Mean scatterer spacing of backscattered ultrasound signals from in vitro human cancellous bone specimens

Acoustic parameters such as the slope of the frequency-dependent attenuation or the sound speed may be considered as surrogate markers for bone mineral density (BMD). However, they do not reveal much about bone microarchitecture which is recognized as being a determinant factor of skeletal strength in addition to BMD. As noninvasive measurements of bone microarchitecture may play a role in predicting fracture risk, ultrasound (US) signals backscattered by bone are processed with the aim of revealing its features, such as mean trabecular spacing. This work applied Mean Scatterer Spacing (MSS) estimation to characterize the micoarchitecture of human cancellous bone. Singular Spectrum Analysis (SSA) is applied to estimate (MSS) from US measurements (1 MHz) of 24 in vitro bone cylinders from human calcanei. The measured MSS values from bone US signals range from 1.0 to 1.7 mm. The SSA MSS estimated correlate significantly to mean trabecular spacing obtained independently by microtomography (r/sup 2/ = 0.68. p<0.05). Thus, SSA applied to US backscattered signals seems to be useful for providing information about bone microarchitecure, which can be potentially added to the ones currently obtained using quantitative US transmission techniques.