Echo train shifted multi-echo FLASH for functional MRI of the human brain at ultra-high spatial resolution
Echo train shifted multi-echo FLASH for functional MRI of the human brain at ultra-high spatial resolution
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DOI：
10.1002/nbm.998
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发表时间：
2005-12-01
影响因子：
2.9
通讯作者：
Frahm, J
中科院分区：
文献类型：
--
作者：
Voit, D;Frahm, J
本文描述了一种新的人脑功能磁共振成像技术的发展，其分辨率为0.135微米L全脑切片。与传统的3 mm各向同性分辨率或27亩L体素大小的研究相比，该方法的性能提高了200倍。为了获得最佳的图像质量，该方法基于多回波快速小角度拍摄(闪光)序列，在频率编码维度上对k空间进行单极遍历，并在相位编码维度上移动回波序列以避免幅度不连续。这些策略确保了平滑的点扩散函数，并消除了图像的重影伪影，而不需要任何相位校正或其他后处理。通过单切片采集、优化的带宽和与头部后部匹配的实验性四通道肩部线圈，可以补偿由于体素尺寸显著减小而造成的信噪比损失。对人脑(2.9T，7个回波，200赫兹/像素带宽，有效回波时间36ms，采集时间6 S)在300微米分辨率(无内插)和1.5 mm层厚下的多回波闪光研究表明，对双眼刺激的主要视觉区域有强烈的激活。这种新方法有望对特定大脑系统的柱状组织进行精细研究，并在层流分辨率下对灰质进行功能评估。版权所有(C)2005 John Wiley&Sons，Ltd.
This paper describes the development of a novel technique for functional MRI of the human brain at 0.135 mu L resolution for a whole brain section. In comparison with conventional studies at 3 mm isotropic resolution or 27 mu L voxel size, the method yields an improvement by a factor of 200. To achieve optimum image quality, the approach is based on a multi-echo fast low-angle shot (FLASH) sequence With Unipolar traversals of k-space in the frequency-encoding dimension and echo train shifting to avoid amplitude discontinuities in the phase-encoding dimension. These strategies ensure a smooth point-spread function and eliminate image ghosting artifacts without the need for any phase correction or other post-processing. Signal-to-noise losses due to the considerably reduced voxel sizes are compensated for by single slice acquisitions, optimized bandwidths and an experimental four-channel Shoulder coil matched to the posterior portion of the head. Multi-echo FLASH studies of the human brain (2.9 T, seven echoes, 200 Hz/pixel bandwidth, effective echo time 36 ms, acquisition time 6 s) at 300 mu m resolution (no interpolation) and 1.5 mm slice thickness revealed robust activations in primary visual areas in response to binocular Stimulation. The new method holds promise for refined studies of the columnar organization of specific brain systems and for functional assessments of the gray matter at laminar resolution. Copyright (c) 2005 John Wiley & Sons, Ltd.