Automated 4D flow MRI pipeline for the quantification of advanced hemodynamic parameters in the left atrium

Figures

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  Fig. 1. Overview of the computational framework for the advanced analysis of 4D flow magnetic resonance imaging of the left atrium. Only data from lower magnetic field strength acquisitions undergoes denoising and upsampling20. Next, a PC-MRA is computed21, followed by automatic segmentation22. The resulting segmentation mask facilitates the isolation of the structure of interest for subsequent quantitative and qualitative hemodynamic characterization. The entire pipeline relies exclusively on open-source software and code, ensuring accessibility and reproducibility. PC-MRA: Phase-contrast Magnetic Resonance Angiogram; Q-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {crit}_{500}$$\end{document}: Ratio of Q-criterion > 500 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {s}^{-2}$$\end{document}. Images created using…

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  Fig. 2. Dice score and Hausdorff 95 distance (mm) for the segmentation experiments of the left atrium. For Experiment 1, the x-axis is the total number of training cases from dataset 3 T (in red), while in Experiment 2, it is the amount of 1.5 T cases (in blue) added on top of the complete 3 T training dataset.

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  Fig. 3. Comparison of the maximal left atrium volume indexed by body surface area (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {LAV}_i$$\end{document}) derived from 2D cine and 4D flow magnetic resonance imaging. On top: scatter plot with the identity line for reference. Bottom: Bland-Altman plot with the bias as a dashed red line, while the 95% confidence intervals are represented by dashed blue lines.

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  Figure 4. Mean and standard error of the mean of the flow rate (ml/s) of the four pulmonary veins and the mitral valve. RS: Right superior; RI: Right inferior; LS: Left superior; LI: Left inferior; MV: Mitral valve; HCM: Hypertrophic cardiomyopathy with no left ventricular diastolic dysfunction (LVDD); G1: HCM with grade I LVDD; G2: HCM with grade II LVDD; G2 - SAM: HCM with grade II LVDD and systolic anterior motion of the mitral valve.

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  Fig. 5. Top: Mean kinetic energy (KE) as the solid line and mean viscous energy loss (VEL) as the dashed line in the left atrium (LA). Bottom: KE and VEL normalized by LA volume. HCM: Hypertrophic cardiomyopathy with no left ventricular diastolic dysfunction (LVDD); G1: HCM with grade I LVDD; G2: HCM with grade II LVDD; G2 - SAM: HCM with grade II LVDD and systolic anterior motion of the mitral valve.

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  Fig. 6. Top: Mean vorticity magnitude (solid line) and standard error of the mean with mitral valve (MV) flow rate (dashed line) for temporal reference. Bottom: Ratio of voxels in the left atrium with Q-criterion > 500 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {s}^{-2}$$\end{document} (solid line), indicating vortex core areas. HCM: Hypertrophic cardiomyopathy without left ventricular diastolic dysfunction (LVDD); G1: HCM with grade I LVDD; G2: HCM with grade II LVDD; G2 - SAM: HCM with grade II LVDD and systolic anterior motion of the MV.

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  Fig. 7. Mean and standard error of the mean of the relative pressure (mmHg) between the left atrium and left ventricle, measured using the vWERP method (solid line), accompanied by the mitral valve flow rate (dashed line). HCM: Hypertrophic cardiomyopathy with no left ventricular diastolic dysfunction (LVDD); G1: HCM with grade I LVDD; G2: HCM with grade II LVDD; G2 - SAM: HCM with grade II LVDD and systolic anterior motion of the mitral valve.

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  Fig. 8. An axial view of the central left atrial vortex across diverse cardiac disorders. The visualization combines the pathlines of particles emitted from the pulmonary veins, color-coded by velocity, and a volumetric rendering of the Q-criterion, indicating the core of the vortices. HCM: Hypertrophic cardiomyopathy with no left ventricular diastolic dysfunction (LVDD); G1: HCM with grade I LVDD; G2: HCM with grade II LVDD; G2 - SAM: HCM with grade II LVDD and systolic anterior motion of the mitral valve. Images created using ParaView (version 5.13.3).

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  Fig. 9. A volumetric rendering of the 4D flow magnetic resonance imaging velocity field in the left heart is shown, encompassing the left atrium, left ventricle, and ascending aorta. During processing, spheres are manually placed within regions of interest to serve as sample volumes to determine the dominant flow direction and define vessel cross-sections (shown in grey) for flow rate computations. On the right, the corresponding flow rates (ml/s) are shown for the mitral valve and the four pulmonary veins. LA: Left atrium, LV: Left ventricle, Asc. Aorta: Ascending aorta, MV: Mitral valve, RS: Right superior, LS: Left superior, RI: Right inferior, LI: Left inferior. Images created using ParaView (version 5.13.3).