Phase Relaxed Localized Excitation Pulses for Inner Volume Fast Spin Echo Imaging
Phase Relaxed Localized Excitation Pulses for Inner Volume Fast Spin Echo Imaging
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DOI：
10.1002/mrm.25996
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发表时间：
2016-09-01
影响因子：
3.3
通讯作者：
Hajnal, Joseph V.
中科院分区：
文献类型：
--
作者：
Malik, Shaihan J.;Hajnal, Joseph V.
目的：设计用于三维快速自旋回波(FSE)序列内体积成像(IVI)的多维空间选择性射频(RF)脉冲。增强的背景抑制是通过利用FSE序列的特殊信号特性来实现的。理论和方法：CPMG条件规定，如果激励脉冲和重聚焦脉冲之间不存在90度的相位差，并且重聚焦翻转角度不是精确的180度，则回波幅度将迅速降低。该机制被认为是通过将剩余激励误差偏置到违反CPMG条件来产生额外的背景抑制以用于空间选择性激励的手段。使用该方法设计了3D球形螺旋轨迹的3D RF脉冲，对于8通道PTX系统，以5.6倍欠采样，在3 TeSla.结果：在体模和活体T2加权脑成像中，3D-FSE IVI的脉冲持续时间约为12ms。图像质量较好，体模和活体图像的平均背景抑制因子分别为103和826。结论：3D-FSE内体积成像技术可在体内使用定制的3D-RF脉冲实现。所提出的设计方法也适用于二维脉冲。Magn Reson Med 76：848-861,2016。(C)2015年提交人。《医学中的磁共振》由Wiley期刊公司代表国际医学磁共振学会出版
Purpose: To design multidimensional spatially selective radio-frequency (RF) pulses for inner volume imaging (IVI) with three-dimensional (3D) fast spin echo (FSE) sequences. Enhanced background suppression is achieved by exploiting particular signal properties of FSE sequences.Theory and Methods: The CPMG condition dictates that echo amplitudes will rapidly decrease if a 90 degrees phase difference between excitation and refocusing pulses is not present, and refocusing flip angles are not precisely 180 degrees. This mechanism is proposed as a means for generating additional background suppression for spatially selective excitation, by biasing residual excitation errors toward violating the CPMG condition. 3D RF pulses were designed using this method with a 3D spherical spiral trajectory, under-sampled by factor 5.6 for an eight-channel PTx system, at 3 Tesla.Results: 3D-FSE IVI with pulse durations of approximately 12 ms was demonstrated in phantoms and for T-2-weighted brain imaging in vivo. Good image quality was obtained, with mean background suppression factors of 103 and 82 6 6 in phantoms and in vivo, respectively.Conclusion: Inner Volume Imaging with 3D-FSE has been demonstrated in vivo with tailored 3D-RF pulses. The proposed design methods are also applicable to 2D pulses. Magn Reson Med 76:848-861, 2016. (C) 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine