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.

The ultrasonic properties of brain have been explored to a limited extent, however the spatial variation of these properties is not well characterized. The goal of this study was to measure the speed of sound and the frequency slope of attenuation in brain tissue at multiple locations to generate parametric images that characterize their spatial distribution. Tissue specimens were 1-cm thick slices of preserved sheep brain prepared from the coronal, sagittal and transverse anatomic planes. Ultrasonic measurements were performed using broadband transducers with center frequencies of 3.5, 5.0, 7.5, and 10 MHz. The transducers were mechanically scanned to acquire signals from all locations on each slice. Structures visible in the parametric images were consistent with the known morphologic features of the brain. White matter and gray matter appeared to be distinguishable in most images. Measured values for the spatial mean and standard deviation of the frequency slope of attenuation ranged between 0.723–1.06 and 0.194–0.501 dBcm−1MHz−1, respectively, depending on the tissue slice and transducer frequency. Measured values for the spatial mean and standard deviation of the speed of sound ranged between 1520–560 and 6–15 ms−1, respectively. Spatial variation of these properties were clearly visualized in the parametric images.

Ultrasound backscatter properties of aggregate brain tissue are available in the literature, however, reporting on the spatial variation of backscatter over tissue volumes is limited. The spatial variation of the apparent integrated backscatter (AIB) and the logarithmic backscatter amplitude decay constant (BADCL) was characterized for 1-cm thick samples from the coronal, sagittal and transverse anatomic planes of fixed sheep brain. Submerged samples were exposed to ultrasound using broadband transducers with center frequencies of 3.5, 5.0, 7.5, and 10 MHz by scanning over the samples in half-beamwidth step sizes to measure the backscattered signal. Parametric images of the AIB and BADCL showed a clear correlation between morphological features in the tissue samples and the images with the AIB giving the better representation of the overall tissue structure. Over all samples and frequencies, the range of the spatial mean of the AIB was −77.7 to −59.8 dB with the standard deviation ranging from 3.14 to 6.99 dB. The spatial mean of the BADCL ranged from 0.0350 to 0.152 μs−1 with standard deviations ranging from 0.0820 to 0.111 μs−1. For both parameters, morphological features of the tissue become more distinctive with increasing frequency.

The global impact of osteoporosis as a major public health problem has generated interest in developing ultrasonic techniques that can be used to screen populations for this bone disease. The goal of this study was to assess the relative performance of three ultrasonic backscatter parameters: apparent integrated backscatter (AIB), frequency slope of apparent backscatter (FSAB) and frequency intercept of apparent backscatter (FIAB). Measurements were performed at the left and right femoral necks of 88 healthy volunteers using an ultrasonic imaging system equipped with a 3 MHz convex multi-element transducer. Backscatter signals from the femoral neck were captured for analysis. AIB was determined from the frequency averaged power in the backscatter signal compensated for the frequency dependent response of the measurement system. FSAB and FIAB were determined from the slope and intercept, respectively, of a line fitted to the compensated spectrum. Linear regression analysis was used to compare measurements performed at the left and right femur. All three parameters demonstrated similar and highly significant (p < 0.000001) correlations between left and right side measurements (RAIB = 0.62, RFSAB = 0.56, RFIAB = 0.51) indicating that they are equally sensitive to naturally occurring variations in the ultrasonic properties of the femoral neck.

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.