Accelerated Multi-Dimensional Flow Encoding by MRI

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The primary focus of my research program is to develop fast MRI methods to quantify cardiovascular physiology. A cornerstone of this work is phase-contrast (PC) MRI, a powerful non-invasive tool for blood flow measurement. Typically, PC MRI involves prescription of a single slice perpendicular to a target vessel, and flow through the slice is measured. Although convenient for measuring flow in long, straight vessels, this approach does not translate well to complex vascular geometries or the heart. To address this limitation, advanced PC MRI methods have been developed to quantify blood flow in three spatial directions over a 3D volume. These so-called `4D Flow' approaches permit visualization of complex blood flow patterns, and can also be used to quantify hemodynamic parameters such as wall shear stress or pressure gradients. However, 4D Flow has seen limited adoption because scan times are relatively long (>10 minutes), making them prone to artifact from patient motion and irregular respiratory patterns. These challenges are exacerbated in pediatrics because subjects are more likely to move during acquisition, and scan times become even longer (~20 minutes) as finer resolution is necessary to visualize small cardiovascular structures. Fortunately, the convergence of 1) MRI hardware advancements that permit rapid scanning, 2) new techniques for motion compensation and 3) new reconstruction strategies which generate high quality images from "undersampled" data, provide an unprecedented opportunity to dramatically improve the efficiency and robustness of 4D Flow. With the goal of making 4D Flow applicable to pediatric subjects, my program seeks to develop acquisition and reconstruction strategies which synergistically combine rapid scanning, motion compensation, and undersampling techniques while ensuring accurate flow measurement. A long-term goal of my research program is to improve our understanding of pediatric cardiovascular physiology. To support this program, funding is requested for trainees to pursue the following Aims: 1.Bulk Motion Detection & Compensation: Pioneer a strategy to detect and compensate for the random motion of restless subjects. 2.Wireless Physiological Motion Detection: Optimize a "wireless" technique for monitoring cardiac and respiratory motion throughout the 4D flow acquisition, eliminating the need for cumbersome monitoring equipment. 3.Accelerated Acquisition & Reconstruction: Create a data acquisition and reconstruction pipeline for accurate flow measurement with highly undersampled 4D Flow data. Fulfillment of these objectives will result in a robust and efficient 4D Flow acquisition and reconstruction scheme with high spatial resolution, a scan time under 10 minutes, and no need for external physiological monitoring devices. This innovative program promises to advance research in developmental cardiovascular physiology while providing trainees with in-demand skills for careers in academia or industry.