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Optimized balanced steady‐state free precession magnetization transfer imaging
Author(s) -
Bieri O.,
Scheffler K.
Publication year - 2007
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.21326
Subject(s) - precession , signal (programming language) , magnetization transfer , flip angle , nuclear magnetic resonance , pulse (music) , pulse sequence , sensitivity (control systems) , materials science , reduction (mathematics) , computer science , contrast (vision) , physics , magnetic resonance imaging , optics , mathematics , medicine , geometry , astronomy , electronic engineering , detector , radiology , programming language , engineering
Balanced steady‐state free precession (bSSFP) suffers from a considerable signal loss in tissues. This apparent signal reduction originates from magnetization transfer (MT) and may be reduced by an increase in repetition time or by a reduction in flip angle. In this work, MT effects in bSSFP are modulated by a modification of the bSSFP sequence scheme. Strong signal attenuations are achieved with short radio frequency (RF) pulses in combination with short repetition times, whereas near full, i.e., MT‐free, bSSFP signal is obtained by a considerable prolongation of the RF pulse duration. Similar to standard methods, the MT ratio (MTR) in bSSFP depends on several sequence parameters. Optimized bSSFP protocol settings are derived that can be applied to various tissues yielding maximal sensitivity to MT while minimizing contribution from other impurities, such as off‐resonances. Evaluation of MT in human brain using such optimized bSSFP protocols shows high correlation with MTR values from commonly used gradient echo (GRE) sequences. In summary, a novel method to generate MTR maps using bSSFP image acquisitions is presented and factors that optimize and influence this contrast are discussed. Magn Reson Med 58:511–518, 2007. © 2007 Wiley‐Liss, Inc.