Improvement of Calculating Efficiency for Proton Nozzle using GEANT4 Multi-threading

Dae-Hyun Kim1,2, Sung-Hwan Ahn1, Kwangzoo Chung1, Jing Sung Kim1, Sungkoo Cho1, Eunhyuk Shin1, JungSuk Shin1, Tae-Suk Suh2, Youngyih Han1 1 Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 2 Department of Biomedical Engineering, College of Medicine, The Catholic University of Korea Abstract Objective: Monte Carlo is the most accurate dose calculation method for proton therapy. However it is very time consuming because a many number of particle histories are needed to achieve a high level of statistical accuracy. The calculation time also depends on the complexity of the geometry such as proton therapy nozzle. The purpose of this study is to develop a Monte Carlo calculation model for a proton treatment nozzle and to diminish the calculation time using GEANT4 multi-threading. Methods and Materials: We developed a Monte Carlo calculation model of proton treatment nozzle at the Samsung Medical Center using GEANT4 toolkit. The nozzle components such as a scatterer, ridge filter, and multi-leaf collimator, were modeled based on drawings provided by the manufacturer. GEANT4 was chosen as the multithreading engine to reduce calculation time. We evaluated efficiency of computation time along the number of CPUs using multithreading. Results: We have successfully developed a proton Monte Carlo dose calculation code, and it was validated with experimental measurements data for all energies. The measured and simulated depth dose agreed less than 1 mm of deviation. The full width at half maximum values and 10-10% width for the measured and simulated lateral fluence profiles agreed within 3% of differences for all energies. The calculation time has linearly decreased with the CPU number, and it faster over 18 times by using 20 CPUs, but the results of depth dose and lateral profile between multithreading and sequential mode were no significant difference. Conclusion: The proton dose calculation model using GEANT4 was developed and validated in the way of minimizing the calculation time. The fast calculation Monte Carlo code will contribute to applicability to clinic and to simplifying beam commissioning for proton therapy. Figure 1. Figure 2.

Figure 1. Comparison of depth dose distributions computed by multi-threaded GEANT4 and measurement in all proton energies. Figure 2. Calculation times as function of the number of threads