Geant4 simulations for microbeam radiation therapy (MRT) dosimetry

Radiation therapy is one of the techniques most commonly used in the treatment of various types of tumors. The microbeam radiation therapy (MRT) is a very promising variant, which exploits the property that tissues can tolerate high doses of radiation in small volumes. The effectiveness of MRT is well represented by the peak-to-valley dose ratios (PVDRs), which are one of the crucial parameters associated with the outcome of the treatment. In this study, we investigate on the factors that influence PVDRs, such as different beam energies and geometries. MRT experiments typically employ rectangular (planar) microbeams of different sizes, but, for convenience of analysis, preliminary computations have been performed also using arrays of cylindrical microbeams. This work shows that the shape of the impinging irradiation field largely influences the dose distribution. It highlights that a bundle of larger microbeams, with a small separation, produces more scattered radiation and therefore lower PVDRs. The study of how dose distributions vary with different setups and irradiation parameters is an essential step in enhancing the comparability of experimental data and simulation results.