Evaluation of Internal Exposure of Nuclear Medicine Staff Using In-vitro and Organ Dose Calculation Methodologies

The manipulation of a wide variety of unsealed sources in nuclear medicine results in a significant risk of internal exposure of the workers. 131 I should be highlighted among the most frequently used radionuclides because of its large application for diagnosis and therapy of thyroid diseases. The increasing use of radionuclides for medical purposes creates a demand for feasible methodologies to perform occupational control of internal contamination. Currently in Egypt, there are ∼200 nuclear medicine centers in operation but individual monitoring is still restricted to the control of external exposure. In a previous study by Rizk et al., [1], we have developed an invitro bioassay technique aimed to assessment of the intake due to inhalation of I-131 by workers in 3 Egyptian hospitals. Urine samples from 11 workers were collected after preparation and administration for I-131 and measured with HPGe detection system. In this study, given these bioassay data, we were able to estimate the average organ dose and committed effective doses of the staff working in the hospitals mentioned above over a period of 50 yrs. It would give us some confidence that the dose measure (as evaluated by MONDAL 3.0 software) might yield reasonable predictions for yet other workers (e.g., radiotherapies) and other dose routes. This paper describes the basic structure and validation of MONDAL 3.0 with a practical use of the software. It also shows if any of the workers need routine monitoring.