GATING PROVIDES IMPROVED ACCURACY FOR DIFFERENTIATING ARTIFACTS FROM TRUE LESIONS IN EQUIVOCAL FIXED DEFECTS ON TECHNETIUM 99M TETROFOSMIN PERFUSION SPECT

Background. Because equivocal fixed perfusion defects on single photon emission computed tomography (SPECT) often cause a diagnostic dilemma in patients with suspected coronary artery disease (CAD), we used rec eiver-operating characteristic (ROC) curve analysis to evaluate the de gree of increased accuracy provided by adding gated images for interpr etation of such cases. Methods and results. One hundred five (29%) of 365 consecutive patients undergoing technetium 99m tetrofosmin gated S PECT for evaluation of CAD demonstrated an equivocal fixed defect. Two independent observers graded the probability for true lesion with a 5 -point system over 3 steps of interpretation: reviewing tomographic im ages alone (step 1), adding projection images (step 2), and adding gat ed cine images (step 3), Based on clinical criteria, 66 patients were categorized as disease negative and 25 as disease positive, while the final diagnosis was undetermined in 14 cases. Diagnostic performance w as significantly higher at step 3 than at step 1 for both observers (p < 0.05 and < 0.0001) and at step 2 for observer B (p < 0.005). The ma ximum accuracy increased from 78.0% to 80.2% at step 2 to 84.6% to 86. 8% at step 3, Moreover, the agreement of interpretation between the 2 observers was higher at step 3 (kappa = 0.53) than at step 1 (kappa = 0.29) or step 2 (kappa = 0.25). Conclusion. In patients showing an equ ivocal fixed defect on Tc-99m tetrofosmin SPECT, gated cine images pro vide improved differential accuracy and enhanced objectivity of interp retation by reducing interobserver variance.