k-Space spatial low-pass filters can increase signal loss artifacts in echo-planar imaging
k-Space spatial low-pass filters can increase signal loss artifacts in echo-planar imaging
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DOI：
10.1016/j.bspc.2007.11.003
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发表时间：
2008-01-01
影响因子：
5.1
通讯作者：
Tomasi, D.
中科院分区：
文献类型：
--
作者：
Caparelli, E. C.;Tomasi, D.
有效横向弛豫率（T（2）*）加权回波平面成像（EPI）因其速度快、对血氧水平依赖（BOLD）信号敏感而被广泛用于功能磁共振成像（fMRI）。尽管如此。它的使用仅限于具有严重静磁场不均匀性的区域，这些区域会导致MR信号沿着时域（k空间）轨迹的频移和T（2）* 驰豫相关失真，从而导致分散的细域信号并产生磁化率诱导的信号损失。回波平面图像通常使用k空间低通滤波器进行平滑，以提高信噪比（SNR）并减少重建伪影。在这里，我们表明，当这样的滤波器被应用到分散的回波信号（不完美地集中在k空间），从对象的图像信息的一部分被删除，从而增强图像中的信号丢失伪影。为了避免这种伪影，分散的回波信号必须在k空间滤波之前重新聚焦。(C)2007爱思唯尔有限公司版权所有。
Effective transverse relaxation rate (T(2)*)-weighted echo-planar imaging (EPI) is extensively used for functional magnetic resonance imaging (fMRI), because of its high speed and good sensitivity to the blood oxygenation level-dependent (BOLD) signal. Nevertheless. its use is limited in areas with severe static magnetic field inhomogeneities that cause frequency shifts and T(2)* relaxation-related distortions of the MR signal along the time-domain (k-space) trajectory, resulting in disperse fine-domain signals and generating susceptibility-induced signal losses. Echo planar images are commonly smoothed with k-space spatial low-pass filters to improve the signal-to-noise ratio (SNR) and reduce reconstruction artifacts. Here, we show that when such filters are applied to the dispersed echo-signals (not perfectly centered in k-space), part of the image information from the object is removed, thereby enhancing signal-loss artifacts in the images. To avoid this artifact, the dispersed echo signal has to be refocused before k-space filtering. (C) 2007 Elsevier Ltd. All rights reserved.