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An optimized framework for quantitative magnetization transfer imaging of the cervical spinal cord in vivo
Author(s) -
Battiston Marco,
Grussu Francesco,
Ianus Andrada,
Schneider Torben,
Prados Ferran,
Fairney James,
Ourselin Sebastien,
Alexander Daniel C.,
Cercignani Mara,
Gandini WheelerKingshott Claudia A.M.,
Samson Rebecca S.
Publication year - 2018
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.26909
Subject(s) - magnetization transfer , magnetic resonance imaging , spinal cord , nuclear magnetic resonance , reproducibility , magnetization , relaxation (psychology) , parametric statistics , computer science , physics , mathematics , nuclear medicine , medicine , statistics , magnetic field , radiology , quantum mechanics , psychiatry
Purpose To develop a framework to fully characterize quantitative magnetization transfer indices in the human cervical cord in vivo within a clinically feasible time. Methods A dedicated spinal cord imaging protocol for quantitative magnetization transfer was developed using a reduced field‐of‐view approach with echo planar imaging (EPI) readout. Sequence parameters were optimized based in the Cramer‐Rao‐lower bound. Quantitative model parameters (i.e., bound pool fraction, free and bound pool transverse relaxation times [ T 2 F ,T 2 B ], and forward exchange rate [ k FB ]) were estimated implementing a numerical model capable of dealing with the novelties of the sequence adopted. The framework was tested on five healthy subjects. Results Cramer‐Rao‐lower bound minimization produces optimal sampling schemes without requiring the establishment of a steady‐state MT effect. The proposed framework allows quantitative voxel‐wise estimation of model parameters at the resolution typically used for spinal cord imaging (i.e. 0.75 × 0.75 × 5 mm 3 ), with a protocol duration of ∼35 min. Quantitative magnetization transfer parametric maps agree with literature values. Whole‐cord mean values are: bound pool fraction = 0.11(±0.01),T 2 F = 46.5(±1.6) ms,T 2 B = 11.0(±0.2) µs, and k FB = 1.95(±0.06) Hz. Protocol optimization has a beneficial effect on reproducibility, especially forT 2 Band k FB . Conclusion The framework developed enables robust characterization of spinal cord microstructure in vivo using qMT. Magn Reson Med 79:2576–2588, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.