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Response of a Plate-type Thermoluminescence Dosimeter to a Therapeutic Carbon Beam
Yusuke Koba,Shigekazu Fukuda,Kiyomitsu Shinsho,Genichiro Wakabayashi,Satoshi Tamatsu 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.7
In order to measure the three-dimensional dose distribution in X-ray radiotherapy, we developeda plate-type thermoluminescence dosimeter (TLD) using the TL phosphor Li3B7O12:Cu, which hasZeff = 7.42 and a density of 1.01 gcm−3. This detector was expected on useful application inadvanced X-ray radiotherapies such as intensity-modulated ratiation therapy (IMRT) etc., becauseit can obtain 3D dose measurements simply and quickly with a single exposure. In this paper, wereport the response of this plate-type TLD to a therapeutic carbon beam at the Heavy Ion MedicalAccelerator in Chiba (HIMAC). Using a plate heater and charge coupled device (CCD) camera, wecaptured thermoluminescence images of plate-type TLDs irradiated by a therapeutic carbon beam. The TL intensity was measured at each water equivalent depth and compared with output of theionization chamber. The relative TL efficiency of this TLD as 60Co gamma-ray equivalent decreasedgradually with increasing dose-averaged linear-energy-transfer (LET), reaching about 20% at theBragg peak of 290 MeV/u carbon ions.
Itashiki, Yutaro,Imahayashi, Youichi,Shigyo, Nobuhiro,Uozumi, Yusuke,Satoh, Daiki,Kajimoto, Tsuyoshi,Sanami, Toshiya,Koba, Yusuke,Matsufuji, Naruhiro The Korean Association for Radiation Protection 2016 방사선방어학회지 Vol.41 No.4
Background: Carbon ion therapy has achieved satisfactory results. However, patients have a risk to get a secondary cancer. In order to estimate the risk, it is essential to understand particle transportation and nuclear reactions in the patient's body. The particle transport Monte Carlo simulation code is a useful tool to understand them. Since the code validation for heavy ion incident reactions is not enough, the experimental data of the elementary reaction processes are needed. Materials and Methods: We measured neutron production double-differential cross-sections (DDXs) on a carbon bombarded with 430 MeV/nucleon carbon beam at PH2 beam line of HIMAC facility in NIRS. Neutrons produced in the target were measured with NE213 liquid organic scintillators located at six angles of 15, 30, 45, 60, 75, and $90^{\circ}$. Results and Discussion: Neutron production double-differential cross-sections for carbon bombarded with 430 MeV/nucleon carbon ions were measured by the time-of-flight method with NE213 liquid organic scintillators at six angles of 15, 30, 45, 60, 75, and $90^{\circ}$. The cross sections were obtained from 1 MeV to several hundred MeV. The experimental data were compared with calculated results obtained by Monte Carlo simulation codes PHITS, Geant4, and FLUKA. Conclusion: PHITS was able to reproduce neutron production for elementary processes of carbon-carbon reaction precisely the best of three codes.
Hirata, Yuho,Watanabe, Kenichi,Uritani, Akira,Yamazaki, Atsushi,Koba, Yusuke,Matsufuji, Naruhiro The Korean Association for Radiation Protection 2016 방사선방어학회지 Vol.41 No.3
Background: We are developing a small size dosimeter for dose estimation in particle therapies. The developed dosimeter is an optical fiber based dosimeter mounting an radiation induced luminescence material, such as an OSL or a scintillator, at a tip. These materials generally suffer from the quenching effect under high LET particle irradiation. Materials and Methods: We fabricated two types of the small size dosimeters. They used an OSL material Eu:BaFBr and a BGO scintillator. Carbon ions were irradiated into the fabricated dosimeters at Heavy Ion Medical Accelerator in Chiba (HIMAC). The small size dosimeters were set behind the water equivalent acrylic phantom. Bragg peak was observed by changing the phantom thickness. An ion chamber was also placed near the small size dosimeters as a reference. Results and Discussion: Eu:BaFBr and BGO dosimeters showed a Bragg peak at the same thickness as the ion chamber. Under high LET particle irradiation, the response of the luminescence-based small size dosimeters deteriorated compared with that of the ion chamber due to the quenching effect. We confirmed the luminescence efficiency of Eu:BaFBr and BGO decrease with the LET. The reduction coefficient of luminescence efficiency was different between the BGO and the Eu:BaFBr. The LET can be determined from the luminescence ratio between Eu:BaFBr and BGO, and the dosimeter response can be corrected. Conclusion: We evaluated the LET dependence of the luminescence efficiency of the BGO and Eu:BaFBr as the quenching effect. We propose and discuss the correction of the quenching effect using the signal intensity ratio of the both materials. Although the correction precision is not sufficient, feasibility of the proposed correction method is proved through basic experiments.