Langton C M
Centre for Metabolic Bone Disease, University of Hull, UK.
Physiol Meas. 1997 Feb;18(1):67-72. doi: 10.1088/0967-3334/18/1/005.
There are now several commercial systems available for the ultrasonic assessment of osteoporosis, differing in anatomical location (calcaneus, tibia and phalanges), measurement parameters (broadband ultrasonic attenuation, BUA, and velocity) and their respective calculation algorithms. Comparison of system performance to date has centred upon precision (reproducibility) defined as coefficient of variation (CV%). It has been shown by both theoretical and in vivo studies that the computational algorithm implemented in the calculation of BUA of the calcaneus may have a significant effect upon CV%. The CV% for BUA is inherently inferior to the CV% for velocity by a factor of approximately seven since no allowance is made for population dynamic range. This note proposes and validates a novel parameter for precision, the standard deviation of the Z-score (ZSD). The precision of ultrasound velocity, even when expressed as ZSD, is superior to BUA by a factor of approximately two in the calcaneus. Since precision defined as ZSD is automatically sealed for both mean value and population dynamic range, and is dimensionless, it may be applied to all densitometric technologies. There is a broad range of precision values within the population and future work should investigate the causes of the variability.
目前有几种用于骨质疏松症超声评估的商业系统，它们在解剖位置（跟骨、胫骨和指骨）、测量参数（宽带超声衰减、BUA和速度）及其各自的计算算法方面存在差异。迄今为止，系统性能的比较主要集中在以变异系数（CV%）定义的精度（再现性）上。理论研究和体内研究均表明，跟骨BUA计算中所采用的计算算法可能对CV%有显著影响。由于未考虑人群动态范围，BUA的CV%在本质上比速度的CV%差约7倍。本报告提出并验证了一种新的精度参数，即Z分数的标准差（ZSD）。在跟骨中，即使以ZSD表示，超声速度的精度也比BUA高约2倍。由于定义为ZSD的精度会自动针对平均值和人群动态范围进行调整，并且是无量纲的，因此它可应用于所有骨密度测量技术。人群中的精度值范围很广，未来的工作应研究变异性的原因。
