Microbeam radiosurgery using synchrotron-generated submillimetric beams: a new tool for the treatment of brain disorders.

Since its advent during the mid-twentieth century, radiosurgery has undergone a steady evolution. Gamma Knife and linear accelerator based systems using rigid frames preceded the development of frameless devices. The present report describes the development of microbeam radiosurgery, a technique which uses submillimetric beams of radiation to treat disease. Typically, the technique is employed using parallel arrays of beams delivered via a high-fluence synchrotron source. Beam widths between 20 and 950 μm have been used with the majority of studies utilizing beam widths less than 100 μm. In addition to its high precision, the technique allows users to take advantage of two unique properties of microbeams. The first is a remarkable tolerance of healthy tissue to microbeams delivered at doses up to several hundred grays, while at the same time, tumors are highly susceptible to the lethal effects of microbeams. Together, these findings allow for a "preferential tumoricidal effect" beyond the typical dose-volume relationship. Although only used in animal experiments so far, we explore the hypothetical clinical role of microbeam radiosurgery which may be feasible in the near future. In addition to the treatment of traditional radiosurgery targets such as malignancies and vascular malformations, microbeams may allow the non-invasive treatment of functional disease such as movement disorders, epilepsy, and mental illness.