Study of the Fluence and LET Distribution of Projectile Fragments Produced from Heavy Ion Therapeutic Beams

The Fluence and LET spectra of each fragment particle are measured down to the Bragg peak energy region for carbon beams at HIMAC. The beams are formed to a therapeutic broad beam of 100 mm in diameter by means of the wobbler method. PMMA is used as atarget. A dE-E counter telescope equipped with a plastic scintillator and a BGO scintillator can identify the type of element for fragment particles. LET spectra are measured by a prportinal counter which is operated using P10 gas. Measured data are checked for accuracy by means of the following comparisons, depth dose distribution with the one measured by an ionization chamber, track averaged LET with calculation and total charge changing cross section of the primary particles with previous results. Fluence, dose averaged LET and dose composition as a function of water equivalent length are reported as a database for heavy ion radiotherapy.World Congress on Medical Physics and Biomedical Engineerin