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Shielding Analysis of Proton Therapy Accelerators: A Demonstration Using Monte Carlo-Generated Source Terms and Attenuation Lengths

Lai, Bo-Lun*; Sheu, Rong-Jiun*†; Lin, Uei-Tyng

doi: 10.1097/HP.0000000000000280
Operational Topics

Monte Carlo simulations are generally considered the most accurate method for complex accelerator shielding analysis. Simplified models based on point-source line-of-sight approximation are often preferable in practice because they are intuitive and easy to use. A set of shielding data, including source terms and attenuation lengths for several common targets (iron, graphite, tissue, and copper) and shielding materials (concrete, iron, and lead) were generated by performing Monte Carlo simulations for 100–300 MeV protons. Possible applications and a proper use of the data set were demonstrated through a practical case study, in which shielding analysis on a typical proton treatment room was conducted. A thorough and consistent comparison between the predictions of our point-source line-of-sight model and those obtained by Monte Carlo simulations for a 360° dose distribution around the room perimeter showed that the data set can yield fairly accurate or conservative estimates for the transmitted doses, except for those near the maze exit. In addition, this study demonstrated that appropriate coupling between the generated source term and empirical formulae for radiation streaming can be used to predict a reasonable dose distribution along the maze. This case study proved the effectiveness and advantage of applying the data set to a quick shielding design and dose evaluation for proton therapy accelerators.

*Institute of Nuclear Engineering and Science, National Tsing-Hua University, 101, Sec. 2, Kuang-Fu Road, Hsinchu, Taiwan; †Department of Engineering and System Science, National Tsing-Hua University, 101, Sec. 2, Kuang-Fu Road, Hsinchu, Taiwan; ‡Institute of Radiological Sciences, Tzu Chi College of Technology, 880, Sec. 2, Chien-Kuo Road, Hualien, Taiwan.

The authors declare no conflicts of interest.

Rong-Jiun Sheu is Associate Professor in the Institute of Nuclear Engineering and Science at National Tsing Hua University (NTHU) in Taiwan. Previously, he was a radiation physicist at National Synchrotron Radiation Research Center in charge of radiation shielding and measurement. He received M.S. and Ph.D. degrees in nuclear engineering from NTHU. At the present time, his main research activities are in the areas of health physics and reactor physics. His email address is

© 2015 by the Health Physics Society