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Magn Reson Med. 2016 Oct;76(4):1127-35. doi: 10.1002/mrm.26009. Epub 2015 Oct 28.

MR fingerprinting with simultaneous B1 estimation.

Author information

1
Istituto Nazionale di Fisica Nucleare (INFN), sezione di Pisa, Largo B. Pontecorvo, Pisa (PI), Italy. guido.buonincontri@pi.infn.it.
2
Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge, United Kingdom.

Abstract

PURPOSE:

MR fingerprinting (MRF) can be used for quantitative estimation of physical parameters in MRI. Here, we extend the method to incorporate B1 estimation.

METHODS:

The acquisition is based on steady state free precession MR fingerprinting with a Cartesian trajectory. To increase the sensitivity to the B1 profile, abrupt changes in flip angle were introduced in the sequence. Slice profile and B1 effects were included in the dictionary and the results from two- and three-dimensional (3D) acquisitions were compared. Acceleration was demonstrated using retrospective undersampling in the phase encode directions of 3D data exploiting redundancy between MRF frames at the edges of k-space.

RESULTS:

Without B1 estimation, T2 and B1 were inaccurate by more than 20%. Abrupt changes in flip angle improved B1 maps. T1 and T2 values obtained with the new MRF methods agree with classical spin echo measurements and are independent of the B1 field profile. When using view sharing reconstruction, results remained accurate (error <10%) when sampling under 10% of k-space from the 3D data.

CONCLUSION:

The methods demonstrated here can successfully measure T1, T2, and B1. Errors due to slice profile can be substantially reduced by including its effect in the dictionary or acquiring data in 3D. Magn Reson Med 76:1127-1135, 2016. © 2015 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

KEYWORDS:

3D; B1; MRF; T1; T2; fingerprinting; relaxometry

PMID:
26509746
PMCID:
PMC5061105
DOI:
10.1002/mrm.26009
[Indexed for MEDLINE]
Free PMC Article

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