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

Our purpose was to evaluate the safety profile and biodistribution behavior in healthy human volunteers of the new myocardial perfusion tracer bis[(dimethoxypropylphosphanyl)ethyl]ethoxye-thylamine N,N'-bis(ethoxyethyl)dithiocarbamato nitrido technetium (V) ( 99m Tc-N-DBODC). Methods: Ten healthy male volunteers were injected with 99m Tc-N-DBODC under both stress and rest conditions. Anterior and posterior planar γ-camera images were collected at 5,30,60,240, and 1,440 min 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, 99m Tc-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% ± 0.13%, 1.16% ± 0.07%, and 10.85% ± 1.72%, respectively, of administered activity. Under stress conditions, heart uptake was significantly higher (2.07% ± 0.22%). Radioactivity in the liver decreased to 3.64% ± 0.98% and 2.37% ± 0.48% at 60 and 240 min, respectively, after injection. This rapid liver clearance led to favorable heart-to-liver ratios, reaching values of 0.74 ± 0.13 at rest and 1.26 ± 0.28 during exercise 60 min after tracer administration. Radiation 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 99m Tc-N-DBODC will allow SPECT images of the left ventricle to be acquired early and with excellent quality.