Estimation of the Effective Dose of Radiation Workers: Optimization Based on the Weight Percentile

Abstract

Radiation workers might be exposed to polyenergetic photon radiation beams at different directions in their working environments. In this regard, their effective dose (E) should be accurately estimated using a two-dosimeter algorithm (TDA), based on the measurements of two thermoluminescent dosimeters (TLDs) or film badges that are mounted on the front and back of the body. However, considering different human anatomies, radiation workers may have a variety of weight percentiles. This work sought to find whether TDA obtained for the reference weight percentile (50th) can be used for higher weight percentiles (including; 65th, 75th, 85th, and 95th). MCNPX was used to simulate different weight percentiles on the revised ORNL phantom by adding extra layers of muscle and adipose on the torso. Then front and back TLD responses were calculated for external beam photon energies of 40 keV to 10 MeV in different irradiation geometries. The results revealed that E value declines with increasing the weight percentile. In this study, three TDA were investigated consisting of Eest = 0.73 Rf + 0.53 Rb (73/53), Eest = 0.55 Rf + 0.50 Rb (55/50), and Eest = 0.70 Rf + 0.30 Rb (70/30). The ratio of Eest/E was calculated for each TDA in different energy bins and weight percentiles. Results obtained using the 55/50 and 70/30 showed higher underestimation for most of the energy bins, especially for PA and AP geometries. Compared to these two TDA, the 73/53 algorithm resulted in higher overestimation for RLAT and LLAT geometries for the same energy bins. Variation of the algorithms showed a similar trend for the studied weight percentiles. To conclude, results obtained by TDA for the 50% weight percentile are applicable for weight percentiles >50%.