Microbeam radiation therapy: a review

Abstract

The radiation effects in tissue depend not only on dose but also on volume exposed, for example, the smaller the volume, the greater the tolerance. Microbeam radiation therapy (MRT), which exploits this effect, can only be achieved with synchrotron X-rays owing to their extraordinarily slight divergence. MRT research over the past 20 years has yielded many results from preclinical trials based on different animal models, including mice, rats, piglets and rabbits. Typically, targets are exposed to multiple quasi-parallel slices of radiation some tens of micrometres wide with on-centre separations of several hundred micrometres. The microplanar beams are produced by a multi-slit collimator, which cuts horizontally microscopic beam sectors from a wigglergenerated fan beam. Peak entrance doses of several hundreds of Gy are surprisingly well tolerated by normal tissues and at the same time show a preferential damage of malignant tumour tissues.