Department of Diagnostic Imaging and Nuclear Medicine and Human Brain Research Center, Kyoto University Graduate School of Medicine, Kyoto, Japan.
AJNR Am J Neuroradiol. 2012 Aug;33(7):1321-5. doi: 10.3174/ajnr.A2969. Epub 2012 Mar 1.
CVJ lesion suffers from a high sensitivity to susceptibility and distortion artifacts, which sometimes makes diffusion image difficult to interpret. Our purpose was to evaluate the potential for diffusion MR imaging using RS-EPI compared with SS-EPI in the assessment of the CVJ.
RS-EPI and SS-EPI DTI images were acquired from 10 healthy volunteers using 3T MRI with a 32-channel head coil. For both sequences, the following parameters were used: 1-mm(2) in-plane resolution; 3-mm section thickness; TR = 5200 ms; 1 acquisition at b = 0 and 12 different encoding directions at b = 1000 seconds/mm(2). The RS-EPI sequence scan time was 9.44 minutes (1 average). The SS-EPI sequence was 9.37 minutes (8 averages). Diffusion tensor calculation and image analysis were performed using DTIStudio software. Diffusion trace images and color-coded fiber orientation maps were evaluated by 2 independent readers for distortion and delineation of fine structure using a semiquantitative scale in selected landmark locations. The absolute distances between the temporal base and the cerebellar contour between the T2-weighted images and the diffusion trace images obtained with RS-EPI and SS-EPI were also compared.
The contours of the temporal lobe and cerebellum were better delineated and distortion artifacts were clearly reduced with the RS-EPI sequence. More fine structures were also visible in the brain stem and cerebellum with the RS-EPI sequence. The amount of distortion was significantly reduced with RS-EPI compared with SS-EPI (P < .01).
The RS-EPI DTI sequence was less prone to geometric distortion than the SS-EPI sequence and allowed a better delineation of CVJ internal structure. Although the acquisition time is still relatively long, the RS-EPI appears as a promising approach to perform DTI studies in CVJ lesions, such as brain stem ischemia, neurodegenerative diseases, brain and skull base tumors, or inflammation.
颅颈交界区（CVJ）病变对磁化率和失真伪影非常敏感，这有时会导致弥散图像难以解读。本研究旨在评估使用重复激发回波平面成像（RS-EPI）与单次激发回波平面成像（SS-EPI）进行 CVJ 弥散磁共振成像（MRI）的潜在价值。
使用配备 32 通道头部线圈的 3T MRI 仪对 10 名健康志愿者进行 RS-EPI 和 SS-EPI 弥散张量成像（DTI）扫描。两种序列的参数如下：2 毫米层厚；1 毫米层间距；重复时间（TR）= 5200 毫秒；b 值为 0 时采集 1 次，b 值为 1000 秒/毫米时采集 12 次不同的编码方向。RS-EPI 序列扫描时间为 9.44 分钟（平均 1 次），SS-EPI 序列为 9.37 分钟（平均 8 次）。使用 DTIStudio 软件进行弥散张量计算和图像分析。在选定的标志性位置，两位独立的观察者使用半定量评分对弥散轨迹图像和彩色编码纤维方向图进行评估，以评价扭曲和细微结构的描绘。还比较了 RS-EPI 和 SS-EPI 获得的 T2 加权图像与弥散轨迹图像之间颞骨基部和小脑轮廓之间的绝对距离。
与 SS-EPI 序列相比，RS-EPI 序列可更好地描绘颞叶和小脑轮廓，显著减少扭曲伪影，并且在脑干和小脑也能显示更多细微结构。RS-EPI 序列的失真程度明显低于 SS-EPI 序列（P<.01）。
与 SS-EPI 序列相比，RS-EPI DTI 序列不易发生几何失真，可更好地描绘 CVJ 内部结构。尽管采集时间仍然相对较长，但 RS-EPI 似乎是一种很有前途的方法，可用于 CVJ 病变（如脑干缺血、神经退行性疾病、脑和颅底肿瘤或炎症）的 DTI 研究。
