磁共振DWI高b值及ADC值在超急性脑缺血中的应用价值

目的 探讨磁共振扩散加权成像(DWI)高b值及表观弥散系数(ADC)值在超急性脑缺血诊断中的价值.方法 选成年SD大鼠,采用随机数字表法分为缺血组和对照组,依据缺血时间长短将缺血组再分为0.25、0.50、1.00、2.00、4.00 h及6.00 h组,每组各6只,共42只.缺血组行右侧大脑中动脉栓塞(MCAO),分别进行头部 T2WI、DWI(b值分别为0、400、800、2000、3000 s/mm2)扫描,记录对比噪声比(CNR)、信噪比(SNR)值,测量 T2WI、DWI高信号最大层面相对面积(rs-T2WI、rs-DWI)及相对表观扩散系数(rADC)值,观察缺血区域的影像学改变,检验灵敏度及特异度.结果 b值为2000、3000 s/mm2时DWI对超急性期脑缺血的诊断率明显高于b值为400、800 s/mm2(P<0.05),b值为400、800、2000、3000 s/mm2在诊断超急性脑缺血的敏感性分别为16.7%、50.0%、100.0%、100.0%,特异度为16.7%、50.0%、100.0%、100.0%.不同b值下ADC值差异有统计学意义(P<0.05).结论 高b值DWI在诊断超急性脑缺血明显优于低b值,尤其在脑缺血0.25 h及0.50 h显示病灶方面更具优势.

Application value of magnetic resonance DWI high b-value and ADC value in hyperacute cerebral ischemia

Objective To investigate the value of DWI high b value and ADC value in the diagnosis of hyperacute cerebral is-chemia.Methods Adult SD rats were selected and divided into the control and ischemic group by adopting the random number table method,the ischemic group was re-divided into 0.25,0.50,2.00,4.00、6.00 h groups according to the ischemic time,6 cases in each group with a total of 42 cases.The ischemic group conducted the right middle cerebral artery occlusion(MCAO)for performing the head T2WI and DWI scanning(b values were 0,400,800,2 000,3 000 s/mm2),the CNR and SNR values were recorded,rs-T2WI, rs-DWI and relative apparent diffusion coefficient(rADC)were measured.Then the imaging change of ischemic area was observed. The sensitivity and specificity were detected.Results In b=2 000 s/mm2and 3 000 s/mm2,the diagnostic rates of DWI for hyper-acute cerebral ischemia were obviously higher than those in b=400 s/mm2and 800 s/mm2,and when the b values were 400,800, 2 000,3 000 s/mm2,the sensitivities were 16.7%,50.0%,100.0% and 100.0% respectively and the specificities were 16.7%, 50.0%,100.0% and 100.0% respectively.The difference of ADC values under different b values had statistical significance(P<0.05).Conclusion High b value DWI in the diagnosis of hyperacute ischemia is significantly better than that of low b value,espe-cially in the aspect of displaying the lesion at 0.25,0.50 h cerebral ischemia.