Earticle

Background: In hospitals, patients injected with radiopharmaceuticals can serve as mobile sources of radiation. This study estimated effective doses for medical staff from these patients. Materials and Methods: Data regarding nuclear medicine and ultrasound examinations conducted at the Cancer Institute Hospital of Japanese Foundation for Cancer Research between January and June 2008 were recorded. Same-day examinations on the same patient were analyzed. Radiation doses of clinical laboratory technicians performing ultrasound examinations were measured as an example of non-radiation workers. Results and Discussion: Among 3,055 patients, 5,223 ultrasound examinations and 3,778 nuclear medicine examinations were conducted. Furthermore, 1,614 cases had both tests on the same day; 772 ultrasounds were performed during the 2–3 hours waiting period for drug accumulation, resulting in potentially substantial radiation exposure. Furthermore, 449 ultrasound examinations were conducted post-acquisition. Positron emission tomography examinations were frequent in the nuclear medicine department. Measurements obtained from 14 clinical laboratory technicians showed effective doses ranging from 0–0.3 mSv/mo; some staff recorded 0.1–0.2 mSv/mo. Upon annualization, eight of 14 (57%) technicians exceeded the public limit of 1 mSv/yr, and the maximum dose was 1.8 mSv/yr. Conclusion: This study estimated radiation doses for medical staff, focusing on clinical laboratory technicians as non-radiation workers. It revealed that some staff members experienced higher doses, even outside of radiation-controlled areas. Although the data is old, from 2008, without detailed records of individual clinical laboratory technicians, it is the only report of its kind in the world, and we look forward to further follow-up investigations.

Background: Studies conducted among young professionals in the field of radiation protection thus far have not focused on the research environment or themes relevant to these professionals. Hence, this study aimed to investigate the demographics, research environments, and research themes of the Young Researchers Association (YRA) of the Japanese Health Physics Society to address the gaps in previous surveys, so as to provide foundational information for academic and government organizations to frame policies supporting the development and research activities of young researchers. Materials and Methods: A web-based questionnaire was distributed to YRA members between July and November 2023. The responses received were analyzed using Pearson’s chisquare test to identify factors influencing job satisfaction, intention to continue for 5 years, and research opportunities, with statistical significance set at p<0.05. Results and Discussion: Out of 126 YRA members, 66 responded, of whom 77.3% were male; 89.4% of the respondents held permanent employment positions. Approximately 65.3% of the respondents were involved in ‘dosimetry’ and ‘applications’ research and 10% focused on ‘effects’ and ‘medicine.’ A significant relationship was found between ‘intent to continue job’ and ‘employment type;’ however, no significant link was found between job satisfaction and research funding. ‘Age’ was significantly associated with research opportunities, while sex and employment type were not. Conclusion: These findings suggest the importance of supporting a wide range of research areas rather than focusing on a single theme. Increasing research opportunities for young researchers through initiatives such as mentorship programs or competitive research grants could foster the further development of radiation protection research.

Background: Low-dose computed tomography (LDCT) is gaining attention for its potential to reduce radiation exposure in clinical imaging, particularly for urinary calculi detection. However, the optimal dose and clinical efficacy of LDCT remain to be fully validated. This study aimed to identify the optimal LDCT scanning parameters using an in vitro model, then apply these findings to clinical diagnosis, and assess the efficacy of the optimal dose in detecting urinary calculi. Materials and Methods: Six distinct compositions of human urinary calculi were selected for analysis, with sizes of 1, 2, 4, and 7 mm. Stones of the same composition but different sizes were transplanted into a pork kidney, followed by computed tomography (CT) scans using decreasing doses of 120, 100, 80, 60, and 40 mAs. These scans were used to analyze the presence, size, and location of the transplanted urinary calculi. Subsequently, 150 patients with clinically suspected urinary calculi were scanned using a conventional CT dose of 120 kVp and 250 mAs, as well as the optimal low-dose parameters of 120 kVp and 60 mAs (obtained from in vitro model). Finally, the computed tomography dose index volume (CTDIvol), dose length product (DLP), and effective dose (ED) were recorded for each patient. Results and Discussion: Using the in vitro model scanning, stones of varying compositions were detected with 100% accuracy under the prescribed radiation doses. A total of 150 patients with suspected urinary calculi were included in the analysis. Both conventional-dose computed tomography (CDCT) and LDCT detected a total of 285 urinary calculi. No significant differences in image quality were observed between LDCT and CDCT (p>0.05). However, there was a substantial reduction in the CTDIvol, DLP, and ED by 81%, 79%, and 79%, respectively (p<0.05). Conclusion: LDCT shows promise in clinical practice, offering a significant reduction in radiation exposure without compromising diagnostic accuracy.

Background: This study aims to compare the pre- and post-application results of university students’ knowledge regarding radiation protection. Materials and Methods: The study was conducted on 116 students enrolled in the medical imaging and radiotherapy program. These students were administered a two-stage, 33-item radiation protection knowledge scale via Google Forms before and after the application course. The application results were analyzed as pre-test and post-test. Results and Discussion: A total of 116 students participated in the study. According to the study results, there was a difference in the students’ awareness of the radiation protection subfactor before and after the application. The primary reason for this is that observing the use of protective equipment during the application has increased their awareness. The importance of protective equipment for both worker health and patient safety has been understood. Conclusion: This study demonstrated the necessity of recording and monitoring radiation exposure during diagnosis and treatment procedures. The need to implement safety protocols to minimize the potential consequences of radiation hazards has also been recognized.

Background: Vaginal cuff brachytherapy after hysterectomy targets radiation to potential residual cancer cells. Our previous study proposed a three-ovoid applicator to improve dose coverage and stability over conventional applicators but was limited to two-dimensional plan comparisons. This study introduces a polymethyl methacrylate (PMMA)-Agar phantom for threedimensional (3D) dosimetric comparison of these applicators and verifies its applicability. Materials and Methods: Cylinder, two-ovoid, and three-ovoid applicators were compared. A PMMA frame (30 cm×20 cm×10 cm) with a central 10 cm diameter cavity for the Agar phantom was constructed. Using treatment plans delivering 3 Gy to a 5 mm thick bolus target, dose distributions were verified using Gafchromic EBT3 film (Ashland Inc.) and an Exradin A1SL thimble ionization chamber (Standard Imaging Inc.). Results and Discussion: Plan evaluations showed the three-ovoid applicator demonstrated improved dose uniformity and target coverage over conventional applicators. It yielded higher mean target doses (1.97 Gy vs. cylinder; 0.78 Gy vs. two-ovoid normal) and notably enhanced dose homogeneity, reducing a key uniformity index (D5 cm³/D99 Vol%) from 2.08 (cylinder) and 1.68 (two-ovoid normal) down to 1.61. These planned advantages were qualitatively supported by A1SL chamber and EBT3 film measurements showing dose distributions consistent with plans, experimentally verifying the three-ovoid’s dosimetric advantage using the PMMA-Agar phantom. Conclusion: In this study, we experimentally verified the three-ovoid applicator’s dosimetric advantage compared to the conventional applicators by using an in-house designed PMMAAgar phantom for vaginal cuff brachytherapy. We plan to improve the experimental 3D dose verification accuracy in the future, considering the more realistic patient’s internal organ structure using a 3D printing technique.

Background: Gamma emission tomography (GET) is one of the most reliable methods for detection of partial-defects within spent nuclear fuel (SNF). In our previous study, we developed and proposed the scintillation crystal-based GET instrument named Yonsei single-photon emission computed tomography (YSECT). However, this conventional YSECT instrument has consequential limitations related to the low inspection accuracy in the central region, which fact is due to the high density of nuclear fuel rods. This study aimed to derive, as proposed in this paper and using Monte Carlo simulation, a multisensor-based YSECT for enhancement of partialdefect detection accuracy. Materials and Methods: The gamma-ray energy spectra for gadolinium aluminum gallium garnet (GAGG), CsI(Tl), CdWO4, and PbWO4 were obtained to determine the appropriate material for image quality improvement in the central region. The shapes of the spectra and the detection efficiencies were compared among the scintillation crystal materials. The tomographic images were acquired with both conventional YSECT and the newly proposed YSECT, and their quality was compared based on the signal-to-noise ratio (SNR). Results and Discussion: CdWO4 was found to have a detection efficiency twice as high as that of GAGG, owing to its high-density despite poor light yield. Based on these results, the optimal scintillation crystal material for enhancement of detection efficiency for high-energy (>662 keV) gamma rays was determined to be CdWO4. In accordance with the optimization study, the SNR of the CdWO4 image was calculated as 7.95, which was higher than that of the GAGG image by a factor of 2. Furthermore, the SNR of the synthesis image was determined to be 9.85, which was higher than that of the single-sensor–based YSECT image by a factor of 1.59. Conclusion: Based on these results, we believe that the multisensor-based YSECT can enhance inspection accuracy for partial defects arising in pressurized water reactor-type SNF. In further studies, the effect and influence of neutrons will be evaluated and noise-reduction methods will be developed.

ackground: Beryllium-7 (Be-7), influenced by various environmental factors, is valuable for tracking radioactive material migration due to its short half-life and dynamic atmospheric distribution. These properties make Be-7 particularly useful for assessing the behavior of radioactive substances under changing environmental conditions or after radiation incidents. This study aims to establish foundational data by examining the correlation between Be-7 concentrations and environmental factors specific to the Republic of Korea. Materials and Methods: Be-7 radiation concentrations from 2013 to 2022 were collected from the National Environmental Radiation Survey Report of the Korea Institute of Nuclear Safety. Precipitation, humidity, particulate matter (PM10), and atmospheric pressure data were sourced from the Korea Meteorological Administration and the Ministry of Environment. Monthly and seasonal trends were analyzed, and Pearson correlation coefficients were used to assess the relationship between Be-7 concentrations and environmental factors, with the significance evaluated using p-values. Results and Discussion: Analysis showed consistent nationwide trends, with Be-7 concentrations significantly decreasing each summer. Precipitation and humidity peaked in summer and negatively correlated with Be-7 concentrations, whereas PM10 and atmospheric pressure were lowest in summer and positively correlated with Be-7 concentrations. All correlations had p-values below 0.001, indicating statistical significance. Conclusion: The findings indicate a significant relationship between Be-7 concentrations and environmental factors in the Republic of Korea, offering essential data for future research on radioactive material migration and informing environmental radiation safety strategies.