长骨裂纹宽度和角度对低阶超声导波的影响

Impact of long bone fracture width and angle on low-order ultrasonic guided waves

超声导波检测长骨骨折和监测骨折愈合已成为一种极具前景的课题,但高频厚积下导波多模式混叠带来的模式识别和分离问题一直是一个难点。为避免上述问题,在低频下仅激励两个低阶兰姆波SO和AO模式,采用二维时域有限差分(2DFDTD)法定量分析裂纹宽度和骨折角度对SO和AO幅度的影响。结果表明,SO与AO模式的幅度均随裂纹宽度的增加而下降;AO的幅度随骨折角度增大而上升,SO幅度随骨折角度增大先下降后上升,转折点约为45°。SO与AO的幅度比值在不同骨折角度下均能较好地表征裂纹宽度的变化,可为横断型和斜切型长骨骨折状况的超声评价及骨折愈合监测提供依据。

Using ultrasonic guided wave to assess long bone fractures and fracture healing has become a promising diagnostic issue. But the multiple guided wave modes alias has always been a big challenge. To solve this problem, a low frequency signal is used in the two-dimension finite-difference time-domain （2D-FDTD） simulation and only SO and A0 modes are excited. The amplitudes of guided waves SO and A0 in long bone with different fracture width and angle are analyzed. The results show that both SO and A0 amplitudes decrease with the increasing of fracture width in different oblique fracture angles. A0 amplitude increases with the increasing of oblique fracture angle while SO amplitude decreases with the increasing of fracture angle then increases with the further increasing of fracture angle with a turning point at around 45°. The ratio parameter between the amplitude of SO and A0 can evaluate the change of fracture width in different fracture angle cases. Thus, it can provide basis for evaluating fractured long bone with vertical and oblique angle and monitoring the healing of fractured long bone.