Development of L-line x-ray fluorescence instrumentation and its applications to in-vivo measurement of lead in bone

Initially, Wielopolski used x-rays from either a {sup 125}I or a {sup 109}Cd source to estimate lead (Pb) in tibial cortical bone in intact legs, postmortem, This system utilized the L{gamma} and L{Beta} x-rays of Ph with energies of 10.5 and 12.6 keV, respectively. The minimum detection limit (MDL) was considered to be comparable with existing K-line x-ray fluorescence (KXRF) instruments, namely, 20-30 ppm. The feasibility of partially polarized radiation was assessed from a {sup 125}I source on Pb (NO{sub 3}){sub 2}, (10,000 ppm) dissolved in water. Reduction of the detector total count rate was observed by a factor of two; and reduction in background by the same factor was appaent. This preliminary study suggested that, with proved design, the MDL might be lowered by a factor of five. A second post-mortem study was carried out using an {sup 125}I source. Tibial Pb concentration at the site of irradiation was subsequently measured by graphite furnace atomic absorption spectroscopy; the latter results ranged from 15 to 35 {mu}g Pb/g wet weight. The MDL for this instrument, calculated by multiplying the square root of background counts by a factor of 3, was estimated to be 22 ppm. The correlation coefficient between LXRFmore » measurements and those carried out by atomic absorption was 0.90 (p < .03). In the same study, the use of a {sup 109}Cd source produced a higher degree of partial polarization with improvement in the sensitivity of the instrument. {sup 109}Cd was preferable, because its photoelectric cross section is higher than that of {sup 125}I.« less