Relationships of Ultrasonic Backscatter With Bone Densities and Microstructure in Bovine Cancellous Bone

This study was designed to investigate the associations among ultrasonic backscatter, bone densities, and microstructure in bovine cancellous bone. Ultrasonic backscatter measurements were performed on 33 bovine cancellous bone specimens with a 2.25-MHz transducer. Ultrasonic apparent backscatter parameters (“apparent” means not compensating for ultrasonic attenuation and diffraction) were calculated with optimal signals of interest. The results showed that ultrasonic backscatter was significantly related to bone densities and microstructure (<inline-formula> <tex-math notation="LaTeX">$R^{2} = 0.17$ </tex-math></inline-formula>–0.88 and <inline-formula> <tex-math notation="LaTeX">$p < 0.05$ </tex-math></inline-formula>). After adjusting the correlations by bone mineral density (BMD), the bone apparent density (BAD) and some trabecular structural features still contributed significantly to the adjusted correlations, with moderate additional variance explained (<inline-formula> <tex-math notation="LaTeX">$\Delta R^{2} = 9.7$ </tex-math></inline-formula>% at best). Multiple linear regressions revealed that both BAD and trabecular structure contributed significantly and independently to the prediction of ultrasound backscatter (adjusted <inline-formula> <tex-math notation="LaTeX">$R^{2} = 0.75$ </tex-math></inline-formula>–0.89 and <inline-formula> <tex-math notation="LaTeX">$p < 0.05$ </tex-math></inline-formula>), explaining an additional 14% of the variance at most, compared with that of BMD measurements alone. The results proved that ultrasonic backscatter was primarily determined by BAD, not BMD, but the combination of bone structure and densities could achieve encouragingly better performances (89% of the variance explained at best) in predicting backscatter properties. This study demonstrated that ultrasonic apparent backscatter might provide additional density and structural features unrelated to current BMD measurement. Therefore, we suggest that ultrasonic backscatter measurement could play a more important role in cancellous bone evaluation.