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.