Numerous studies have performed in vitro ultrasonic measurements of cancellous bone in water to develop techniques for ultrasonic bone assessment. Because cancellous bone is a highly porous medium, ultrasonic reflections at the water-bone interface may be frequency dependent. The goal of this study was to investigate the effect of porosity on the frequency dependence of the reflected power. Ultrasonic measurements were performed in a water tank at room temperature on 15 specimens of cancellous bone prepared from the proximal end of 9 human femurs using single element, broadband transducers with center frequencies of 3.5, 5, 7.5, and 10 MHz. Power spectra of pulses reflected from the water-specimen interface were corrected for the frequency response of the measurement system to obtain the reflected power in decibels RdB( f). To suppress random phase cancellation effects, RdB( f) was averaged over multiple sites on multiple specimens. A frequency dependence of RdB( f) was observed in the 2.6–10 MHz range. The frequency dependence was moderate, with a maximum change of less than 6 dB over the entire frequency range. RdB( f) was greatest for low porosity specimens. The frequency averaged intensity reflection coefficient ranged from 7.4 × 10−4 to 7.8 × 10−3 for high and low porosity specimen groups, respectively.

Osteoporosis is a degenerative bone disease that affects millions of people worldwide. The goal of this study was to test a new ultrasonic technique developed for clinical bone assessment called the backscatter amplitude decay constant (BADC). Ultrasonic backscatter measurements were performed on 97 volunteers at the left and right femoral necks using an ultrasonic imaging system (Terason T3000) equipped with a 3.5 MHz convex array transducer. The backscatter signals were analyzed to determine the backscatter amplitude decay constant (BADC), a parameter that measures the exponential decay in the amplitude of the backscatter signal. For comparison, additional ultrasonic measurements were performed at the left and right heels using an ultrasonometer (GE Achilles EXPII) to measure the stiffness index of the calcaneus. BADC demonstrated weak but statistically significant correlations with stiffness index (R < 0.25, p < 0.05). With further refinement of the measurement technique, BADC may be a useful parameter for ultrasonic bone assessment.

Introduction: Ultrasonic backscatter techniques are being developed to detect changes in bone caused by osteoporosis. The goal of this study was to evaluate the clinical utility of backscatter difference measurements at the femoral neck. Methods: Backscatter signals were acquired from the left and right femoral necks of 97 human volunteers using an ultrasonic imaging system (Terason T3000). The signals were analyzed to measure the normalized mean of the backscatter difference (nMBD), a quantity that represents the power difference between two portions of the same backscatter signal. Also, a bone sonometer (GE Achilles EXPII) was used to measure the stiffness index (SI) of the left and right heel bones. Results: Linear regression analysis was used to compare nMBD measurement at the femoral neck to SI measurements at the heel. A statistically significant (R ≥ 0.2) correlation was observed between nMBD and SI. Conclusion: These results suggest that nMBD is sensitive to naturally occurring variations in bone tissue, and thus may be able to detect larger changes in bone caused by osteoporosis.

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.

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