MYOCARDIAL TECHNETIUM 99M-LABELED SESTAMIBI SINGLE-PHOTON EMISSION COMPUTED TOMOGRAPHIC IMAGING IN THE DETECTION OF CORONARY-ARTERY-DISEASE- COMPARISON BETWEEN EARLY (15 MINUTES) AND DELAYED (60 MINUTES) IMAGING

Background. Previous studies have demonstrated that there is a ''parti al'' myocardial redistribution of Tc-99m-labeled sestamibi (MIBI) betw een 1 and 3 hours after intravenous injection at stress. The purpose o f this prospective study was to compare MIBI single-photon emission co mputed tomographic (SPECT) imaging performed 15 and 60 minutes after t he injection at stress in the detection of coronary artery disease. Me thods and results. Thirty-five patients with coronary artery disease ( 26 undenrent coronary angiography and 23 had a positive Tl-201 Study r esult) were included in this study. SPECT imaging started 15 minutes a fter the injection of 25 to 30 mCi MIBI at peak stress (180-degree arc , 32 angles, 25 sec/view, and high-resolution collimator). Patients un derwent reimaging at 60 minutes according to the same protocol and wit h the same gamma camera. A rest study was obtained 75 minutes after th e injection of MIBI (25 to 30 mCi) at rest, 48 hours later. Images (di vided for a total of 19 segments per patient) were interpreted by two blinded observers for patient diagnosis and segmental comparison. The patient diagnosis was the same for the two protocols: normal = 3, isch emia = 27, and scar = 5. The segmental agreement (kappa = 0.90) was 63 2/665 (95.0%). The imaging performed at 15 minutes detected normal, is chemia, and scar in 413, 189, and 63 segments, respectively, whereas t he imaging performed at 60 minutes detected 422, 180, and 63 segments, respectively (difference not significant). The early and delayed imag es were placed side by side for subjective comparison of the extent of the defect. Early imaging showed slightly larger defects in six patie nts, equal defects in 24 patients, and slightly smaller defects in fiv e patients. Ischemic/normal wall ratios were 0.67 +/- 0.16 at 15 minut es and 0.68 +/- 0.15 at 60 minutes. Conclusions. There is no clinicall y significant difference between SPECT imaging performed at 15 minutes or 60 minutes after the injection of MIBI at stress. Furthermore, thi s study showed that it is feasible to obtain good-quality MIBI images even 15 minutes after the injection at stress.