Optimal timing for initial and redistribution technetium 99m-N-NOET image acquisition.
BACKGROUND
Bis (N-ethoxy, N-ethyl dithiocarbamato) nitrido technetium-99m (V) (Tc-99m-N-NOET) is a new Tc-99m-labeled myocardial perfusion imaging agent that redistributes. We sought to determine the optimal timing for acquiring initial and delayed images to maximize sensitivity for the detection of coronary stenoses.


METHODS
Twelve anesthetized dogs with critical stenoses of the left anterior descending coronary artery were infused with adenosine (250 microg/kg/min) or MRE-0470, an adenosine A2a agonist (0.6 microg/kg/min x 10 minutes), and Tc-99m-N-NOET (8 mCi; 296 MBq) was injected intravenously at peak flow. Myocardial and lung Tc-99m-N-NOET activities were determined by serial quantitative imaging and arterial blood sampling was performed over 2 hours.


RESULTS
Left anterior descending/left circumflex artery defect count ratios showed rapid redistribution during the first 10 minutes after Tc-99m-N-NOET injection (0.66 +/- 0.02 at 2 minutes to 0.73 +/- 0.01 at 10 minutes; P < .01). Redistribution was nearly complete by 120 minutes (defect ratio = 0.87 +/- 0.03; P < or = .01 vs 2 minutes). Lung activity fell significantly during the first 10 minutes from a heart/lung activity ratio of 1.07 +/- 0.05 (2 minutes) to 1.44 +/- 0.09 (10 minutes; P < or = .01).


CONCLUSIONS
Initial stress Tc-99m-N-NOET images should be acquired within 10 minutes after injection, whereas delayed images can be obtained as early as 2 hours later. Lung activity clears rapidly, permitting acquisition of good-quality poststress cardiac images. These Tc-99m-N-NOET uptake and redistribution kinetics after vasodilator stress provide important information for designing clinical imaging protocols for optimal identification of inducible ischemia.
Petruzella
F D
FD
University of Virginia Health Sciences Center, Charlottesville 22908, USA.
Ruiz
M
M
Katsiyiannis
P
P
Watson
D D
DD
Pasqualini
R
R
Beller
G A
GA
Glover
D K
DK
D000818:Animals; D003326:Coronary Circulation; D004285:Dogs; D006321:Heart / Q000000981:diagnostic imaging*; D006439:Hemodynamics; D008657:Metabolic Clearance Rate; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics; D019275:Radiopharmaceuticals; D013859:Thiocarbamates / Q000493:pharmacokinetics; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon
D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D013859:Thiocarbamates; C093922:technetium Tc 99m, bis(N-ethoxy-N-ethyldithiocarbamato)nitrido-