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Original Article

Korean Journal of Medical Physics 2015; 26(1): 12-17

Published online March 31, 2015

Copyright © Korean Society of Medical Physics.

Monte Carlo Simulation of the Carbon Beam Nozzle for the Biomedical Research Facility in RAON

Jae-Beom Bae*, Byung-Cheol Cho*, Jung-Won Kwak*, Woo-Yoon Park, Young-Kyung Lim, Hyun-Tai Chung§

*Department of Radiation Oncology, Asan Medical Center, Seoul, Department of Radiation Oncology, Chungbuk National University Hospital, Chengju, Proton Therapy Center, National Cancer Center, Ilsan, §Department of Neurosurgery, Seoul National University, Seoul, Korea

Received: March 11, 2015; Revised: March 13, 2015; Accepted: March 16, 2015

Abstract

The purpose of the Monte Carlo simulation study was to provide the optimized nozzle design to satisfy the beam conditions for biomedical researches in the Korean heavy-ion accelerator, RAON. The nozzle design was required to produce C12 beam satisfying the three conditions; the maximum field size, the dose uniformity and the beam contamination. We employed the GEANT4 toolkit in Monte Carlo simulation to optimize the nozzle design. The beams for biomedical researches were required that the maximum field size should be more than 15×15 cm2, the dose uniformity was to be less than 3% and the level of beam contamination due to the scattered radiation from collimation systems was less than 5% of total dose. For the field size, we optimized the tilting angle of the circularly rotating beam controlled by a pair of dipole magnets at the most upstream of the user beam line unit and the thickness of the scatter plate located downstream of the dipole magnets. The values of beam scanning angle and the thickness of the scatter plate could be successfully optimized to be 0.5o and 0.05 cm via this Monte Carlo simulation analysis. For the dose uniformity and the beam contamination, we introduced the new beam configuration technique by the combination of scanning and static beams. With the combination of a central static beam and a circularly rotating beam with the tilting angle of 0.5o to beam axis, the dose uniformity could be established to be 1.1% in 15×15 cm2 sized maximum field. For the beam contamination, it was determined by the ratio of the absorbed doses delivered by C12 ion and other particles. The level of the beam contamination could be achieved to be less than 2.5% of total dose in the region from 5 cm to 17 cm water equivalent depth in the combined beam configuration. Based on the results, we could establish the optimized nozzle design satisfying the beam conditions which were required for biomedical researches.

KeywordsAccelerator, GEANT4, Heavy ion, Carbon, Nozzle, RAON

Korean Society of Medical Physics

Vol.35 No.2
June 2024

pISSN 2508-4445
eISSN 2508-4453
Formerly ISSN 1226-5829

Frequency: Quarterly

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