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- Title
Respiration induced B1+ changes and their impact on universal and tailored 3D kT‐point parallel transmission pulses for 7T cardiac imaging.
- Authors
Aigner, Christoph Stefan; Dietrich, Sebastian; Schmitter, Sebastian
- Abstract
Purpose: Human heart imaging at ultra‐high fields is highly challenging because of respiratory motion‐induced artefacts and spatially heterogeneous B1+ profiles. This work demonstrates that respiration resolved 3D B1+‐maps can be used with a dedicated tailored and universal parallel transmission (pTx) pulse design to compensate respiration related B1+ changes in subjects performing shallow and deep breathing (SB/DB). Methods: Three‐dimensional (3D) B1+‐maps of the thorax were acquired in 31 subjects under SB and in 15 subjects under SB and DB. Different universal and tailored non‐selective pTx pulses were designed from non‐respiration resolved (NRR) and respiration resolved (RR) reconstructions of the SB/DB B1+‐maps. The performance of all pulses was tested with RR‐SB/DB B1+‐maps. Respiration‐robust tailored and universal pulses were applied in vivo in 5 subjects at 7T in 3D gradient‐echo free‐breathing scans. Results: All optimized pTx pulses performed well for SB. For DB, however, only the universal and the tailored respiration‐robust pulses achieved homogeneous flip angles (FAs) in all subjects and across all respiration states, whereas the tailored respiration‐specific pulses resulted in a higher FA variation. The respiration‐robust universal pulse resulted in an average coefficient of variation in the FA maps of 12.6% compared to 8.2% achieved by tailored respiration‐robust pulses. In vivo measurements at 7T demonstrate the benefits of using respiration‐robust pulses for DB. Conclusion: Universal and tailored respiration‐robust pTx pulses based on RR B1+‐maps are highly preferred to achieve 3D heart FA homogenization at 7T when subjects perform DB, whereas universal and tailored pulses based on NRR B1+‐maps are sufficient when subjects perform SB.
- Subjects
CARDIAC imaging; RESPIRATION
- Publication
Magnetic Resonance in Medicine, 2022, Vol 87, Issue 6, p2862
- ISSN
0740-3194
- Publication type
Article
- DOI
10.1002/mrm.29183