The feasibility of measuring silver concentrations in vivo with x-ray fluorescence.

X-ray fluorescence (XRF) has been demonstrated to be an extremely useful technique for measuring trace quantities of heavy metals in various tissues in the body. This study investigates the applicability of XRF to the measurement of silver concentrations in skin. The system chosen employs an 125I source to excite the silver K x-rays, with the source, sample and detector arranged in a 90 degrees geometry. Experiments with silver-doped skin phantoms indicate that a minimum detectable concentration of 3-4 ppm is possible in 10-20 min measurement periods. Based on estimates of silver concentrations in the skin of patients suffering from argyria, the proposed system has sufficient sensitivity to warrant further investigation into its usefulness for non-invasive monitoring of exposed populations. Specifically, such a measurement may well allow for the identification of individuals at risk of subsequently exhibiting argyria, an irreversible skin pigmentation arising from silver exposure.