Application of Vibro-Acoustography to bone elasticity imaging

The aim of the study is the use of the Vibro-Acoustography technique for bone imaging. This method consists in applying a highly-localized low frequency vibration inside the object and observing with an hydrophone the low frequency pressure field radiating by this vibration. The results obtained with this imaging method show that this technique is, in a precise set-up configuration (in terms of central frequency, difference frequency and exposure time), adapted to bone imaging, with transverse resolutions lower than 300mum. Two bones which are very sensitive to decalcification have been tested: the calcaneus bone and the femoral neck. Correlation has then been made between our in vitro bone images and images providing from other techniques proportional to different characteristics of the medium. These techniques are Bone Ultrasound Attenuation (BUA) and Computed Tomography (CT). The amplitudes of vibro-acoustic signals. radiating from phosphocalcic ceramics (bone substitute of calcium hydroxyapatite) with different porosities have been evaluated to test our imaging system. The good agreement between these results and the description of our images let us suggest that bone decalcification could be detected thanks to vibro-acoustic bone images.