Cortical porosity and the accuracy of 109Cd K XRF bone lead measurements in pre-menopausal women

Studies were performed to test whether tibia cortical porosity could create measurement artifacts in 109Cd K XRF bone lead (Pb) measurements using Pb-doped plaster of Paris phantoms with a three-dimensional (3D) printed PLA lattice. Phantoms were modelled in MCNP to test the effect of cortical porosity; heterogeneous distributions of Pb; and extremely large tissue overlay thickness on bone Pb measurement accuracy. Modelling showed that cortical porosity of the tibia did not affect the measurement accuracy; measurements were inaccurate in phantoms with extreme heterogeneous distributions of Pb. However, it is only at unrealistic levels of heterogeneity (that are unlikely to be encountered in vivo) that the measurement becomes inaccurate; and large tissue overlay thicknesses resulted in inaccurate 109Cd K XRF bone Pb measurements. When blood and 109Cd K XRF bone Pb data of morbidly obese women were excluded, age related changes in endogenous exposure to Pb were observed in pre-menopausal women.