Attenuation-corrected ^99mTc-tetrofosmin single-photon emission computed tomography in the detection of viable myocardium: Comparison with positron emission tomography using ¹⁸F-fluorodeoxyglucose

Objectives. The purpose of this study was to assess the efficacy of attenuation-corrected (AC) technetium-99m (^99mTc)tetrofosmin single- photon emission computed tomography (SPECT) in detecting viable myocardium compared to ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET). Background. The role of ^99mTc-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 ^99mTc-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 ^99mTc-tetrofosmin and FDG on the patient basis increased from 79.8% ± 14.0% (mean ± SD) on the NC images to 90.8% ± 10.6% on the AC images (p = 0.002). The percentage of ^99mTc-tetrofosmin defect segments within PET-viable segments, an estimate for the degree of underestimation of viability, decreased from 19,8% ± 15.2% on the NC images to 9.7% ± 12.6% on the AC images (p = 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 ^99mTc-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.