title: Tc-99m-N-MPO: novel cationic Tc-99m radiotracer for myocardial perfusion imaging.
abstract: BACKGROUND
  Technetium 99m-N-MPO ([Tc-99m-N(mpo)(PNP5)](+)) is a cationic Tc-99m nitrido complex. The objective of this study is to evaluate its potential as a new radiotracer for myocardial perfusion imaging.
  
  
  RESULTS
  Biodistribution studies were performed in Sprague-Dawley rats and guinea pigs to compare the myocardial uptake and excretion kinetics of Tc-99m-N-MPO from noncardiac organs, such as the liver and lungs, with those of the known cationic Tc-99m radiotracers: Tc-99m-N-DBODC5 and Tc-99m-sestamibi. Planar imaging was performed in Sprague-Dawley rats to evaluate the utility of Tc-99m-N-MPO as a myocardial perfusion imaging agent. Metabolism studies were carried out by use of both Sprague-Dawley rats and guinea pigs. In general, the heart uptake of Tc-99m-N-MPO was between that of Tc-99m-sestamibi and Tc-99m-N-DBODC5 over the 2-hour study period. However, the heart-liver ratio of Tc-99m-N-MPO (12.75 +/- 3.34) at 30 minutes after injection was more than twice that of Tc-99m-N-DBODC5 (6.01 +/- 1.45) and approximately 4 times higher than that of Tc-99m-sestamibi (2.90 +/- 0.22). The heart uptake and heart-liver ratio of Tc-99m-N-MPO and Tc-99m-sestamibi in guinea pigs were significantly lower than those obtained in Sprague-Dawley rats. The metabolism studies demonstrated no detectable Tc-99m-N-MPO metabolites in the urine and feces samples of the Sprague-Dawley rats at 120 minutes after injection. In guinea pigs no Tc-99m-N-MPO metabolites were detected in the urine at 120 minutes, but only approximately 60% of Tc-99m-N-MPO remained intact in the feces samples. In contrast, there was no intact Tc-99m-sestamibi detected in urine samples, and less than 15% of Tc-99m-sestamibi remained intact in the feces samples. Planar imaging studies indicated that clinically useful images of the heart may be obtained as early as 15 minutes after injection of Tc-99m-N-MPO.
  
  
  CONCLUSIONS
  The combination of favorable organ biodistribution and myocardial uptake with rapid liver clearance makes Tc-99m-N-MPO a very promising myocardial perfusion radiotracer worthy of further evaluation in various preclinical animal models.
authors.affiliation: School of Health Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Young-Seung
authors.initials: YS
authors.lastname: Kim
authors.forename: Jianjun
authors.initials: J
authors.lastname: Wang
authors.forename: Alexis
authors.initials: A
authors.lastname: Broisat
authors.forename: David K
authors.initials: DK
authors.lastname: Glover
authors.forename: Shuang
authors.initials: S
authors.lastname: Liu
mesh_terms: D000818:Animals; D002412:Cations / Q000493:pharmacokinetics; D005260:Female; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000000981:diagnostic imaging* / Q000378:metabolism*; D006801:Humans; D008297:Male; D008657:Metabolic Clearance Rate; D009928:Organ Specificity; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution
chemical_list: D002412:Cations; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C532955:technetium 99m (2-mercaptopyridine N-oxide)(N-ethoxyethyl-N,N-bis(2-(bis(3-methoxypropyl)phosphino)ethyl)amine)