超声血流向量成像技术探讨颈动脉球部壁面剪切应力的影响因素

Study on influencing factors of wall shear stress of carotid bulb by ultrasound vector flow imaging(V Flow)technique

目的:运用超声血流向量成像(VectorFlowImaging,V Flow)技术探讨颈动脉球部自体解剖结构及血流动力学因素对壁面剪切应力(Wall Shear Stress,WSS)的影响。方法:选取颈动脉超声检查正常患者70例,将V Flow感兴趣区置于颈总动脉分叉部及颈内动脉起始段。测量颈动脉球部与颈总动脉间角度(θ)、测量收缩末期颈动脉球部(Carotid Bulb,CB)膨大最明显处内径(D_(CB))与颈总动脉末段内径(D_(CCA))的比值(D_(CB)/D_(CCA))、测量颈动脉球部分流量(Q_(CB))与颈总动脉末段流量(Q_(CCA))的比值(Q_(CB)/Q_(CCA))、描记颈动脉球部血流紊乱区可视化面积(A_(CB))以及测量颈动脉球部起始段内侧平均壁面剪切应力(WSS_(I-CB))和外侧平均壁面剪切应力(WSS_(E-CB)),并对上述各项参数进行统计学分析。结果:(1)颈动脉球部起始段WSS_(I-CB)值为(0.88±0.30)Pa,外侧WSS_(E-CB)值为(0.32±0.15)Pa,外侧壁明显小于内侧壁,差异有统计学意义(P<0.01)。(2)颈动脉球部与颈总动脉夹角θ值为(24.5±12.1)°,与WSS_(E-CB)相关系数为r=−0.171,二者无相关性且差异无统计学意义(P>0.05);颈动脉球部膨大最明显处内径与颈总动脉末段内径比值D_(CB)/D_(CCA)为(0.66±0.09),与WSS_(E-CB)值呈负相关,相关系数为r=−0.312,差异有统计学意义(P<0.05)。(3)颈动脉球部分流量与颈总动脉末段流量比值Q_(CB)/Q_(CCA)为(0.69±0.15),与WSS_(E-CB)值呈正相关,相关系数为r=0.428,差异有统计学意义(P<0.01);颈动脉球部血流紊乱区面积A_(CB)为(0.27±0.17)cm2,与WSS_(E-CB)值呈负相关,相关系数分别为r=−0.545,差异有统计学意义(P<0.01)。结论:颈动脉球部血流量、血流紊乱区面积及膨大程度是影响外侧壁面剪切应力WSS的主要因素,而与颈动脉球部发出角度的关系并不密切。

Objective:To investigate the effect of carotid artery bifurcation anatomy and hemodynamics on wall shear stress by using ultrasound vector flow imaging(V Flow)technique.Methods:A total of 70 normal patients after carotid artery ultrasound examination were selected as the study subjects.By placing the V Flow region of interest at the bifurcation of the carotid artery,the ratio(D_(CB)/D_(CCA))of the inner diameter of carotid bulb(D_(CB))where the area is the most obvious expansion at the end-systolic to the inner diameter of terminal segment of common carotid artery(D_(CCA)),the angle(θ)between the carotid bulb and the common carotid artery,and the ratio(Q_(CB)/Q_(CCA))of the blood flow of the carotid bulb(Q_(CB))to the terminal segment of common carotid artery(Q_(CCA))were measured.And the visualized area of blood flow disorder in the carotid bulb(A_(CB))was recorded and the average shear stress of the inner wall&outer wall of the carotid bulb was measured.All the above parameters were analyzed by statistical method.Results:(1)The WSS_(I-CB) value of the inner wall of the carotid bulb was(0.88±0.30)Pa,and the WSS_(E-CB) value of the outer wall was(0.32±0.15)Pa,the WSS_(E-CB) value of the outer wall was significantly smaller than the WSS_(I-CB) of the inner wall,and the difference was statistically significant(P<0.01).(2)The angle between the carotid bulb and the common carotid artery was(24.5±12.1)°,and its correlation coefficient with WSS_(E-CB) was r=−0.171,i.e.there was no correlation between them,their difference was not statistically significant(P>0.05).The ratio of the most obvious enlargement of carotid bulb to the inner diameter of common carotid artery(D_(CB)/D_(CCA))was(0.66±0.09),which was negatively correlated with WSS_(E-CB) value,the correlation coefficient r=−0.312,and their difference was statistically significant(P<0.05).(3)The ratio of the volume of carotid bulb to the volume of terminal carotid artery(Q_(CB)/Q_(CCA))was(0.69±0.15),which was positively correlated with WSS_(E-CB) value,the correlation coefficient was r=0.428,and their difference was statistically significant(P<0.01).The area of blood flow disorder in the carotid bulb(A_(CB))was(0.27±0.17)cm2,which was negatively correlated with WSS_(E-CB) value,the correlation coefficient was r=−0.545,and their difference was statistically significant(P<0.01).Conclusions:The blood flow of internal carotid artery,the area of the bifurcation where the blood flow is diffuse and amorphous,and the degree of bulbar enlargement are the main factors affecting the lateral wall WSS,but it is not closely related to the angle of the internal carotid artery.