| Liu Hongming,Chen Bo,Zhuo Weihai.Simulation of detection efficiency of a portable NaI(Tl) γ spectrometer for monitoring 131I in the thyroid[J].Chinese Journal of Radiological Medicine and Protection,2022,42(8):618-623 |
| Simulation of detection efficiency of a portable NaI(Tl) γ spectrometer for monitoring 131I in the thyroid |
| Received:April 20, 2022 |
| DOI：10.3760/cma.j.cn112271-20220420-00168 |
| KeyWords:131I Thyroid-neck phantom Portable gamma spectrometer Detection efficiency Monte Carlo simulation |
| FundProject:国家自然科学基金（11775053，12175043） |
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| Abstract:: |
| Objective To simulate the effects of different thyroid-neck phantoms and monitoring positions on the detection efficiency of portable γ spectrometer, and to provide guidance for more accurate on-site measurement of 131I activity in the human thyroid.Methods Based on the models of 4 typical thyroid-neck phantoms and a 3-inch NaI (TI) γ spectrometer used for the measurement of 131I in the thyroid and combined with the possible field monitoring scenarios, the Monte Carlo method was used to simulate and calculate the detection efficiency of the spectrometer under different conditions of monitoring distance, thyroid depth and thyroid volume.Results The detection efficiency decreased significantly with the increase in the distance between the detector and the neck surface. The efficiency close to the neck surface was about 15 times that at 15 cm away from the neck surface. The detection efficiency decreased significantly with the increase in thyroid depth. When it was measured at the surface of the neck, the detection efficiency of thyroid at depth of 2 mm was about 3.6 times that of 30 mm. The detection efficiency decreases with the increase in thyroid volume. When it was measured at the neck surface, the detection efficiency of thyroid with 1 ml volume was 1.71 times that with 30 ml. The detection efficiency decreased with the center-point offset of the detector, especially at the neck surface, an offset of 2 cm would reduce the detection efficiency by about 15%.Conclusions Not only the measurement distance used in calibration, but also the information of the depth and volume of thyroid in the neck-thyroid phantom, is important to know in advance for an accurate measurement of 131I activity in thyroid by using a portable gamma spectrometer. |
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