Microbeam
radiation therapy (MRT) is an innovative technique to treat
brain tumors. The
synchrotron generated x-ray beam, used for the treatment, is collimated and delivered in an array of narrow micrometer-sized planar rectangular fields. Several preclinical experiments performed at the Brookhaven National Laboratory (BNL) and at the European
Synchrotron Radiation Facility (ESRF) have shown the sparing effect of the healthy tissue and the ablation of
tumors in several animal models. It has also been determined that MRT yields a higher therapeutic index than nonsegmented beams of the same energy. This therapeutic index could be greatly improved by loading the
tumor with high atomic number (Z)
contrast agents. In this work, the dose enhancement factors and the peak to valley dose ratios (PVDRs) are assessed for different
gadolinium (Z = 64) concentrations in the
tumor and different microbeam energies by using Monte Carlo simulations (PENELOPE 2006 code). A significant decrease in the PVDR values in the
tumor, and therefore a relevant increase in the dose deposition, is found in the presence of
gadolinium. The optimum energy for the dose deposition in the
tumor while keeping a high PVDR in the healthy tissues, which guaranties their sparing, has been investigated.