Rapid and Reliable Quantitative MRI of Central Nervous System (CNS) at Ultra-High Field MRI (7T)

Abstract

Quantitative Magnetic Resonance Imaging (qMRI) surpasses traditional MRI, which primarily focuses on local image contrast. It reveals specific physical parameters related to the nuclear spin of protons in water and macromolecules. Parameters from qMRI, including longitudinal and transverse relaxation rates, magnetic susceptibility, proton density, and magnetization transfer, provide key insights into myelination, iron content, and cell membranes in the living central nervous system (CNS). qMRI has identified crucial, highly sensitive biomarkers in both health and disease, continually aiding longitudinal clinical trials as a non-invasive means to monitor changes in tissue. It offers insights into disease mechanisms that may precede visible changes in anatomical or structural images. Given the complementary nature of qMRI methods- such as T2* relaxometry, myelin imaging, magnetization transfer, and quantitative susceptibility mapping- to traditional contrast-weighted MRI, developing and implementing reliable acquisition and processing qMRI methods tailored to ultra-high field (7T) MR settings is vital for reliably assessing biophysical measures within a clinically feasible timeframe. The specific goals of this work were: (i) to implement a protocol to accurately quantify T2*, QSM, qMT and MWF in-vivo at 7T ; (ii) to assess the reproducibility of the quantified values using scan-rescan experiments; (iii) to develop a robust technique for fast imaging of the human CNS; and (iv) to use the developed custom sequence to quantify myelin content with an increased acquisition speed by Compressed Sensing (CS). The primary aim of this work is to develop time-efficient, innovative, and non-invasive techniques capable of delivering quantitative insights into pathology, assisting in the monitoring of disease progression, and evaluating treatment effectiveness.