An X-ray fluorescence technique for in vivo determination of lead concentration in a bone matrix

We have previously reported the in vivo detection of lead in the skeleton of man by means of X-ray fluorescence analysis using a 740 MBq 57Co source for excitation and a 1 cm(3) Ge(Li) detector for registration of the Pb Kalpha and Kbeta radiation. The varying geometry, density and atomic composition of the tissues of interest (mainly fingers) introduce several problems in estimation of the true concentration of a given element. A two-component cylindrical finger phantom was therefore constructed from silica paraffin wax and animal bone ash. The diameter of the finger bone was estimated from X-ray examinations in two orthogonal projections. The bone mineral concentration was then estimated from the quotient of the number of coherent and Compton scattered primary photons. The lead concentration in the finger bones was then derived from a measurement on a finger phantom made of silica paraffin wax and bone ash with the same size and bone mineral concentration as the real bone. The minimum detectable lead concentration in a finger bone was 14 microgram g(-1) for 15 min measuring time. The lead concentration measured in workers from a metal industry was found to be in the range of 40-100 microgram g(-1).