Inhomogeneous magnetization transfer imaging: Concepts and directions for further development

David C. Alsop, Ece Ercan, Olivier M. Girard, Alex L. Mackay, Carl A. Michal, Gopal Varma, Elena Vinogradov, Guillaume Duhamel

Research output: Contribution to journalReview articlepeer-review

Abstract

Off-resonance radio frequency irradiation can induce the ordering of proton spins in the dipolar fields of their neighbors, in molecules with restricted mobility. This dipolar order decays with a characteristic relaxation time, T1D, that is very different from the T1 and T2 relaxation of the nuclear alignment with the main magnetic field. Inhomogeneous magnetization transfer (ihMT) imaging is a refinement of magnetization transfer (MT) imaging that isolates the MT signal dependence on dipolar order relaxation times within motion-constrained molecules. Because T1D relaxation is a unique contrast mechanism, ihMT may enable improved characterization of tissue. Initial work has stressed the high correlation between ihMT signal and myelin density. Dipolar order relaxation appears to be much longer in membrane lipids than other molecules. Recent work has shown, however, that ihMT acquisitions may also be adjusted to emphasize different ranges of T1D. These newer approaches may be sensitive to other microstructural components of tissue. Here, we review the concepts and history of ihMT and outline the requirements for further development to realize its full potential.

Original languageEnglish (US)
JournalNMR in biomedicine
DOIs
StateAccepted/In press - 2022

Keywords

  • dipolar order
  • magnetization transfer
  • myelin

ASJC Scopus subject areas

  • Molecular Medicine
  • Radiology Nuclear Medicine and imaging
  • Spectroscopy

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