A Novel Multiparametric Approach to 3D Quantitative MRI of the Brain

TLDR

Tissue MR properties such as relaxation times, proton density, and magnetic susceptibility can be quantified in multiple ways. The study proposes a comprehensive approach to generate 3D high‑resolution quantitative maps of arbitrary body regions, focusing on the brain. The method uses fast steady‑state acquisitions to map R1, R2, R2*, proton density, and magnetic susceptibility, applies a novel denoising scheme, and compensates RF inhomogeneity biases via an information‑theory approach. The approach yields high‑resolution quantitative maps in healthy controls and multiple sclerosis patients, demonstrating its feasibility and potential clinical relevance.

Abstract

Magnetic Resonance properties of tissues can be quantified in several respects: relaxation processes, density of imaged nuclei, magnetism of environmental molecules, etc. In this paper, we propose a new comprehensive approach to obtain 3D high resolution quantitative maps of arbitrary body districts, mainly focusing on the brain. The theory presented makes it possible to map longitudinal (R1), pure transverse (R2) and free induction decay (R 2 *) rates, along with proton density (PD) and magnetic susceptibility (χ), from a set of fast acquisition sequences in steady-state that are highly insensitive to flow phenomena. A novel denoising scheme is described and applied to the acquired datasets to enhance the signal to noise ratio of the derived maps and an information theory approach compensates for biases from radio frequency (RF) inhomogeneities, if no direct measure of the RF field is available. Finally, the results obtained on sample brain scans of healthy controls and multiple sclerosis patients are presented and discussed.