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

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。

Effects of stenoses on non-Newtonian flow of blood in blood vessels

In this paper, a mathematical model for steady blood flow through blood vessels with uniform cross-section in stenoses arteries has been proposed. Blood is assumed to be non- Newtonian, incompressible and homogeneous fluid. Blood in human artery is represented as Bingham plastic fluid. Expressions for flow rate, wall shear stress, and resistance to flow against stenoses size have been obtained. Obtained results indicate that stenoses size decreases the flow rate and increases the wall shear stress as well as resistance to flow.