An optimized framework for quantitative magnetization transfer imaging of the cervical spinal cord in vivo

Marco Battiston*, Francesco Grussu, Andrada Ianus, Torben Schneider, Ferran Prados, James Fairney, Sebastien Ourselin, Daniel C. Alexander, Mara Cercignani, Claudia A.M. Gandini Wheeler-Kingshott, Rebecca S. Samson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

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 [T2 F, T2 B], and forward exchange rate [kFB]) 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 mm3), 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), T2 F = 46.5(±1.6) ms, T2 B = 11.0(±0.2) µs, and kFB = 1.95(±0.06) Hz. Protocol optimization has a beneficial effect on reproducibility, especially for T2 B and kFB. Conclusion: The framework developed enables robust characterization of spinal cord microstructure in vivo using qMT. Magn Reson Med 79:2576–2588, 2018.

Original languageEnglish
Pages (from-to)2576-2588
Number of pages13
JournalMagnetic Resonance in Medicine
Volume79
Issue number5
Early online date16 Sept 2017
DOIs
Publication statusPublished - 1 May 2018

Keywords

  • myelin
  • protocol optimization
  • quantitative magnetization transfer
  • reduced field-of-view
  • spinal cord

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