Diagnostic value of thallium-201 myocardial perfusion IQ-SPECT without and with computed tomography-based attenuation correction to predict clinically significant and insignificant fractional flow reserve

The aim of this study was to clarify the predictive value of fractional flow reserve (FFR) determined by myocardial perfusion imaging (MPI) using thallium (Tl)-201 IQ-SPECT without and with computed tomography-based attenuation correction (CT-AC) for patients with stable coronary artery disease (CAD). We assessed 212 angiographically identified diseased vessels using adenosine-stress Tl-201 MPI-IQ-SPECT/CT in 84 consecutive, prospectively identified patients with stable CAD.We compared the FFR in 136 of the 212 diseased vessels using visual semiquantitative interpretations of corresponding territories on MPI-IQ-SPECT images without and with CT-AC. FFR inversely correlated most accurately with regional summed difference scores (rSDS) in images without and with CT-AC (r= 0.584 and r= 0.568, respectively, both P< .001). Receiver-operating characteristics analyses using rSDS revealed an optimal FFR cut-off of<0.80 without and with CT-AC. Although the diagnostic accuracy of FFR <0.80 did not significantly differ, FFR ≥0.82 was significantly more accurate with, than without CT-AC. Regions with rSDS ≥2 without or with CT-AC predicted FFR <0.80, and those with rSDS 1without andwith CT-AC predicted FFR≥0.81, with 73% and 83% sensitivity, 84% and 67% specificity, and 79% and 75% accuracy, respectively. Although limited by the sample size and the single-center design, these findings showed that the IQ-SPECT system can predict FFR at an optimal cut-off of<0.80, and we propose a novel application of CT-AC to MPI-IQ-SPECT for predicting clinically significant and insignificant FFR even in nonobese patients. Abbreviations: 3D-OSCGM = 3-dimensional ordered subset conjugate gradient modification, AC = attenuation correction, AUC = area under the curve, CAD = coronary artery disease, CAG = coronary angiography, CI = confidence interval, CT = computed tomography, CT-AC = computed tomography-based attenuation correction, CZT = cadmium-zinc-telluride, DLP = dose-length product, ECG = electrocardiography, FFR = fractional flow reserve, HLA = horizontal long-axis, IDI = integrated discrimination improvement, LAD = left anterior descending artery, MPI =myocardial perfusion imaging, MPR =myocardial perfusion reserve, NRI = net reclassification improvement, QCA = quantitative coronary angiography, QPS = quantitative perfusion single-photon emission computed tomography, ROC = receiver-operating characteristics, rSDS = regional summed difference score, rSRS = regional summed rest score, rSSS = regional summed stress score, SA = short-axis, SD = standard deviation, SPECT = single-photon emission computed tomography, Tl-201 = thallium-201, VLA = vertical long-axis.