Radiation Response of Normal Tissues and Tumors to Carbon Ion Irradiation

摘要

Carbon ions show an increased relative biological effectiveness, which increases with penetration depth. This differential RBE between peak and plateau may be used to increase the biological effective dose in the tumor while still sparing the surrounding normal tissue. For clinical application, a RBE-model such as the local effect model (LEM) is required to describe the dependence of RBE on dose and LET. To validate these models, experiments in normal tissues and tumors are necessary. The spinal cord and a prostate tumor in the rat were irradiated with photons and carbon ions using different fractionation schedules and dose response curves were determined. In the spinal cord experiment, the LEM overestimated the RBE in the plateau for small doses and underestimated the RBE in the Bragg-peak region over the whole dose range. A significant fractionation effect was found only for the plateau region. For the prostate tumor, local control could be achieved and significantly increased RBE-values were found for single and split doses. The acquired data contribute to the validation of the LEM and the quantification of the involved uncertainties.