Simultaneous mapping of T1and B1+ in human brain at 7T
(2022) In Magnetic Resonance in Medicine 87(6). p.2637-2649- Abstract
- Purpose
To map T1 and the local flip angle (B1+) in human brain using a single MP3RAGE sequence with 3 rapid acquisitions of gradient echoes (RAGEs).
Theory and methods
A third RAGE with a relatively high flip angle was appended to an MP2RAGE sequence. Through curve fitting and a rational approximation for small flip angles and short TR, closed form solutions for T1 and B1+ were derived. The influence of different k-space encoding schemes on precision and whether edge enhancement artifacts could be reduced with a saturation pulse applied prior to the third RAGE were explored. Validation of T1 estimates was performed using single-slice inversion... (More) - Purpose
To map T1 and the local flip angle (B1+) in human brain using a single MP3RAGE sequence with 3 rapid acquisitions of gradient echoes (RAGEs).
Theory and methods
A third RAGE with a relatively high flip angle was appended to an MP2RAGE sequence. Through curve fitting and a rational approximation for small flip angles and short TR, closed form solutions for T1 and B1+ were derived. The influence of different k-space encoding schemes on precision and whether edge enhancement artifacts could be reduced with a saturation pulse applied prior to the third RAGE were explored. Validation of T1 estimates was performed using single-slice inversion recovery (IR) and a subsequent region-of-interest–based comparison, whereas validation of B1+ was performed using a whole brain pixelwise comparison to a DREAM flip angle mapping protocol. Lastly, MP3RAGE was compared to T1-mapping by MP2RAGE with separate B1+ correction.
Results
Whole brain maps of T1 and B1+ at 1 mm isotropic resolution were obtained with MP3RAGE in 06:37 min. A linear–reverse centric–reverse centric phase-encoding order of the 3 RAGEs improved precision, and artifacts were successfully reduced with the saturation pulse. Estimations of T1 and B1+ deviated +2.5 ± 3.1% and −1.7 ± 8.6% from their respective references.
Conclusion
T1 and B1+ can be mapped simultaneously using MP3RAGE. The approach can be thought of as combining MP2RAGE with a dual flip angle T1-mapping protocol. Both maps can be solved for analytically and will be inherently co-registered at the high resolution associated with MPRAGE.
(Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/6b696448-0041-48ef-8695-74c71675414d
- author
- Olsson, Hampus
LU
; Andersen, Mads
LU
; Kadhim, Mustafa
LU
and Helms, Gunther
LU
- organization
- publishing date
- 2022
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- 7T, B1+ mapping, dual flip angle, MPRAGE, T1- mapping
- in
- Magnetic Resonance in Medicine
- volume
- 87
- issue
- 6
- pages
- 2637 - 2649
- publisher
- John Wiley & Sons Inc.
- external identifiers
-
- scopus:85122733294
- pmid:35037283
- ISSN
- 1522-2594
- DOI
- 10.1002/mrm.29151
- project
- Measuring T1 using MP2RAGE in Human Brain at 7T
- Gradient echo-based quantitative MRI of human brain at 7T
- language
- English
- LU publication?
- yes
- id
- 6b696448-0041-48ef-8695-74c71675414d
- date added to LUP
- 2022-01-17 14:40:44
- date last changed
- 2022-10-27 07:42:37
@article{6b696448-0041-48ef-8695-74c71675414d, abstract = {{Purpose<br/>To map T<sub>1</sub> and the local flip angle (B<sub>1</sub><sup>+</sup>) in human brain using a single MP3RAGE sequence with 3 rapid acquisitions of gradient echoes (RAGEs).<br/><br/>Theory and methods<br/>A third RAGE with a relatively high flip angle was appended to an MP2RAGE sequence. Through curve fitting and a rational approximation for small flip angles and short TR, closed form solutions for T<sub>1</sub> and B<sub>1</sub><sup>+</sup> were derived. The influence of different k-space encoding schemes on precision and whether edge enhancement artifacts could be reduced with a saturation pulse applied prior to the third RAGE were explored. Validation of T<sub>1</sub> estimates was performed using single-slice inversion recovery (IR) and a subsequent region-of-interest–based comparison, whereas validation of B<sub>1</sub><sup>+</sup> was performed using a whole brain pixelwise comparison to a DREAM flip angle mapping protocol. Lastly, MP3RAGE was compared to T<sub>1</sub>-mapping by MP2RAGE with separate B<sub>1</sub><sup>+</sup> correction.<br/><br/>Results<br/>Whole brain maps of T<sub>1</sub> and B<sub>1</sub><sup>+</sup> at 1 mm isotropic resolution were obtained with MP3RAGE in 06:37 min. A linear–reverse centric–reverse centric phase-encoding order of the 3 RAGEs improved precision, and artifacts were successfully reduced with the saturation pulse. Estimations of T<sub>1</sub> and B<sub>1</sub><sup>+</sup> deviated +2.5 ± 3.1% and −1.7 ± 8.6% from their respective references.<br/><br/>Conclusion<br/>T<sub>1</sub> and B<sub>1</sub><sup>+</sup> can be mapped simultaneously using MP3RAGE. The approach can be thought of as combining MP2RAGE with a dual flip angle T<sub>1</sub>-mapping protocol. Both maps can be solved for analytically and will be inherently co-registered at the high resolution associated with MPRAGE.<br/>}}, author = {{Olsson, Hampus and Andersen, Mads and Kadhim, Mustafa and Helms, Gunther}}, issn = {{1522-2594}}, keywords = {{7T, B1+ mapping, dual flip angle, MPRAGE, T1- mapping}}, language = {{eng}}, number = {{6}}, pages = {{2637--2649}}, publisher = {{John Wiley & Sons Inc.}}, series = {{Magnetic Resonance in Medicine}}, title = {{Simultaneous mapping of T<sub>1</sub>and B<sub>1</sub><sup>+</sup> in human brain at 7T}}, url = {{http://dx.doi.org/10.1002/mrm.29151}}, doi = {{10.1002/mrm.29151}}, volume = {{87}}, year = {{2022}}, }