THE USE OF LOW-ENERGY, ION-INDUCED NUCLEAR-REACTIONS FOR PROTON RADIOTHERAPY APPLICATIONS

Medical radiotherapy has traditionally relied upon the use of external photon beams and internally implanted radioisotopes as the chief mean s of irradiating tumors. However, advances in accelerator technology a nd the exploitation of novel means of producing radiation may provide useful alternatives to some current modes of medical radiation deliver y - with reduced total dose to surrounding healthy tissue, reduced exp ense, or increased treatment accessibility. This paper will briefly ov erview currently established modes of radiation therapy, techniques st ill considered experimental but in clinical use and innovative concept s under study that may enable new forms of treatment or enhance existi ng ones. The potential role of low energy, ion-induced nuclear reactio ns in radiotherapy applications is examined specifically for the 650 k eV d(He-3,p)He-4 nuclear reaction. This examination will describe the basic physics associated with this reaction's production of 17.4 MeV p rotons and the processes used to fabricate the necessary materials use d in the technique. Calculations of the delivered radiation dose, heat generation, and required exposure times are presented. Experimental d ata is also presented validating the dose calculations. The design of small, lower cost ion accelerators, as embodied in ''nested''-tandem a nd radio frequency quadrupole accelerators is examined, as is the pote ntial use of high-output 3He and deuterium ion sources. Finally, poten tial clinical applications are discussed in terms of the advantages an d disadvantages of this technique with respect to current radiotherapy methods and equipment.