论文部分内容阅读
TOPAS is a newly developed Monte Carlo simulation tool that combines extensive radiation physics libraries available in Geant4 code and easy-to-use geometry and visualization features.Although TOPAS has been tested for electron and proton accelerators,it has not been demonstrated with heavy-ion radiotherapy.Purpose:To evaluate the feasibility of adopting TOPAS for Monte Carlo-based dosimetric studies of heavy-ion therapy at IMP in Lanzhou.Methods:A commercial version of the TOPAS(currently in the released version)is an innovative Monte Carlo research platform for radiation therapy based on the toolkit Geant4,which is specially designed for particle radiotherapy simulations,calculations and visualizations.We obtained the results of the Bragg peak and SOBP of carbon ions with different energies in water,and compared them with the measurements conducted at IMP in Lanzhou.Then,the treatment nozzle was simulated using the construction data provided by IMP.Results:Results for the Bragg peaks and SOBP in water of different energetic carbon ions(from 100 to 400 MeV/u)showed that the simulated results agreed well with the measurements.Only divergence observed in low-energy(100MeV/u)which is actually not used for radiotherapy at IMP,the reason of the difference is thought to be due to the experimental conditions.The special components used in passive scattering modality,including the Ridge Filter and Multi-Leaf Collimator were also simulated to study both the lateral and longitudinal profiles of the dose distribution.Conclusions:With the right parameter settings,TOPAS allows us to obtain carbonion beam dosimetric data that agreed well with the measurements.Because TOPAS is specially designed for particle therapy,important special components in treatment nozzle have been predefined,thus making it easy and suitable for the simulation of carbon-ion therapy machine without having to use Geant4.On-going effort is using TOPAS to validate treatment planning system at IMP.