In the past, the main research and use of scintillators in extreme environments were mainly limited to high energy physics and the well-logging industry, but their applications are now expanding to reactor monitoring systems, marine and space exploration, nuclear fusion, radiation therapy, etc. In this article, we review and summarize single-crystal inorganic scintillator candidates that can be applied to radiation detection in extreme environments. Crucial scintillation properties to consider for use in extreme environments are temperature dependence and radiation resistance, along with scintillators’ susceptibility to moisture and mechanical shock. Therefore, we report on performance change, with a focus on radiation resistance and temperature dependence, and the availability of inorganic scintillator for extreme environments—high radiation, temperature, humidity and vibration—according to their applications. In addition, theoretical explanations for temperature dependence and radiation resistance are also provided.

Study Design. Measurement of radiation dose from C-arm fluoroscopy during a simulated intraoperative use in spine surgery. Objective. To assess how the radiation dose is affected by changes in the types of thyroid shields used and by the arrangements or ways in which they are worn during the intraoperative use of C-arm fluoroscopy. Summary of Background Data. Although the danger to the thyroid from exposure to radiation is well known, there are no guidelines for the proper use of thyroid shields. Methods. Two photoluminescence dosimeters were used to measure the dose of scattered radiation arriving at the location of the thyroid in a whole-body phantom in the position of the surgeon. On an operating table beside this setup was an anthropomorphic chest phantom representing a patient for which treatment with C-arm fluoroscopy was simulated. Radiation doses were measured using 3 different arrangements of the thyroid shield: worn tightly, worn loosely, and worn loosely with a bismuth masking reagent. The same tests were performed using 2 kinds of thyroid shield: lead and lead-equivalent. Results. For the lead-shield group, radiation doses were measured in 3 arrangements; worn tightly, worn loosely, and worn loosely with a bismuth masking reagent, for which the results were 1.91 ± 0.13, 2.35 ± 0.22, and 1.86 ± 0.13 μSv/min, respectively. Wearing the shield tight against the throat and wearing it loose with a bismuth masking reagent led to lower radiation exposure levels than by simply wearing the shield loosely (P ≤ 0.001). For the lead-equivalent shield group, doses were measured for the same 3 arrangements, for which the results were 1.79 ± 0.12, 1.82 ± 0.11, and 1.74 ± 0.12 μSv/min. Lower scattered radiation doses were delivered to the thyroid in the lead-equivalent thyroid shield group compared with the lead thyroid shield group (P ≤ 0.001). The unshielded thyroid group received a radiation dose of 16.32 ± 0.48 μSv/min. Conclusion. The use of some form of thyroid shield is essential during the use of C-arm fluoroscopy. It was found that the best way to reduce scattered radiation exposure to the thyroid was wearing the thyroid shield tightly or wearing it loosely in combination with a bismuth masking reagent. Level of Evidence: 2

The O-arm system has recently been introduced and has the capability of combined two-dimensional (2-D) fluoroscopy imaging and three-dimensional computed tomography imaging. In this study, an orthopaedic surgical procedure using C-arm and O-arm systems in their 2-D fluoroscopy modes was simulated and the radiation doses to susceptible organs to which operators can be exposed were investigated. The experiments were performed in four configurations of the location of the X-ray source and detector. Shielding effects on the thyroid surface and the direct exposure delivered to the surgeon's hands were also compared. The results obtained show that the O-arm delivered higher doses to the sensitive organs of the operator in all configurations. The thyroid shield cut-off 89 % of the dose in the posteroanterior configuration of both imaging systems. Thus, the operators need to pay more attention to managing radiation exposure, especially when using the O-arm system.

This study was performed to measure the equivalent scattered radiation dose delivered to susceptible organs while simulating orthopaedic surgery using conventional and mini C-arm fluoroscopy. In addition, shielding effects on the thyroid, thymus, and gonad, and the direct exposure delivered to the patient’s hands were also compared. A conventional and mini C-arms were installed in an operating room, and a hand and an operator phantom were used to simulate a patient’s hand and a surgeon. Photoluminescence dosimeters were used to measure the equivalent dose by scattered radiation arriving at the thyroid, thymus, and gonad on a whole-body phantom in the position of the surgeon. Equivalent scattered radiation doses were measured in four groups: (1) unshielded conventional C-arm group; (2) unshielded mini C-arm group; (3) lead-shielded conventional C-arm group; and (4) lead-shielded mini C-arm group. Equivalent scattered radiation doses to the unshielded group were significantly lower in the mini C-arm group than those in the conventional C-arm group for all organs. The gonad in the lead-shielded conventional C-arm group showed the highest equivalent dose among operator-susceptible organs, and radiation dose was reduced by approximately 96% compared with that in the unshielded group. Scattered radiation was not detected in any susceptible organ in the lead-shielded mini C-arm group. The direct radiation dose to the hand phantom measured from the mini C-arm was significantly lower than that measured from the conventional C-arm. The results show that the equivalent scattered radiation dose to the surgeon’s susceptible organs and the direct radiation dose to a patient’s hand can be decreased significantly by using a mini C-arm rather than a conventional C-arm. However, protective lead garments, such as a thyroid shield and apron, should be applied to minimize radiation exposure to susceptible organs, even during use of mini C-arm fluoroscopy.

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The nuclear accident that occurred in Fukushima, Japan, in 2011, resulted in considerable radiation leaks and mass exposure owing to an insufficient initial response to the disaster. To prevent similar disasters in the future, their cause should be identified, analyzed, and addressed using radiation-monitoring systems. The core component of a radiation-monitoring system is the gamma camera. It consists mainly of a gamma detector and a collimator. We proposed a diverging collimator that incorporates a novel concept of a curved surface such that the collimator hole length is constant for all the incident hole angles. Therefore, the sensitivity is likely to be more uniform across the field of view (FOV) compared with the case of the conventional flat collimator. Through a simulation study, we determined the collimator parameters and compared the performance of the curved collimator with that of the conventional flat collimator. The results revealed the feasibility of achieving higher uniform sensitivity, up to 10.5% at the edge of the FOV by using the proposed curved collimator. The average peak-to-background ratio (PBR) of the curved collimator was determined to be higher by 10.8% across the entire FOV. This indicates that it produced a more distinct signal than the flat collimator. In our future research, we intend to fabricate a curved collimator and evaluate its performance experimentally.