COMPARISON OF DEFECT SIZE BETWEEN TL-201 AND TC-99M TETROFOSMIN MYOCARDIAL SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY IN PATIENTS WITH SINGLE-VESSEL CORONARY-ARTERY DISEASE

Defect size on exercise-rest technetium (Tc)-99m tetrofosmin myocardia l perfusion imaging was compared with that on exercise-reinjection tha llium-201 imaging in 20 patients with 1-vessel coronary artery disease . In each patient, exercise-reinjection thallium-201 single-photon emi ssion computed tomography (SPECT) and exercise-rest Tc-99m tetrofosmin SPECT imaging were performed. For visual analysis of the obtained SPE CT images, the left ventricular myocardium was divided into 20 segment s based on 3 short-axis slices from the apical, middle, and basal vent ricular levels. For quantitative analysis, a square region of interest was placed on the center of each segment which was used for visual an alysis, and relative regional activity to the normal reference region was calculated for each segment. By visual interpretation of the image s, exercise Tc-99m tetrofosmin imaging showed a smaller defect size th an exercise thallium-201 imaging (6.9 +/- 3.9 vs 8.8 +/- 3.0 segments, p < 0.01). In contrast, rest Tc-99m tetrofosmin imaging showed a defe ct size similar to that on reinjection thallium-201 imaging (5.9 +/- 3 .6 vs 5.6 +/- 3.9 segments, p = NS). Similarly, the mean defect sizes during exercise determined by quantitative analysis were smaller on Tc -99m tetrofosmin SPECT than those on thallium-201 SPECT at all tested threshold cutoff points ranging from 50% to 70%, whereas there were no significant differences in defect sizes between rest Tc-99m tetrofosm in and reinjection thallium-201 Imaging. These data indicate that exer cise Tc-99m tetrofosmin SPECT defect size determined either by visual analysis or by quantitative analysis may be smaller than that on exerc ise thallium-201 SPECT.