Organ biodistribution and myocardial uptake, washout, and redistribution kinetics of Tc-99m N-DBODC5 when injected during vasodilator stress in canine models of coronary stenoses

Background. Technetium 99m N-DBODC5 is a new myocardial perfusion tracer shown to exhibit high heart uptake and rapid liver clearance in normal rats. The objectives of this canine study were (1) to compare the organ biodistribution and myocardial uptake, washout, and redistribution kinetics of Tc-99m N-DBODC5 with Tc-99m sestamibi over a period of 3 hours in a more clinically relevant large animal species and (2) to compare the myocardial uptake of Tc-99m N-DBODC5 with thallium 201 when co-injected during vasodilator stress in dogs with coronary stenoses. Methods and Results. At peak adenosine-induced hyperemia, 10 dogs with critical left anterior descending artery stenoses received either Tc-99m N-DBODC5 (n = 6) or Tc-99m sestamibi (n = 4) and microspheres, followed by serial imaging and blood sampling over a period of 3 hours. Another 14 dogs with either critical (n = 7) or mild (n = 7) left anterior descending artery stenoses underwent simultaneous injection of Tc-99m N-DBODC5, TI-201, and microspheres during peak vasodilator stress. Like sestamibi, Tc-99m NDBODC5 showed good myocardial uptake with slow washout and minimal redistribution over a period of 3 hours (P = not significant); however, Tc-99m N-DBODC5 cleared more rapidly from the liver (heart-lung ratio at 30 minutes, 0.92 +/- 0.11 versus 0.51 +/- 0.05; P < .05). When injected during hyperemic flow, the myocardial extraction plateau for Tc-99m NDBODC5 was lower than that for TI-201 and was intermediate between Tc-99m sestamibi and Tc-99m tetrofosmin. Conclusions. Excellent organ biodistribution and myocardial uptake and clearance kinetic properties, combined with rapid liver clearance and a favorable How-extraction relationship, make Tc-99m N-DBODC5 a very promising new myocardial perfusion imaging agent.