Online motion correction for diffusion-weighted segmented-EPI and FLASH imaging
Online motion correction for diffusion-weighted segmented-EPI and FLASH imaging
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DOI：
10.1007/s10334-004-0036-x
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发表时间：
2004-05-01
影响因子：
2.3
通讯作者：
Norris, DG
中科院分区：
文献类型：
--
作者：
Weih, KS;Driesel, W;Norris, DG
本文探讨了使用导航回波的在线运动校正在分割EPI和FLASH技术中的应用。在分段EPI中，这具有优于采集后校正的优点，即每个分段在k空间中的位置不再经受由旋转引起的任意移位。在扩散加权的FLASH中，与消除对体运动的敏感性的其他方法相比，其具有可以利用全磁化的优点，在其他方法中，灵敏度减半。健康受试者进行了调查的3 T全身系统中的硬件已被修改，使导航回波可以记录在个人电脑上，产生必要的磁场梯度校正脉冲和移位的拉莫尔频率在800 μ s内。心电图触发被用来避免非刚体大脑运动的时期。采用两个正交导航回波。对于分段EPI，发现必须将导航回波的T2* 加权最小化至约10 ms，以获得可靠的结果。两种方法均获得了高质量的图像。在线运动校正给弥散加权分割EPI和FLASH技术带来了直接的好处。
This paper explores the application of online motion correction using navigator echoes to the segmented-EPI and FLASH techniques. In segmented EPI this has the advantage over post-acquisition correction that the position in k-space of each segment is no longer subject to arbitrary shifts caused by rotation. In diffusion-weighted FLASH it has the advantage that the full magnetisation can be utilised in comparison to other methods of eliminating the sensitivity to bulk motion, in which the sensitivity is halved. Healthy subjects were investigated on a 3 T whole-body system in which the hardware has been modified so that navigator echoes can be recorded on a personal computer which generates the necessary magnetic field gradient correction pulses and shifts in the Larmor frequency within 800 mus. ECG triggering was used to avoid the period of non-rigid-body brain motion. Two orthogonal navigator echoes were employed. For segmented EPI it was found essential to minimise the T2* weighting of the navigator echoes to about 10 ms to obtain reliable results. High quality images were obtained for both methods examined. Online motion correction brings direct benefits to both the diffusion-weighted segmented-EPI and FLASH techniques.