Room: Exhibit Hall | Forum 9
Purpose: The adverse health effects of human lead (Pb) exposure were studied for the past several decades. Research led to measures (removal from common chemicals) that saw a decrease in the Pb exposure. Health concerns still remain in developing countries and in children where developmental problems were linked to very low Pb blood concentration (<10 Î¼g/dL). Since 95% of the human Pb burden is in the bone, its Pb concentration is a better metric of exposure than blood Pb used in clinical studies. The L-shell x-ray fluorescence (LXRF) is a bone Pb measurement method pioneered in the 1980s which uses an x-ray tube for Pb excitation. In an in vivo bone Pb measurement, x-ray attenuation in the soft tissue overlying the bone is required to convert LXRF data into Pb concentration. We recently developed a grazing-angle XRF method which enhanced Pb detection by reducing x-ray scatter. Here we tested the measurement of the linear attenuation coefficient of a soft tissue phantom (Âµ) using an x-ray transmission setup.
Methods: A plaster-of-Paris bone phantom doped with Pb (74 Âµg/g concentration) was covered by a cylindrical-shell (15 mm inner radius) polyoxymethylene (POM) soft tissue phantom. Two 1-mm and 3-mm thick phantoms were used. The poP-POM phantom was placed between the detector and the beam and moved across the beam in 20 and 100 Âµm steps using a positioning stage. One 10-s x-ray spectrum was acquired for each position. The scattered bremsstrahlung data of each x-ray spectrum was binned and reduced to a 14-22 keV energy range attenuation data.
Results: The measured Âµ values at each photon energy were within 5% of the calculated values using the NIST photon cross section data and the POM elemental composition and mass density.
Conclusion: The results demonstrated a phantom-based calibration method for LXRF bone Pb concentration measurements.