Estimation of skeletal burden of "bone-seeking" radionuclides in man from in vivo scintillation measurements of the head
Cohen, N.; Spitz, H.B.; Wrenn, M.E.
Health Physics 33: 431-441
1977
ISSN/ISBN: 0017-9078 PMID: 201594 Document Number: 117771
A method for estimating the skeletal burden of various bone-seeking low-energy photon-emitting radionuclides, e.g., 210Pb, 241Am and 238,9Pu, was developed utilizing the technique of in vivo scintillation measurement of photon activity from human skull bones. The head (skull), which represents a structure comprising more than 12% of the skeletal mass, is surrounded by 3 NaI(Tl)CsI(Tl) dual crystal scintillation detectors to maximize counting efficiency and minimize detection variability. In addition to measuring the low-energy photons (< 100 keV) of important radionuclides known to deposit in or on the surfaces of bone, these detectors are employed to simultaneously monitor the higher energy gamma-ray spectra of natural radioactivity such as 40K. From this information it was possible to optimize the accuracy of background correction, thereby minimizing the detectable levels of a bone-seeking contaminant. Considerations of accurate phantom head construction and the precision of head counting methodology were investigated. Once the amount of activity deposited in the skull bones is determined, it is possible to estimate the contribution from the nuclide in the thoracic skeleton to in vivo measurements of activity in the lungs.