RADIOISOTOPIC ASSESSMENT OF EXTRAVASCULAR ALBUMIN AS AN INDEX OF LYMPH TRANSPORT

Abstract

During the recent investigations into dosimetric problems of endolymphatic therapy we became acutely aware of the need for a quantitative and physiologic means for assessing lymphatic transport (1). Cannulation of efferent lymphatic ducts to observe flow is the most quantitative method available, however, this method is neither physiologic nor practical as a routine clinical tool.

The rate of isotope appearance in a point distal to an interstitial isotope injection has been used by many as an index of lymphatic flow (2). Radiocolloid injection into the foot followed by assessment of isotopic activity over the groin as a radiocolloid transit time, although advocated by some, is neither physiologic nor quantitative. The toe to groin transit time is easy to perform, but limited by the problems of in­ constant variables i. e. isotope diffusion from the interstitial injection, peripheral lymphatic pick-up of the radiocolloid which may be influenced by the interstitial injection, and lymph node trapping of the radiocolloid (e.g. popliteal nodes) which may not be constant and thereby, affect the ultimate shape of the isotopic accretion curve at a site cephalad to the node. In view of these considerations, if one wishes to study only lymphatic transport, it would seem more reasonable to select a labeled substance which is not accreted to variable extents by the lymphatic nodes in the interspersing area from the sites of injection to the site of assessment.