Orthopaedic Bioengineering Research Lab, Department of Biomedical Engineering, State University of New York at Stony Brook, Stony Brook, NY 11794-5281, USA.
Physiol Meas. 2011 Aug;32(8):1301-13. doi: 10.1088/0967-3334/32/8/019. Epub 2011 Jul 15.
Ultrasound has been widely used to nondestructively evaluate various materials, including biological tissues. Quantitative ultrasound has been used to assess bone quality and fracture risk. A pulsed phase-locked loop (PPLL) method has been proven for very sensitive tracking of ultrasound time-of-flight (TOF) changes. The objective of this work was to determine if the PPLL TOF tracking is sensitive to bone deformation changes during loading. The ability to noninvasively detect bone deformations has many implications, including assessment of bone strength and more accurate osteoporosis diagnostics and fracture risk prediction using a measure of bone mechanical quality. Fresh sheep femur cortical bone shell samples were instrumented with three 3-element rosette strain gauges and then tested under mechanical compression with eight loading levels using an MTS machine. Samples were divided into two groups based on internal marrow cavity content: with original marrow, or replaced with water. During compressive loading ultrasound waves were measured through acoustic transmission across the mid-diaphysis of bone. Finite element analysis (FEA) was used to describe ultrasound propagation path length changes under loading based on µCT-determined bone geometry. The results indicated that PPLL output correlates well to measured axial strain, with R(2) values of 0.70 ± 0.27 and 0.62 ± 0.29 for the marrow and water groups, respectively. The PPLL output correlates better with the ultrasound path length changes extracted from FEA. For the two validated FEA tests, correlation was improved to R(2) = 0.993 and R(2) = 0.879 through cortical path, from 0.815 and 0.794 via marrow path, respectively. This study shows that PPLL readings are sensitive to displacement changes during external bone loading, which may have potential to noninvasively assess bone strain and tissue mechanical properties.
超声已广泛应用于评估各种材料，包括生物组织的无损检测。定量超声已被用于评估骨质量和骨折风险。已证明脉冲锁相环（PPLL）方法非常适用于对超声飞行时间（TOF）变化的灵敏跟踪。本工作旨在确定 PPLL TOF 跟踪是否对加载过程中的骨变形变化敏感。非侵入性地检测骨变形的能力具有许多意义，包括评估骨强度和使用骨机械质量的测量值更准确地诊断骨质疏松症和预测骨折风险。新鲜羊股骨皮质骨壳样本用三个 3 元件玫瑰状应变计进行了仪器化，然后在 MTS 机上用 8 个加载水平进行机械压缩测试。根据内部骨髓腔含量将样本分为两组：有原始骨髓，或用水替换。在压缩加载过程中，通过穿过骨的中轴的声传输测量超声波。有限元分析（FEA）用于根据 µCT 确定的骨几何形状描述加载下的超声传播路径长度变化。结果表明，PPLL 输出与测量的轴向应变相关性良好，骨髓组和水组的 R(2) 值分别为 0.70 ± 0.27 和 0.62 ± 0.29。PPLL 输出与从 FEA 提取的超声路径长度变化的相关性更好。对于两个经过验证的 FEA 测试，通过皮质路径将相关性提高到 R(2) = 0.993 和 R(2) = 0.879，分别从 0.815 和 0.794 通过骨髓路径。这项研究表明，PPLL 读数对外部骨加载过程中的位移变化敏感，这可能具有非侵入性评估骨应变和组织机械性能的潜力。
