Summers P, Staempfli P, Jaermann T, Kwiecinski S, Kollias S
Institute for Neuroradiology, University Hospital Zurich, Zurich, Switzerland.
AJNR Am J Neuroradiol. 2006 Oct;27(9):1952-61.
Diffusion tensor and diffusion-weighted spinal cord imaging remain relatively unexplored techniques despite demonstrations that such images can be obtained and may yield clinically relevant findings. In this study, we examined the temporal dynamics of spinal cord motion and their impact on diffusion tensor image quality.
Four healthy volunteers underwent phase contrast-based velocity mapping and segmented echo-planar diffusion tensor scans of the cervical spinal cord. Regions of interest in the cord were used to identify the temporal patterns of motion. The delay of data acquisition after the cardiac trigger was varied to correspond to either quiescence or motion of the cord.
The cervical spinal cord consistently displayed maximal velocities in the range of 0.5 cm/s and accelerations of up to 25 cm/s(2). In both these respects, the cervical cord values were greater than those of the medulla. Despite this pronounced motion, approximately 40% of the cardiac cycle can be described as relatively calm, with absolute velocities and accelerations less than 20% of the maximum values. Confining image acquisition to this window reduced ghosting artifacts and increased the consistency with which the dominant direction of diffusion was along the rostral-caudal axis in both gray and white matter of the spine. Preliminary clinical application and fiber tracking in pathologic cases was feasible, and alterations of the diffusion properties by multiple sclerosis lesions, tumor, and syringomyelia were seen.
Acquiring DTI data during the quiescent phase of spinal cord motion can reduce ghosting artifacts and improve fiber tracking.
尽管已有研究表明可以获取扩散张量成像（DTI）和扩散加权脊髓成像并可能得出具有临床意义的结果，但这些技术仍相对未被充分探索。在本研究中，我们研究了脊髓运动的时间动态及其对扩散张量图像质量的影响。
4名健康志愿者接受了基于相位对比的速度映射和颈椎脊髓的分段回波平面扩散张量扫描。利用脊髓中的感兴趣区域来识别运动的时间模式。改变心脏触发后数据采集的延迟，以对应脊髓的静止或运动状态。
颈髓的最大速度始终在0.5 cm/s范围内，加速度高达25 cm/s²。在这两个方面，颈髓的值均大于延髓的值。尽管存在这种明显的运动，但在大约40%的心动周期内脊髓运动相对平静，其绝对速度和加速度小于最大值的20%。将图像采集限制在这个时间段内可减少鬼影伪影，并增加了脊髓灰质和白质中扩散的主导方向沿头尾轴的一致性。在病理病例中的初步临床应用和纤维追踪是可行的，并且观察到了多发性硬化病变、肿瘤和脊髓空洞症引起的扩散特性改变。
在脊髓运动的静止期采集DTI数据可减少鬼影伪影并改善纤维追踪。
