Analysis of the factors that disturb dose concentration in carbon beam therapy and its solution

It is important for heavy ion therapy to evaluate the contribution from the fragmentation reactions. In the previous research, we established the method to identify fragmentation reactions on an event-by-event basis, and we improved this method to evaluate the following quantities: energy dependency of cross sections and the distribution of charged particle multiplicity in fragmentation reactions. The results are compared with Monte Carlo simulation calculations incorporating with two theoretical models (JQMD and Binary Cascade) of fragmentation reactions. In this energy range, cross sections of fragmentation reactions were almost constant without depending on energy. The calculation reproduced experimental cross sections. However, the observed charged particle multiplicity distribution is not reproduced by the calculation. In order to apply this method to more realistic examples, we made two types of phantoms; a water phantom and a layered hepatocyte-cancer phantom. Measurements and calculations are compared in these cases. (author)