Methods for fluid dynamics simulations of human fetal cardiac chambers based on patient-specific 4D ultrasound scans

Abstract

Previous studies provided evidence that the mechanical forces of blood flow in embryos and fetuses may play a role in causing congenital cardiovascular. It is thus important to understand the fluid mechanical forces in the human fetuses. In the current study, we present a new technique for performing computational fluid dynamics of the cardiac chambers, based on patient-specific clinical ultrasound scans of human fetuses. Ultrasound images were acquired using the Spatio-Temporal Image Correlation (STIC) mode. The images were segmented for the right ventricle blood space at various time points. A mathematical model of ventricular wall motion was developed and used to define mesh motion for computational fluid dynamics simulation of fluid within the ventricle. The ventricular mesh models created by the mathematical model was shown to satisfactorily agree with the ventricular geometries segmented from ultrasound images. Fluid dynamics simulations successfully provided details of spatial gradients of pressures, ventricular wall shear stresses, and vorticity dynamics in the ventricle. Results showed that the right ventricle diastolic flows featured two prominent vortex rings, which were sustained until systole, when part of the vorticity structures were ejected through the pulmonary outflow tract. Diastolic wall shear stress was in the range of 0.4-1.2 Pa, while systolic shear stress elevated near to the outflow tract at 1.5-3.9 Pa. In conclusion, We have established methodologies for performing patient-specific simulations of the fluid mechanics in the heart chambers of human fetuses, based on clinical ultrasound scans, and demonstrated its feasibility on a 20 weeks human fetus right ventricle.

Computational Modeling of Blood Flow Hemodynamics for Biomechanical Investigation of Cardiac Development and Disease

“…Here, convergence is generally defined by evaluating the flow rate, pressure, or other flow parameters at a particular region in the flow domain. Usually, the residual of the continuity equation should be on the order of 10 −5 for a solution to converge [ 47 , 48 , 49 ]. The total number of mesh elements is required to be increased until reaching solution convergence.…”

“…Ventricle dynamics of human fetal hearts were investigated by a research group [ 35 , 40 , 41 , 47 ] using CFD models generated via 4D ultrasound scans. The movements of right and left ventricles are recorded during the cardiac cycle and applied as boundary conditions of dynamic mesh as shown in Figure 6 [ 41 ].…”

“…Wiputra et al (2016) investigated 20-week human right fetal ventricles using 4D CFD models [ 47 ]. Two main vortex structures were observed in the right ventricle and sustained until the systolic phase.…”

“…Due to the rotational flow in vortices, wall proximity of vortex flow is exposed to higher shear forces. According to the CFD results, WSS is within 0.4–1.2 Pa in the diastolic phase and 1.5–3.9 Pa in the systolic phase [ 47 ]. Peak WSS levels are observed on the regions close to the outflow tract.…”

Biomechanics of Human Fetal Hearts with Critical Aortic Stenosis

“…The segmentation surface was then smoothed with Geomagic StudioÒ (Geomagic Inc., Morrisville, NC, USA), as previously described. 52 A validated cardiac motion estimation algorithm was then applied to propagate the segmentation to other time points. 50 This algorithm involved iterative curve-fitting of a global motion model (spatial B-splines of temporal Fourier function) onto a group of pair-wise image registration at various time points, and was validated via published echo data with MRI ground truths.…”