Researchers at Brookhaven National Laboratory (BNL), along with colleagues at Stony Brook University, the IRCCS NEUROMED Medical Center in Italy, and Georgetown University, say that improvements made to an experimental form of radiation therapy could make the technique more effective, leading to use in hospitals. Results on the improved method, which was tested in rats, were published online in June in the Proceedings of the National Academy of Sciences.

The technique, microbeam radiation therapy (MRT), previously used a high-intensity synchrotron X-ray source to produce parallel arrays of very thin planar X-ray beams of 25 to 90 micrometers instead of solid, broad beams used in conventional radiation treatment. Previous studies at BNL and at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, demonstrated MRT’s ability to control malignant tumors in animals with high radiation dosages while subjecting adjacent normal tissue to little collateral damage. But the technique has limitations. For instance, only certain synchrotrons can generate its very thin beams at adequate intensity, and such facilities are available at only a few research centers around the world.

“The new development seeks a way out of this situation,” explained BNL scientist Avraham Dilmanian, lead author of the new study. In this paper, the scientists report results that demonstrate the potential efficacy of significantly 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 retaining the technique’s hallmark feature of sparing healthy tissue outside that target.

First, the scientists exposed the spinal cords and brains of healthy rats to thicker (0.27 to 0.68 millimeter) 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 millimeter showed no or little damage to the nervous system. Next, they demonstrated the ability to “interlace” two parallel arrays of the thicker microbeams at a 90-degree angle to form a solid beam at a small target volume in the rats’ brains, and measured 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 showed 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. “The dose of radiation delivered to the target volume would have been enough to ablate a malignant tumor,” Dilmanian said. “These results show that thick microbeams generated by special x-ray tubes in hospitals could eventually be used to destroy selective targets while sparing healthy tissue.”

Said collaborator Eliot Rosen, a radiation oncologist at Lombardi Comprehensive Cancer Center, Georgetown University, “This form of microbeam radiation therapy could improve the treatment of many forms of cancer now treated with radiation, because it can deliver a more lethal dose to the tumor while minimizing damage to surrounding healthy tissue. It may also extend the use of radiation to cases where it is now used only judiciously, such as brain cancer in patients under three years of age, because of the high sensitivity of young brain tissue to radiation.”

And according to collaborators David Anschel, a neurologist at Stony Brook University and BNL, and Pantaleo Romanelli, a neurosurgeon from NEUROMED Medical Center, the technique may also have applications in treating a wide range of benign and malignant brain tumors and other functional brain disorders such as epilepsy and Parkinson’s disease.

For more information, contact Karen McNulty Walsh at (631) 344-8350, kmcnulty@bnl.gov.

Read the paper presented to the Proceedings of the National Academy of Sciences.