评价长骨的超声激发振动声导波方法研究

Ultrasonic guided waves have been applied to the bone quality evaluation and osteoporosis diagnosis. However, basing on the traditional excitation method, the guided signals are always recorded as overlapping multimodes. Therefore, improvement of the stimulation mechanism requires further research and can facilitate the ultrasonic evaluation of long bone with scientific importance and potential application. In this proposal, we intend to combine the ultrasound-stimulated acoustic emission (USAE) technique with ultrasonic guided waves theory for long bone strength assessment. The stimulation machanism and the propagation characteristics of the acoustic radiation force will be analyzed in the theory, simulation and experiment. The influence of the long cortical bone dispersive and strength property will be examined. Furthermore,we will investigate the selective excitation method of the lower-order modes in the long bone. With respect to the signal processing aspect, the compressed sensing will be utilized to improve the channel-number deficiency of the array measurements. The cortical strength parameters will be obtained for the bone quality evaluation and fracture risk prediction. The major innovation is the methodology analysis of the ultrasound-stimulated vibro-acoustic guided waves in the long bone. The advantage of the proposed vibro-acoustic guided waves approach is that it is able to only excite several low-order guided modes, which highly reduces the multimodal overlap and simplifies the data processing. Achievement of the proposed aims would enrich the ultrasonic guided wave research and establish new methodology and new technique of the bone strength evaluation with significant importance for the development of osteoporosis diagnostic assessment and fracture risk prediction.

超声导波已被用于骨质状况检测与骨质疏松评价，但传统激励方式下的长骨导波信号模式较多且相互混迭。若能从源头上改进激励机制，对促进长骨超声评价具有重要科学意义与潜在应用价值。 本项目旨在将超声激发声发射技术与超声导波理论相结合评价长骨强度状况。本研究将综合理论、仿真与实验，研究长骨中超声辐射力激发机制与振动声导波传播特性；分析长骨皮质骨频散特性与骨强度对超声辐射力激励与振动声导波传播的影响；研究长骨中低频振动声导波模式的选择性激励技术；研究低测量通道数条件下阵列导波信号的压缩感知算法，获取皮质骨强度参数，进而评价骨质状况、预测骨折风险。主要创新点是长骨中超声激发振动声导波方法的研究，该方法主要优点为可确保只激发数个低阶导波模态，使测量信号模式简单易分析。本研究在丰富超声导波研究的同时，可为长骨强度的超声导波评价提供新方法与新技术，对促进骨质疏松诊断技术发展与骨折风险预测的研究具有重要意义。

超声导波已被用于骨折愈合与骨质疏松评价，但传统单探头脉冲激励方式难于实现长骨导波信号模式分离,给后续数据分析与参数估计带来挑战。改进激励机制并提出与之相适应的信号处理技术，对促进长骨超声评价具有重要科学意义与应用前景。.本研究提出将超声激发声发射技术（USAE）与超声导波理论相结合评价长骨状况。综合理论、仿真与实验，研究了长骨中超声辐射力激发机制与振动声导波传播特性；分析长骨皮质骨频散特性与骨强度对超声辐射力激励与振动声导波传播的影响；研究长骨中低频振动声导波模式的选择性激励技术；提出一种宽带频散反转（WDR）技术可用于在板中激发自补偿的单一模式脉冲信号，从而有助于导波模式的识别与分离。结果表明，宽带导波模式的WDR信号可在前向传播过程中自我补偿。脉冲的持续时间参数能反映信号的自我补偿情况，并可用于检测材料特性与厚度评价。以上两项创新可在长骨中选择性激发数个低阶导波模态，使测量信号模式简单易分析。.多通道测量及相关信号处理技术，如经典的二维傅氏变换法，已被用于改善多模式导波信号频散提取与模式分离。在实践中，因所记录信号的持续时间通常较长，能够确保较高的频率分辨率；然而对空间位置的采样往往受限于探头设计与采样空间等，导致波数分辨率较低。本研究将波数稀疏惩罚算子与奇异值分解（SVD）相结合，提出了一种基于稀疏SVD分解的超声导波频散曲线提取方法。该算法能克服波数域的有限光圈局限，增强信噪比并实现高分辨率的频散曲线提取。.在上述工作基础上，以高分辨率导波频散曲线提取为基础，提出基于频散曲线提取的估计厚度的信号处理方法，将WDR编码激励技术用于长骨皮质骨中导波模式选择与厚度估计，将导波模型转换理论用于骨折愈合评价。.以上研究结果有助于长骨中超声导波频散特性的测量与分析，并可促进基于超声导波技术的长骨评价。本文研究方法对超声导波工业无损检测与评价也有一定的借鉴意义。