磁共振扩散加权成像对不同时期脑梗死的诊断意义

Diagnostic significance of diffusion weighted imaging for cerebral infarction in different periods

目的探讨磁共振扩散加权成像(diffusion weighted imaging,DWI)在不同时期脑梗死的信号变化特点。方法搜集经临床确诊并经磁共振证实的脑梗死患者130例,均同时进行了磁共振平扫检查和DWI检查。根据发病到行磁共振检查的时间分为超急性期(<6 h)30例,急性期(6~72 h)40例,亚急性期(3~10 d)30例,慢性期(>11 d)30例。测定各期梗死灶及对侧正常组织表观扩散系数值(apparent diffusion coefficient,ADC),分析不同时期脑梗死DWI信号变化的特点。结果超急性期病灶DWI显示为高信号,病变组织的ADC值明显低于正常组织,差异有统计学意义(P<0.05);急性期病灶DWI显示为高信号,病变组织的ADC值低于正常组织,差异有统计学意义(P<0.05);亚急性期病灶DWI显示为稍高信号,较急性期信号下降,29例病变组织的ADC值稍低于正常组织,1例病变组织的ADC值高于正常组织,差异有统计学意义(P<0.05);慢性期病灶DWI显示为稍高信号13例,等或低信号17例,病变组织的ADC值与正常组织间差异无统计学意义(P>0.05)。结论DWI能对超急性期、急性期、亚急性期的脑梗死病灶信号变化作出明确的诊断,对超急性期、急性期病灶的敏感度较高。脑梗死的DWI信号和ADC值的变化具有特征性的时间演变规律,DWI结合常规MRI可以推断脑梗死时期。

Objective To investigate the characteristics of signal changes of the diffusion weighted imaging(DWI)of magnetic resonance imaging(MRI)for cerebral infarction in different periods.Methods A total of 130 patients with cerebral infarction confirmed by MRI clinically were collected,and underwent both magnetic resonance plain scan and DWI examination simultaneously.Based on the time interval between onset and magnetic resonance examination,these patients were divided into hyperacute group(<6 h,n=30),acute group(6-72 h,n=40),subacute group(3-10 d,n=30),chronic group(>11 d,n=30).Apparent diffusion coefficients(ADC)of infarct foci and contralateral normal tissues were determined,and the characteristics of DWI signal changes in cerebral infarction in different periods were analyzed.Results DWI of hyperacute lesion showed high signal,and the ADC value of lesion tissue was significantly lower than that of normal tissue,suggesting significant difference(P<0.05).DWI of acute lesion showed high signal,the ADC value of lesion tissue was lower than that of tnormal tissue,and the difference was statistically significant(P<0.05).DWI of subacute lesion showed slightly high signal,which was lower than that of acute lesions,and the ADC values of 29 cases of lesions were slightly lower than those of normal tissue,whereas 1 case of lesion was higher than that of normal tissue,with significant difference(P<0.05).DWI of chronic lesions showed slightly higher signal in 13 patients,and equal or low signal in 17 patients.There was no significant difference between the ADC value of lesion tissue and that of normal tissue(P>0.05).Conclusion DWI can make a definite diagnosis of the signal changes of cerebral infarction in hyperacute,acute and subacute phases,with higher sensitivity to hyperacute and acute lesions.The changes of DWI signal and ADC value of cerebral infarction are in line with the characteristic time-evolution law,and DWI combined with conventional MRI can be used to infer the period of cerebral infarction.