PLASMA EXUDATION IN THE SKIN MEASURED BY EXTERNAL DETECTION OF CONVERSION ELECTRONS

A novel technique for measurement of plasma exudation in the skin is d escribed, Transferrin labelled in vivo with indium-113m is used as a p lasma tracer. The conversion electrons from In-113m are detected with a polystyrene crystal mounted on a photomultiplier tube, Owing to the short range of the electrons in tissue, background radiation from trac er circulating in underlying tissue will be very small, allowing plasm a exudation in the skin to be detected with a high signal to noise rat io. The characteristics of the detector system are described in model experiments using sheets of mylar to simulate soft tissue, The acute i nflammatory response to histamine provocation was studied in guinea pi g skin, A dose-related increase in count rate representing vasodilatat ion and plasma exudation was detected over the skin after histamine pr ovocation, The electron radiation system appears suitable for detectio n of low levels of superficial radioactivity and for pathophysiologica l studies of the skin.