Use of spherical harmonic deconvolution methods to compensate for nonlinear gradient effects on MRI images
Use of spherical harmonic deconvolution methods to compensate for nonlinear gradient effects on MRI images
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DOI：
10.1002/mrm.20122
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发表时间：
2004-07-01
影响因子：
3.3
通讯作者：
Doddrell, DM
中科院分区：
文献类型：
--
作者：
Janke, A;Zhao, HW;Doddrell, DM
MR技术中的空间编码通过在存在磁场梯度的情况下对作为时间的函数的信号进行采样来实现。假设梯度产生6个线性磁场梯度，并且典型的图像重建依赖于该近似。然而，当前一代MRI扫描仪中的高速梯度常常为了速度的提高而牺牲线性度。这种非线性导致图像失真。根据第一性原理，提出了一种基于梯度场球谐展开的校正方法。在我们的情况下，在头部成像所需的典型视场（FOV）内测量的失真量足够大，以至于在不使用某种失真校正技术的情况下，图像对于需要精确体积信息的立体定向或纵向研究的用途有限。(C)2004 Wiley-Liss，Inc.
Spatial encoding in MR techniques is achieved by sampling the signal as a function of time in the presence of a magnetic field gradient. The gradients are assumed to generate 6 linear magnetic field gradient, and typical image reconstruction relies upon this approximation. However, high-speed gradients in the current generation of MRI scanners often sacrifice linearity for improvements in speed. Such nonlinearity results in distorted images. The problem is presented in terms of first principles and a correction method based on a gradient field spherical harmonic expansion is proposed. In our case, the amount of distortion measured within a typical field of view (FOV) required for head imaging is sufficiently large that without the use of some distortion correction technique, the images would be of limited use for stereotaxy or longitudinal studies, where precise volumetric information is required. (C) 2004 Wiley-Liss, Inc.