Development of an ultrasonic probe with measurement of contact pressure distribution

We have developed an ultrasonic probe with a film-type pressure sensor installed on its contact surface. The film-type pressure sensor, which uses aluminum nitride (AIN) as a piezoelectric material, is thin, flexible, durable and heat-resistant. The AIN is deposited on a polyimide film in high orientation using the sputtering method. The sensor can measure contact pressure directly, with little effect on ultrasonic transmission. We have demonstrated the simultaneous acquisition of tissue images and contact pressure distribution for the human carotid artery. Internal tissue was successfully visualized and the pulsating arterial wall was observed. At the same time, a pulse wave of blood pressure is observed with characteristic waveshapes. The results indicate the possibility of estimating the viscoelasticity of biological tissue.