OBJECTIVE(99m)Tc-[bis (dimethoxypropylphosphinoethyl)-ethoxyethylamine (PNP5)]-[bis (N-ethoxyethyl)-dithiocarbamate (DBODC)] nitride ([(99m)Tc (N) (PNP5) (DBODC)](+)) is a new myocardial perfusion tracer with high heart uptake and rapid liver clearance. The objectives of this study were to compare the myocardial imaging of [(99m)Tc (N) (PNP5) (DBODC)](+) with (99m)Tc-MIBI in a canine model of acute myocardial ischemia.

METHODSThe left anterior descending artery (LAD) was occluded in 12 adult beagle dogs, adenosine was then infused intravenously at a rate of 0.14 mg.kg(-1).min(-1) for 6 min. At the end of 3 min of adenosine infusion, 185 MBq of [(99m)Tc (N) (PNP5) (DBODC)](+) or (99m)Tc-MIBI was injected intravenously. The occluder was released after 6 min adenosine infusion. Serial myocardial SPECT imaging acquisitions were obtained at 0.5, 1, 1.5 and 2 h after tracer injection, respectively. Rest myocardial SPECT imaging was acquired in the next day.

RESULTSSimilar as (99m)Tc-MIBI, [(99m)Tc (N) (PNP5) (DBODC)](+) exhibited high heart uptake, minimal lung uptake and minimal redistribution. No significant myocardial washout was observed with both tracers over a period of 2 hours. [(99m)Tc (N) (PNP5) (DBODC)](+) clearance from the liver was more rapid than that with (99m)Tc-MIBI (heart-liver radio at 60 min, 1.36 +/- 0.43 vs. 0.58 +/- 0.21, P = 0.005). [(99m)Tc (N) (PNP5) (DBODC)](+) the ability to detect myocardial ischemia was also comparable between the two tracers ([(99m)Tc (N) (PNP5) (DBODC)](+) detected 3.60 +/- 1.52 defect segments, (99m)Tc-MIBI detected 4.25 +/- 0.96 defect segments, P = 0.48). The image quality of [(99m)Tc (N) (PNP5) (DBODC)](+) was better than (99m)Tc-MIBI.

CONCLUSION[(99m)Tc (N) (PNP5) (DBODC)](+) is comparable to (99m)Tc-MIBI on detecting myocardial ischemia in this model and liver clearance is more rapid and the image quality is better than (99m)Tc-MIBI.