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Wavelet Domain Radiofrequency Pulse Design Applied to Magnetic Resonance Imaging. PLoS One 2015;10(10):e0141151

Date

10/31/2015

Pubmed ID

26517262

Pubmed Central ID

PMC4627821

DOI

10.1371/journal.pone.0141151

Scopus ID

2-s2.0-84950326643   3 Citations

Abstract

A new method for designing radiofrequency (RF) pulses with numerical optimization in the wavelet domain is presented. Numerical optimization may yield solutions that might otherwise have not been discovered with analytic techniques alone. Further, processing in the wavelet domain reduces the number of unknowns through compression properties inherent in wavelet transforms, providing a more tractable optimization problem. This algorithm is demonstrated with simultaneous multi-slice (SMS) spin echo refocusing pulses because reduced peak RF power is necessary for SMS diffusion imaging with high acceleration factors. An iterative, nonlinear, constrained numerical minimization algorithm was developed to generate an optimized RF pulse waveform. Wavelet domain coefficients were modulated while iteratively running a Bloch equation simulator to generate the intermediate slice profile of the net magnetization. The algorithm minimizes the L2-norm of the slice profile with additional terms to penalize rejection band ripple and maximize the net transverse magnetization across each slice. Simulations and human brain imaging were used to demonstrate a new RF pulse design that yields an optimized slice profile and reduced peak energy deposition when applied to a multiband single-shot echo planar diffusion acquisition. This method may be used to optimize factors such as magnitude and phase spectral profiles and peak RF pulse power for multiband simultaneous multi-slice (SMS) acquisitions. Wavelet-based RF pulse optimization provides a useful design method to achieve a pulse waveform with beneficial amplitude reduction while preserving appropriate magnetization response for magnetic resonance imaging.

Author List

Huettner AM, Mickevicius NJ, Ersoz A, Koch KM, Muftuler LT, Nencka AS

Authors

Kevin M. Koch PhD Center Director, Professor in the Radiology department at Medical College of Wisconsin
Nikolai J. Mickevicius PhD Assistant Professor in the Radiology department at Medical College of Wisconsin
Lutfi Tugan Muftuler PhD Associate Professor in the Neurosurgery department at Medical College of Wisconsin
Andrew S. Nencka PhD Director, Associate Professor in the Radiology department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Algorithms
Humans
Magnetic Resonance Imaging
Neuroimaging
Wavelet Analysis