# The effect of respiratory motion compensation in intracardiac 4D flow magnetic resonance imaging on left ventricular flow dynamics, multicomponent particle tracing, and valve tracking

## TL;DR

This study shows that compensating for respiratory motion in 4D flow MRI improves the accuracy of tracking heart flow patterns and valve movements.

## Contribution

The study introduces a method to assess the impact of respiratory motion compensation on intracardiac flow dynamics using 4D flow MRI.

## Key findings

- Respiratory motion compensation reduces mismatch in particle tracing compared to valve tracking.
- Data quality assessment is crucial for reliable particle tracing in 4D flow MRI.
- Stroke volume and ejection fraction differences remain significant even after compensation.

## Abstract

4D flow magnetic resonance imaging (MRI) has enabled evaluation of intracardiac flow dynamics by particle tracing for visualizing and quantifying complex flow patterns. The aim of this study was to assess the impact of respiratory motion compensation on 4D flow MRI–based left ventricular four-component particle tracing, valve tracking, and haemodynamics.

In this prospective cohort study, 4D flow MRI with and without respiratory motion compensation was performed in 15 healthy volunteers. Intracardiac particle tracing considered four components: direct flow, delayed ejection flow (DEF), retained inflow (RI), and residual volume. Data quality was assessed by comparing DEF and RI components. Particle tracing, valve tracking, kinetic energy (KE), and vorticity were compared between scan methods. Paired sample t-tests and intraclass correlation analysis were performed with an alpha of 0.05. DEF, RI, ejection fraction, and stroke volume were different between scan methods. Five participants showed DEF-RI mismatch > 10%. After excluding these, differences in flow fractions were non-significant. Differences in stroke volume, ejection fraction, and valvular flow mismatch between scan methods remained. Valve tracking was comparable between scan methods and correlated well with particle tracing. Absolute mismatch between particle tracing– and valve tracking–based mitral flow, and KE and vorticity at A-peak, was higher for non-compensated MRI.

Respiratory motion compensation can improve accuracy of intracardiac particle tracing based on 4D flow MRI by decreasing mismatch to retrospective valve tracking. For intracardiac particle tracing, respiratory motion compensation is advised. Robust data quality assessment for particle tracing–based analyses is equally crucial.

Graphical Abstract