Effect of Doppler ultrasound and high-frame-rate ultrasound particle image velocimetry derived inlet boundary conditions on wall shear stress parameters in the stented superficial femoral artery

BACKGROUND AND OBJECTIVES: Hemodynamic predictions by computational fluid dynamics (CFD) strongly depend on inlet boundary conditions (IBC). One-dimensional Doppler ultrasound (DUS) is typically used for estimating flow IBCs, despite its sensitivity to the operator, ultrasound hardware and assumptions in flow rate computation. An alternative is two-dimensional high-frame-rate ultrasound particle image velocimetry (echoPIV). This study investigated the differences between DUS and echoPIV-derived IBCs and their effect on wall shear stress parameters in the stented superficial femoral artery. METHODS: CFD simulations using DUS and echoPIV-derived IBCs were performed for three patients with a superficial femoral artery stenosis that were treated with a stent. Spatiotemporal velocity profiles were compared at 0 - 50 mm from the inlet. Differences were quantified with the root-mean-square error (RMSE). Regions of low time-averaged wall shear stress (TAWSS) and high oscillatory shear index (OSI) using a literature-based threshold of 0.4 Pa and 0.2, respectively, and an IBC-specific threshold (lower third and upper third, respectively) were determined. Co-localization was quantified using the Jaccard similarity index. RESULTS: The DUS and echoPIV-derived IBCs differed in flow rate and velocity profile, with the largest difference found at peak systole (RMSE: > 50 cm/s). Using the literature-based threshold, similarity in low TAWSS was high for two patients (0.85 - 0.88) and low for one (0.57). Agreement in high OSI was low in two patients (0.45 - 0.48) and high in one patient (0.83). The IBC-specific threshold increased the agreement for both low TAWSS and high OSI (≥0.75). CONCLUSIONS: Differences in DUS and echoPIV-derived IBCs affected the TAWSS and OSI magnitudes. Regions of low TAWSS and high OSI corresponded well using an IBC-specific threshold. The literature-based threshold resulted in lower similarity values and different interpretations of restenosis risk that may cause differences in follow-up intensity or medical management.