Quantitative evaluation of stress thallium-201 myocardial perfusion imaging for detection of the severity of coronary artery disease.

This study was done to evaluate the quantification of thallium-201 myocardial perfusion imaging (MPI) for the detection of coronary artery disease (CAD). Segmental analysis of stress and delayed MPI was performed in 33 patients with angiographically proved CAD. They were divided into two groups : 22 patients without previous infarction (Group 1) and 11 patients with prior myocardial infarction (Group 2). Using computer analysis of MPI, 9 region-of-interests (ROIs) were set on the left ventricular image. We defined 3 indices as follows : initial uptake (%) = a ratio of ROI counts to the highest ROI counts on the exercise image ; washout rate (WR) = a ratio of [(ROI counts of the exercise image) - (those on the delayed image)] to those on the exercise image : redistribution index (ROI)= a ratio of the maximal WR to WR. Coronary arteriograms were evaluated according to Pujadas' method. In group 1, the region supplied by the coronary artery with significant stenosis showed a lower initial uptake (p < 0.005) and a higher ROI (p < 0.001) than the region supplied by the coronary artery without significant stenosis. If an initial uptake less than 83% and/or a RDI greater than 1.15 are defined as abnormal, the sensitivity for detecting CAD, including the detection of a stenosis site, was 76% and the specificity was 84%. In group 2, the sensitivity was 76% and the specificity was 80%. The mean WR could also indicate the severity of CAD. In all patients studied., the average of mean WR was 0.451 in one-vessel disease (n=18), 0.446 in two-vessel disease (n=6) and 0.305 in three-vessel disease (n=8). In conclusion, the quantitative evaluation of stress MPI using initial uptake, RDI and WR appear to be useful for noninvasive and objective diagnosis of CAD, particularly in detecting the severity and location of stenotic coronary arteries.