EURADOS Intercomparison of age-dependent thyroid phantoms for thyroid monitoring in nuclear or radiological emergencies

Direct in-vivo measurement of radioiodine in the thyroid by gamma spectrometry is usually the preferred method for assessing intake of ¹³¹I. To obtain reliable values of the committed doses related to these accidental intakes, detector systems have to be properly calibrated, using age-dependent thyroid phantoms for simulating the internal contamination for individuals of different age groups. In-vivo monitoring laboratories all over the world usually use adult thyroid phantoms for calibrating purposes, however, only a few of them have age-dependent thyroid phantoms. For improving and harmonizing the calibration procedures for in-vivo thyroid monitoring, particularly for children in case of radiological or nuclear emergencies, members of the EURADOS WG7 “Internal Dosimetry” have organized and carried out an intercomparison exercise aimed at comparing different age-dependent thyroid phantoms. Intercomparison measurements were conducted at the Whole Body Counter Laboratory (WBC) of CIEMAT. This paper presents the design and development of the campaign as well as a summary of the most relevant results obtained and conclusions.