LEAD BODY STORES ASSESSED IN-VIVO BY X-RAY FLUORESCENCE.
Abstract
The use of a **1**0**9Cd gamma -ray source to excite lead X-rays has furthered the development of a system for in-vivo measurement of lead in tibia. The effects of overlying tissue, variation in bone marrow size and of scattering from tissue behind the bone have been investigated using bone and leg phantoms. It is shown that normalising the lead peaks to the elastic scatter peak from the bone matrix minimises the importance of geometric uncertainties and overlying tissue depth. Measurements made on 8 tibia autopsy samples from non-occupationally exposed subjects showed lead levels ranging from 14 ppm to 51 ppm. An in-vivo detection limit of 12 ppm for a mean absorbed dose of 0. 07 mGy (7 mrad) has been established, the dose being calculated using a Monte Carlo code and measured using thermoluminescent dosimetry.