弥散加权成像诊断弥漫性轴索损伤的实验研究

Experimental study of diffusion weighted imaging in diagnosis of diffuse axonal injury

目的观察大鼠弥漫性轴索损伤(DAI)后弥散加权成像(DWI)的变化规律。方法采用Marmarou致伤装置制备135只不同程度(轻度、中度、重度)DAI的SD大鼠模型,在大鼠致伤后4、8、24h行磁共振成像检查;另取8只大鼠作为正常对照组。对各组大鼠的磁共振成像结果进行分析,比较各组表观弥散系数(ADC)。结果致伤后各组大鼠磁共振成像未发现明确可视性病灶。伤后4h,各DAI组大鼠ADC值均下降,中、重度组与对照组的差异有统计学意义(P<0.05);伤后8h,各DAI组ADC值均升高,与对照组的差异无统计学意义(P>0.05);伤后8h与伤后4h相比,重度组ADC值的差异有统计学意义(P<0.05),而中度、轻度组的差异无统计学意义(P>0.05)。伤后24h,各DAI组ADC值继续升高,以重度DAI组升高最显著。结论通过测定ADC值可以检测到DAI后常规磁共振成像不能显示的外伤性改变;大鼠DAI急性期ADC值下降,随后上升,其变化幅度可能与DAI严重程度有关。

Objective To observe the changes of diffusion weighted imaging （DWI） after diffuse axonal injury （DAI） in rats. Methods Models of various degrees of DAI （mild, moderate and severe） were established in 135 SD rats by Marmarou method, and MRI examinations were performed 4, 8 and 24 h after injury. Another 8 rats were served as control group. The findings of MRI were analysed, and the apparent diffusion coefficient （ADC） values were compared among each group. Results No clear traumatic lesion was found from MRI in rats after injury. Four hours after injury, ADC values decreased in each DAI group, and there were significant differences between moderate DAI group and control group, and between severe DAI group and control group （P〈0.05）. Eight hours after injury, ADC values increased in each DAI group, and there was no significant difference between DAI groups and control group （P〉0.05）. There were significant differences in ADC values between 8 h after injury and 4 h after injury in severe DAI group （P〈0.05）, while there was no significant difference in moderate and mild DAI groups （P〉0.05）. Twenty-four hours after injury, ADC values continuously increased, especially in severe trauma group. Conclusion ADC values may reveal traumatic changes that can not be demonstrated by MRI. ADC values decrease in acute phase of DAI in rats, then increased, and the degree of variation may be related to the severity of DAI.