Radiofrequency bias correction of magnetization prepared rapid gradient echo mri at 7.0 tesla using an external reference in a sequential protocol
Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
At field strengths of 7 T and above, T1-weighted imaging of human brain suffers increas-ingly from radiofrequency (RF) B1 inhomogeneities. The well-known MP2RAGE (magnetization prepared two rapid acquisition gradient echoes) sequence provides a solution but may not be readily available for all MR systems. Here, we describe the implementation and evaluation of a sequential protocol to obtain normalized magnetization prepared rapid gradient echo (MPRAGE) images at 0.7, 0.8, or 0.9-mm isotropic spatial resolution. Optimization focused on the reference gradient-recalled echo (GRE) that was used for normalization of the MPRAGE. A good compromise between white-gray matter contrast and the signal-to-noise ratio (SNR) was reached at a flip angle of 3◦ and total scan time was reduced by increasing the reference voxel size by a factor of 8 relative to the MPRAGE resolution. The average intra-subject coefficient-of-variation (CV) in segmented white matter (WM) was 7.9 ± 3.3% after normalization, compared to 20 ± 8.4% before. The corresponding inter-subject average CV in WM was 7.6 ± 7.6% and 13 ± 7.8%. Maps of T1 derived from forward signal modelling showed no obvious bias after correction by a separately acquired flip angle map. To conclude, a non-interleaved acquisition for normalization of MPRAGE offers a simple alternative to MP2RAGE to obtain semi-quantitative purely T1-weighted images. These images can be converted to T1 maps, analogously to the established MP2RAGE approach. Scan time can be reduced by increasing the reference voxel size which has only a miniscule effect on image quality.
Originalsprog | Engelsk |
---|---|
Tidsskrift | Tomography |
Vol/bind | 7 |
Udgave nummer | 3 |
Sider (fra-til) | 434-451 |
Antal sider | 18 |
ISSN | 2379-1381 |
DOI | |
Status | Udgivet - 2021 |
Eksternt udgivet | Ja |
Bibliografisk note
(Ekstern)
Funding Information:
This research was funded by the Swedish Research Council, grant numbers NT-2014-6193 and M-2017-00995. The APC was funded in part by Lund University.
Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.
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