Direct beta measurements to determine in vivo whole-body activities of ⁹⁰Sr in residents of the Southern Urals: description of a new method

Abstract

For 44 individuals living in areas of the Southern Urals with historical ⁹⁰Sr contamination, whole-body activities of this radionuclide were investigated using a new mobile detection system. β-particles from ⁹⁰Sr/⁹⁰Y decay were measured in vivo via two proportional counters mounted in front of the forehead and above the head, respectively. In order to correct for absorption by the skin, scalp thickness was measured using ultrasonic techniques. Corrections are given with respect to self-absorption by the bone matrix and absorption by hair. A procedure is described to extrapolate from measured ⁹⁰Sr activity of the skull bone to total ⁹⁰Sr skeleton burden. As a result, ⁹⁰Sr whole-body activities of up to 50 kBq were recorded in the selected cohort. For the same individuals, ⁹⁰Sr was measured via the detection of bremsstrahlung using an established whole-body counting device. The overall results of both systems agree within 15%, but differences exceeding a factor of 2 were observed in some cases.