Improved diagnostic performance of CT-derived FFR using 70-keV monoenergetic spectral CT in coronary artery disease

To compare the diagnostic performance of coronary CT-derived fractional flow reserve (CT-FFR) calculated from conventional polychromatic CT images with 70-keV monoenergetic reconstructions derived from spectral CT data. This retrospective study enrolled patients who underwent spectral coronary CT angiography followed by invasive FFR measurements. The CT-FFR values were computed from conventional polychromatic and 70-keV monoenergetic images. Image quality was assessed using the contrast-to-noise ratio (CNR). Comparison of the CT-FFR with invasive FFR provided mean absolute error (MAE), Pearson's correlation, Bland-Altman analysis, and receiver operating characteristic (ROC) curve analysis. Hemodynamically significant stenosis was defined as an invasive FFR < 0.80. Thirty-two patients (21 men, 11 women; mean age, 68.5 ± 8.4 years) with 47 coronary artery lesions were included in this study. The 70-keV images demonstrated significantly higher CNR than conventional images (36.4 ± 15.2 vs. 25.3 ± 7.4; p < 0.01). CT-FFR derived from 70-keV images yielded lower MAE (0.07 ± 0.05 vs. 0.12 ± 0.08; p < 0.01) and showed stronger correlation with invasive FFR (R = 0.769 vs. R = 0.439). Bland-Altman analysis revealed narrower limits of agreement for the 70-keV CT-FFR. In 17 lesions with hemodynamically significant stenosis, the area under the ROC curve of 70-keV CT-FFR was significantly higher than that of conventional CT-FFR (0.929 vs. 0.807; p = 0.01). CT-FFR derived from 70-keV monoenergetic spectral CT images demonstrated promising agreement with invasive FFR and may offer exploratory insight into improving functional assessment of coronary stenosis.