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    J Magn Reson. 2008 Nov;195(1):76-84. Epub 2008 Aug 30.

    High-flip-angle slice-selective parallel RF transmission with 8 channels at 7 T.

    Setsompop K, Alagappan V, Zelinski AC, Potthast A, Fontius U, Hebrank F, Schmitt F, Wald LL, Adalsteinsson E.

    Department of Electrical Engineering and Computer Science, MIT, 77 Massachusetts Ave., Building 36, Room 766, Cambridge, MA 02139, USA.

    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.

    PMID: 18799336 [PubMed - indexed for MEDLINE]

    PMCID: 2610679

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