Wavelet Domain Radiofrequency Pulse Design Applied to Magnetic Resonance Imaging. PLoS One 2015;10(10):e0141151
Date
10/31/2015Pubmed ID
26517262Pubmed Central ID
PMC4627821DOI
10.1371/journal.pone.0141151Scopus ID
2-s2.0-84950326643 (requires institutional sign-in at Scopus site) 4 CitationsAbstract
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 ASAuthors
Kevin M. Koch PhD Center Director, Professor in the Radiology department at Medical College of WisconsinNikolai J. Mickevicius PhD Assistant Professor in the Biophysics department at Medical College of Wisconsin
Lutfi Tugan Muftuler PhD 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
AlgorithmsHumans
Magnetic Resonance Imaging
Neuroimaging
Wavelet Analysis