Dosimetric studies of microbeam radiation therapy (MRT) with Monte Carlo simulations

Microbeam Radiation Therapy (MRT) is a technique utilizing the fact that normal tissue can sustain high doses of radiation in small volumes without significant damage. The synchrotron generated X-ray beam, used for the treatment, is collimated and delivered in an array of narrow micrometer-sized planar rectangular fields. In this work, the Monte Carlo code PENELOPE was used for simulating the dose deposition. This code provides an accurate treatment of low-energy electron transport which is important when performing dose calculations in micron-sized ranges. A comparison with earlier results was done for a few typical cases. The buildup of dose near the phantom surface and the lateral variation of dose around the microbeams were also studied. It was confirmed that the dose in the valley region mainly depends on Compton scattered electrons and that the electron scattering model used in the MC code is a key point. Finally a comparison between MC simulations and experimental microdosimetry, with radiochromic films and MOSFET detectors, gave important indications on possible refinements of the MC simulations for future investigations.