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Magn Reson Med. 2011 Apr;65(4):1021-35. doi: 10.1002/mrm.22685. Epub 2010 Dec 8.

Correction of main and transmit magnetic field (B0 and B1) inhomogeneity effects in multicomponent-driven equilibrium single-pulse observation of T1 and T2.

Author information

1
Centre for Neuroimaging Research, Institute of Psychiatry, King's College London, London, United Kingdom. sdeoni@mac.com

Abstract

Multicomponent-driven equilibrium single-component observation of T(1) and T(2) offers a new approach to multiple component relaxation time and myelin water analysis. The method derives two-component relaxation information from spoiled and fully balanced steady-state (SPGR and bSSFP) imaging data acquired over multiple flip angles. Although these steady-state imaging techniques afford rapid acquisition times and high signal-to-noise ratio efficiency, they are also sensitive to main (B(0) ) and transmit (B(1) ) magnetic field inhomogeneities. These effects alter the measured signal from their theoretical values and lead to substantive errors in the derived myelin volume fraction estimates. Here, we incorporate correction techniques to mitigate these effects. DESPOT1-HIFI is used to first calibrate the transmitted flip angles; and B(0) affects are removed through the inclusion of an additional parameter in the multicomponent-driven equilibrium single-component observation of T(1) and T(2) fitting, coupled with the acquisition of multiple phase-cycled bSSFP data. The performance of these correction techniques was evaluated using numerical simulations, demonstrating effective removal of B(0) and B(1)-induced errors in the derived myelin fraction relaxation parameters. The approach was also successfully demonstrated in vivo, with near artifact-free whole-brain, high spatial resolution (1.7 mm × 1.7 mm × 1.7 mm isotropic voxels) myelin water fraction maps acquired in a clinically feasible 16 min.

PMID:
21413066
PMCID:
PMC3777237
DOI:
10.1002/mrm.22685
[Indexed for MEDLINE]
Free PMC Article

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