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

Aims: 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.

Methods and results: 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.

Conclusion: 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.