Ultrasonic bone assessment: ability of apparent backscatter techniques to detect changes in the microstructure of human cancellous bone.

Ultrasonic backscatter techniques may offer a useful approach for detecting changes in bone caused by osteoporosis. The goal of the present study was to investigate how bone mineral density (BMD) and the microstructure of human cancellous bone affect three ultrasonic backscatter parameters that have been identified as potentially useful for ultrasonic bone assessment purposes: apparent integrated backscatter (AIB), frequency slope of apparent backscatter (FSAB), and frequency intercept of apparent backscatter (FIAB). Ultrasonic measurements were performed with a 3.5 MHz broadband transducer on 54 specimens of human cancellous bone prepared from the proximal femur. Microstructural parameters and BMD were measured using x-ray micro-computed tomography (micro-CT). Relationships between AIB, FSAB, FIAB and the micro-CT parameters were investigated using univariate and multivariate statistical analysis techniques. Moderate to strong univariate correlations were observed between the backscatter parameters and microstructure and BMD in many cases. Partial correlation analysis indicated that the backscatter parameters depended on microstructure independently of BMD in some cases. Multiple stepwise linear regression analysis used to generate multivariate models found that microstructure was a significant predictor of the backscatter parameters in most cases.