In 2011, the International Commission on Radiological Protection (ICRP) recommended a significant reduction in the lens-equivalent radiation dose limit, thus from an average of 150 to 20 mSv/year over 5 years. In recent years, the occupational dose has been rising with the increased sophistication of interventional radiology (IVR); management of IVR staff radiation doses has become more important, making real-time radiation monitoring of such staff desirable. Recently, the i3 real-time occupational exposure monitoring system (based on RaySafe^TM) has replaced the conventional i2 system. Here, we compared the i2 and i3 systems in terms of sensitivity (batch uniformity), tube-voltage dependency, dose linearity, dose-rate dependency, and angle dependency. The sensitivity difference (batch uniformity) was approximately 5%, and the tube-voltage dependency was <±20% between 50 and 110 kV. Dose linearity was good (R² = 1.00); a slight dose-rate dependency (~20%) was evident at very high dose rates (250 mGy/h). The i3 dosimeter showed better performance for the lower radiation detection limit compared with the i2 system. The horizontal and vertical angle dependencies of i3 were superior to those of i2. Thus, i3 sensitivity was higher over a wider angle range compared with i2, aiding the measurement of scattered radiation. Unlike the i2 sensor, the influence of backscattered radiation (i.e., radiation from an angle of 180°) was negligible. Therefore, the i3 system may be more appropriate in areas affected by backscatter. In the future, i3 will facilitate real-time dosimetry and dose management during IVR and other applications.

The International Commission on Radiological Protection has lowered the annual equivalent eye-lens dose to 20 mSv. Although occupational exposure can be high in nuclear medicine (NM) departments, few studies have been conducted regarding eye-lens exposure among NM staff. This study aimed to estimate the annual lens doses of staff in an NM department and identify factors contributing to lens exposure. Four nurses and six radiographers performing positron emission tomography (PET) examinations and four radiographers performing radioisotope (RI) examinations (excluding PET) were recruited for this study. A lens dosimeter was attached near the left eye to measure the 3-mm-dose equivalent; a personal dosimeter was attached to the left side of the neck to measure the 1-cm- and 70-µm-dose equivalents. Measurements were acquired over six months, and the cumulative lens dose was doubled to derive the annual dose. Correlations between the lens and personal-dosimeter doses, between the lens dose and the numbers of procedures, and between the lens dose and the amounts of PET drugs (radiopharmaceuticals) injected were examined. Wilcoxon’s signed-rank test was used to compare lens and personal-dosimeter doses. The estimated annual doses were 0.93 ± 0.13 mSv for PET nurses, 0.71 ± 0.41 mSv for PET radiographers, and 1.10 ± 0.53 mSv for RI radiographers. For PET nurses, but not for PET or RI radiographers, there was a positive correlation between the numbers of procedures and lens doses and between amounts injected and lens doses. There was a significant difference between the lens and personal-dosimeter doses of PET nurses. The use of protective measures, such as shielding, should prevent NM staff from receiving lens doses > 20 mSv/year. However, depending on the height of the protective shield, PET nurses may be unable to assess the lens dose accurately using personal dosimeters.

Brachytherapy is a practical, effective procedure for the local treatment of cancer; it delivers a high radiation dose to a limited tissue volume while sparing the surrounding normal tissues. Although the clinical benefit of brachytherapy is clear, there have been very few studies on the radiation dose received by physicians during the procedure. Furthermore, no study has investigated the eye radiation dose received by physicians performing ¹⁹⁸Au grain (seed) brachytherapy, using an eye dosimeter. Recently, the International Commission on Radiological Protection (ICRP) recommended significantly reducing the occupational lens dose limit, from 150 to 20 mSv/yr (100 mSv/5 years). Therefore, it has become essential to evaluate the eye radiation doses of medical workers. We evaluated the eye radiation dose of a brachytherapy physician performing ¹⁹⁸Au permanent grain implantation for tongue cancer; this is the first study on this topic. The maximum eye dose was ~0.1 mSv/procedure, suggesting that it is unlikely to exceed the ICRP limit (20 mSv/yr) for the lens, unless many procedures are performed with inappropriate radiation protection. To reduce the dose of radiation received by ¹⁹⁸Au grain brachytherapy physicians, it is necessary to use additional lead shielding equipment when preparing the treatment needles, i.e., when loading the grains. This study provides useful information on radiation exposure of physicians conducting ¹⁹⁸Au permanent grain brachytherapy.

Occupational radiation exposure in nuclear medicine presents complex spatial and temporal patterns due to the use of unsealed radiopharmaceuticals and prolonged proximity to patients. Traditional passive dosimetry provides only cumulative dose values, limiting its usefulness in identifying task-specific exposures or capturing momentary fluctuations. This study applied a real-time dosimetry system capable of second-by-second measurements, combined with time-series analysis, to evaluate staff exposure during myocardial perfusion imaging using technetium-99m. Dosimeters were placed on the left and right sides of the neck and head of two radiological technologists. Dose rates were continuously recorded throughout the injection and imaging phases. The right side of the neck received the highest cumulative and peak dose rates among all sites. Although no significant difference in total dose was observed between the injection and imaging phases, specific high-exposure events were detected. Notably, ECG lead placement and post-injection handling produced dose spikes. A positive correlation was found between administered activity and dose rate at neck-level sites but not at head-level sites. These findings demonstrate the value of real-time dosimetry in identifying procedural actions associated with elevated exposure. Time-series analysis further contextualized these peaks, supporting improved task-specific protective strategies beyond the capabilities of conventional dosimetry.

Dental cone beam computed tomography (CBCT) is a diverse 3D X-ray imaging technique that has enabled clear visualization of the teeth and surrounding structures. The most common diagnostic purpose of dental CBCT examination in children is ectopic eruption and impacted teeth, and a small field of view (FOV) is often used. Since it is difficult for children to control their body movements, reducing the rotation angle is effective. However, no studies have examined the effects of different rotation angles on radiation doses to highly radiosensitive organs in children using small FOVs. The purpose of this study was to examine the effects of small FOVs (4 × 4 cm and 6 × 6 cm) and rotation angles (360° and 180°) on doses that highly sensitize organs in children using dental CBCT. The entrance surface doses to lenses, thyroid lobes, parotid glands, and sublingual glands of a pediatric whole-body phantom were measured. By reducing the FOV from 6 × 6 cm to 4 × 4 cm, the dose to the sublingual gland could be significantly decreased. Additionally, by reducing the rotation angle from 360° to 180°, the lens dose can be decreased significantly. As the rate of dose reduction varies among organs, it is important to consider the relative positions of different organs with respect to the FOV and the trajectory of the X-ray tube.