Analysis of Energy Deposition in Hadrontherapy Using Monte Carlo Simulation Toolkit GEANT4

Abstract

This work focuses on one of the most important stages of hadrontherapy treatment planning. The simulation is performed using Monte Carlo (MC) Treatment Planning toolkit GEANT4 which is considered as the most accurate three-dimensional (3-D) dose calculation algorithm for studying Bragg peaks in tissue-equivalent material and dosimetric validation. In hadrontherapy, the study of a significant difference in the position of the Bragg peak is important to get realistic results. Proton therapy treatment planning involves a wider and sensitive range of parameters to be evaluated carefully from studying stopping power, linear energy transfer, the energy imparted to secondary particles and their range. The technical parameters from scanning, modification, accuracy and time also need to be assessed precisely as these vary from patient to patient depending on the health condition. All these parameters vary with Monte Carlo inputs and a slight variation in input generates different results, where, hadrontherapy treatment demands high precision. In this preliminary work, we studied one of the crucial factors ‘Step limit’ which shows the maximum ‘step size’ and limited by the accuracy and time factor of simulation. The simulation in GEANT4 is executed by activating suitable Physics Model ‘QGSP_BIC’ with default electromagnetic physics model em_option_3 implemented in Geant4 taking proton as an incident particle with energies 70, 100 and 130 MeV. For simulation, the implemented step size is 0.5 and 0.05 mm step size. The step size value 0.05 mm is found superlative for simulation taking into account simulation time and accuracy.