MICRO-RADIOSURGERY - A NEW CONCEPT FOR RADIOTHERAPY BASED UPON LOW-ENERGY, ION-INDUCED NUCLEAR-REACTIONS

Traditionally, proton radiotherapy has required the use of high energy proton beams (50-200 MeV) which can penetrate into a patient's body t o the site of a tumor that is to be destroyed through irradiation. How ever, substantial damage is still done to healthy tissue along the pat h of the incident proton beam, as much as 30% of that done at the tumo r site. We propose a new concept for the production and delivery of en ergetic protons for use in medical radiotherapy, based upon the fact t hat low energy, ion-induced nuclear reactions can produce radiation pr oducts suitable for use in radiotherapy applications. By employing spe cially fabricated ''conduit needles'' to deliver beams of energetic io ns to selected target materials plugging the end of the needle, ion be am-induced nuclear reactions can be generated at the needle tip, emitt ing reaction-specific radiation products directly at the tumor site. I n this paper, we show that the 13.6 MeV protons produced by the d(He-3 ,p)He-4 nuclear reaction can deliver a lethal dose (7 krad) of radiati on to a 4.4 mm diameter sphere of tissue in only 30 s using a 1 muA, 8 00 keV He-3 ion beam. If also proven clinically feasible, the use of l ow energy, ion-induced nuclear reactions would allow the utilization o f relatively inexpensive, compact, low energy ion accelerators for pro ton radiotherapy and minimize unintended radiation damage to healthy t issue by providing much greater precision in controlling the irradiate d volume.