Optimization of white-matter-nulled magnetization prepared rapid gradient echo (MP-RAGE) imaging.
Magn. Reson. Med.. 2014-05-29; 73(5): 1786-1794
DOI: 10.1002/mrm.25298
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1. Magn Reson Med. 2015 May;73(5):1786-94. doi: 10.1002/mrm.25298. Epub 2014 May 29.
Optimization of white-matter-nulled magnetization prepared rapid gradient echo
(MP-RAGE) imaging.
Saranathan M(1), Tourdias T, Bayram E, Ghanouni P, Rutt BK.
Author information:
(1)Department of Radiology, Stanford, California, USA.
PURPOSE: To optimize the white-matter-nulled (WMn) Magnetization Prepared Rapid
Gradient Echo (MP-RAGE) sequence at 7 Tesla (T), with comparisons to 3T.
METHODS: Optimal parameters for maximizing signal-to-noise ratio (SNR) efficiency
were derived. The effect of flip angle and repetition time (TR) on image blurring
was modeled using simulations and validated in vivo. A novel two-dimensional (2D)
-centric radial fan beam (RFB) k-space segmentation scheme was used to shorten
scan times and improve parallel imaging. Healthy subjects as well as patients
with multiple sclerosis and tremor were scanned using the optimized protocols.
RESULTS: Inversion repetition times (TS) of 4.5 s and 6 s were found to yield the
highest SNR efficiency for WMn MP-RAGE at 3T and 7T, respectively. Blurring was
more sensitive to flip in WMn than in CSFn MP-RAGE and relatively insensitive to
TR for both regimes. The 2D RFB scheme had 19% and 47% higher thalamic SNR and
SNR efficiency than the 1D centric scheme for WMn MP-RAGE. Compared with 3T, SNR
and SNR efficiency were higher for the 7T WMn regime by 56% and 41%,
respectively. MS lesions in the cortex and thalamus as well as thalamic subnuclei
in tremor patients were clearly delineated using WMn MP-RAGE.
CONCLUSION: Optimization and new view ordering enabled MP-RAGE imaging with 0.8-1
mm(3) isotropic spatial resolution in scan times of 5 min with whole brain
coverage.
© 2014 Wiley Periodicals, Inc.
DOI: 10.1002/mrm.25298
PMCID: PMC4247820
PMID: 24889754 [Indexed for MEDLINE]