Two-dimensional phase cycled reconstruction for inherent correction of echo-planar imaging Nyquist artifacts.
Two-dimensional phase cycled reconstruction for inherent correction of echo-planar imaging Nyquist artifacts.
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DOI：
10.1002/mrm.22896
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发表时间：
2011-10
影响因子：
3.3
通讯作者：
Song, Allen W.
中科院分区：
文献类型：
--
作者：
Chen, Nan-Kuei;Avram, Alexandru V.;Song, Allen W.
回波平面成像（EPI）中k空间轨迹的不一致性导致奈奎斯特伪影。传统技术通常仅校正沿着频率编码方向的相位误差（1D校正），这可能留下显著的残余伪影，特别是对于平面EPI或存在交叉项涡流的情况。与一维校正相比，二维（2D）相位校正可以更有效地抑制奈奎斯特伪影。然而，大多数现有的2D校正方法需要参考扫描，并且通常可能不适用于不同的成像协议。此外，具有2D相位校正的EPI重建易受由于受试者运动引起的误差放大的影响。为了解决这些限制，我们报告了一个固有的和一般的二维相位校正技术EPI奈奎斯特去除。首先，通过使用2D重建框架循环通过相位误差的不同可能值，从原始数据集生成一系列图像。第二，使用基于分类和S形加权信号中的背景能量的标准从第一步骤中生成的图像中识别具有最低伪影水平的图像。在这份报告中，我们证明了我们的新方法在单次拍摄，分段和并行EPI中去除奈奎斯特鬼的有效性，而无需获得额外的参考扫描和随后的误差放大。
The inconsistency of k-space trajectories results in Nyquist artifacts in echo-planar imaging (EPI). Traditional techniques often only correct for phase errors along the frequency-encoding direction (1D correction), which may leave significant residual artifacts, particularly for oblique-plane EPI or in the presence of cross-term eddy currents. As compared with 1D correction, two-dimensional (2D) phase correction can be much more effective in suppressing Nyquist artifacts. However, most existing 2D correction methods require reference scans and may not be generally applicable to different imaging protocols. Furthermore, EPI reconstruction with 2D phase correction is susceptible to error amplification due to subject motion. To address these limitations, we report an inherent and general 2D phase correction technique for EPI Nyquist removal. First, a series of images are generated from the original dataset, by cycling through different possible values of phase errors using a 2D reconstruction framework. Second, the image with the lowest artifact level is identified from images generated in the first step using criteria based on background energy in sorted and sigmoid-weighted signals. In this report, we demonstrate the effectiveness of our new method in removing Nyquist ghosts in single-shot, segmented and parallel EPI without acquiring additional reference scans and the subsequent error amplifications.
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