title: Four-dimensional spectral-spatial RF pulses for simultaneous correction of B1+ inhomogeneity and susceptibility artifacts in T2*-weighted MRI.
abstract: Susceptibility artifacts and excitation radiofrequency field B(1)+ inhomogeneity are major limitations in high-field MRI. Parallel transmission methods are promising for reducing artifacts in high-field applications. In particular, three-dimensional RF pulses have been shown to be useful for reducing B(1)+ inhomogeneity using multiple transmitters due to their ability to spatially shape the slice profile. Recently, two-dimensional spectral-spatial pulses have been demonstrated to be effective for reducing the signal loss susceptibility artifact by incorporating a frequency-dependent through-plane phase correction. We present the use of four-dimensional spectral-spatial RF pulses for simultaneous B(1)+ and through-plane signal loss susceptibility artifact compensation. The method is demonstrated with simulations and in T(2)*-weighted human brain images at 3 T, using a four-channel parallel transmission system. Parallel transmission was used to reduce the in-plane excitation resolution to improve the slice-selection resolution between two different pulse designs. Both pulses were observed to improve B(1)+ homogeneity and reduce the signal loss artifact in multiple slice locations and several human volunteers.
authors.affiliation: Department of Medicine, John A. Burns School of Medicine, Honolulu, Hawaii 96813-2427, USA.
authors.forename: Cungeng
authors.initials: C
authors.lastname: Yang
authors.forename: Weiran
authors.initials: W
authors.lastname: Deng
authors.forename: Vijayanand
authors.initials: V
authors.lastname: Alagappan
authors.forename: Lawrence L
authors.initials: LL
authors.lastname: Wald
authors.forename: V Andrew
authors.initials: VA
authors.lastname: Stenger
mesh_terms: D016477:Artifacts; D001921:Brain / Q000000981:diagnostic imaging*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D011846:Radio Waves; D011859:Radiography