Multiband RF pulses with improved performance via convex optimization

• Published in: Journal of magnetic resonance (1997) 2016-01, Vol.262, p.81-90
• Main Authors: Shang, Hong, Larson, Peder E.Z., Kerr, Adam, Reed, Galen, Sukumar, Subramaniam, Elkhaled, Adam, Gordon, Jeremy W., Ohliger, Michael A., Pauly, John M., Lustig, Michael, Vigneron, Daniel B.
• Format: Article
• Language: English
• Subjects: Algorithms; Balancing; Brain; Calibration; Carbon Isotopes; Computational geometry; Convex optimization; Convexity; Generalized flip angle; Humans; Improved pulse performance; Lactates - chemistry; Low pass filters; Magnetic Resonance Imaging - methods; Magnetic Resonance Spectroscopy - methods; Multiband; Optimization; Performance enhancement; Phantoms, Imaging; Protons; Pyruvates - chemistry; Radio Waves; RF pulse design; Saturation; Shinnar–Le Roux algorithm; Tradeoffs; Urea - chemistry
• ISSN: 1090-7807; 1096-0856
• DOI: 10.1016/j.jmr.2015.11.010

[Display omitted] •Spectral sparsity was exploited to improve RF pulse performance by specifying a multiband profile.•A framework for RF pulse design was developed using the SLR algorithm and convex optimization.•It can create RF pulses with multiband magnitude profile, arbitrary phase profile, and generalized flip angle.•We present three examples of RF pulse design for hyperpolarized 13C MRI and 1H MRS. Selective RF pulses are commonly designed with the desired profile as a low pass filter frequency response. However, for many MRI and NMR applications, the spectrum is sparse with signals existing at a few discrete resonant frequencies. By specifying a multiband profile and releasing the constraint on “don’t-care” regions, the RF pulse performance can be improved to enable a shorter duration, sharper transition, or lower peak B1 amplitude. In this project, a framework for designing multiband RF pulses with improved performance was developed based on the Shinnar–Le Roux (SLR) algorithm and convex optimization. It can create several types of RF pulses with multiband magnitude profiles, arbitrary phase profiles and generalized flip angles. The advantage of this framework with a convex optimization approach is the flexible trade-off of different pulse characteristics. Designs for specialized selective RF pulses for balanced SSFP hyperpolarized (HP) 13C MRI, a dualband saturation RF pulse for 1H MR spectroscopy, and a pre-saturation pulse for HP 13C study were developed and tested.