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

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• 作者：Kawin Setsompop ; Vijayan ; Alagappan ; Adam C. Zelinski ; Andreas Potthast ; Ulrich Fontius ; Franz Hebrank ; Franz Schmitt ; Lawrence L. Wald ; Elfar Adalsteinsson
• 关键词：Parallel transmission ; High flip-angle ; Slice-selective excitation ; RF inhomogeneity ; Multidimensional pulse
• 刊名：Journal of Magnetic Resonance
• 出版年：2008
• 出版时间：November 2008
• 年：2008
• 卷：195
• 期：1
• 页码：76-84
• 全文大小：634 K

文摘

At high magnetic field, 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° and 180° spin-echo slice-selective excitations that mitigate severe inhomogeneity. The method was validated on an 8-channel transmit array at 7 T using a water phantom with 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 B₀ field strengths where large inhomogeneity is present.