Lymph kinetics with technetium-99m labeled radiopharmaceuticals. Animal studies

Abstract

Aim of this study was to characterize suitable technetium-99m labeled tracers for lymphoscintigraphy by comparative animal tests. To evaluate the influence of the particle size and the organ tracer-uptake on lymphtransport animal experiments were performed on six different agents (including one control group). Activity distributions were examined in Sprague-Dawley-rats by lymphoscintigraphy; the maximum uptake (count-rate) of the whole body and in lymph nodes were analyzed by regions-of-interest-technique, respectively. Additionally, for characterization of lymphatic and extralymphatic traceruptake an intra-individual relative count-rate ratio of the liver, lung, kidneys, and spleen has been calculated following organ extraction. Organ specific differences of distribution were clearly demonstrated. Our results indicate that the kinetics of lymphoscintigraphic (99m)Tc-bound agents substantially depends on particle size. Reliable transport from the interstitium to initial lymph vessels and lymph node uptake suggested for tracers suited for lymphoscintigraphy a median size of about <100 nm. Our data could improve standardization of diagnostic methods and lead to an objective consideration of therapeutic procedures.