Variability in XRF-measured tibia lead levels

Abstract

A few studies have examined the variability in 109Cd-based K-shell x-ray fluorescence (KXRF) bone lead measurements from replicate measurements made either at the same time or over a period of time, and one of these studies has shown that the uncertainty in an individual measurement is an underestimate of the standard deviation of replicate measurements. Variability in KXRF tibia lead measurements was assessed from ten cadaver intact legs, from the bare tibiae dissected from nine of these legs, and from four in vivo volunteers. Cadaver legs underwent replicate measurements on multiple occasions. In vivo volunteers underwent single measurements of the left tibia monthly for one year. Average tibia lead levels in the cadaver legs and in vivo volunteers ranged from 6 to 50 and from 6 to 13 microg Pb per g of bone mineral respectively. The factors influencing the standard deviation of replicate measurements were investigated. Both cadaver and in vivo measurements confirmed that the uncertainty in an individual measurement is an underestimate of the standard deviation of replicate measurements, suggesting a methodological deficiency probably shared by most current 109Cd-based K-shell XRF lead measurement systems.

Associations of lead biomarkers and delta-aminolevulinic acid dehydratase and vitamin D receptor genotypes with hematopoietic outcomes in Korean lead workers

“…Tibia lead was determined with a 30-minute measurement at the left mid-tibia shaft using 109 cadmium-induced K-shell X-ray fluorescence, as previously described (24)(25)(26). For tibia lead the unit of measurement was micrograms of lead per gram of bone mineral (hereafter referred to as µg/g) (25).…”

Early experiences with the Mount Allison University four-detector X-ray fluorescence bone lead measurement system

“…Measurement uncertainties obtained from the energy spectrum curve fitting procedure can be regarded as an estimate of standard deviations expected from repeated XRF measurements [12,13]. However, actual standard deviations are generally observed to be higher [14] than the estimates obtained from measurement uncertainties. We have observed a similar trend in the case of our new system, where the standard deviation values were found to be on average 19% higher than the corresponding average uncertainty values.…”

The Influence of Bone-Density on in Vivo K X-Ray Fluorescence Bone-Lead Measurements

“…Since the coherent scatter cross section is extremely sensitive to atomic number (Z), the plaster of Paris calibration cylinders exhibit a response that differs slightly from that of human bone. This difference is accommodated by use of the coherent conversion factor (CCF), which is defined as the ratio of coherent scatter cross sections at 88.034 keV for plaster of Paris and human bone at the angle of detection (Todd et al 2000). Despite the normalization process, person-to-person variations in tissue thickness and bone mineral mass impact in vivo K-XRF measurement precision.…”