Ultrasonic bone assessment using backscatter difference measurements at 1 MHz

There is interest in developing ultrasonic techniques that can be used to detect changes in bone caused by osteoporosis. One approach, called the backscatter difference technique, measures the power difference between two portions of a backscatter signal from cancellous bone. Previous laboratory studies have tested the technique using transducers with center frequencies > 2 MHz. The present study uses a 1 MHz transducer which may improve performance at central skeletal sites such as the hip and spine. Measurements were performed in vitro on 54 cube shaped specimens of cancellous bone from 14 human femurs using a broadband, single element 1 MHz transducer. Received backscatter signals were analyzed to determine the normalized mean of the backscatter difference (nMBD) which was computed by measuring the power difference between two gated portions of the backscatter signal in decibels and dividing by the gate separation in microseconds. Linear regression analysis found weak to moderate correlations (0.13 ≦ R ≦ 0.66) between nMBD and bone density, depending on which portions of the signals were analyzed. These results suggest that backscatter difference measurements using a 1 MHz transducer may be able to detect changes in bone caused by osteoporosis.