In Vivo Quantitative MRI of Hemodynamics, Endothelial Function, and Metabolites

Abstract

Magnetic resonance (MR) hemodynamic imaging involves the study of vascular blood circulation. The regulation of tissue oxygenation depends directly on the regulation of blood flow. Impaired blood flow, oxygen supply, oxygen consumption, and vascular integrity are major contributors to organ dysfunction as these can limit the supply of nutrients and clearance of toxic substrates. MR metabolite imaging, also known as MR spectroscopic imaging (MRSI), is the detection and quantification of in vivo chemical compounds (metabolites) by protons (1H), phosphorus (31P), or other atoms attached to the molecules. Changes in metabolite content are an early marker of diseases and in general, may precede anatomical/structural changes. Therefore, efficient techniques for robust measurement of blood flow, endothelial function, and metabolite content can be very beneficial to investigate pathology in various organs. The specific goals of this work were: (i) to determine the feasibility of a novel technique for real-time simultaneous measurement of arterial blood flow, perfusion, venous oxygen saturation, and bioenergetics (31P MRS) in the human skeletal muscle; (ii) to develop a novel technique to measure perfusion and blood-brain barrier (BBB) permeability using magnetization transfer (MT) and arterial spin labeling (ASL) in the human brain; (iii) to develop a robust technique for high-resolution fast 1H MRSI of the human brain using non-Cartesian (rosette) trajectory; and (iv) to demonstrate high-resolution human spinal cord imaging using motion-insensitive rosette trajectory with MT preparation and compressed sensing MRI. The overarching goal of the work presented here is to develop new non-invasive techniques that can provide novel information about pathology and help monitor disease progression and the efficacy of treatment.