Backscattered Ultrasound Periodicity Characterization on Trabecular Bone-Mimicking Phantoms: A Spectral and Wavelets Approach

In an attempt to provide better diagnostic techniques using quantitative ultrasound to assess bone’s microarchitecture (e.g. osteoporosis), this work aimed at characterizing the periodicity of trabecular bone-mimicking phantoms using backscattered ultrasound signals, by means of spectral methods and the continuous wavelet transform (CWT). Two transducers (3.5 and 7.5 MHz) were used on a pulse-echo configuration. Two bone-mimicking phantoms were studied, with different stiffness but similar mean scatterer spacing (MSS) distributions (varying from 1.5 to 2.5 mm). Transducers were translated parallel to the phantoms to collect signals for processing with the spectral autocorrelation (SAC), singular spectrum analysis (SSA), quadratic transformation (Simon’s method) and continuous wavelet transform for MSS estimation. Some methods were able to estimate MSS values inside the range informed by the factory. Differences in trabecular thickness led to differences in MSS estimates, mainly for 7.5 MHz. There is a possibility that spectral methods find more than one periodicity pattern.