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In vivo measurement of a new source of contrast, the dipolar relaxation time, T 1 D , using a modified inhomogeneous magnetization transfer (ihMT) sequence
Author(s) -
Varma Gopal,
Girard Olivier M.,
Prevost Valentin H.,
Grant Aaron K.,
Duhamel Guillaume,
Alsop David C.
Publication year - 2017
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.26523
Subject(s) - magnetization transfer , nuclear magnetic resonance , relaxation (psychology) , white matter , dipole , magnetization , contrast (vision) , magnetic resonance imaging , offset (computer science) , flip angle , in vivo , pulse sequence , physics , computer science , magnetic field , optics , medicine , neuroscience , biology , radiology , microbiology and biotechnology , quantum mechanics , programming language
Purpose This paper describes a technique that can be used in vivo to measure the dipolar relaxation time, T 1 D , of macromolecular protons contributing to magnetization transfer (MT) in tissues and to produce quantitative T 1 D maps. Theory and Methods The technique builds upon the inhomogeneous MT (ihMT) technique that is particularly sensitive to tissue components with long T 1 D . A standard ihMT experiment was altered to introduce a variable time for switching between positive and negative offset frequencies for RF saturation. A model for the dependence of ihMT was developed and used to fit data acquired in vivo. Results Application of the method to images from brains of healthy volunteers produced values of T 1 D = (5.9 ± 1.2) ms in gray matter and T 1 D = (6.2 ± 0.4) ms in white matter regions and provided maps of the T 1 D parameter. Conclusion The model and experiments described provide access to a new relaxation characteristic of tissue with potentially unique diagnostic information. Magn Reson Med 78:1362–1372, 2017. © 2016 International Society for Magnetic Resonance in Medicine.