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 complicated by ambient radiation fields that vary both spatially and temporally. This variability arises from routine radiopharmaceutical handling and from patients who act as temporary mobile radiation sources after administration. Passive dosimetry provides cumulative information but cannot resolve short-term fluctuations arising during routine operations. This study integrated fixed-location optically stimulated luminescence (OSL) dosimetry with time-resolved Geiger-Müller monitoring to characterise spatial variations in ambient dose equivalent and temporal variations in dose-rate 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. Location-based estimates of annual effective dose (AED) and excess lifetime cancer risk were derived from the OSL measurements. At the functional-area level, the syringe placement area showed the highest monthlyH*(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 ± 0.24µSv h-1). Functional-area AED indicators ranged from 1.18 to 5.30 mSv y-1, reflecting spatial variation in the annualised exposure estimates.H*(10) did not differ significantly among the three zones (p= 0.262), it differed significantly among locations within the controlled zone (p= 0.046). Time-resolved monitoring further revealed transient dose-rate peaks that were not apparent in cumulative dosimetry. Integrated monitoring may provide a more comprehensive basis for spatial prioritization and workflow-informed optimisation of radiation protection.