L-shell X-ray Fluorescence Detection of Lead in Bone and Soft Tissue Phantoms Using a Microbeam and a Grazing-Incidence Method.

Lead (Pb) is a known toxic element. Human Pb exposure was significantly reduced by removing Pb from gasoline and paints, but health concerns posed by low Pb blood (<10 μg/dL) remain. Pb accumulates in the bone, hence, exposure is best assessed via bone Pb concentration measurements, not blood Pb. Tibia bone Pb K-shell X-ray Fluorescence (KXRF) measurement method using a Cd-109 radionuclide was developed in the mid-1980s and used later for in vivo studies. Its counterpart, the L-shell X-ray Fluorescence (LXRF) method, can use the more practical x-ray tube and silicon x-ray detector devices. However, its lower sensitivity and issues with the early calibration method deemed the method as not feasible. In our lab, a microbeam from an integrated x-ray tube and polycapillary x-ray lens unit and a silicon x-ray detector were used to measure detection limits in Pb-doped plaster-of-Paris bone and polyoxymethylene (POM) soft tissue phantoms. Using a grazing-incidence XRF geometry, detection limits from 2 to 36 μg/g were obtained for POM thickness values in the 0 to 5 mm range. The study demonstrated the importance of the XRF geometry in the x-ray scatter reduction and improvement of bone Pb detection.