131-I intake survey and effective dose calculation for personnel in a nuclear medicine department

Abstract

The staff of a nuclear medicine department is subject to the risk of 131-I intake as consequence of oversights in the radiation safety procedures, the occurrence of an accident, or malicious acts. The intake can be estimated by using a detection system based on NaI(Tl) or HpGe. This paper presents a methodological proposal for the use of a gamma-camera for detection of occupational intakes of 131-I in the Nuclear Medicine staff. We used a Siemens e.cam gamma camera (GC) as the radionuclide intake detection system. GC sensitivity and minimum detectable activity were determined to quantify activity retained in the thyroid gland. A whole-body anthropomorphic phantom REMCAL was also used to simulate and quantify the intake in the thyroid gland. To estimate the minimal uptake and the minimal committed effective dose E(50) that can be quantified with the gammacamera, the AIDE (Activity and Internal Dose Estimates) software was used. The gammacamera can detect 131-I activity in thyroid, as low as 175 Bq without collimators, and 5948 Bq with high-energy collimators. The calculation of E(50) shows to be as low as 5% of the annual limit. This work has shown the utility of the gammacamera to detect intakes of 131I and to estimate the E(50).