EVALUATION OF TC-99(M)-BICISATE AS A RENAL IMAGING AGENT

Tc-99(m)-bicisate (Tc-99(m)-ECD), often used as a brain perfusion agen t, is rapidly converted following intravenous injection to the polar m onoacid (Tc-99(m)-ECM) and diacid (Tc-99(m)-EC) metabolites. Such pola r metabolites, which are eliminated principally by renal clearance, ar e potential renal imaging agents. In this study, Tc-99(m)-ECD was comp ared for the first time with Tc-99(m)-EC, Tc-99(m)-mercaptoacetyltrigl ycine (Tc-99(m)-MAG3) and I-131-orthoiodohippurate (OIH) as renal imag ing agents in rabbits. Whole-body images and renograms were obtained f or all three of the Tc-99(m) agents, and pharmacokinetic parameters in cluding plasma and urinary clearance were studied for all four agents. The plasma clearance of Tc-99(m)-EC (37 mi min(-1)) was slower than t hat of Tc-99(m)-ECD (51 mi min(-1)), which could be accounted for by t he higher liver uptake of Tc-99(m)-ECD. The urinary clearance of Tc-99 (m)-ECD (35 mi min(-1)), Tc-99(m)-EC (34 mi min(-1) and Tc-99(m)-MAG3 (39 mi min(-1) was similar. The renal images obtained with Tc-99(m)-EC D were comparable to those for Tc-99(m)-MAG3 and Tc-99(m)-EC. However, liver uptake was more prominent with Tc-99(m)-ECD than with the other agents. The Tc-99(m)-ECD renogram curves showed a prolonged decrease in renal activity compared to both Tc-99(m)-EC and Tc-99(m)-MAG3. In p otential human studies, the relatively high liver uptake of Tc-99(m)-E CD superimposed on right renal activity may be a limitation. Therefore , we conclude that Tc-99(m)-ECD is less favourable when compared to ex isting renal agents due to its high extrarenal uptake and renal kineti cs.