Attenuation-Corrected Tc-Tetrofosmin Single-Photon Emission Computed Tomography in the Detection of Viable Myocardium: Comparison With Positron Emission Tomography Using F-Fluorodeoxyglucose

Objectives. The purpose of this study was to assess the efficacy of attenuation-corrected (AC) technetium-99m (Tc)tetrofosmin single-photon emission computed tomography (SPECT) in detecting viable myocardium compared to Ffluorodeoxyglucose (FDG) positron emission tomography (PET). Background. The role of Tc-labeled perfusion tracers in the assessment of myocardial viability remains controversial. Attenuation artifacts affect the diagnostic accuracy of SPECT images. Methods. Twenty-four patients with coronary artery disease (mean left ventricular ejection fraction 30%) underwent resting Tc-tetrofosmin SPECT and FDG PET imaging. Both AC and non–attenuation-corrected (NC) SPECT images were generated. Results. Using a 50% threshold for viability by FDG PET, the percentage of concordant segments of viability between Tctetrofosmin and FDG on the patient basis increased from 79.8% 6 14.0% (mean 6 SD) on the NC images to 90.8% 6 10.6% on the AC images (p 5 0.002). The percentage of Tc-tetrofosmin defect segments within PET-viable segments, an estimate for the degree of underestimation of viability, decreased from 19.8% 6 15.2% on the NC images to 9.7% 6 12.6% on the AC images (p 5 0.01). Similar results were obtained when a 60% threshold was used to define viability by FDG PET. When the anterior-lateral and inferior-septal regions were separately analyzed, the effect of attenuation correction was significant only in the inferior-septal region. Conclusions. The results indicate that AC Tc-tetrofosmin SPECT improves the detection of viable myocardium mainly by decreasing the underestimation of viability particularly in the inferior-septal region, although some underestimation/ overestimation of viability may still occur even with attenuation correction. (J Am Coll Cardiol 1998;32:927–35) ©1998 by the American College of Cardiology