A performance test was carried out using five different gamma-ray spectrometers applicable to thyroid monitoring. The energy resolution and efficiency for 7.6-cm × 7.6-cm NaI(Tl), 5.1-cm × 5.1-cm CeBr3, 3.8-cm × 3.8-cm SrI2(Eu), and 2.5-cm × 2.5-cm SrI2(Eu) gamma-ray scintillation spectrometers and a CdTe gamma-ray semiconductor spectrometer were evaluated using the Oak Ridge Institute for Nuclear Studies thyroid-neck phantom with a mock 131I source for prompt thyroid monitoring after a nuclear emergency. The respective energy resolutions of the full-energy peak for ~0.360 MeV of 3.8-cm × 3.8-cm SrI2(Eu) and 2.5-cm × 2.5-cm SrI2(Eu) scintillation spectrometers were 4.2% and 4.3%, and these values were very close to the value obtained by the CdTe semiconductor spectrometer. The efficiencies of four of the gamma-ray spectrometers were compared based on the efficiency of the 7.6-cm × 7.6-cm NaI(Tl) scintillation spectrometer at 0 cm from the phantom surface, and these values were ~70% for 5.1-cm × 5.1-cm CeBr3, ~30% for 3.8-cm × 3.8-cm SrI2(Eu), 10% for 2.5-cm × 2.5-cm SrI2(Eu) and 2% for 1-cm2 × 0.1-cm CdTe. Furthermore, the detection limits at various dose rates for the four gamma-ray scintillation spectrometers were evaluated using the method based on International Organization for Standardization publication ISO 11929:2010.
1Hirosaki University Graduate School of Health Sciences, 66-1 Hon-cho, Hirosaki, Aomori 036-8564, Japan;
2Hirosaki University, Institute of Radiation Emergency Medicine, 66-1 Hon-cho, Hirosaki, Aomori 036-8564, Japan;
3Advanced Fusion Technology, Co., Ltd., 5-6-3 Sotokanda, Chiyoda-ku, Tokyo 101-0021, Japan;
4EMF Japan Co., Ltd., 1-1-4 Nankadai, Kawachinagano-shi, Osaka 586-0077, Japan;
5National Institute for Fusion Science/The Graduate University for Advanced Studies (SOKENDAI), 322-6 Oroshi-cho, Toki-shi, Gifu 509-5292, Japan.
The authors declare no conflicts of interest.
For correspondence contact Shinji Tokonami, 66-1 Hon-cho, Hirosaki, Aomori 036-8564, Japan, or email at firstname.lastname@example.org.
(Manuscript accepted 13 July 2018)