Establishment of the evaluation method of the ¹²C pencil beam profile in matter for cancer therapy

The dose distribution of scanning irradiation is formed by superimposing the carbon beam. But, its dose distribution changes due to the variations in the energy and the profile of the beam in matter. Two causes of the profile variation are the nuclear fragmentation reaction and the multiple Coulomb scattering. Thus, it is necessary to quantitatively evaluate the influence of fragmentation reactions on the profile. The objective of this study is to establish the evaluation method of the carbon pencil beam profile in matter for cancer therapy by separately evaluating the profiles for the fragmentation reaction and the multiple Coulomb scattering. In the previous research, we established a method to identify fragmentation reactions on an event-by-event basis. We improved this method to evaluate the pencil beam profile and selectively obtained the profile of fragment particles. In this experiment, we showed that the profile measurement of the nuclear fragmentation reaction was possible. (author)