Abstract
Taipei Veterans General Hospital plans to build the first heavy-ion (carbon) radiotherapy treatment center in Taiwan, specializing in difficult-to-treat cancer cases. Shielding analyses for such an accelerator involve many computational difficulties: source term estimations, complicated geometry modeling, deep-penetration calculations and streaming evaluations. Monte Carlo simulations are considered the most accurate method for complex accelerator shielding analyses, but less-experienced users may find them to be time-consuming and error-prone. Analytical models based on point-source line-of-sight approximation are intuitive and widely used in practice because of their ease of use. However, the accuracies and limitations of simplified models need to be evaluated. In this study, a set of shielding data, including source terms and attenuation lengths for several common targets (copper, iron, graphite, and tissue) and shielding materials (concrete, iron, and lead), were generated by performing Monte Carlo simulations for carbon ions of energies with 400 and 800 MeV. Potential applications and appropriate use of the data set for evaluating dose distributions outside a typical carbon-ion treatment room were demonstrated. A comparison of the model predictions and Monte Carlo calculated results revealed the effectiveness and advantage of applying the data set to a quick shielding design and dose analysis for heavy-ion therapy accelerators.