A Methodology to Estimate Radiation Dose Reported On a Personal Radiation Monitor
V Juneja*, N Busse, A Jones, UT MD Anderson Cancer Center, Houston, TXTU-A-116-8 Tuesday 8:00AM - 9:55AM Room: 116
Purpose: The purpose of this study was to estimate the expected reading on a personal radiation monitor (PRM) in a fluoroscopy procedure and to determine what information can be deduced from PRM reports. Our institution received a PRM report indicating a deep dose equivalent (DDE) exceeding our ALARA III level (1250 mrem) during a monitoring period. The employee (a radiation therapist) reported she underwent a 2 hour upper GI fluoroscopy examination and her PRM was in her purse 1 meter away during the procedure.
Methods: Typical, minimum, and maximum dose area products (DAP) and x-ray field sizes (FS) for upper GI examination were estimated based on a literature review. The ratio of DAP and FS gave an estimate of the entrance air kerma (EAK). The air kerma (K) at the location of the PRM was calculated by multiplying the EAK by the side-scatter fraction at 1 meter. K at the PRM was corrected to 1 cm tissue depth to estimate DDE.
Results: The DDE based on the scenario reported was estimated to be 12 mrem. Minimum and maximum readings were estimated as 3 and 26 mrem, respectively. If the reported DDE was due to the upper GI examination only, the EAK would be approximately 30 Gy. The PRM report also noted that imaging results were inconclusive. Shallow dose equivalent (SDE) was 5% less than DDE.
Conclusions: The scenario reported by the employee is highly unlikely to have resulted in the DDE observed on the PRM. Reported beam quality from the PRM report and the relative ratio of shallow to deep dose suggest a higher energy beam (such as scatter in a radiation therapy room) to be the more likely cause.