MR Visualization of Spinal Dural Arterio-Venous Fistula Using T2-Weighted 3D SPACE—A Spin-Echo Technique

Spinal dural arteriovenous fistulas (SDAVF) account for about 70% of all spinal AV shunts. We re-port on a 56-year-old male patient with progressive neurological symptoms. Pre- and post-contrast MR imaging of the spine, including contrast-enhanced MR angiography was done on a 1.5 T MR scanner. In addition a special (pre-contrast) 3D turbo-spin-echo sequence with variable flip angle evolution (SPACE) was performed providing a slice thickness of 0.9 mm. T2-weighted images showed extensive widened and tortuous vascular structures with typical flow voids intradurally due to dilated pial veins. The origin of the spinal dural arteriovenous fistula was found to be the radiculomeningeal artery at level D10/11 on the left side, visualized by the T2-weighted 3D SPACE sequence and CE MRA. After imaging the patient was referred to an interventional neuroradiology department for therapy. With the detailed information from MR imaging concerning the fistula level the interventional radiologist was able to find the fistula immediately and consequently treated it successfully by endovascular therapy. Interpreting the MR images of this obvious case of a SDAVF, SPACE sequence after post processing with 3D MPR software directly led to the location of the AV shunt at D10/11 on the left side, better than 3D contrast-enhanced MR angiography did. Therefore, SPACE can be a useful adjunct in further evaluation of spinal dural arteriovenous fistula and especially in defining fistula level.

磁共振3D神经成像对腰骶丛显示的对比研究

目的探讨1.5T磁共振三维快速自旋回波成像(3D sampling perfection with application optimized contrasts by using different flip angle evolutions,3D-SPACE)与多回波融合成像(multiple echo data image combination,3D-MEDIC)序列对正常人腰骶丛神经的显示。方法 31例无症状正常志愿者行MRI检查,包括常规腰椎MRI、3D-SPACE及MEDIC序列扫描,原始图像传入后处理工作站行多平面图像重组。结合原始及重组图像,比较3D-SPACE及MEDIC序列图像腰骶丛神经根的信噪比及对神经的显示评分。结果 3D-MEDIC序列显示神经根的信噪比高于3D-SPACE序列(分别为70.15±24.03及28.78±7.12,P=0.000)。3D-MEDIC序列对腰骶丛的显示评分高于3D-SPACE序列(P=0.000)。结论1.5T磁共振腰骶丛神经显像中,3D-MEDIC序列优于3D-SPACE序列,可清晰显示神经根走行,是常规腰椎MRI的重要补充。

结合突变论和离散聚类思想的视点空间划分算法

针对视点空间划分问题中算法复杂以及计算复杂度大的问题,提出了一种结合突变论和离散聚类思想的新方法。利用突变论获得视觉事件的空间切割曲面方程,然后在视点空间球面上选取有序采样并计算每个样点的符号序列,通过对符号序列的判断实现对离散点的聚类,使用点集替代传统的边界线方程来表达视点空间分划结果。该方法避免了突变理论中求解视点空间分划线方程数值解以及从分划线相互关系中寻找闭合区域的过程。实验结果表明该方法能够有效地提高三维目标识别的实时性,计算时间不足原算法的15%。