Refracto-Vibrometry Visualization of Ultrasonic Wave Fronts Interacting with Bone Mimicking Phantoms and Heel Bones

Ultrasonic measurements of the heel bone (calcaneus) are used commonly for osteoporosis screening. Pulses emitted by an ultrasound transducer are incident on the calcaneus, and the transmitted wave fronts are detected with a separate transducer. In the current study, full field videos were obtained using refracto-vibrometry of ultrasonic pulses interacting with bone mimicking phantoms, and human calcaneus samples. Pulses were emitted by a 500 kHz Panametrics V303 transducer. The measurement beam from a Polytec PSV-400 scanning laser Doppler vibrometer laser was directed through a water tank towards a stationary retroreflective surface. Acoustic wave fronts (density variations) which pass through the measurement laser cause variations in the integrated optical path length. The time-varying signals detected by the vibrometer at numerous scan points were used to determine the time evolution of ultrasonic wave fronts. The resulting videos enable visualization of the propagating wave fronts and the backscattered and transmitted wave fronts. These videos enable direct investigation of wave front distortion due to reflection, refraction and diffraction effects.