Whole-Body Biodistribution and Radiation Dosimetry of the New Cardiac Tracer 99mTc-N-DBODC

Our purposewas to evaluate the safety profile andbiodistribution behavior in healthy human volunteers of the new myocardial perfusion tracer bis[(dimethoxypropylphosphanyl)ethyl]ethoxye-thylamineN,N9-bis(ethoxyethyl)dithiocarbamatonitrido technetium (V) (99mTc-N-DBODC). Methods: Ten healthy male volunteers were injected with 99mTc-N-DBODC under both stress and rest conditions. Anterior and posterior planar g-camera images were collected at 5, 30, 60, 240, and1,440min after injection,with organ uptake quantified by region-of-interest analysis. Tracer kinetics in body fluids were determined by collecting blood and urine samples at different time points. Results: After injection, 99mTc-N-DBODC showed significant accumulation in the myocardium and prolonged retention. Under rest conditions, uptake in the heart, lungs, and liver at 5 min after injection was 1.67 % 6 0.13%, 1.16 % 6 0.07%, and 10.85 % 6 1.72%, respectively, of administered activity. Under stress conditions, heart uptake was significantly higher (2.07%6 0.22%). Radioactivity in the liver de-creased to3.64%60.98%and2.37%60.48%at60and240min, respectively, after injection. This rapid liver clearance led to favor-ableheart-to-liver ratios, reaching valuesof 0.746 0.13at rest and 1.266 0.28 during exercise 60min after tracer administration. Ra-diation dose estimates were comparable to those obtained with other myocardial perfusion cationic compounds. Conclusion: The high uptake in the myocardium and the fast liver washout of 99mTc-N-DBODC will allow SPECT images of the left ventricle to be acquired early and with excellent quality. Key Words: cardiac perfusion imaging; monocationic com-plexes; nitrido complexes; 99mT