Radiotherapy is one of the most powerful treatments for brain tumor. Penetrating ionizing particles is aimed toward the tumor, delivering as high radiation to it as is usefully suppressive of tumor growth, and tolerated by normal vital tissues inevitably irradiated with the tumor. The use of a high-energy synchrotron-radiation thin X-ray beams (microplanar beams, or microbeams) produced through a multi-slit collimator has been reported to enhance the tolerance of normal tissue to radiation. The high collimation and dose rate of synchrotron X-ray beams favor radiotherapy. Irradiation with parallel arrays of microbeam, planar slices of spares normal brain, and preferentially damages tumors. The width of the peak region was 20-25 μm, and the spacing between the regions was 100-300 μm. We firstly examined the dose distribution with micro-scale resolution in order to clarify this phenomenon. Secondary, radiotherapy of malignant brain tumors in rats was performed. The treatment results in extended median survival time. The effects are mediated, at least in part, by the tissue’s microvasculature that seems to effectively repair itself in normal brain but fails to do so in tumors.
