Conception of a biomedical transducer for characterization of the cortical bone

The ultrasound devices for assessing the human tibia are based on detecting the first arriving signal, corresponding to a wave propagating at, or close to, the bulk longitudinal velocity in bone. However, human long bones are effectively irregular hollow tubes and should theoretically support the propagation of more complex guided modes similar to Lamb waves in plates. Guided waves are attractive because they propagate throughout the bone thickness and can potentially yield more information on bone material properties and architecture. The principle of the method is to generate such waves into the cortical layer of long bones. Lamb's waves generation and detection is performed with special low-frequency tapered transducers designed for this purpose. An ultrasonic transducers (transmitter and receiver) vibrating at 100 kHz was set up to measure the wave velocity in the cortical bone.