Lymph kinetics with technetium-99m labeled radiopharmaceuticals

Abstract

Summary Aim of this study was to characterize suitable technetium- 99m labeled tracers for lymphoscintigraphy by comparative animal tests. Animals, methods: 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. Results: Organ specific differences of distribution were clearly demonstrated. Our results indicate that the kinetics of lymphoscintigraphic 99mTc-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. Conclusion: Our data could improve standardization of diagnostic methods and lead to an objective consideration of therapeutic procedures.