Objective: Noninvasive fractional flow reserve (FFR) has been extensively studied and gained clinical recognition. However, the effect of an interventional catheter and a pressure wire in the arteries on the noninvasive FFR was not considered in previous studies. We provide quantitative analysis of how a catheter and a pressure wire can affect the estimation of noninvasive FFR using computational fluid dynamics (CFD) techniques. Methods: Six patients are studied. We calibrate our CFD model with patient-specific conditions so that the noninvasive FFR matches the FFR measured by the pressure wire. Then, we numerically remove the pressure wire and compute the noninvasive FFR again. This allows us to analyze the effect of the pressure wire on FFR. Results: The presence of a catheter and a pressure wire can reduce distal pressure from -0.1 mmHg to -8.1 mmHg, resulting in a reduction of FFR by 5.8% in average (0.012 to 0.107 or -1.2% to -16.8%). The insertion also reduces the time-averaged flow rate at the stenosis by up to 16.2% (4.9% in average). Conclusion: The impact of the pressure wire on the measured FFR depends on the characteristics of the patient-specific lesion. Significant linear correlations are found between the minimum diameter of the stenotic arteries and the reduction in FFR. Significance: The impact we found may contribute to provide a correction and improve the estimation of the noninvasive FFR technique for use in clinical practice.

Accurate and fast prediction of the hemodynamics of the artificial pump-lung is critical in the design process. In this study, a comprehensive computational framework, including a sliding mesh method, a coupled free flow and porous media flow model, a hemolysis prediction method, a k−ω shear stress transport turbulence model, and solution algorithms, is introduced to accurately predict the velocity field, pressure heads, and hemolysis. The framework is used to do the shape design of an artificial pump-lung on a supercomputer. High-resolution hemodynamics simulation results are obtained and analyzed, and the parallel performance of the algorithm is studied. The numerical results indicate that the proposed framework is capable of accurately predicting the velocity field, pressure heads, and hemolysis, and the performance of the designed artificial pump-lung meets the biocompatibility requirements. Additionally, the parallel performance results demonstrate the potential of the framework to efficiently perform the design of artificial pump-lungs using a large number of processors.

In this paper, we present a discrete unified gas kinetic scheme (DUGKS) on unstructured grids for high-speed viscid compressible flows on the basis of double distribution function (the density and the total energy distribution functions) Boltzmann-BGK equations. In the DUGKS, the discrete equilibrium distribution functions are constructed based on a D2Q17 circular function. In order to accelerate the simulation, we also illustrate a corresponding parallel algorithm. The DUGKS is validated by two benchmark problems, i.e., flows around the NACA0012 airfoil and flows past a circular cylinder with the Mach numbers range from 0.5 to 2.5. Good agreements with the referenced results are observed from the numerical results. The results of parallel test indicate that the DUGKS is highly parallel scalable, in which the parallel efficiency achieves $ 93.88\% $ on a supercomputer using up to $ 4800 $ processors. The proposed method can be utilized for high-resolution numerical simulation of complex and high Mach number flows.

With the advancement of fractional flow reserve (FFR) derived from computed tomography (FFR_CT), virtual stenting technology has gradually developed. This study investigated the performance of virtual stenting based on FFR_CT in predicting post-percutaneous coronary intervention (PCI) FFR. Data from 75 patients (78 blood vessels) was collected retrospectively. We randomly allocated the participants to discovery (n = 26) and validation (n = 52) cohorts. The FFR_CT was calculated using pre-PCI coronary computed tomography angiography images. Virtual stent implantation was simulated using blinded and non-blinded virtual stenting methods to obtain post-virtual stenting FFR_CT. The median FFR_CT before PCI and invasive FFR were 0.70 (0.60–0.77) and 0.69 (0.63–0.76), respectively. The median FFR_CT were 0.91 (0.86–0.95) and 0.91 (0.87–0.94) in the blinded and non-blinded groups, respectively; the invasive post-PCI FFR was 0.90 (0.88–0.93). The difference between the FFR_CT after using the blinded/non-blinded method and the invasive post-PCI FFR were 0.010 (95% limits of agreement: −0.064 to 0.084) and 0.009 (−0.050 to 0.068) in the discovery cohort and −0.005 (−0.075 to 0.064) and −0.0002 (−0.064 to 0.064) in the validation cohort, respectively. Virtual stenting technology based on FFR_CT can effectively predict functional outcomes after PCI and could be a reliable tool for PCI procedural planning.