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MRI Flow Imaging: Validation, Assessment of Complex Hemodynamics, and the Power of Functional Challenges

Kolloquium der Abteilung 8

2D phase contrast MRI is an established technique to quantify blood flow and velocities. Recent hardware and methodology advances have enabled the use of 4D Flow MRI in clinically acceptable scan times. 4D Flow MRI provides a comprehensive measure of dynamic velocity vector fields with whole organ coverage, thereby enabling more complex hemodynamic analysis to derive secondary parameters of interest such as vorticity, wall shear stress, pulse wave velocity, and others. This presentation will review various innovative imaging paradigms that quantify cerebro- and cardiovascular hemodynamics with a special focus on response to functional challenges. Such challenges can be a powerful amendment to standard diagnostic tests as they have the potential to elicit differences earlier in the disease processes or treatment responses compared to imaging performed under normal resting conditions. Applications include (1) cardiac imaging during exercising in the bore, (2) assessing the effect of right ventricular afterload reduction through pharmacological challenges (sildenafil) and heart rate reduction with metoprolol, (3) cardiac response to hypoxia, (4) hepatic flow in response to a meal challenge , and (5) cerebrovascular response to hypoxia and hypercapnia. Challenges for the in vivo validation of hemodynamic parameters will also be considered.