Assessment Of Fractional Flow Reserve Based On Computational Fluid Dynamics And Coronary Computed Tomography Angiography

Coronary heart disease is the leading cause of death worldwide.The increase in its mortality rate in combination with a trend shifting toward a younger age has caused many concerns.Fractional flow reserve（FFR）is currently considered as the gold standard for assessment of functionally significant stenosis causing ischemia.Image-based FFR computation can overcome the limitation of pressured wire-derived FFR and increase the utility of FFR assessment.Computational fluid dynamics（CFD）has been successfully applied to image-based FFR.It requires reconstruction of patient-specific coronary geometry and estimation of hyperemic flow rate.Currently,coronary computed tomography angiography（CCTA）and invasive coronary angiography（ICA）are two dominating imaging modalities used for the geometrical reconstruction.The primary objective of this study was to investigate the impact of image resolution as inherently associated with these two imaging modalities on geometrical reconstruction and the subsequent FFR calculation.Patients with mild or intermediate coronary stenoses who underwent both CCTA and ICA were retrospectively included.CCTA images were acquired either by 320-row area detector CT or by 128-slice dual-source CT.Two geometrical models were segmented and reconstructed separately from CCTA and ICA.The reconstructed geometrical models were subsequently used for CFD simulation.The hyperemic volumetric flow rate derived by the frame count method on the ICA images was applied as the inlet boundary condition.After simulation,the pressure at each position of the reconstructed artery can be obtained.FFR_CTA and FFR_QCA were calculated using the pressures at the most proximal and distal positions of the interrogated vessel.Finally,statistical analysis was performed.The results showed that FFR_CTAand FFR_QCA had reasonably good correlation.The difference between FFR_CTA and FFR_QCA was correlated with the deviation between minimal lumen areas by CCTA and by 3D QCA,but not with plaque volume or with calcified plaque volume.Applying the same cutoff value of≤0.80 to both FFR_CTA and FFR_QCA,the agreement between FFR_CTA and FFR_QCA in discriminating functional significant stenoses was moderate.Disagreement in diagnosis of functionally significant lesion was found in 10（17.5%）vessels.Our results indicated that image resolution had a significant impact on FFR computation based on CCTA image.