Gai Neville D, Chou Yi Yu, Pham Dzung, Butman John A
Radiology and Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, MD, USA..
Radiology and Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, MD, USA.; Center for Neuroscience and Regenerative Medicine, Henry M. Jackson Foundation, Bethesda, MD, USA.
Magn Reson Imaging. 2017 Dec;44:119-124. doi: 10.1016/j.mri.2017.08.011. Epub 2017 Sep 1.
To implement and evaluate interleaved blip-up, blip-down, non-segmented 3D echo planar imaging (EPI) with pseudo-continuous arterial spin labeling (pCASL) and post-processing for reduced susceptibility artifact cerebral blood flow (CBF) maps.
3D EPI non-segmented acquisition with a pCASL labeling sequence was modified to include alternating k-space coverage along phase encoding direction (referred to as "blip-reversed") for alternating dynamic acquisitions of control and label pairs. Eight volunteers were imaged on a 3T scanner. Images were corrected for distortion using spatial shifting transformation of the underlying field map. CBF maps were calculated and compared with maps obtained without blip reversal using matching gray matter (GM) images from a high resolution 3D scan. Additional benefit of using the correction for alternating blip-up and blip-down acquisitions was assessed by comparing to corrected blip-up only and corrected blip-down only CBF maps. Matched Student t-test of overlapping voxels for the eight volunteers was done to ascertain statistical improvement in distortion.
Mean CBF value in GM for the eight volunteers from distortion corrected CBF maps was 50.8±9.9ml/min/100 gm tissue. Corrected CBF maps had 6.3% and 4.1% more voxels in GM when compared with uncorrected blip up (BU) and blip down (BD) images, respectively. Student t-test showed significant reduction in distortion when compared with blip-up images and blip-down images (p<0.001). When compared with corrected BU and corrected BD only CBF maps, BU and BD corrected maps had 2.3% and 1% more voxels (p=0.006 and 0.04, respectively).
Pseudo-continuous arterial spin labeling with non-segmented 3D EPI acquisition using alternating blip-reversed k-space traversal and distortion correction provided significantly better matching GM CBF maps. In addition, employing alternating blip-reversed acquisitions during pCASL acquisition resulted in statistically significant improvement over corrected blip-up and blip-down CBF maps.
采用伪连续动脉自旋标记（pCASL）技术以及后处理方法，实现并评估交错式升频、降频、非分段三维回波平面成像（EPI），以生成减少了磁化率伪影的脑血流量（CBF）图。
对采用pCASL标记序列的三维EPI非分段采集进行修改，使其在相位编码方向上包括交替的k空间覆盖（称为“反转跳变”），用于交替动态采集对照和标记对。8名志愿者在3T扫描仪上进行成像。利用基础场图的空间移位变换对图像进行失真校正。计算CBF图，并与使用来自高分辨率三维扫描的匹配灰质（GM）图像且未进行跳变反转获得的图进行比较。通过与仅校正升频和仅校正降频的CBF图进行比较，评估对交替升频和降频采集进行校正的额外益处。对8名志愿者重叠体素进行配对学生t检验，以确定失真方面的统计学改善。
经失真校正的CBF图中，8名志愿者灰质中的平均CBF值为50.8±9.9ml/分钟/100克组织。与未校正的升频（BU）和降频（BD）图像相比，校正后的CBF图在灰质中的体素分别多6.3%和4.1%。学生t检验显示，与升频图像和降频图像相比，失真显著降低（p<0.001）。与仅校正BU和仅校正BD的CBF图相比，同时校正BU和BD的图的体素分别多2.3%和1%（p分别为0.006和0.04）。
采用交替反转跳变k空间遍历和失真校正的非分段三维EPI采集的伪连续动脉自旋标记，可提供明显更好的匹配灰质CBF图。此外，在pCASL采集期间采用交替反转跳变采集，在统计学上比校正后的升频和降频CBF图有显著改善。
