Correcting corrupted-phases by blood perfusion, diffusion and body motion in MRI imaging.

纠正 MRI 成像中血液灌注、扩散和身体运动造成的损坏相位。

基本信息

批准号：
04650314
负责人：
TAMURA Shinichi
金额：
$ 1.41万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1994
项目状态：
已结题

项目摘要

When taking perfusion or diffusion images of small flow, artifact is easily caused by body motion. In this research, we developed artifact correction algorithms for translational, rotational, and expanding-shrinking body motions.(1) Translational rigid body motion : Using the fact that Fourier transform F (x, n) of MRI signal f (x, n) in the n-th view (phase encode) shows the object position along the frequency axis (x), we corrected the corrupted phases by a body motion. We have also developed a method which can correct independently of x-axis the body motion alosng y-axis.(2) Rotational rigid body motion : For a step rotation with unkown rot ation center and rotation angle, first we estimated the rotaion angle so that energy in outside region of the reconstructed image becomes minimum. Then we applied the phase retreaval algorithm to reduce the phase disturbance caused by the off-origin of the rotation center.(3) Expanding-shrinking deformable body motion : In case of such as abdomen expanding and shrinking proportionally in x-and y-axs, we have shown that we can reduce the artifact by ; first obtain x-directional motion from the projection onto the frequency axis as the same as (1), and then correct phases corresponding to y-axis by the phase retreaval algorithm.These algorithms can also be applied to the artifact correction caused by body motion of child and old person who cannot lay still for the image taking time of several to several ten minutes with conventional MRI.In order to make the algorithm more close to the practical use, it's a future task to model the more flexible motion with more number of freedom.

在拍摄小流量的灌注或弥散图像时，身体运动很容易造成伪影。在这项研究中，我们开发了用于平移、旋转和膨胀收缩身体运动的伪影校正算法。(1)平移刚体运动：利用 MRI 信号 f (x, n) 的傅立叶变换 F (x, n) 的事实在第 n 个视图（相位编码）中，显示了沿频率轴 (x) 的对象位置，我们通过身体运动纠正了损坏的相位。我们还开发了一种可以独立于 x 轴校正沿 y 轴的身体运动的方法。 (2) 旋转刚体运动：对于未知旋转中心和旋转角度的步进旋转，首先我们估计旋转角度，以便重建图像外部区域的能量变得最小。然后我们应用相位检索算法来减少由于旋转中心偏离原点而引起的相位扰动。（3）膨胀收缩变形体运动：例如腹部在x轴和y轴上按比例膨胀和收缩的情况，我们已经证明我们可以通过以下方式减少伪影：首先同(1)一样从频率轴上的投影得到x方向的运动，然后通过相位重建算法校正y轴对应的相位。这些算法也可以应用于身体运动引起的伪影校正传统 MRI 的图像拍摄时间为数分钟到数十分钟，无法保持静止不动的儿童和老人。为了使算法更贴近实际使用，未来的任务是对更多数量的更灵活的运动进行建模的自由。