Real-time radiation dose management is important because staff members working in interventional radiology may be exposed to relatively high doses of primary and scattered radiation from the body of a patient. In this study, we investigated the dependence of energy and dose rate of the commercially available semiconductor detector named Pocket Geiger (POKEGA) for personal monitoring in diagnostic X-rays. In the energy-dependence study, a suitable metal filter and the threshold level were examined for energy compensation using a Monte Carlo calculation code. Moreover, the energy dependence of the POKEGA with an optimal metal filter was compared with that of commercially available active personal dosimeters (APDs). With an aluminum filter, the difference of the ratio of the absorbed dose of silicon to that of air was ±7% for a tube voltage of 70-110 kV and a cutoff energy of 23 keV in the calculation. The energy response of the APDs, except the PDM-122B-SHC and the POKEGA, met the required JIS standard from 50 to 110 kV. In the dose rate-dependence study, a high linearity was observed up to 2.2 mGy h using the POKEGA with an aluminum filter.
The ionisation chamber for computed tomography (CT) is an instrument that is most commonly used to measure the computed tomography dose index. However, it has been reported that the 10 cm effective detection length of the ionisation chamber is insufficient due to the extent of the dose distribution outside the chamber. The purpose of this study was to estimate the basic characteristics of a plastic scintillating fibre (PSF) detector with a long detection length of 50 cm in CT radiation fields. The authors investigated position dependence using diagnostic X-ray equipment and dependencies for energy, dose rate and slice thickness using an X-ray CT system. The PSF detector outputs piled up at a count rate of 10 000 counts ms in dose rate dependence study. With calibration, this detector may be useful as a CT dosemeter with a long detection length except for the measurement at high dose rate.
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