Quantitative X-ray fluorescence measurements of Pb in plaster-of-Paris bone phantoms

X-ray fluorescence (XRF) is the emission of characteristic x-rays by an excited atom. An important XRF application is the in vivo human bone lead (Pb) concentration measurement. An established method uses the K-shell XRF emissions using the Pb excitation of the gamma rays from a Cd¹⁰⁹ radionuclide. The alternative is the L-shell XRF (LXRF) method. The LXRF disadvantage is lower intensities of Pb x-rays at 10.5 and 12.6 keV; its advantage is using x-ray tube and detectors for large population studies. The unknown x-ray attenuation of the soft tissue affects the LXRF measurement. Cylindrical plaster-of-Paris (poP) bone phantoms doped with [Pb] of 0,8,16,29,59, and 74 µg/g and polyoxymethylene soft tissue phantoms of 1, 2, and 3 mm thickness were used to simulate the in vivo setting. Sr was present in the poP material and found in human bone in concentrations ~10 times higher than Pb. A new calibration method based on the XRF peak height ratio of strontium (Sr) x-rays was explored. The deviations between calculated and known Pb concentration values were within the three standard deviation interval for more than 90% of the data.