Integrated spatiotemporal assessment of ambient radiation fields in a nuclear medicine department using OSL and time-resolved Geiger–Müller monitoring

Occupational radiation protection in nuclear medicine is challenged by ambient radiation fields that vary both spatially and temporally. This variability arises from routine radiopharmaceutical handling and injected patients, who become temporary mobile radiation sources. Conventional surveillance based on passive dosimetry provides cumulative information but cannot resolve short-term operational fluctuations. This study integrated area-mounted optically stimulated luminescence (OSL) dosimetry with time-resolved Geiger-Müller (GM) survey monitoring to characterize both spatial dose distribution and temporal dose-rate behavior in a clinical nuclear medicine department. Monthly ambient dose equivalent, H*(10), was measured at 34 positions grouped into 14 functional areas across controlled, supervised, and uncontrolled zones, while ambient dose rate was recorded at 1-s intervals during routine working hours (08:00-16:00 h) over four weeks. Estimated annual effective dose (AED) and excess lifetime cancer risk (ELCR) were derived from the OSL data. The syringe placement area showed the highest monthly H*(10) (0.405 mSv month⁻¹), followed by the patient waiting room (0.288 ± 0.214 mSv month⁻¹) and injection room (0.204 ± 0.101 mSv month⁻¹). The patient waiting room also recorded the highest four-week mean dose rate (1.21 ± 0.24 µSv h⁻¹). Functional-area AED indicators ranged from 1.18 to 5.30 mSv y⁻¹, indicating location-specific variation in the annualized exposure estimates. The between-zone difference in H*(10) was not significant (p = 0.262), whereas variation among controlled-area locations was significant (p = 0.046). Time-resolved monitoring further revealed transient dose-rate peaks not captured by cumulative dosimetry. Integrated monitoring may provide a more complete basis for spatial prioritization and workflow-informed optimization in nuclear medicine workplaces.