Monte Carlo computation of dose deposited by carbon ions in radiation therapy

Background: High-velocity carbon ion beams represent the most advanced tool for radiotherapy of deep-seated tumors. Currently, the superiority of carbon ion therapy is more prominent on lung cancer or hepatomas. Materials and Methods: The data for lateral straggling and projected range of monoenergetic 290 MeV/u (3.48 GeV) carbon ions in muscle tissue were obtained from the stopping and range of ions in matter (SRIM) computer code. The data were transformed to determine the carbon ion trajectories in tissue by means of the Monte Carlo method. Consequently, the lateral dose distributions in the Bragg peak as well as the thickness of a thin disc-shaped tumor in the lateral direction were computed. The absorbed dose in the tissue was obtained as a function of the diameter of a carbon ion pencil beam. Results: More than 90% of the radiation dose in the lateral direction is deposited in the Bragg peak. The simulation results are in agreement with the existing data. Conclusion: It was confirmed that this method is reliable for estimation of dose deposited in human tissue by carbon ion beams.