THE INFLUENCE OF POROSITY AND PORE-SIZE ON THE ULTRASONIC PROPERTIES OF BONE INVESTIGATED USING A PHANTOM MATERIAL

Ultrasonic propagation in bone has been investigated using the Leeds U ltrasonic Bone Phantom Material. Phantoms were produced with different porosities in the range of 45-83% and pore sizes of 1.3 and 0.6 mm. T he phase velocity at 600 kHz was found to follow a second-order polyno mial as a function of porosity. Phase velocity values between 1545 and 2211 m s(-1) were measured and found to be largely independent of por e size for a given porosity. The slope of the phase velocity as a func tion of frequency (dispersion) decreases with increasing porosity. The values obtained from samples having different pore sizes were also si miliar. The attenuation coefficient and normalized broadband ultrasoni c attenuation (nBUA) reached a maximum at about 50%. The normalized at tenuation ranged from 6 to 25 dB cm(-1) over the porosity range availa ble and consistently showed higher values for the larger pore size. Si milarly, the nBUA values were found to be between 14 and 53 dB MHz(-1) cm(-1), with the values for the larger pore size being roughly 10 dB MHz(-1) cm(-1) greater than those for the smaller pore size. These fin dings demonstrate that the Leeds phantom can be used to investigate th e effect of structural changes in bone and to aid the understanding of quantitative ultrasound. The results support the assumption that the velocity in trabecular bone is not dependent on pore size but is influ enced by the mechanical properties of the bone's constituents and the overall framework, whereas the attenuation and BUA are also influenced by structure.