磁共振DWI高b值及ADC值在超急性脑缺血中的应用价值

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

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、4.00h及6.00h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、2 000、3 000s/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2 000、3 000s/mm2时DWI对超急性期脑缺血的诊断率明显高于b值为400、800s/mm2(P<0.05),b值为400、800、2 000、3 000s/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0.25h及0.50h显示病灶方面更具优势。

Objective To investigate the value of DWI high b value and ADC value in the diagnosis of hyperacute cerebral ischemia. 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/mm2 and 3 000 s/mm2 ,the diagnostic rates of DWI for hyperacute cerebral ischemia were obviously higher than those in b=400 s/mm2 and 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,especially in the aspect of displaying the lesion at 0.25,0.50 h cerebral ischemia.