Microbeam Technique Improves Radiation Therapy

Findings on the improved technique, which was assessed in rats, was published online June 10, 2006, in the Proceedings of the [U.S.] National Academy of Sciences. The researchers conducting the study were from the U.S. Department of Energy's Brookhaven U.S. National Laboratory and colleagues at Stony Brook University (Brookhaven, NY, USA), the IRCCS Neuromed Medical Center (Pozzilli, Italy), and Georgetown University (Washington DC, USA).

The technique, microbeam radiation therapy (MRT), previously utilized a high-intensity synchrotron x-ray source such as a superconducting wiggler at Brookhaven's National Synchrotron Light Source (NSLS) to produce parallel arrays of very thin (25-90 micrometers) planar x-ray beams instead of the unsegmented (solid), broad beams used in traditional radiation treatment.

Earlier studies performed at Brookhaven and at the European Synchrotron Radiation Facility (ESRF; Grenoble, France) demonstrated MRT's ability to control malignant tumors in animals with high radiation doses while subjecting adjacent healthy tissue to little collateral damage.

In the study, the scientists report findings that demonstrate the potential efficacy of considerably thicker microbeams, as well as a way to "interlace” the beams within a well-defined target inside the subject to increase their killing potential there, while keeping the technique's characteristic feature of sparing healthy tissue outside that target.

First, they exposed the spinal cords and brains of healthy rats to thicker (0.27-0.68 mm) microbeams at high doses of radiation and monitored the animals for signs of tissue damage. After seven months, animals exposed to beams as thick as 0.68 mm showed no or little damage to the nervous system.

Next, the scientists demonstrated the ability to "interlace” two parallel arrays of the thicker microbeams at a 90o angle to form a solid beam at a small target volume in the rats' brains, and assessed the effects of varying doses of radiation on the targeted tissue volume and the surrounding tissue using magnetic resonance imaging (MRI) scans. The MRI scans demonstrated that at a particular dose of radiation, the new configuration could produce major damage to the target volume but virtually no damage beyond the target range.



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Brookhaven National Laboratory