Optimal timing for initial and redistribution technetium 99m-N-NOET image acquisition

J Nucl Cardiol. Mar-Apr 2000;7(2):123-31. doi: 10.1016/s1071-3581(00)90032-1.

Abstract

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).

Conclusion: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Coronary Circulation
  • Dogs
  • Heart / diagnostic imaging*
  • Hemodynamics
  • Metabolic Clearance Rate
  • Organotechnetium Compounds* / pharmacokinetics
  • Radiopharmaceuticals*
  • Thiocarbamates* / pharmacokinetics
  • Time Factors
  • Tomography, Emission-Computed, Single-Photon

Substances

  • Organotechnetium Compounds
  • Radiopharmaceuticals
  • Thiocarbamates
  • technetium Tc 99m, bis(N-ethoxy-N-ethyldithiocarbamato)nitrido-