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 (R 1), pure transverse (R 2) and free induction decay () 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.
Highlights
Multi-parametric quantitative Magnetic Resonance Imaging based on the relaxometry properties of intracranial tissues has long been and still is an active field of research in medicine and physics [1]
We show that high Signal-to-Noise Ratio (SNR) full brain coverage with a sub-millimeter resolution may be obtained in a total acquisition time of 14 minutes
We have described a 3D acquisition protocol that yields multiple quantitative parametric maps (R1, R2, RÃ2, proton density (PD) and χ) based on the relaxometric properties of brain tissues
Summary
Multi-parametric quantitative Magnetic Resonance Imaging (qMRI) based on the relaxometry properties of intracranial tissues has long been and still is an active field of research in medicine and physics [1]. Several approaches have been used, aiming at obtaining quantitative estimates of the longitudinal relaxation rate (R1), transverse relaxation rate (R2) and proton density (PD) of brain tissues [2,3,4,5,6,7]. We present a new acquisition and processing procedure that, starting from a set of conventional high resolution 3D Steady State sequences, makes it possible to achieve full brain coverage for absolute measurements of intracranial compartments. For the first set of tissue properties, Radio Frequency (RF) B1 inhomogeneities can create problems. As pointed out in [9], a 3D acquisition protocol is preferred to PLOS ONE | DOI:10.1371/journal.pone.0134963 August 18, 2015
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