THYMON

THYMON is a compact NaI(Tl)-based detector specifically conceived to fast, yet reliably, measure I-131 contamination in thyroid. Its compactness, ruggedness, light-weight, together with its simple and intuitive built-in software interface, make the device perfectly suited for emergency screening applications. The instrument can be used either hand-held or hands-free. The instrument is composed by three main subparts:

• Detector probe: a 1.5” x 1.5” collimated NaI(Tl) crystal coupled to a SiPM matrix and extremely compact readout electronics and MCA
• Extendable support: designed as both table-top and standalone, providing the possibility of hands-free operation
• Control tablet: rugged, IP65-rated capacitive touchscreen designed for reliable use in harsh environments

The probe mechanics is specifically designed to ensure optimal positioning with respect to the thyroid, guaranteeing excellent detector alignment and minimizing positioning uncertainties.

Intuitive and comprehensive control software integrates advanced automatic calculation routines, requiring no operator intervention. Data are stored locally on the tablet and can be easily reviewed or downloaded for advanced post-processing and analysis.

The automatic I-131 activity calculation is given for pre-defined age groups: 1 yo, 5 yo, 10 yo, 15 yo, Adult Female, and Adult Male. Additional age groups can be defined by the User. Counts-to-activity conversion coefficients are calculated by dedicated Monte Carlo simulations based on detailed detector and thyroid numerical models. The instrument response function was validated through experimental measurements using physical age-dependent neck phantoms at CIEMAT. The results demonstrated excellent performance across all age groups and full compliance with IEC 61582 requirements.

The measured activity is compared against two user-defined threshold levels, independently set for each age group, according to the two Action Levels logic.

An MDA as low as about 100 Bq can be achieved in 2-minutes screenings, which can be further lowered enabling the automatic background subtraction.