title: Robust slice-selective broadband refocusing pulses.
abstract: Slice-selective broadband refocusing pulses are of great interest in localized MR spectroscopy for improving spatial selectivity, reducing chemical-shift displacement errors, and reducing anomalous J modulation. In practice the bandwidth of RF pulses is limited by the maximum available B1 amplitude. The goal of the present work is to design slice-selective and broadband refocusing pulses which are tolerant against B1 deviations. Pulse design is performed by numerical optimization based on optimal control theory. A comprehensive study of different cost functions and their effect on the optimization is given. The optimized slice-selective broadband refocusing pulses are compared to conventional Shinnar-Le Roux (SLR), broadband SLR, and hyperbolic secant pulses. In simulations and experiments optimized pulses were shown to fulfill broadband slice specifications over a range of ±20% B1 scalings. Experimental validation showed a reduction of chemical-shift displacement error by a factor of 3 compared to conventional SLR pulses.
authors.affiliation: Technische Universität München, Department of Chemistry, Munich, Germany.
authors.forename: Martin A
authors.initials: MA
authors.lastname: Janich
authors.forename: Rolf F
authors.initials: RF
authors.lastname: Schulte
authors.forename: Markus
authors.initials: M
authors.lastname: Schwaiger
authors.forename: Steffen J
authors.initials: SJ
authors.lastname: Glaser
mesh_terms: D000465:Algorithms; D002138:Calibration; D004574:Electromagnetic Fields; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D019047:Phantoms, Imaging; D011846:Radio Waves; D015203:Reproducibility of Results; D009626:Terminology as Topic