Effect of gate choice on backscatter difference measurements of cancellous bone

A variety of ultrasonic techniques have been developed to detect changes in bone caused by osteoporosis. One approach, called the backscatter difference technique, analyzes the power difference between two different portions of a backscatter signal. Analysis gates with a certain delay tau(d), width tau(w), and separation ss are used to define portions of the backscatter signal for analysis. The goal of the present study was to investigate how different choices of tau(d), tau(w), and tau(s) affect four backscatter difference parameters: the normalized mean of the backscatter difference (nMBD), the normalized slope of the backscatter difference (nSBD), the normalized intercept of the backscatter difference (nIBD), and the normalized backscatter amplitude ratio (nBAR). Backscatter measurements were performed on 54 cube shaped specimens of human cancellous bone. nMBD, nSBD, nIBD, and nBAR were determined for 34 different combinations of tau(d), tau(w), and tau(s) for each specimen. nMBD and nBAR demonstrated the strongest correlations with apparent bone density (0.48 <= R-s <= 0.90). Generally, the correlations were found to improve as tau(w) + tau(s) was increased and as tau(d) was decreased. Among the four backscatter difference parameters, the measured values of nMBD were least sensitive to gate choice (< 16%). (C) 2017 Acoustical Society of America.