Quantification of myocardial infarct size by thallium - 201 single - photon emission computed tomography : experimental validation in the dog FLORENCE PRIGENT

To evaluate the potential advantages of thallium-201 (201T1) single-photon emission computerized tomography (SPECT) to assess myocardial infarct size in the experimental animal, six normal dogs and 14 dogs with 6 to 8 hr closed-chest coronary occlusion (eight left anterior descending and six left circumflex) were studied. Ten minutes after intravenous administration of 2 mCi of 201T1, 30 projections were obtained over 180 degrees. The dogs were killed and their hearts sliced and stained by triphenyl tetrazolium chloride (TTC). Pathologic infarct size was calculated for each slice and for the entire left ventricular myocardium as percent weight. Tomograms were quantified by automatically generating maximum-count circumferential profiles, which were compared with normal limit profiles derived from the six normal dogs. Tomographic infarct size was defined as the percentage of circumferential points falling below normal for each tomogram. SPECT and TTC infarct size on 71 slices correlated highly (mean SD 27.9 ± 23.4% and 26.7 25.3%, respectively; r = .93, p < .001, SEE = 9.4%). To determine SPECT infarct size as percent total left ventricular myocardial weight, infarct sizes from each slice were added to one another after each was multiplied by a coefficient that reflected the contribution of that slice to the total left ventricular weight. SPECT and TTC infarct size for the entire left ventricle correlated closely (mean ± SD 20.5 ± 7.6% and 19.3 ± 8.3%, respectively; r = .86, p < .001, SEE = 4.5%). It is concluded that 201T1 SPECT is a valid method for the noninvasive assessment of experimental myocardial infarct size. Circulation 74, No. 4, 852-861, 1986. PROGNOSIS in acute myocardial infarction has been shown to be related to the extent of the necrotic myocardium.1-t Several noninvasive, nonimaging,6-8 and imaging5' 121 methods have been developed for measurement of infarct size. With planar imaging or limited-angle tomography,9-13 thallium-201 (201T1) myocardial perfusion and technetium-99m-pyrophosphate infarct-avid scintigraphy are suboptimal for quantitaFrom the Department of Medicine, Division of Cardiology, and the Department of Nuclear Medicine, Cedars-Sinai Medical Center, and the Department of Medicine, University of California, Los Angeles, School of Medicine, Los Angeles. Supported in part by NIH SCOR grant 17651 and grants from the American Heart Association, Greater Los Angeles Affiliate. Address for correspondence: Jamshid Maddahi, M.D., Division of Cardiology, Cedars-Sinai Medical Center, P.O. Box 48750, Los Angeles, CA 90048. Received May 6, 1985; revision accepted July 3, 1986. Presented in part at the 57th Scientific Sessions of the American Heart Association, Miami Beach, November 1984. *Present address: Miami University, Miami, FL. **Present address: Emory University, Atlanta, GA. 852 tion of infarct size because of overlap of normal and abnormal regions. Single-photon emission computerized rotational tomography (SPECT) has a theoretical advantage over planar imaging and limited-angle tomography for the accurate assessment of infarct size because of 180 or 360 degree angular sampling of the myocardium, which results in reduced overlap and improved contrast of the images 22, 23 Although quantification of infarct size with SPECT using 20'T1 has been shown to be feasible,14-18 these previous studies used subjective measurements or computerized planimetric approaches that were dependent on detection of myocardial edges of the normal and nonvisualized regions (with severe perfusion defects). In this study we sought (1) to develop an objective, computerized method for quantification of infarct size using maximum counts circumferential profile analysis, independent of edge detection, and (2) to validate the method in a living canine closed-chest preparation. CIRCULATION by gest on N ovem er 7, 2017 http://ciajournals.org/ D ow nladed from LABORATORY INVESTIGATION-MYOCARDIAL INFARCTION