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Rapid measurement of brain macromolecular proton fraction with transient saturation transfer MRI
Author(s) -
Gelderen Peter,
Jiang Xu,
Duyn Jeff H.
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.26304
Subject(s) - magnetization transfer , proton , nuclear magnetic resonance , saturation (graph theory) , pulse (music) , relaxation (psychology) , time constant , transient (computer programming) , fraction (chemistry) , human brain , pulse sequence , chemistry , magnetic resonance imaging , materials science , analytical chemistry (journal) , physics , mathematics , chromatography , optics , nuclear physics , computer science , biology , medicine , combinatorics , operating system , electrical engineering , neuroscience , detector , radiology , engineering
Purpose To develop an efficient MRI approach to estimate the nonwater proton fraction ( f ) in human brain. Methods We implement a brief, efficient magnetization transfer (MT) pulse that selectively saturates the magnetization of the (semi‐) solid protons, and monitor the transfer of this saturation to the water protons as a function of delay after saturation. Results Analysis of the transient MT effect with two‐pool model allowed robust extraction of f at both 3 and 7 T. This required estimating the longitudinal relaxation rate constant (R 1,MP and R 1,WP ) for both proton pools, which was achieved with the assumption of uniform R 1,MP and R 1,WP across brain tissues. Resulting values of f were approximately 50% higher than reported previously, which is partly attributed to MT‐pulse efficiency and R 1,MP being higher than assumed previously. Conclusion Experiments performed on human brain in vivo at 3 and 7 T demonstrate the ability of the method to robustly determine f in a scan time of approximately 5 min. Magn Reson Med 77:2174–2185, 2017. © 2016 International Society for Magnetic Resonance in Medicine