Dose calculations of microbeam radiation therapy (MRT) in water and head equivalent phantoms using GEANT4 simulation

Microbeam radiation therapy (MRT) is an innovative experimental method used for radioresistant tumours such as glioma especially in pediatric cancer. In MRT, the patient is irradiated with arrays of parallel and high-intensity X-ray microbeams. The MRT offers dose profiles consisting of a pattern of peaks and valleys. The peak-to-valley dose ratio (PVDR) is the most important metric determining the effectiveness of MRT. Its value has to be maximized in normal tissue, and minimized in cancerous tissue in order to avoid any recovery. The main aim of this study is to investigate the possible effect of beam parameters on PVDR. To do so, the 3D dose distributions in water and head equivalent phantoms are computed with various microbeam configurations using GEANT4 simulation. The results show that the most promising PVDR are obtained at 100keV and ESRF spectrum. In addition, using a 300keV beam is not suitable for microbeams separation distance below 400μm. By increasing radiation field size, microbeam’s width and their separation, PVDR decreases for all energies. PVDRs in the bone rapidly fall because of the dominant photoelectric phenomenon for such a high-Z material.