Three‐dimensional quantification of circulation using finite‐element methods in four‐dimensional flow MR data of the thoracic aorta

Abstract

Purpose Three‐dimensional (3D) quantification of circulation using a Finite Elements methodology. Methods We validate our 3D method using an in‐silico arch model, for different mesh resolutions, image resolution and noise levels, and we compared this with a currently used 2D method. Finally, we evaluated the application of our methodology in 4D Flow MRI data of ascending aorta of six healthy volunteers, and six bicuspid aortic valve (BAV) patients, three with right and three with left handed flow, at peak systole. The in‐vivo data was compared using a Mann‐Whitney U‐test between volunteers and patients (right and left handed flow). Results The robustness of our method throughout different image resolutions and noise levels showed subestimation of circulation less than 45 cm2/s in comparison with the 55cm2/s generated by the current 2D method. The circulation (mean ± SD) of the healthy volunteer group was 13.83 ± 28.78 cm2/s, in BAV patients with right‐handed flow 724.37 ± 317.53 cm2/s, and BAV patients with left‐handed flow −480.99 ± 387.29 cm2/s. There were significant differences between healthy volunteers and BAV patients groups (P‐value < .01), and also between BAV patients with a right‐handed or left‐handed helical flow and healthy volunteers (P‐value < .01). Conclusion We propose a novel 3D formulation to estimate the circulation in the thoracic aorta, which can be used to assess the differences between normal and diseased hemodynamic from 4D‐Flow MRI data. This method also can correctly differentiate between the visually seen right‐ and left‐handed helical flow, which suggests that this approach may have high clinical sensitivity, but requires confirmation in longitudinal studies with a large cohort.

Changes in aorta hemodynamics in Left-Right Type 1 bicuspid aortic valve patients after replacement with bioprosthetic valves: An in-silico study

“…Barker et al [ 58 ] reported that type 1 BAVs with RL-fusion are associated with significantly elevated WSS at focal regions in the AAo, and these regions correspond to the aortic jet impingement locations. Sotelo et al [ 27 ] have reported, through 4D flow MRI-based measurements, that BAV patients exhibit strong, positive axial circulation in the AAo which extends until the aortic arch. In comparison, healthy volunteers exhibited considerably weaker positive axial circulation.…”

“…A recent study by Dux-Santoy et al [ 26 ] compared WSS on the AAo in 46 BAV patients to 44 healthy volunteers using time-resolved 3D MRI and found that regions exposed to low and oscillating wall shear stress in BAV patients did not match those with the highest prevalence of dilation. In other studies, the group also showed, through cardiac MRI analysis and in silico modeling that BAV patients exhibited strong helical flows in the aorta, with increased axial circulation [ 27 ] and circumferential wall shear stress [ 28 ] compared to healthy controls. Further, they showed that the magnitude and circumferential component of the local WSS vector correlated strongly in BAV patients with the risk of AAo growth rate [ 29 ].…”

Fully Three-Dimensional Hemodynamic Characterization of Altered Blood Flow in Bicuspid Aortic Valve Patients With Respect to Aortic Dilatation: A Finite Element Approach

“…The hemodynamic parameters and the diameters in the entire thoracic aorta were obtained based on a finite-element method described previously ( 32 – 36 ) ( Figure 1A ). To provide a ground for location-specific comparisons, 16 regions ( Figure 1D ) were semi-automatically selected.…”