Comparison of Immersed Boundary Simulations of Heart Valve Hemodynamics against In Vitro 4D Flow MRI Data

TL;DR

This study compares immersed boundary method simulations of heart valve hemodynamics with in vitro 4D flow MRI data, demonstrating good qualitative and quantitative agreement to validate computational models against experimental measurements.

Contribution

The paper presents a methodology for constructing computational models of physical heart valve experiments for direct comparison with experimental data, aiding validation of FSI simulations.

Findings

Simulations showed excellent qualitative agreement with MRI data.

Integral flow metrics matched closely between simulation and experiment.

Reasonable error levels were observed across the flow domain.

Abstract

The immersed boundary (IB) method is a mathematical framework for fluid-structure interaction problems (FSI) that was originally developed to simulate flows around heart valves. Direct comparison of FSI simulations around heart valves against experimental data is challenging, however, due to the difficulty of performing robust and effective simulations, the complications of modeling a specific physical experiment, and the need to acquire experimental data that is directly comparable to simulation data. Such comparators are a necessary precursor for further formal validation studies of FSI simulations involving heart valves. In this work, we performed physical experiments of flow through a pulmonary valve in an in vitro pulse duplicator, and measured the corresponding velocity field using 4D flow MRI (4-dimensional flow magnetic resonance imaging). We constructed a computer model of this pulmonary artery setup, including modeling valve geometry and material properties via a technique called design-based elasticity, and simulated flow through it with the IB method. The simulated flow fields showed excellent qualitative agreement with experiments, excellent agreement on integral metrics, and reasonable relative error in the entire flow domain and on slices of interest. These results illustrate how to construct a computational model of a physical experiment for use as a comparator.