Development and numerical assessment of an analytical model for dose estimation in FLASH proton therapy with 3D range modulators

Details

Supervisors

Lee, John Aldo

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil en mathématiques appliquées, à finalité spécialisée

Abstract

Radiation therapy is one of the oldest and most used treatments for cancer. Recently, a new technique using ultra-high dose rates called FLASH proton therapy showed promising results for the treatment of cancer with advantages over the conventional method. A patient specific range modulator must be modelized to match the Spread Out Bragg Peak (SOBP) with the tumor to treat. However, the most accurate existing simulations models use Monte Carlo and are too slow. The aim of this work is to develop an analytical model that gives acceptable results with a 3D range modulator in an reasonable time. The realization of this model is mainly based on the convolution principle. The scattering of the beam as it penetrates the water is modeled by successive convolutions of the beam with a Gaussian whose standard deviation has been calculated using MCsquare. The other central element of the simulation is the energy loss also coming from a model like MCsquare instead of a database like PSTAR to take into account the range straggling phenomenon. The results of the studied model are consistent and can be used to get a first idea of the dose distribution in a reasonable time. But they are not sufficiently accurate for a direct clinical use. Moreover, the study of geometrical characteristics of the range modulator shows their importance for the dose distribution and gives perspectives for future use of this model. Finally, it allows, in an acceptable time, a visualization of the individual impact of each element constituting a range modulator. This can help to better understand the advantages and disadvantages of each possible configuration. This analytical model is a tool to simulate more quickly a proton beam. It may contribute to find the shape of the 3D range modulator allowing the desired dose distribution.