Xu Kailiang, Ta Dean, He Runxin, Qin Yi-Xian, Wang Weiqi
Department of Electronic Engineering, Fudan University, Shanghai, China.
Department of Electronic Engineering, Fudan University, Shanghai, China.
Ultrasound Med Biol. 2014 Apr;40(4):817-27. doi: 10.1016/j.ultrasmedbio.2013.10.019. Epub 2014 Jan 13.
Mode conversion occurs when the ultrasonic guided waves encounter fractures. The aim of this study was to investigate the feasibility of fracture assessment in long cortical bone using guided-mode conversion. Mode conversion behavior between the fundamental modes S0 and A0 was analyzed. The expressions proposed for modal velocity were used to identify the original and converted modes. Simulations and phantom experiments were performed using 1.0-mm-thick steel plates with a notch width of 0.5 mm and notch depths of 0.2, 0.4, 0.6 and 0.8 mm. Furthermore, in vitro experiments were carried out on nine ovine tibias with 1.0-mm-wide partial transverse gap break and cortical thickness varying from 2.10 to 3.88 mm. The study confirmed that mode conversion gradually becomes observable as fracture depth increases. Energy percentages of the converted modes correlated strongly with fracture depth, as illustrated by the frequency-sweeping experiments on steel phantoms (100-1100 kHz, r(2) = 0.97, p < 0.0069) and the fixed-frequency experiments on nine ovine tibias (250 kHz, r(2) = 0.97, p < 0.0056). The approaches described, including mode excitation, velocity expressions and energy percentage criteria, may also contribute to ultrasonic monitoring of long bone fracture healing.
当超声导波遇到骨折时会发生模式转换。本研究的目的是探讨使用导波模式转换评估长皮质骨骨折的可行性。分析了基模S0和A0之间的模式转换行为。使用提出的模态速度表达式来识别原始模式和转换模式。使用厚度为1.0毫米、缺口宽度为0.5毫米、缺口深度为0.2、0.4、0.6和0.8毫米的钢板进行了模拟和体模实验。此外，对九根羊胫骨进行了体外实验，这些胫骨有宽度为1.0毫米的部分横向间隙骨折，皮质厚度在2.10至3.88毫米之间变化。该研究证实，随着骨折深度增加，模式转换逐渐变得可观察到。转换模式的能量百分比与骨折深度密切相关，如在钢质体模上进行的频率扫描实验（100 - 1100千赫，r(2) = 0.97，p < 0.0069）以及对九根羊胫骨进行的固定频率实验（250千赫，r(2) = 0.97，p < 0.0056）所示。所描述的方法，包括模式激发、速度表达式和能量百分比标准，也可能有助于对长骨骨折愈合进行超声监测。
