# Microbeam radiation therapy (MRT)

Source: https://onco.cc/technologies/microbeam-radiotherapy/  
OnCo record `microbeam-radiotherapy` (Technology). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Microbeam radiotherapy splits an X-ray beam into many very thin parallel slices, each narrower than a hair, with gaps between them. Healthy tissue between the slices recovers, while the tumour, hit from several directions, does not. It has been tested in animals and is being prepared for first use in people.

## Summary

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.

## Fields

- Kind: Technology
- Status: preclinical
- Last checked: 2026-11-03
- Also known as: microbeam radiotherapy; synchrotron microbeam radiation therapy; MRT
- Principle: An array of quasi-parallel synchrotron X-ray beams tens of micrometres wide, separated by gaps a few times wider, delivers very high peak doses in the beams and low valley doses between them; tissue repairs from the valleys, and crossfiring makes the target dose uniform.
- Since: 1992
- Strengths: Marked normal tissue sparing in animal studies; Very high dose rate overlaps with the FLASH effect; Suited to brain tumours, where sparing matters most
- Limitations: Needs a synchrotron; very few facilities can deliver it; Dosimetry at micrometre scale is difficult; No completed clinical trial in people

## Sources

- Slatkin et al. 1992, Medical Physics: Microbeam radiation therapy: https://doi.org/10.1118/1.596771
- Eling et al. 2019, Radiotherapy and Oncology: ultra high dose rate synchrotron microbeam radiation therapy, preclinical evidence in view of a clinical transfer: https://doi.org/10.1016/j.radonc.2019.06.030

## Connected records

- cancers: [Glioma & glioblastoma](https://onco.cc/cancers/glioblastoma/)
- fronts: [Radiation Therapy](https://onco.cc/fronts/radiation/)
- technologies: [FLASH radiotherapy](https://onco.cc/technologies/flash-rt/), [Lattice and GRID radiotherapy](https://onco.cc/technologies/lattice-radiotherapy/), [Stereotactic radiosurgery (Gamma Knife, CyberKnife, linac SRS)](https://onco.cc/technologies/radiosurgery-srs/)
- institutions: [European Synchrotron Radiation Facility](https://onco.cc/institutions/esrf/)

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