Abstract 13531: 99mTc-N-MPO, New Perfusion Agent Exhibiting High Myocardial Uptake and Rapid Liver Clearance: Comparison with 99mTc-Sestamibi And 99mTc-15C5-PNP in Rats
SPECT perfusion imaging agents with enhanced myocardial uptake and reduced liver radioactivity are clinically desirable. New cationic 99mTc-nitrido complexes and 99mTc(I)-tricarbonyl complexes have been introduced in recent years, in which crown ether functional groups are used to improve liver clearance. In this study, we performed dynamic imaging studies to compare radiopharmaceutical kinetics of cationic 99mTc-nitrido complex, 99mTc-N-MPO (MPO), with 99mTc-sestamibi (MIBI) and 99mTc(I)-tricarbonyl complex, 99mTc-15C5-PNP (PNP). Dynamic cardiac images were acquired for 60 minutes after intravenous tracer injection (4.0 mCi) using a stationary small-animal SPECT system in three groups of healthy adult rats (n=6, each). Myocardial and liver time-activity curves were generated for kinetic model analysis. As shown in Fig 1, excellent visualization of the left ventricular wall could be achieved 5-10 min after MPO administration. The quality of normal myocardial perfusion images with MPO was comparable to that with MIBI. MPO images showed higher and more uniform myocardial distribution than PNP for equivalent acquisition parameters. The liver washout of MPO was significantly faster and greater than that of MIBI, but similar to that of PNP. Normalized kinetic curves plotted from 5 to 60 min demonstrated that myocardial retention (% activity at 5 min ) at 60 min was significantly higher in MPO (119.9 ± 2.8) compared to MIBI (99.3 ± 7.8, P<0.05) and PNP (78.1±7.9, P<0.05), respectively. MPO residual liver activity (%) (14.6 ± 5.9) at 60 min post-injection was lower than MIBI (71.8 ± 7.7, P<0.01) and not different compared to PNP (11.2 ± 2.4, P>0.05). In conclusion, our imaging data in the rats indicated that 99mTc-N-MPO exhibits high myocardial uptake and rapid liver clearance. This improvement of heart and liver kinetics with 99mTc-N-MPO may overcome difficulties in visualizing and quantifying the perfusion of the inferior wall of the left ventricle by SPECT imaging.
- © 2011 by American Heart Association, Inc.