Monte Carlo Simulation Of Proton Radiation Dose Based On TOPAS

Radiotherapy is a treatment, which uses the ray emitted by ionizing radiation to kill tumor cells in irradiated regions. With conventional rays (electrons, photons) treatment is different, the proton physical properties inherent in the inverted depth dose distribution, makes when using proton beam therapy, can be great radiation dose in the tumor area and nearby normal tissue is rarely radiation dose, the killing of tumor cells at the same time, the greatest degree of protection of normal tissue around the tumor, the less even from harm. Dose calculation is the most core part in radiation therapy and Monte Carlo algorithm has a large advantage in terms of dose calculation. Commonly used proton radiation therapy Monte Carlo software includes FLUKA, GEANT4, MCNP, etc., but this software for clinical physicist is over complicated. TOPAS (TOol for PArticle Simulation) is based on the Monte Carlo toolkit Geant4 extension, which is a not complicated and easy to use for user, specialized for proton therapy.In this paper, using the TOPAS particle transport simulation software, through the simulation environment and the realization of the geometry, the particle source, a large number of simulation experiments. First of all, to simulate the different energy proton beam spread in the air, shows the TOPAS simulation software powerful visualization and geometry editing capabilities; To simulate the different energy of proton beam depth dose distribution in the water, and the range of the simulation and measurement data of the fitting formula for the comparison of accuracy of TO APS simulation program is verified. Secondly, through the simulation of different energy and the proton beam step length, the SOBP synthesis method research; And simulates the proton beam in different beam and the dose distribution in homogeneous and heterogeneous organization characteristics, points out the problems requiring attention in the actual clinical treatment; This article also is often used in dose calculation parsing algorithm for heterogeneous medium modified equivalent path method is verified, equivalent path method is verified with different thickness and position of the correction of inhomogeneous medium effect; Finally use TOPAS on a typical passive, to simulate the scattering type treatment head realized by adjusting the modulation wheel of different energy proton beam Bragg peak broadening technology, analyzes the different energy proton beam width of SOBP dose distribution characteristics.Simulation research of proton radiation therapy research of this article made some preliminary exploration, has achieved a lot of meaningful research results, the TOPAS particle transport software in terms of proton therapy had the further understanding of, study provides certain help for subsequent proton radiotherapy.