Mathematical Simulation of the Doses inside Patient Body under Prostate Irradiation with Carbon Ion Beam

Abstract

Purpose: The radiotherapy methods using heavy charged particles become popular nowadays due to its high efficiency in treatment of oncological patients. On the other side, the practical application of such particles is deeply connected to the influence of secondary radiation, which is a result of nuclear collisions, that can affect the patients’ tissues and organs outside the treatment field. Doses in the out-of-field volumes should be considered from the standpoint of radiological protection. In this study we perform mathematical simulations of the absorbed dose in various organs under the prostate irradiation with carbon ion beam and compared these dose values with existing reference values from CT procedures, and known radiological protection recommendations against current practice of clinical use of carbon ions. Material and methods: The simulation tool is general application Monte-Carlo code FLUKA widely used for ionizing radiation transport modeling and simulations in radiological protection field. The patient model is one of the most detailed voxelized anthropomorphic phantom Vishum. During the simulation the absorbed dose of segmented organs has been assessed under the spread-out Bragg peak of carbon ions uniformly covering the prostate with the physical dose. The resulted dose in organs is normalized to the prostate dose. This is the qualitative assessment of radiation treatment procedure which allowed us to analyze the out-of-field doses in distant organs from the viewpoint of radiological protection in ion beam therapy, following existing ICRP Publication 127 guidelines. Results: The results show that the levels of dose due to prostate irradiation in the regimes widely used in the world practice are two level of magnitude lower than dose levels under the full body CT examination, and are comparable to the aircraft crew doses. Conclusion: Thus, the obtained results might be interested from the risks assessment point of view, including the secondary radiation-induced cancers or other observable or expected treatment effects.