlo algorithm,and then compared to measurements made at multiple depths with a 2D ionization array for 44 patient portals.The comparisons utilized a Gamma analysis.Results:A total of 124 measurements were performed for proton and carbon ion patient portals.Using a small Gamma criteria of 2%/2 mm,an average of 93%and 97%of measurement points passed for each portal for pencil beam and Monte Carlo calculations,respectively.The passing rate was substantially higher for Monte Carlo calculations than for pencil beam calculations for portals that used a range shifter.Conclusions:The implemented independent method has been verified against measurements.The high passing rate with small tolerances leads to the possibility of reducing the number of required quality assurance measurements.展开更多
Objective:To develop and implement an ion beam teletherapy verification system based upon simulations of induced radioactivity and comparison with patient positron emission tomography(PET)scans.Methods:A Monte Carlo a...Objective:To develop and implement an ion beam teletherapy verification system based upon simulations of induced radioactivity and comparison with patient positron emission tomography(PET)scans.Methods:A Monte Carlo algorithm was integrated into an in-house built treatment,information,management,and planning system(TIMPS■)to calculate distributions of positron emitters induced by ion beams.These distribu-tions are processed to simulate PET images taking into account positron diffusion,radioactive decay,biological washout,and detector blurring.Additional tools were developed to register simulated PET images with planning CT images and perform comparisons of measured and simulated PET images.Results:Production cross-sections were generated for various isotopes and materials.Treatment plans for several different body sites were used to verify the functioning and utility of the new tools for both proton and carbon ion beams.Conclusions:Several tools have been developed to simulate PET scans of patients irradiated with ion beams and compare the simulated images to measurements.After commissioning and implementation into the clinic,the appropriate sizes for margins that account for uncertainties may be investigated.展开更多
文摘The purpose of this study was to grasp current potential problems of dose error in intensity-modulated proton therapy (IMPT) plans. We were interested in dose differences of the Varian Eclipse treatment planning system (TPS) and the fast dose calculation method (FDC) for single-field optimization (SFO) and multi-field optimization (MFO) IMPT plans. In addition, because some authors have reported dosimetric benefit of a proton arc therapy with ultimate multi-fields in recent years, we wanted to evaluate how the number of fields and beam angles affect the differences for IMPT plans. Therefore, for one brain cancer patient with a large heterogeneity, SFO and MFO IMPT plans with various multi-angle beams were planned by the TPS. Dose distributions for each IMPT plan were calculated by both the TPS’s conventional pencil beam algorithm and the FDC. The dosimetric parameters were compared between the two algorithms. The TPS overestimated 400 - 500 cGy (RBE) for minimum dose to the CTV relative to the dose calculated by the FDC. These differences indicate clinically relevant effect on clinical results. In addition, we observed that the maximum difference in dose calculated between the TPS and the FDC was about 900 cGy (RBE) for the right optic nerve, and this quantity also has a possibility to have a clinical effect. The major difference was not seen in calculations for SFO IMPT planning and those for MFO IMPT planning. Differences between the TPS and the FDC in SFO and MFO IMPT plans depend strongly on beam arrangement and the presence of a heterogeneous body. We advocate use of a Monte Carlo method in proton treatment planning to deliver the most precise proton dose in IMPT.
文摘IMPT plans with various multi-angle beams were planned by the Varian Eclipse treatment planning system for one case of brain cancer. Dose distributions for each plan, along with the associated linear energy transfer distributions, were recomputed using an in-house fast Monte Carlo dose calculator with a FRBE of 1.1 or with a previously published VRBE model. We then compared dosimetric parameters obtained by the VRBE with those obtained by the FRBE. Biological doses obtained by the VRBE for the clinical target volume in all plans were 1% - 2% larger than those obtained by the FRBE. The minimum dose obtained by the VRBE for the right optic nerve in the MFO IMPT with 4 fields was 70% larger than that obtained by the FRBE, but the difference was only 18.1 cGy (RBE). The difference in maximum dose for the right optic nerve in the MFO IMPT with 5 fields was less than 10.4%, but the difference was 131.8 cGy (RBE). The mean difference in maximum dose was less than 2% for all other organs at risk. We found that biological dose with the FRBE had any dose errors in IMPT with various multi-angle beams.
文摘Objective:To determine under what conditions and criteria comparisons between calculations made with the current clinical treatment planning system(Syngo)and an in-house built TPS(TIMPS)would allow skipping of in-beam portal-specific measurements.Methods:Measurements were made with an array of 24 ion chambers in a water phantom for 227 proton and 313 carbon ion portals with and without a range shifter(RS).These measurements were compared with calculations performed with Syngo and TIMPS using metrics of average dose difference and Gamma index.Results:For proton portals without RS,if a Gamma comparison between TIMPS and Syngo passed using criteria of 90%of tested points being within 3%and 3 mm,then 74%of measurements would agree with both TIMPS and Syngo.For proton portals with RS,more than 80%of measurements would agree with both calculations using the same criteria.For carbon ion portals without RS,if a Gamma evaluation between TIMPS and Syngo passed with criteria of 90%of tested points being within 2%and 2 mm,85%of measurements would agree with both cal-culations.For carbon ion portals with RS,if a Gamma evaluation between TIMPS and Syngo passed with criteria of 90%of tested points being within 3%and 3 mm,60%of measurements would agree with both calculations.Conclusions:Both the pencil beam algorithm in Syngo and the FDC algorithm in TIMPS can provide accurate dose calculations in water for most clinical portals.For about 75%of portals,physicists can perform comparisons of calculations instead of phantom measurements to verify Syngo calculations thereby saving a large amount of beam time.There are some portals,however,such as for low-energy protons without RS and high-energy carbon ions,where agreement between the two calculations and measurements are not yet satisfactory to allow the elimination of all measurements.
文摘Objective:To verify the accuracy of an independent dose calculation method,as incorporated into an in-house developed treatment planning system(TPS),for performing quality assurance of dose distributions delivered to a water phantom planned by a clinical TPS.Methods:A Monte Carlo based track repeating algorithm was incorporated into an in-house treatment planning system for proton and carbon ion beams.Calculations were performed in a flat water phantom for both a traditional pencil beam algorithm and a new Monte Carlo algorithm,and then compared to measurements made at multiple depths with a 2D ionization array for 44 patient portals.The comparisons utilized a Gamma analysis.Results:A total of 124 measurements were performed for proton and carbon ion patient portals.Using a small Gamma criteria of 2%/2 mm,an average of 93%and 97%of measurement points passed for each portal for pencil beam and Monte Carlo calculations,respectively.The passing rate was substantially higher for Monte Carlo calculations than for pencil beam calculations for portals that used a range shifter.Conclusions:The implemented independent method has been verified against measurements.The high passing rate with small tolerances leads to the possibility of reducing the number of required quality assurance measurements.
文摘Objective:To develop and implement an ion beam teletherapy verification system based upon simulations of induced radioactivity and comparison with patient positron emission tomography(PET)scans.Methods:A Monte Carlo algorithm was integrated into an in-house built treatment,information,management,and planning system(TIMPS■)to calculate distributions of positron emitters induced by ion beams.These distribu-tions are processed to simulate PET images taking into account positron diffusion,radioactive decay,biological washout,and detector blurring.Additional tools were developed to register simulated PET images with planning CT images and perform comparisons of measured and simulated PET images.Results:Production cross-sections were generated for various isotopes and materials.Treatment plans for several different body sites were used to verify the functioning and utility of the new tools for both proton and carbon ion beams.Conclusions:Several tools have been developed to simulate PET scans of patients irradiated with ion beams and compare the simulated images to measurements.After commissioning and implementation into the clinic,the appropriate sizes for margins that account for uncertainties may be investigated.
