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Multi-compartment T2 relaxometry using a spatially constrained multi-Gaussian model.

TitleMulti-compartment T2 relaxometry using a spatially constrained multi-Gaussian model.
Publication TypeJournal Article
Year of Publication2014
AuthorsRaj A, Pandya S, Shen X, LoCastro E, Nguyen TD, Gauthier SA
JournalPLoS One
Volume9
Issue6
Paginatione98391
Date Published2014
ISSN1932-6203
KeywordsBrain, Humans, Image Interpretation, Computer-Assisted, Magnetic Resonance Imaging, Models, Theoretical, Multiple Sclerosis, Myelin Sheath, White Matter
Abstract

The brain's myelin content can be mapped by T2-relaxometry, which resolves multiple differentially relaxing T2 pools from multi-echo MRI. Unfortunately, the conventional fitting procedure is a hard and numerically ill-posed problem. Consequently, the T2 distributions and myelin maps become very sensitive to noise and are frequently difficult to interpret diagnostically. Although regularization can improve stability, it is generally not adequate, particularly at relatively low signal to noise ratio (SNR) of around 100-200. The purpose of this study was to obtain a fitting algorithm which is able to overcome these difficulties and generate usable myelin maps from noisy acquisitions in a realistic scan time. To this end, we restrict the T2 distribution to only 3 distinct resolvable tissue compartments, modeled as Gaussians: myelin water, intra/extra-cellular water and a slow relaxing cerebrospinal fluid compartment. We also impose spatial smoothness expectation that volume fractions and T2 relaxation times of tissue compartments change smoothly within coherent brain regions. The method greatly improves robustness to noise, reduces spatial variations, improves definition of white matter fibers, and enhances detection of demyelinating lesions. Due to efficient design, the additional spatial aspect does not cause an increase in processing time. The proposed method was applied to fast spiral acquisitions on which conventional fitting gives uninterpretable results. While these fast acquisitions suffer from noise and inhomogeneity artifacts, our preliminary results indicate the potential of spatially constrained 3-pool T2 relaxometry.

DOI10.1371/journal.pone.0098391
Alternate JournalPLoS ONE
PubMed ID24896833
PubMed Central IDPMC4045663
Grant List1R01NS075425 / NS / NINDS NIH HHS / United States
5P41RR02953 / RR / NCRR NIH HHS / United States

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