Otimização da metodologia de monitoração in vivo de 123I na tireoide em trabalhadores que atuam na produção de radiofármacos

Abstract

123I is a radionuclide used for diagnosis in nuclear medicine. Its production in Radiopharmacy Centers poses a risk of external and internal exposure to the workers involved in this practice. Controlling this type of exposure through individual monitoring is necessary to estimate the magnitude of occupational doses. The In Vivo Monitoring Laboratory (LABMIV-IRD) develops techniques aimed at meeting the demand for in vivo monitoring of workers. This paper describes the calibration of a HPGe detection system for monitoring 123I in thyroid geometry in occupationally exposed individuals (OEI). In order to obtain the calibration curve in Efficiency (cps/dps) vs Energy (keV), it is used a thyroid-neck phantom containing a certified activity of 166mHo homogeneously distributed. Based on the calibration curve it is calculated the specific calibration factor for the quantification of 123I in the thyroid. The sensitivity of the technique is evaluated by determining the minimum detectable activity (MDA), minimum detectable intake (MDI) and minimum detectable effective dose (MDED). It was obtained a calibration factor of (0.0079 ± 0.0001) cps/dps, a MDA of 5Bq, a MDI of 2.78x106 Bq and a MDED of 3.23x10-1 mSv. The technique is sufficiently sensitive for in vivo measurement of 123I in the thyroid and is suitable for the monitoring of workers occupationally exposed to this radionuclide in  radiopharmaceutical production plants.