拉伸指数与单指数模型DWI对单侧大脑前循环动脉狭窄者的评价

Diffusion weighted imaging with stretched-exponential model and mono-exponential model in patients with cerebral anterior circulation arteriostenosis

目的:以单侧大脑前循环动脉不同程度狭窄的患者为研究对象,比较DWI的拉伸指数模型、单指数模型的各参数值在左、右半球之间的差异。方法:对申请头颈部动脉CTA检查的患者,在无MRI检查禁忌及患者知情同意的情况下行单指数和拉伸指数模型的扩散加权检查。采用的b值序列是:0、5、10、20、50、100、200、400、600、1000、1500、2000、3000s/mm2,通过工作站计算表观扩散系数(ADC)值、分布扩散系数(DDC)值和α值三个参数。根据颈内动脉系统是否狭窄及狭窄程度将患者分为A(无狭窄)、B(轻、中度狭窄)、C(重度狭窄或闭塞)三组,统计各组左右两侧大脑中动脉供血区的各参数值,运用非参数秩和检验法比较两侧值的组间差异及组内差异。结果:进入统计分析的患者共39例,其中A组11例,B组13例,C组15例。经统计学检验发现,ADC值、DDC值的左右侧差值及左右侧比值的对数值的各组间比较、C组的组内比较差异均有统计学意义(P<0.05);B组DDC值的左右侧差值及左右侧比值的对数值的组内比较差异均有统计学意义(P<0.05);B组ADC值的左右侧差值比较差异无统计学意义(P>0.05),左右侧比值的对数值的比较差异有统计学意义(P<0.05)。α值的上述差异均无统计学意义(P>0.05)。结论:运用多b值DWI技术定量分析大脑前循环狭窄时,单指数模型的ADC值和拉伸指数模型的DDC值在无动脉狭窄和狭窄者之间的差异均有明显体现,而DDC值对不同程度狭窄者之间的差异更敏感。

Objective：To compare the differences of parameters of diffusion weighted imaging（DWI） with both stretched-exponential and mono-exponential model between left and right cerebral hemisphere in patients with unilateral arteriostenosis.Methods：Patients who underwent head-neck CTA scan in our hospital and had no MR imaging contraindication and signed the informed consent were included in our study.The b-values were 0,5,10,20,50,100,200,400,600,1000,1500,2000,3000s/mm2,and apparent diffusion coefficient（ADCs） values,distributed diffusion coefficients（DDCs） and α values were calculated through workstation.According to the stenotic degrees of internal carotid artery system,patients were divided in three groups：group A with no stenosis,group B with mild and moderate stenosis,and group C with severe stenosis or complete occlusion.We calculated every parameters of both cerebral side in every groups,and compared the differences among groups and within groups by using Kruskal-Wallis statistic for Wilcoxon rank sum test.Results：39 cases were enrolled in our study.The numbers of group A,B and C were 11,13 and 15,respectively.By statistic analysis,the differences between left and right and Ln（left/right） of ADCs and DDCs among three groups and within group C had statistical significance（P0.05）.In group B,the differences between left and right and Ln（left/right） of DDCs had statistical significance（P0.05）;the differences between left and right of ADCs had no statistical significance（P0.05）,the Ln（left/right） of ADCs had statistical significance（P0.05）.Besides,the above mentioned differences of α values were not significant（P0.05）.Conclusion：When applying multi-b values in DWI to evaluate the cerebral anterior circulation arteriostenosis quantitatively,ADC of mono-exponential model and DDC of stretched-exponential model reflected significant differences between arteriostenosis and normal,but DDC was more sensitive among various stenotic degrees.