RF peak power reduction in CAIPIRINHA excitation by interslice phase optimization

Sbrizzi, Alessandro, Poser, Benedikt A., Tse, Desmond H. Y., Hoogduin, Hans, Luijten, Peter R. and van den Berg, Cornelis A. T. (2015) RF peak power reduction in CAIPIRINHA excitation by interslice phase optimization. NMR in Biomedicine, 28 11: 1393-1401. doi:10.1002/nbm.3360

Author Sbrizzi, Alessandro
Poser, Benedikt A.
Tse, Desmond H. Y.
Hoogduin, Hans
Luijten, Peter R.
van den Berg, Cornelis A. T.
Title RF peak power reduction in CAIPIRINHA excitation by interslice phase optimization
Journal name NMR in Biomedicine   Check publisher's open access policy
ISSN 1099-1492
Publication date 2015-11-01
Year available 2015
Sub-type Article (original research)
DOI 10.1002/nbm.3360
Open Access Status Not yet assessed
Volume 28
Issue 11
Start page 1393
End page 1401
Total pages 9
Place of publication Chichester, West Sussex, United Kingdom
Publisher John Wiley & Sons
Language eng
Formatted abstract
The purpose of this work was to show that the overall peak power of RF pulses for CAIPIRINHA excitation can be substantially reduced by applying interslice phase relaxation. The optimal phases are scan dependent and can be quickly calculated by the proposed method.

The multi-band RF pulse design is implemented as the minimization of a linear objective function with quadratic constraints. The interslice phase is considered to be a variable for optimization. In the case of a phase cycling scheme (CAIPIRINHA), the peak power is considered over all pulses.

The computation time (about 1 s) is compatible with online RF pulse design. It is shown that the optimal interslice phases depend on the CAIPIRINHA scheme used and that RF peak power is reduced when the CAIPIRINHA phase cycling is taken into account in the optimization.

The proposed method is extremely fast and results in RF pulses with low peak power for CAIPIRINHA excitation. The MATLAB implementation is given in the appendix; it allows for online determination of scan-dependent phase parameters. Furthermore, the method can be easily extended to pTx shimming systems in the context of multi-slice excitations, and this possibility is included in the software.
Keyword Active-set
Interslice phase relaxation
Linear program
RF peak power
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID 332933
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: Centre for Advanced Imaging Publications
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