Calibration for in vivo monitoring of thyroid of exposed population at risk of intakes of radioiodine isotopes due to a nuclear or radiological emergency

Abstract

This work presents an improvement of the calibration of a broad energy germanium detector (BEGe) using age dependent neck-thyroid phantoms for thyroid monitoring of exposed individuals (workers and members of the public), allowing the detection and quantification of incorporated radioiodine isotopes in a nuclear medicine frame or in case of accident of a nuclear reactor.A BEGe detector was calibrated using a family of age-dependent thyroid-neck phantoms that simulate thyroids of 1, 5, 10, 15 year-old children and (male and female) adults, based in ICRP Publication 8 (ICRP, 2002) and ANSI 13.44 Standard (ANSI, 2014).The calibration of the BEGe detector for all neck phantoms was performed with the same counting geometry, centered under the BE Ge detector and at the same distance of 15 cm. Using same counting parameters allows to compare efficiency curves of thyroid monitoring depending with age. The in vivo measurements with the BE Ge detector allow to identify X rays and gamma emissions between 10 and 1000 keV with a great resolution and to quantify activities of radioiodine isotopes in the thyroid of exposed population.Calibration curves have been obtained for different sizes of the thyroid, depending with age. This study of counting efficiency using the main energies of the most important radioiodine isotopes result in accurate activity calculations. Detection limits were obtained for each radioiodine isotope, using blank phantoms of each age.