A two-dimensional K-shell X-ray fluorescence model applied to strontium measurements in a lamb bone sample*

Human bones store elements such as calcium, phosphorus, and strontium, and accumulate toxic elements such as lead. In vivo measurements of elemental bone concentration can be predominantly employed in this field to develop calibration methods that link x-ray fluorescence (XRF) measurements to concentrations. A simple and fast two-dimensional K-shell XRF (KXRF) model was developed to compute the KXRF signal of elements in bone and overlying soft tissue samples; the model is an alternative to Monte Carlo methods and could guide future bone XRF studies. Contours of bone and soft tissue cross sections were elliptical and only KXRF signals from absorption of primary photons were considered. Predictions of the model were compared to Sr KXRF measurements using the bare lamb bone (LB) and the LB with overlying leather. XRF experiments employed a microbeam from an integrated x-ray tube and polycapillary x-ray lens unit, silicon x-ray detector, and three positioning stages. Linear attenuation coefficients of the leather and LB were measured and used in the model. Measured and model-derived values of the Sr leather attenuation and Sr Kβ/Kα ratio agreed, but estimated bone Sr concentrations were likely overestimated.