title: High-flip-angle slice-selective parallel RF transmission with 8 channels at 7 T.
abstract: At high magnetic field, B(1)(+) non-uniformity causes undesired inhomogeneity in SNR and image contrast. Parallel RF transmission using tailored 3D k-space trajectory design has been shown to correct for this problem and produce highly uniform in-plane magnetization with good slice selection profile within a relatively short excitation duration. However, at large flip angles the excitation k-space based design method fails. Consequently, several large-flip-angle parallel transmission designs have recently been suggested. In this work, we propose and demonstrate a large-flip-angle parallel excitation design for 90 degrees and 180 degrees spin-echo slice-selective excitations that mitigate severe B(1)(+) inhomogeneity. The method was validated on an 8-channel transmit array at 7T using a water phantom with B(1)(+) inhomogeneity similar to that seen in human brain in vivo. Slice-selective excitations with parallel RF systems offer means to implement conventional high-flip excitation sequences without a severe pulse-duration penalty, even at very high B(0) field strengths where large B(1)(+) inhomogeneity is present.
authors.affiliation: Department of Electrical Engineering and Computer Science, MIT, 77 Massachusetts Ave., Building 36, Room 766, Cambridge, MA 02139, USA.
authors.forename: Kawin
authors.initials: K
authors.lastname: Setsompop
authors.forename: Vijayanand
authors.initials: V
authors.lastname: Alagappan
authors.forename: Adam C
authors.initials: AC
authors.lastname: Zelinski
authors.forename: Andreas
authors.initials: A
authors.lastname: Potthast
authors.forename: Ulrich
authors.initials: U
authors.lastname: Fontius
authors.forename: Franz
authors.initials: F
authors.lastname: Hebrank
authors.forename: Franz
authors.initials: F
authors.lastname: Schmitt
authors.forename: Lawrence L
authors.initials: LL
authors.lastname: Wald
authors.forename: Elfar
authors.initials: E
authors.lastname: Adalsteinsson
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007089:Image Enhancement / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D014159:Transducers
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