Author + information
- Received October 28, 1991
- Revision received January 28, 1992
- Accepted February 17, 1992
- Published online September 1, 1992.
- Rob Beanlands, MD, FRCP(C)1,
- Otto Muzik, PhD2,
- Ngoc Nguyen, BS,
- Neil Petry, MS and
- Markus Schwaiger, MD, FACC∗
- ↵∗Address for correspondence: Markus Schwaiger, MD, Division of Nuclear Medicine, B1G505, Department of Internal Medicine, University of Michigan Medical Center, East Medical Center Drive, Ann Arbor, Michigan, 48109-0028.
Objectives. The aim of this study was to define the temporal changes in the relationship between technetium-99m teboroxime tissue retention and myocardial blood flow in a canine model.
Background. Technetium-99m teboroxime is a new neutral lipophilic myocardial perfusion agent. It is known to be highly extracted by the myocardium but to have a rapid clearance rate.
Methods. A wide range of myocardial blood flow was induced in each experiment by regional coronary occlusion and dipyridamole infusion. Myocardial retention of technetium-99m teboroxime was determined by in vitro tissue counting at 1, 2 or 5 min after injection of the tracer. Tracer retention was correlated with microsphere-determined blood flow and the data were fitted to nonlinear functions.
Results. Correlation coefficients for these functions were 0.92, 0.95 and 0.95 at 1, 2, and 5 min, respectively. At 1 min after injection, the relationship of technetium-99m teboroxime retention to blood flow was linear over a wide flow range, becoming nonlinear at flow rates > 4.5 ml/min per g. After 5 min the retention-flow relationship was linear only to 2.5 ml/min per g, above which little change in retention was noted. Normalized myocardial retention, expressed as a percent of the retention at 1 ml/min per g, was also calculated. At flow rates of 1, 2, 3, 4 and 5 ml/min per g, normalized retention was 100, 169, 228, 277 and 317% at 1 min and 100, 171, 217, 239 and 237% at 5 min after injection.
Conclusions. At 1 min after injection, the relationship of technetium-99m teboroxime myocardial retention to blood flow is well maintained over a wide range of flow. However, after only 5 min, tracer retention underestimates flow changes at moderate and high flow rates. Thus, rapid acquisition protocols are necessary to fully exploit the potential of this promising new tracer in the evaluation of myocardial perfusion.
↵1 Dr. Beanlands is a research fellow supported by the Heart and Stroke Foundation of Canada, Ottawa, Ontario, Canada.
↵2 Dr. Muzik is supported by Project J0473-MED from the Austrian Erwin Schroedinger Foundation, Vienna, Austria.
☆ This study was carried out during the tenure of Dr. Schwaiger, an established investigator of the American Heart Association, Dallas, Texas and was supported in part by a grant from Squibb Diagnostics, Princeton, New Jersey.
- Received October 28, 1991.
- Revision received January 28, 1992.
- Accepted February 17, 1992.