EDDY CURRENT INDUCED IMAGE WARPING IN DIFFUSION WEIGHTED EPI

前言：MRI检测蛛网膜下腔出血(SAH)是 一个重要但有争议的监测急性中风的工具 病人。最近的出版物将FLAIR(流体 衰减反转恢复)MRI对CT的诊断价值 检测急性蛛网膜下腔出血。然而，这种MR图像对比度的来源 还没有被很好地理解。这项研究的目的是调查 通过比较不同种类的FLAIR图像来确定SAH对比度的来源 血液/脑脊液(CSF)与大脑的混合物。方法：生鲜 脑脊液取自枕大池，动脉血 取自大鼠股动脉。五个样品管 制备：1)肝素化血液，2)50%/50%非肝素化血液 磷酸盐缓冲盐水(PBS)，3)脑脊液中50%/50%非肝素化血液， 4)非肝素化血液；5)纯脑脊液。在4小时的安顿之后 一次，这些管子被放置在一只大鼠的头部旁边，并迅速 自旋回波FLAIR图像采集的活体大脑和样本 同时使用2T Ge CSI光谱仪。横向(T2) 并测量其纵向(T1)弛豫时间。结果 结论：所有血块在FLAIR上均与脑等信号 图像。凝血过程导致T1和T2缩短到 与大脑的值相似，导致几乎没有对比 脑脊液和大脑中的凝块之间的天赋。相比之下，这些细胞 在肝素化的血液中沉淀物的亮度比大脑高约50% 才华。此外，每一根含有血栓的管子都显示出一种薄薄的 一层沉淀的血细胞，也是高信号。T2值 对于非凝块细胞来说，高于大脑，但低于 脑脊液。SAH的FLAIR图像上的高信号可能是由于 蛛网膜下腔血中未凝结的部分，最好使用Long 回声时间。

Introduction: MRI detection of subarachnoid hemorrhage (SAH) is an important but controversial tool for monitoring acute stroke patients. Recent publications favorably compare FLAIR (fluid attenuated inversion recovery) MRI to computed tomography (CT) for the detection of acute SAH. However, the source of this MR image contrast is not well understood. The purpose of this study was to investigate the source of the SAH contrast by comparing FLAIR images of various blood/cerebrospinal fluid (CSF) mixtures with brain. Methods: Fresh CSF was obtained from the cisterna magna and arterial blood was obtained from the femoral artery of rats. Five sample tubes were prepared: 1) heparinized blood, 2) 50/50% nonheparinized blood in phosphor buffered saline (PBS), 3) 50/50% nonheparinized blood in CSF, 4) nonheparinized blood, and 5) pure CSF. After 4 hours of settling time, the tubes were positioned next to the head of a rat and fast spin-echo FLAIR images were acquired of in-vivo brain and the sample tubes simultaneously using a 2 T GE CSI spectrometer. Transverse (T2) and longitudinal (T1) relaxation times were also measured. Results and Conclusion: All blood clots were isointense to brain on the FLAIR images. The process of clotting causes shortening of T1 and T2 to values similar to those of brain which results in little contrast on FLAIR between clots in CSF and brain. In contrast, the cells which settled in the heparinized blood were ~50% brighter than brain on FLAIR. In addition, each of the tubes containing a clot showed a thin layer of settled blood cells which was also hyperintense. T2 values for non-clotted cells were higher than for brain but less than for CSF. Hyperintensities on FLAIR images of SAH are probably due to the unclotted portion of subarachnoid blood and are best seen using long echo times.