Matrix description of general motion correction applied to multishot images
Matrix description of general motion correction applied to multishot images
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DOI：
10.1002/mrm.20656
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发表时间：
2005-11-01
影响因子：
3.3
通讯作者：
Larkman, D
中科院分区：
文献类型：
--
作者：
Batchelor, PG;Atkinson, D;Larkman, D
对象的运动会降低MR图像的质量，因为采集是时间相关的，因此k空间的采样不一致。这会导致幽灵。目前的运动校正方法对运动的类型做了限制性的假设，例如，它是平移或旋转，并使用k空间的特殊性质来进行这些变换。然而，这种方法不容易推广到非刚性类型的动作，甚至在多个镜头中的旋转也可能是一个问题。本文提出了一种处理一般非刚体运动模型的方法。一个通用的矩阵方程给出了理想物体的受污染图像。因此，对该系统进行反转，可以从被破坏的图像中得到理想的图像。通过将傅立叶变换和共轭梯度法相结合的有效方法，可以实现这种反演。讨论了一种速度更快但经验性的反演以及确定运动的方法。使用模拟的三维仿射数据、二维脉动数据和活体非刚性数据进行了验证。所有示例都是多镜头图像，其中对象在快照之间移动。结果表明，尽管计算时间仍然是一个问题，但现在可以校正代表许多类型患者运动的非刚性运动类型。
Motion of an object degrades MR images, as the acquisition is time-dependent, and thus k-space is inconsistently sampled. This causes ghosts. Current motion correction methods make restrictive assumptions on the type of motions, for example, that it is a translation or rotation, and use special properties of k-space for these transformations. Such methods, however, cannot be generalized easily to nonrigid types of motions, and even rotations in multiple shots can be a problem. Here, a method is presented that can handle general nonrigid motion models. A general matrix equation gives the corrupted image from the ideal object. Thus, inversion of this system allows us to get the ideal image from the corrupted one. This inversion is possible by efficient methods mixing Fourier transforms with the conjugate gradient method. A faster but empirical inversion is discussed as well as methods to determine the motion. Simulated three-dimensional affine data and two-dimensional pulsation data and in vivo nonrigid data are used for demonstration. All examples are multishot images where the object moves between shots. The results indicate that it is now possible to correct for nonrigid types of motion that are representative of many types of patient motion, although computation times remain an issue.