Evaluation of the Measurement Efficiency of GM Tube and NaI(Tl)-Based Radiation Detectors in High Magnetic Fields

초록

The present study evaluated the performance changes of detectors that may occur when measuring radiation in a high magnetic field environment using a GM tube-based radiation detector and a NaI(Tl) scintillation detector owned by the Radiation Safety Management Team of the Korea Institute of Radiological and Medical Sciences. The experiment was conducted in a high-magnetic field environment in the small animal imaging room at the Radiation Medicine Research Institute of the Korea Institute of Radiological and Medical Sciences. The experiment utilised a 333 kBq Cs-137 as the radiation source. Subsequently, the source was positioned at a distance of 100 cm from the center of the MRI bore, with the distance between the source and the measuring instrument fixed at 20 cm. The performance of each detector was compared by moving the desk towards the door at intervals of 0 cm, 30 cm, and 75 cm, for a total of 80 measurements. The statistical significance of these results was verified using non-parametric testing. The GM tube-based detector exhibited an approximate 25% reduction in radiation dose when compared to 0.85 mu Sv/h measured in a non-magnetic environment. In a measuring device utilising a NaI(Tl) detector, the counts decreased by approximately 80% compared to 15,215 counts measured in a non-magnetic environment, and it was confirmed that measurement was impossible at the center position. This study is considered to provide fundamental data for evaluating the practicality of radiation measurement instruments in the event of radioactive contamination under high magnetic field conditions.

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