Personal Dosimeter Use In Australian Nuclear Medicine Practice

Introduction: Anecdotally, Australian Nuclear Medicine staff wear a single thermoluminescent dosimeter (TLD) for monitoring purposes and tend to wear their TLD in a variety of body positions including but not limited to the chest, waist and shoulder. There is a paucity of published data directly relating to the effect of placement of the TLD on whole body dose measurements. Methodology: A survey was undertaken of current protocol and procedures employed for personal radiation monitoring of occupationally exposed staff in Nuclear Medicine departments across Australia. The study design utilised a self-administered questionnaire to provide participant confidentiality. The experimental study utilised a quasi-experimental, repeated measure (within subjects) design of eight Nuclear Medicine staff volunteers. TLD data was collected for two consecutive monitoring periods of two months duration each. All participants wore two TLDs simultaneously, one positioned on the chest and the second positioned at the waist. Results: The position for the primary TLD of staff was predominantly at the waist (92.8%) with the remainder (7.2%) placing their primary TLD at the chest. A further 34.8% use a second TLD on the chest, 15.9% on the finger, 5.8% on the collar and 1.4% each for the pocket, umbilicus and under the apron. The mean x-ray / gamma ray dose for TLDs positioned at the chest was 287.5 μSv while the corresponding waist dose records had a mean of 178.8 μSv. The matched pairs t test demonstrated a statistically significant difference between matched pairs (P = 0.001) with a mean decrease in recorded doses for the waist of 108.8 μSv (95% CI of 50.2 to 167.3 μSv). Conclusion: Comparing occupational radiation doses within Nuclear Medicine departments and amongst Nuclear Medicine departments is fraught with danger. There is a need for the development of uniform policy and practice in relationship to TLD position.