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
Prescriptions for radiation therapy are given in terms of dose-volume constraints (DVCs). Solving the fluence map optimization (FMO) problem while satisfying DVCs often requires a tedious trial-and-error for selecting...Prescriptions for radiation therapy are given in terms of dose-volume constraints (DVCs). Solving the fluence map optimization (FMO) problem while satisfying DVCs often requires a tedious trial-and-error for selecting appropriate dose control parameters on various organs. In this paper, we propose an iterative approach to satisfy DVCs using a multi-objective linear programming (LP) model for solving beamlet intensities. This algorithm, starting from arbitrary initial parameter values, gradually updates the values through an iterative solution process toward optimal solution. This method finds appropriate parameter values through the trade-off between OAR sparing and target coverage to improve the solution. We compared the plan quality and the satisfaction of the DVCs by the proposed algorithm with two nonlinear approaches: a nonlinear FMO model solved by using the L-BFGS algorithm and another approach solved by a commercial treatment planning system (Eclipse 8.9). We retrospectively selected from our institutional database five patients with lung cancer and one patient with prostate cancer for this study. Numerical results show that our approach successfully improved target coverage to meet the DVCs, while trying to keep corresponding OAR DVCs satisfied. The LBFGS algorithm for solving the nonlinear FMO model successfully satisfied the DVCs in three out of five test cases. However, there is no recourse in the nonlinear FMO model for correcting unsatisfied DVCs other than manually changing some parameter values through trial and error to derive a solution that more closely meets the DVC requirements. The LP-based heuristic algorithm outperformed the current treatment planning system in terms of DVC satisfaction. A major strength of the LP-based heuristic approach is that it is not sensitive to the starting condition.展开更多
Purpose: Combination of Prostate Seed Implant (PSI) with External Beam Radiation Therapy (EBRT) remains as an attractive option for patients with intermediate or high-risk prostate cancer. One of the most widely used ...Purpose: Combination of Prostate Seed Implant (PSI) with External Beam Radiation Therapy (EBRT) remains as an attractive option for patients with intermediate or high-risk prostate cancer. One of the most widely used approaches is to use external beam radiation therapy (EBRT) to deliver boost doses after permanent prostate seed implant (PSI). In this study, the feasibility of using Intensity Modulated Proton Therapy (IMPT) as an alternative EBRT boost treatment for PSI patients was investigated in the presence of a large number of high Z metallic seeds. The dosimetry of IMPT boost plans was compared with that of conventional Intensity Modulated Radiation Therapy (IMRT) boost plans. Methods: Ten post prostate seed implants with seeds of I-125 were randomly selected for this study. Proton treatment plans were created with two lateral opposed proton beams in Eclipse treatment planning system. IMRT boost plans were generated with seven co-planner beams for comparison. Several plan evaluation parameters such as the planning target volume (PTV) dose homogeneity, dose conformity and dose to surrounding normal tissues were evaluated. Results: Compared to conventional IMRT boost plans, IMPT demonstrated better sparing of normal tissues while providing similar satisfactory PTV coverage. The high Z implanted seeds is not a problem for IMPT as boost treatment. Conclusions: PSI with an IMPT boost can be a valuable option for prostate cancer patient treatment. It delivers comparable or better radiation dose distribution in terms of normal tissue sparing compared to IMRT boost plan.展开更多
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Prescriptions for radiation therapy are given in terms of dose-volume constraints (DVCs). Solving the fluence map optimization (FMO) problem while satisfying DVCs often requires a tedious trial-and-error for selecting appropriate dose control parameters on various organs. In this paper, we propose an iterative approach to satisfy DVCs using a multi-objective linear programming (LP) model for solving beamlet intensities. This algorithm, starting from arbitrary initial parameter values, gradually updates the values through an iterative solution process toward optimal solution. This method finds appropriate parameter values through the trade-off between OAR sparing and target coverage to improve the solution. We compared the plan quality and the satisfaction of the DVCs by the proposed algorithm with two nonlinear approaches: a nonlinear FMO model solved by using the L-BFGS algorithm and another approach solved by a commercial treatment planning system (Eclipse 8.9). We retrospectively selected from our institutional database five patients with lung cancer and one patient with prostate cancer for this study. Numerical results show that our approach successfully improved target coverage to meet the DVCs, while trying to keep corresponding OAR DVCs satisfied. The LBFGS algorithm for solving the nonlinear FMO model successfully satisfied the DVCs in three out of five test cases. However, there is no recourse in the nonlinear FMO model for correcting unsatisfied DVCs other than manually changing some parameter values through trial and error to derive a solution that more closely meets the DVC requirements. The LP-based heuristic algorithm outperformed the current treatment planning system in terms of DVC satisfaction. A major strength of the LP-based heuristic approach is that it is not sensitive to the starting condition.
文摘Purpose: Combination of Prostate Seed Implant (PSI) with External Beam Radiation Therapy (EBRT) remains as an attractive option for patients with intermediate or high-risk prostate cancer. One of the most widely used approaches is to use external beam radiation therapy (EBRT) to deliver boost doses after permanent prostate seed implant (PSI). In this study, the feasibility of using Intensity Modulated Proton Therapy (IMPT) as an alternative EBRT boost treatment for PSI patients was investigated in the presence of a large number of high Z metallic seeds. The dosimetry of IMPT boost plans was compared with that of conventional Intensity Modulated Radiation Therapy (IMRT) boost plans. Methods: Ten post prostate seed implants with seeds of I-125 were randomly selected for this study. Proton treatment plans were created with two lateral opposed proton beams in Eclipse treatment planning system. IMRT boost plans were generated with seven co-planner beams for comparison. Several plan evaluation parameters such as the planning target volume (PTV) dose homogeneity, dose conformity and dose to surrounding normal tissues were evaluated. Results: Compared to conventional IMRT boost plans, IMPT demonstrated better sparing of normal tissues while providing similar satisfactory PTV coverage. The high Z implanted seeds is not a problem for IMPT as boost treatment. Conclusions: PSI with an IMPT boost can be a valuable option for prostate cancer patient treatment. It delivers comparable or better radiation dose distribution in terms of normal tissue sparing compared to IMRT boost plan.
