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- Title
MP3RAGE: Simultaneous mapping of T<sub>1</sub> and B1+ in human brain at 7T.
- Authors
Olsson, Hampus; Andersen, Mads; Kadhim, Mustafa; Helms, Gunther
- 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 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.
- Subjects
CURVE fitting; BRAIN mapping; HUMAN beings
- Publication
Magnetic Resonance in Medicine, 2022, Vol 87, Issue 6, p2637
- ISSN
0740-3194
- Publication type
Article
- DOI
10.1002/mrm.29151