Radiofrequency bias correction of magnetization prepared rapid gradient echo MRI at 7.0 Tesla using an external reference in a sequential protocol
(2021) In Tomography : a journal for imaging research 7(3). p.434-451- Abstract
- At field strengths of 7 T and above, T1-weighted imaging of human brain suffers increasingly 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... (More) - At field strengths of 7 T and above, T1-weighted imaging of human brain suffers increasingly 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 as 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. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/eede6974-9cfb-400c-8b3f-521257ad2b8a
- author
- Olsson, Hampus LU ; Novén, Mikael LU ; Lätt, Jimmy LU ; Wirestam, Ronnie LU and Helms, Gunther LU
- organization
- publishing date
- 2021
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Bias correction, Intensity correction, MPRAGE, MP2RAGE, B1, 7T, Ultra-high field, Longitudinal relaxation, T1, T1-mapping
- in
- Tomography : a journal for imaging research
- volume
- 7
- issue
- 3
- pages
- 434 - 451
- publisher
- Grapho Publications LLC
- external identifiers
-
- scopus:85115292423
- ISSN
- 2379-1381
- project
- Gradient echo-based quantitative MRI of human brain at 7T
- Automated data pipeline for clinical quantitative 7T MRI
- Multiparametric mapping of the brain at 7T using gradient echoes
- language
- English
- LU publication?
- yes
- id
- eede6974-9cfb-400c-8b3f-521257ad2b8a
- alternative location
- https://www.mdpi.com/2379-139X/7/3/38/htm
- date added to LUP
- 2021-09-13 11:59:27
- date last changed
- 2023-10-11 00:52:39
@article{eede6974-9cfb-400c-8b3f-521257ad2b8a, abstract = {{At field strengths of 7 T and above, T1-weighted imaging of human brain suffers increasingly 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,<br/>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 as 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.}}, author = {{Olsson, Hampus and Novén, Mikael and Lätt, Jimmy and Wirestam, Ronnie and Helms, Gunther}}, issn = {{2379-1381}}, keywords = {{Bias correction; Intensity correction; MPRAGE; MP2RAGE; B1; 7T; Ultra-high field; Longitudinal relaxation; T1; T1-mapping}}, language = {{eng}}, number = {{3}}, pages = {{434--451}}, publisher = {{Grapho Publications LLC}}, series = {{Tomography : a journal for imaging research}}, title = {{Radiofrequency bias correction of magnetization prepared rapid gradient echo MRI at 7.0 Tesla using an external reference in a sequential protocol}}, url = {{https://lup.lub.lu.se/search/files/102355637/21_Olsson_tomography_07_00038.pdf}}, volume = {{7}}, year = {{2021}}, }