title: Simultaneous z-shim method for reducing susceptibility artifacts with multiple transmitters.
abstract: The signal loss susceptibility artifact is a major limitation in gradient-echo MRI applications. Various methods, including z-shim techniques and multidimensional tailored radio frequency (RF) pulses, have been proposed to mitigate the through-plane signal loss artifact, which is dominant in axial slices above the sinus region. Unfortunately, z-shim techniques require multiple steps and multidimensional RF methods are complex, with long pulse lengths. Parallel transmission methods were recently shown to be promising for improving B1 inhomogeneity and reducing the specific absorption rate. In this work, a novel method using time-shifted slice-select RF pulses is presented for reducing the through-plane signal loss artifact in parallel transmission applications. A simultaneous z-shim is obtained by concurrently applying unique time-shifted pulses on each transmitter. The method is shown to reduce the signal loss susceptibility artifact in gradient-echo images using a four-channel parallel transmission system at 3T.
authors.affiliation: UH-QMC Magnetic Resonance Research Center, Department of Medicine, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii 96813-2427, USA. weiran@hawaii.edu
authors.forename: Weiran
authors.initials: W
authors.lastname: Deng
authors.forename: Cungeng
authors.initials: C
authors.lastname: Yang
authors.forename: Vijayanand
authors.initials: V
authors.lastname: Alagappan
authors.forename: Lawrence L
authors.initials: LL
authors.lastname: Wald
authors.forename: Fernando E
authors.initials: FE
authors.lastname: Boada
authors.forename: V Andrew
authors.initials: VA
authors.lastname: Stenger
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted