Microbeam radiation therapy (MRT)

Microbeam radiation therapy (MRT) was proposed by Slatkin and colleagues at Brookhaven National Laboratory in 1992: crossfire an array of parallel, closely spaced microbeams of synchrotron-generated X-rays, each about 25 micrometres wide, through a brain target. Their reasoning was that endothelium lethally irradiated inside a microbeam is replaced from the minimally irradiated tissue between beams, so normal tissue outside the target is spared, while overlapping beams at the isocentre deplete the target of dividing cells and cause necrosis.

The method needs the very bright, nearly parallel X-rays of a synchrotron, and much of the animal work has been done on the biomedical beamline ID17 of the European Synchrotron Radiation Facility in Grenoble (the ESRF listed ID17 as on hold until further notice in November 2026). A 2019 review from the ID17 group describes it as an emerging form of radiosurgery for brain tumours that operates at very high dose rate (kGy per second), with normal tissue sparing partly mediated by the FLASH effect, and sets out the preclinical evidence in view of a clinical transfer. It belongs with lattice and GRID radiotherapy to the family of spatially fractionated techniques, but at a much finer scale and higher dose rate.