视放射区纤维束MRI弥散张量成像及梗死后改变

目的：利用弥散张量成像不同成像参数探索正常视觉通路的显示情况和枕颞叶视放射区脑梗死纤维束的变化。方法对20例正常志愿者和45例枕颞叶视放射区脑梗死患者，分别行常规磁共振检查、弥散加权成像及弥散张量成像，显示枕颞叶视放射区的纤维束走行，并测量梗死侧及对侧视放射区的各向异性值、表观扩散系数值、体积相对各向异性值及指数各向异性值。结果在正常对照组不同区域设置感兴趣区，可以较好地显示视神经、视束、视放射的走行。枕颞叶视放射梗死区弥散加权成像及弥散扩散张量成像各参数值的变化，FA值在超急性期略升高，其余各期有不同程度的减低，ADC值在超急性期、急性期和亚急性期不同程度升高，慢性期减低；VRA与FA呈正相关关系（ r ＝0．789）， EA与ADC呈负相关关系（ r ＝-0．743）。结论弥散加权成像及弥散扩散张量成像可以较好显示视觉通路和枕颞叶视放射区纤维束的走行及梗死后的改变，有利于梗死预后的判断。

The application of MR DTI in showing normal and infarcted optic radiation

Objective To study the normal fiber of visual pathway and changes in optic radiation infarction with diffusion tensor imaging （DTI） .Methods Conventional MRI ,DWI and DTI were performed in twenty healthy volunteers and ty-five patients with optic radiationinfarction .The fiber of visual pathway was depicted ,and the fractional anisotropy （FA） , apparent diffusion coefficient （ADC） ,volume relative anisotropy （VRA） and exponential anisotropy （EA） were measured and analyzed .Results Regions of interest （ROIs） were selected in different parts of volunteers for tracking the visual pathways .The different parameters were measured in infarction areas and contralateral normal areas .FA values in hyper-acute were increased slightly and were decreased in acute ,subacute and chronic phases .The ADC values in infarction re-gions were decreased in hyperacute ,acute and subacute phases .VRA and FA appeared positive correlation while EA ,and negative with ADC .Conclusion DTI could track the fiber of visual pathway ,which could be used in depicting fibers of in-farction zone and tracking prognosis of patients .