评估量化超急性期缺血性脑卒中发病时间窗的研究

目的利用高场MR多模态成像序列评估及找出脑卒中的早期迹象影像证据，为早期rt-PA溶栓治疗时间窗提供直观和个体化的影像学信息。材料与方法利用线栓法栓塞右侧大脑中动脉，制备MCAO大鼠模型10只，在不同的时间点采用DWI、病灶的表观扩散系数（ADC）和常规T2WI评估MCAO大鼠模型脑缺血性病变区域的特性。通过MRS、并应用LCModel后处理来绝对定量在不同的时间点病灶内局部特异性代谢物浓度的变化。结果10只MCAO大鼠，6 h内T2WI均未显示明确病变灶；而大脑中动脉梗塞10 min后，DWI均能在大脑中动脉供血相应纹状体区及顶叶皮层区显示出异常的高信号，与DWI相应病变区ADC图均显示有异常的低信号。MRS研究发现，大脑中动脉梗塞1 h后病变中心区对比相应对侧正常区Lac峰明显增高，NAA峰明显下降；谷氨酸和牛磺酸绝对浓度2 h内逐渐上升达峰值，随后3 h段明显下降。结论 MR多模态成像序列，特别是利用T2WI、DWI及1H MRS可定性诊断超早期缺血性脑卒中，并能评估及量化超急性脑卒中发病时间窗，为筛选适合rt-PA溶栓治疗者提供客观和个体化的影像学信息。

Quantitative assessment of hyperacute ischemic stroke onset time window

Objective：To assess and quantify the ischemic onset time window of middle cerebral artery infarction hyperacute stroke of MCAO rat model at 7.0 T MRI diffusion weighted imaging （DWI） and by proton magnetic resonance spectrum （1H MRS）. Materials and Methods：Diffusion-weighted imaging （DWI） and conventional T2WI were employed on 10 cases of MCAO rat model in measuring the average ADC lesion at different time periods. Quantiifcation of local changes in the concentrations of metabolites within the lesions at different time zones was performed using magnetic resonance spectrum. Results：High signal area appeared half an hour after occlusion in DWI （100%）. No abnormal signal was observed in 6 hours with general T2WI. 1H MRS display was consistent with elevated lactate （Lac） and reduced n-acetyl aspartic acid salt （NAA）. Glutamate and taurine reached a maximum in rats 2 h after MCAO but began to decrease 3 h after MCAO. Conclusions：Hyperacute cerebral infarction can be pointed out with the application of T2WI, DWI and 1H MRS. These methods may also be used to assess quantitatively the ischemic onset time of a hyperacute stroke.