Institute for Biomechanics, ETH Zürich, Zürich, Switzerland.
Human Performance Lab, Schulthess Clinic, Zürich, Switzerland.
Ultrasonics. 2019 Apr;94:109-116. doi: 10.1016/j.ultras.2018.11.012. Epub 2018 Nov 30.
Axial transmission quantitative acoustics (ax-QA) has shown to be a promising tool for assessing bone health and properties in a safe, inexpensive, and portable manner. This study investigated the efficacy of low-frequency ax-QA measured at the tibia, paired with a support vector machine (SVM) approach for combining multiple acoustic indicators, to diagnose osteoporosis as defined by bone mineral density.
This pilot study measured 41 female subjects using ax-QA (flexural mode, 3 kHz) at the tibia and using dual X-ray absorptiometry (DXA) at the lumbar spine, femoral neck, and distal radius. For each location, a threshold classifier and SVM were trained to differentiate between healthy and non-healthy subjects based on the phase velocity at different frequencies. Receiver Operating Characteristics and area under curve values (AUC) were used to assess the classifiers' performances for various thresholds and class-weights.
The SVM outperformed the threshold classifier for all three bone locations at low false positive rates. While differentiation between healthy and non-healthy bone states was poor for the spine (AUC: 0.56 ± 0.04), good to moderate performances were observed for the radius (AUC: 0.83 ± 0.03) and hip (AUC: 0.71 ± 0.04).
Low-frequency ax-QA has demonstrated potential for complementing DXA in screening for osteoporosis at the radius and hip. Through further addition of acoustic indicators ax-QA could provide a diagnostic alternative in third-world countries, and bring bone health screening and monitoring into the hands of clinicians and general health practitioners everywhere.
轴向传输定量声学（ax-QA）已被证明是一种有前途的工具，可安全、廉价且便携地评估骨骼健康和特性。本研究调查了低频轴向 QA 在胫骨处的测量效果，结合支持向量机（SVM）方法，将多个声学指标组合在一起，以根据骨密度定义诊断骨质疏松症。
本研究采用 ax-QA（弯曲模式，3 kHz）对 41 名女性受试者的胫骨进行测量，采用双能 X 射线吸收法（DXA）对腰椎、股骨颈和桡骨远端进行测量。对于每个部位，基于不同频率的相速度，使用阈值分类器和 SVM 训练来区分健康和非健康受试者。使用接收器操作特性和曲线下面积（AUC）值来评估各种阈值和类权重下分类器的性能。
在低假阳性率下，SVM 在所有三个骨部位的表现均优于阈值分类器。虽然脊柱的健康和非健康骨状态区分较差（AUC：0.56±0.04），但桡骨（AUC：0.83±0.03）和髋部（AUC：0.71±0.04）的表现良好到中等。
低频 ax-QA 已显示出在桡骨和髋部筛查骨质疏松症方面补充 DXA 的潜力。通过进一步增加声学指标，ax-QA 可以为第三世界国家提供一种诊断替代方法，并使骨骼健康筛查和监测在临床医生和普通健康从业者手中。
