In vivo measurement of lead in bone using X-ray fluorescence

Abstract

The factors affecting the accuracy and minimum detectable concentration of in vivo tibia lead measurement are discussed, and it is demonstrated that the use of a 109Cd source in a backscatter geometry and using the 88 keV coherently scattered photon for normalisation optimizes both criteria. The measurement is shown to be independent of variations in source-sample distance, thickness of overlying tissue and tibia size and shape. Applying the same technique in vitro to samples of human tibia and metatarsals, it is shown that the results are not significantly different (p approximately equal to 0.9) from atomic absorption spectrometry results from another laboratory. The results of Monte Carlo dose distribution calculations are presented and compared with measurements using thermoluminescent dosemeters: the mean absorbed dose to a 20 cm leg section is less than 0.1 mGy (10 mrad) and the maximum absorbed skin dose is 0.45 mGy (45 mrad). For this dose the minimum detectable lead concentration is 10 micrograms g-1. Finally, the technique has been applied to groups of normals and occupationally exposed workers, and the means have been shown to be significantly different, namely 10 and 31 micrograms g-1 respectively. In the normal subjects tibia lead correlated strongly with age (r = 0.63, p less than 0.001).

A Longitudinal Study of Chronic Lead Exposure and Physical Growth in Boston Children

“…We measured bone lead in the tibia and patella of each patient using our prototype K-XRF instrument (ABIOMED, Inc., Danvers, MA). The physical principles, technical specifications, and validity of K-XRF instruments are described in detail elsewhere (28)(29)(30).…”

The Use of K X-Ray Fluorescence for Measuring Lead Burden in Epidemiological Studies: High and Low Lead Burdens and Measurement Uncertainty

“…The unit of measurement is in micrograms lead/gram bone mineral. Previous authors have outlined the close correspondence between this unit ofmeasurement and micrograms oflead per gram of bone ash (12).…”

“…The unit of measurement derived is in micrograms of lead/gram bone mineral, an accurate proxy for micrograms of lead/gram bone ash (12). The instrument provides, in addition, an estimate ofmeasurement uncertainty (the expected standard deviation of multiple measurements at the same site) that is theoretically dependent on the duration ofthe measurement and the mass ofbone being measured and relatively independent of the actual lead concentration.…”

Bone lead (Pb) content at the tibia is associated with thinner distal tibia cortices and lower volumetric bone density in postmenopausal women

“…Because actual number of counts may fall below those predicted by the background curve, bone lead measurement values <0 μg lead/ g bone mineral were possible. Bone lead measurements of the calcaneus and tibia have previously been shown to be reproducible with a median uncertainty of 4.26 μg lead/g bone [23] and valid as compared to atomic absorption spectrometry of autopsy samples [24].…”