Polarised x-rays in XRF-analysis for improved in vivo detectability of cadmium in man

Abstract

A technique was described for the in vivo XRF[X-ray fluorescence]-analysis of Cd in the kidney cortex of man using plane polarized photons for excitation. The polarized photons were produced by scattering the radiation from an X-ray tube (W anode, 150 kV, 15 mA) in a polymethylmethacrylate disc at a 90.degree. angle. The beam paths (X-ray tube to scatterer, scatterer to sample, sample to detector) represented 3 mutually orthogonal directions. The minimum detectable concentration for a counting time of 1800 s and a skin-kidney distance of 30 mm was 8 .mu.g/g. This was a factor of 2.5 lower than earlier methods with direct excitation using the 59.5 keV photons from 241Am. The energy imparted was lowered from 0.4 to 0.2 mJ. The Cd concentration in the kidney cortex of 6 occupationally exposed persons varied between 15-170 .mu.g/g.