The in vitro measurement of ultrasound in cancellous bone

This paper describes our recent findings on the relationships between ultrasonic measurements (velocity and broadband ultrasonic attenuation) and some physical properties of human and bovine cancellous bone (density, trabecular orientation and Young's modulus of elasticity). We have found velocity to be an extremely effective measure of Young's modulus (R2 approximately 95%). When velocity is combined with a measure of apparent density R2 improves to approximately 97%. We demonstrate that this is due to the ability of ultrasound velocity to measure structural anisotropy in the tissue. The findings for broadband ultrasonic attenuation (BUA) are more complex. In the same specimens BUA is not as good as velocity at predicting Young's modulus (R2 approximately 62%). We demonstrate that this is due to a non-linear relationship between BUA and tissue density (porosity). However there is a strong indication that BUA is also affected by variation in cancellous structure.