Application of the limited-memory quasi-Newton algorithm for multi-dimensional, large flip-angle RF pulses at 7T

Vinding, Mads S., Brenner, Daniel, Tse, Desmond H. Y., Vellmer, Sebastian, Vosegaard, Thomas, Suter, Dieter, Stöcker, Tony and Maximov, Ivan I. (2017) Application of the limited-memory quasi-Newton algorithm for multi-dimensional, large flip-angle RF pulses at 7T. Magnetic Resonance Materials in Physics, Biology and Medicine, 30 1: 29-39. doi:10.1007/s10334-016-0580-1


Author Vinding, Mads S.
Brenner, Daniel
Tse, Desmond H. Y.
Vellmer, Sebastian
Vosegaard, Thomas
Suter, Dieter
Stöcker, Tony
Maximov, Ivan I.
Title Application of the limited-memory quasi-Newton algorithm for multi-dimensional, large flip-angle RF pulses at 7T
Journal name Magnetic Resonance Materials in Physics, Biology and Medicine   Check publisher's open access policy
ISSN 0968-5243
1352-8661
Publication date 2017-02-01
Year available 2017
Sub-type Article (original research)
DOI 10.1007/s10334-016-0580-1
Open Access Status Not yet assessed
Volume 30
Issue 1
Start page 29
End page 39
Total pages 11
Place of publication Heidelberg, Germany
Publisher Springer
Language eng
Formatted abstract
Objective
Ultrahigh field MRI provides great opportunities for medical diagnostics and research. However, ultrahigh field MRI also brings challenges, such as larger magnetic susceptibility induced field changes. Parallel-transmit radio-frequency pulses can ameliorate these complications while performing advanced tasks in routine applications. To address one class of such pulses, we propose an optimal-control algorithm as a tool for designing advanced multi-dimensional, large flip-angle, radio-frequency pulses. We contrast initial conditions, constraints, and field correction abilities against increasing pulse trajectory acceleration factors.

Materials and methods
On an 8-channel 7T system, we demonstrate the quasi-Newton algorithm with pulse designs for reduced field-of-view imaging with an oil phantom and in vivo with scans of the human brain stem. We used echo-planar imaging with 2D spatial-selective pulses. Pulses are computed sufficiently rapid for routine applications.

Results
Our dataset was quantitatively analyzed with the conventional mean-square-error metric and the structural-similarity index from image processing. Analysis of both full and reduced field-of-view scans benefit from utilizing both complementary measures.

Conclusion
We obtained excellent outer-volume suppression with our proposed method, thus enabling reduced field-of-view imaging using pulse trajectory acceleration factors up to 4.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

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