Nonlinear phase correction for navigated diffusion imaging
Nonlinear phase correction for navigated diffusion imaging
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DOI：
10.1002/mrm.10531
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发表时间：
2003-08-01
影响因子：
3.3
通讯作者：
Pauly, JM
中科院分区：
文献类型：
--
作者：
Miller, KL;Pauly, JM
弥散加权成像（DWI）过程中的运动会引入相位误差，从而导致脑图像中出现明显的伪影。校正这些误差的一种方法使用附加的导航器数据来测量相位破坏。标准的导航仪方法校正刚体运动，但不能校正与心动周期相关的大脑的非刚性变形。这项工作推导出一个广义的重建，纠正非刚性运动的基础上最小二乘制定。由于这种重建具有计算昂贵的缺点，提出了一种近似，称为重聚焦重建。重新聚焦重建是高效和直接的。每个读出在图像空间中乘以导航图像的相位共轭，然后将这些重定相的读出相加。在此基础上，讨论了再聚焦重建的充分条件和提高再聚焦图像质量的方法。特别地，采集与心动周期的同步可以提供对于重新聚焦重建良好调节的数据，而不会招致传统上与心脏门控相关联的大的时间损失。这些方法适用于稳态DWI，一个有前途的脉冲序列，是特别敏感的运动引起的相位伪影。重新聚焦重建显着改善SS-DWI超过标准的刚体校正。(C)2003 Wiley-Liss，Inc.
Motion during diffusion-weighted imaging (DWI) introduces phase errors that can cause significant artifacts in brain images. One method of correcting these errors uses additional navigator data to measure the phase corruptions. Standard navigator methods correct for rigid-body motion but cannot correct for nonrigid deformations of the brain related to the cardiac cycle. This work derives a generalized reconstruction that corrects for nonrigid motion based on a least-squares formulation. Since this reconstruction has the disadvantage of being computationally expensive, an approximation is presented, called a refocusing reconstruction. The refocusing reconstruction is both efficient and straightforward. Each readout is multiplied in image space by the phase conjugate of the navigator image, and these rephased readouts are then summed. The conditions under which the refocusing reconstruction is sufficient are considered and methods to improve the quality of refocused images are discussed. In particular, synchronization of the acquisition to the cardiac cycle can provide data that is well-conditioned to the refocusing reconstruction without incurring the large time penalty traditionally associated with cardiac gating. These methods are applied to steady-state DWI, a promising pulse sequence that is particularly sensitive to motion-induced phase artifacts. The refocusing reconstruction is shown to significantly improve SS-DWI over standard rigid-body corrections. (C) 2003 Wiley-Liss, Inc.