Evaluation of 99mTc-dextran as a lymphoscintigraphic agent in rabbits

Abstract

Dextran (clinical grade, average mol. wt. 82,200) was labelled with 99mTc and the labelling efficiency was checked by paper and thin-layer chromatography and electrophoresis. The amount of free 99mTcO-4 was always less than 1%. The radiopharmaceutical was injected ID into the web space in hind legs of ten rabbits (200-600 microCi/0.05 ml). Scintigrams were taken at 10-min intervals up to 3 h in three rabbits. The injection site and the hind legs were massaged after injection in the other seven rabbits and scintigrams were taken at 10-min intervals up to 2 h. Blood samples were obtained at 5, 15, 30, 90 and 120 min in both groups. In addition a 180-min sample was also taken in the first group. At the end of the study the rabbits were killed and the popliteal lymph nodes and the organs were removed to be weighed and counted. Our results indicated a high concentration of radioactivity in the popliteal lymph nodes and massage at the injection site increased the average uptake of the popliteal lymph node from 1.12% +/- 0.77% to 4.28% +/- 1.57% at 3 and 2 h, respectively (P less than 0.001). In scintigrams the lymph channels and the nodes were very well visualised. The blood radioactivity levels were too low to present a background problem. With massage 30% of the injected dose was removed from the injection site in 2 h. We have shown that 99mTc-dextran is a good radiopharmaceutical for the visualisation of the lymph system and deserves further experimental and clinical studies.

99MTc-Dextran-Antibody Conjugates : Labelling procedures

“…In earlier reports concerning 99mTc-dextran, the authors have claimed labelling efficiencies exceeding 95% (8,9). These high yields could not be reproduced in this study.…”

“…TLC cannot separate labelled ligand from SnC1,-reduced pertechnetate or colloidal Tc (1 1). The low pH obtained in these earlier methods (8,9) promotes the formation of colloidal forms of Tc. The discrepancy between TLC and GFR demonstrated in this study indicates a lack of adequate separation by TLC.…”

“…Schwochau gives a comprehensive review of various 99mTc radiopharmaceuticals (16). Technetium-labelled dextran has been used for lymphoscintigraphy and for blood and heart imaging (8)(9)(10). Using dextran as a spacer for the labelling of polypeptides could be a useful extension of previous applications of the y9mTc-carbohydrate complex.…”

Past and Present Scenario of Imaging Infection and Inflammation: A Nuclear Medicine Perspective

“…99m Tc-dextran is a potential radiopharmaceutical for infection/inflammation imaging owing to its easy labeling procedure and economical pricing. Dextran (average molecular weight 60,000–90,000 kDa) can be labeled almost quantitatively with 99m Tc by Sn +2 reduction according to a method modified 56 from Henze and colleagues. 57 99m Tc-dextran has been evaluated in both experimental abscesses in mice 58 and arthritis in rabbits 59 and in patients with inflammatory lesions, including ulcerative colitis.…”

“…Its superiority over other agents was attributed to its smaller size and neutral charge, facilitating higher outflow to the lesion from the vascular pool compared to negatively charged proteins such as Human Serum Albumin (HSA) and HIG. 56,62…”