3D T2-weighted imaging at 7T using dynamic kT-points on single-transmit MRI systems

Eggenschwiler, Florent, O'Brien, Kieran Robert, Gallichan, Daniel, Gruetter, Rolf and Marques, Jose Pedro (2016) 3D T2-weighted imaging at 7T using dynamic kT-points on single-transmit MRI systems. Magnetic Resonance Materials in Physics, Biology and Medicine, 29 3: 347-358. doi:10.1007/s10334-016-0545-4

Author Eggenschwiler, Florent
O'Brien, Kieran Robert
Gallichan, Daniel
Gruetter, Rolf
Marques, Jose Pedro
Title 3D T2-weighted imaging at 7T using dynamic kT-points on single-transmit MRI systems
Formatted title
3D T2-weighted imaging at 7T using dynamic kT-points on single-transmit MRI systems
Journal name Magnetic Resonance Materials in Physics, Biology and Medicine   Check publisher's open access policy
ISSN 0968-5243
Publication date 2016-04-08
Year available 2016
Sub-type Article (original research)
DOI 10.1007/s10334-016-0545-4
Open Access Status Not Open Access
Volume 29
Issue 3
Start page 347
End page 358
Total pages 12
Place of publication Heidelberg, Germany
Publisher Springer
Collection year 2017
Language eng
Formatted abstract
Objectives: For turbo spin echo (TSE) sequences to be useful at ultra-high field, they should ideally employ an RF pulse train compensated for the B1+ inhomogeneity. Previously, it was shown that a single kT-point pulse designed in the small tip-angle regime can replace all the pulses of the sequence (static kT-points). This work demonstrates that the B1+ dependence of T2-weighted imaging can be further mitigated by designing a specific kT-point pulse for each pulse of a 3D TSE sequence (dynamic kT-points) even on single-channel transmit systems

Materials and methods: By combining the spatially resolved extended phase graph formalism (which calculates the echo signals throughout the sequence) with a gradient descent algorithm, dynamic kT-points were optimized such that the difference between the simulated signal and a target was minimized at each echo. Dynamic kT-points were inserted into the TSE sequence to acquire in vivo images at 7T.

Results: The improvement provided by the dynamic kT-points over the static kT-point design and conventional hard pulses was demonstrated via simulations. Images acquired with dynamic kT-points showed systematic improvement of signal and contrast at 7T over regular TSE—especially in cerebellar and temporal lobe regions without the need of parallel transmission.

Conclusion: Designing dynamic kT-points for a 3D TSE sequence allows the acquisition of T2-weighted brain images on a single-transmit system at ultra-high field with reduced dropout and only mild residual effects due to the B1+ inhomogeneity.
Keyword B1+inhomogeneity correction
Dynamic kT-points
Spatially resolved extended phase graph
T2-weighted imaging
TSE sequence
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: HERDC Pre-Audit
Centre for Advanced Imaging Publications
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