Study of 99mTc-DMSA biodistribution in experimental animals

Abstract

99mTc-DMSA, succimer (99m Tc), is a radiopharmaceutical commonly used in nuclear medicine for renal function evaluation by imaging. In order to achieve adequate labeling of the product with good radiochemical yield and standardized biological distribution, the interval of 185 - 3700 MBq should be kept in a maximum volume of 3 mL for product labeling. Moreover, one should avoid exposing the reconstituted solution to oxygen and using the product after four hours post labeling. The aim of the study was to quantify and evaluate the influence of different DMSA complexes on biological distribution of the radiopharmaceutical in experimental animals, taking in account variations in the labeling parameters. Radiochemical purity was determined by paper and thin layer chromatography using both acetone/Whatman 3MM, 0.9% NaCl/TLC-SG and npropanol/ H2O/acetic acid (4:3:1 V/V/V)/TLC-SG systems respectively for quantification of 99mTcO4 - and 99mTcO2 plus some 99mTc-DMSA complexes. The labeling activity did not significantly affect the extent of the main complex generation. The presence of oxygen and the concentration of 99Tc did not markedly change the percentage of the radiochemical impurities in the preparation. Radiochemical purity tests of the DMSA-99mTc based on IPEN-CNEN DMSA-TEC reagent and on another producer’s reagent showed similar results. Although the routine method used by IPEN-CNEN to determine the radiochemical yield of 99mTc-DMSA was not able to discriminate among 99mTc-DMSA complexes, the renal uptake and the kidney to liver plus spleen uptake ratio in rats met the official compendia criteria for the radiopharmaceutical.