Zang L H, Fielden J, Wilbrink J, Takane A, Koizumi H
Department of Research and Engineering, Hitachi Instruments, Inc., San Jose, CA 95134.
Magn Reson Med. 1993 Mar;29(3):327-34. doi: 10.1002/mrm.1910290308.
In this paper, we describe a method for detecting and correcting in-plane bulk translational motion in multislice spin-echo imaging using self-calibration and postprocessing. A constant phase encoding offset between slices is used to evenly spread out the low spatial frequency echoes to allow accurate motion detection by self-calibration. Motion detection in both x and y directions is achieved by interchanging the readout and phase encoding directions for the alternate slices. Displacements are determined by cross correlating the modulus of each 1D transformed echo with a reference box car function whose width equals that of the imaged object. In addition, phase errors induced by the velocity in the readout direction are estimated and corrected using the displacement data. The results obtained from knee studies at 0.5 T and 1.5 T show that the artifacts due to translational motions are significantly suppressed upon correction. The method does not require any additional pulses or time, and the data processing can be easily implemented.
在本文中，我们描述了一种在多层自旋回波成像中使用自校准和后处理来检测和校正平面内整体平移运动的方法。各层之间恒定的相位编码偏移用于均匀分散低空间频率回波，以便通过自校准进行精确的运动检测。通过交替交换各层的读出和相位编码方向来实现x和y方向的运动检测。位移通过将每个一维变换回波的模与宽度等于成像对象宽度的参考方波函数进行互相关来确定。此外，利用位移数据估计并校正由读出方向上的速度引起的相位误差。在0.5 T和1.5 T场强下对膝关节的研究结果表明，校正后由平移运动引起的伪影得到了显著抑制。该方法不需要任何额外的脉冲或时间，并且数据处理易于实现。
