Comprehensive Review and System-Level Safety Enhancements Following an Extremity Overexposure Incident In a Nuclear Medicine Department
Abstract
Purpose
To investigate an extremity radiation overexposure incident involving a radiochemistry technologist, determine underlying causes, and implement evidence-based corrective and preventive strategies to strengthen occupational radiation safety in nuclear medicine operations.
Methods
Routine dosimetry revealed a cumulative left index finger dose of 628.5 mSv, exceeding the International Commission on Radiological Protection (ICRP) annual extremity limit of 500 mSv. The event was prospectively reported to Singapore's National Environment Agency (NEA). A multidisciplinary review was conducted encompassing workflow analysis, shielding assessment, task observation, and cross-institutional benchmarking. Root causes identified included delayed dosimeter feedback, lack of interim escalation mechanisms, high individual workload, and suboptimal vial shielding.
Results
Immediate interventions included suspension of high-activity procedures, installation of 6-mm lead shielding, staff rotation, and deployment of an electronic personal dosimeter (EPD) system for real-time exposure tracking. Process optimization involved needle recapping modification to reduce direct hand contact, revised dispensing schedules, and vial shield replacement. Radiation monitoring frequency was increased with dual verification (NEA bimonthly, Nagase monthly). These measures resulted in a 67% reduction in extremity dose rate, from 4.0 mSv/day to 1.3 mSv/day by April 2025, stabilizing at approximately 1.1 mSv/day from June 2025 onwards.
Conclusion
The incident catalyzed a system-level reform of radiation safety governance across SingHealth institutions. Engineering and procedural enhancements—including improved shielding, workflow restructuring, and needle recapping protocols—effectively reduced extremity dose while maintaining clinical efficiency. Establishment of the SingHealth Radiation Safety Governance Committee and standardized escalation processes now ensure sustained compliance with ALARA principles and rapid response to radiological anomalies. This case exemplifies how structured, data-driven interventions can transform adverse events into enduring safety improvements.