Myocardial uptake and redistribution of 99mTc-N-NOET in dogs with either sustained coronary low flow or transient coronary occlusion: comparison with 201Tl and myocardial blood flow.
BACKGROUND
99mTc-N-NOET (NOET) is a new myocardial perfusion imaging agent that redistributes over time. We sought to better define the redistribution kinetics of NOET using open-chest canine models of sustained low coronary flow (protocol 1) and transient coronary occlusion followed by reflow (protocol 2).


RESULTS
In protocol 1 (n=10), NOET and 201Tl were injected during low flow in the left anterior descending coronary artery (LAD) that was sustained for 2 hours. Protocol 2 dogs (n=6) were injected with NOET during 20 minutes of LAD occlusion followed by 2 hours of reflow. In both protocols, serial NOET planar images were acquired, and myocardial flow and 2-hour tracer activities were determined by gamma-well counting. Defect resolution was observed on images in both protocols. Initial defect count ratios, reflecting flow disparity at injection (0.66+/-0.03 and 0.57+/-0.04, respectively), increased over 2 hours (0.73+/-0.02 and 0.75+/-0.04, respectively; P<.001 versus initial). Quantitative imaging showed that NOET redistribution resulted from greater clearance from normal areas versus low-flow or transiently occluded areas. In protocol 1, 2-hour NOET and 201Tl stenotic-to-normal tissue activity ratios were similar (0.76+/-0.06 versus 0.73+/-0.04, P=NS) and higher than injection flow ratios (0.52+/-0.06 and 0.56+/-0.07, respectively, P<.001), consistent with tracer redistribution. In protocol 2, NOET redistributed to an even greater extent (injection flow ratio, 0.27+/-0.04; 2-hour tissue activity ratio, 0.84+/-0.03, P<.001).


CONCLUSIONS
NOET is the first 99mTc-labeled myocardial imaging agent with kinetics similar to 201Tl in experimental models, permitting redistribution imaging. NOET appears to be a promising agent for assessing patients with coronary artery disease.
Vanzetto
G
G
Experimental Cardiology Laboratory, University of Virginia, Charlottesville 22908, USA.
Calnon
D A
DA
Ruiz
M
M
Watson
D D
DD
Pasqualini
R
R
Beller
G A
GA
Glover
D K
DK
D000818:Animals; D001794:Blood Pressure; D003326:Coronary Circulation / Q000502:physiology*; D003327:Coronary Disease / Q000000981:diagnostic imaging / Q000503:physiopathology*; D003331:Coronary Vessels / Q000502:physiology / Q000503:physiopathology*; D004285:Dogs; D006321:Heart / Q000000981:diagnostic imaging*; D006339:Heart Rate; D006439:Hemodynamics; D008297:Male; D008863:Microspheres; D009206:Myocardium / Q000378:metabolism*; D015609:Organotechnetium Compounds / Q000097:blood / Q000493:pharmacokinetics*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D012039:Regional Blood Flow; D013793:Thallium / Q000097:blood / Q000493:pharmacokinetics*; D013859:Thiocarbamates / Q000097:blood / Q000493:pharmacokinetics*; D014018:Tissue Distribution; D016277:Ventricular Function, Left
D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D013859:Thiocarbamates; D013793:Thallium; C093922:technetium Tc 99m, bis(N-ethoxy-N-ethyldithiocarbamato)nitrido-