Carbon proton beam comparisons

Based on theoretical considerations and on results obtained from two preliminary Bevalac experiments, the authors have tentatively confirmed their hypothesis that carbon and neon beams are potentially better for beam localization than protons or helium ions of comparable range. When a small beam is used, multiple scatter broadens the beam as it penetrates an absorber. The scattering for carbon beams is about √12 times less than for proton beams. The same can be said for the straggling. The end result is that the Bragg peak/plateau ratio is reduced for protons much more than for carbon, and the proton beam is physically broadened. Further experiments are planned with Bevalac protons and carbon-ion beams to evaluate the importance of multiple scattering to the successful delivery of sharply-defined and narrowly-collimated dose distributions at clinically significant depths of penetration for the treatment of eye tumors and brain lesions