Secondary x-ray fluorescence for in vivo transdermal absorption measurements

Abstract

A modification of an X-ray fluorescence (XRF) technique that could be applied to the noninvasive measurement of transdermal absorption in human subjects with a low absorbed radiation dose was investigated. Secondary X-rays that were produced in a samarium foil by an isotopic 241Am source were used to induce iodine Kα X-rays in an iodine-containing compound. The disappearance of this compound was measured following topical administration to a human volunteer. The use of the secondary X-ray fluorescence technique resulted in an 11-fold reduction in the absorbed radiation dose to the skin compared to conventional XRF bringing the technique within acceptable dosimetry limits for human studies.