Ultrasound Transducers for Therapeutic and Surgical Instruments

Modern intravascular lithotripsy is based on piezoelectric ultrasound transducers / catheters: They are used to treat the cause of arterial fibrillation with the help of targeted lesions, to prepare the area of treatment for a catheter-supported aortic valve implantation (TAVI, TAVR) with ultrasonic waves, or to contactlessly destroy intravascular or aortic plaque. These instruments have to be ultracompact while working reliably and highly efficiently. Smallest piezo components make this combination possible – they drive the tools reliably and enable gentle but effective treatments.

To defer a transcatheter aortic valve implantation (TAVI) procedure, our customer AorticLab created a transcatheter debridement solution for ultrasonic histotripsy. It is designed to gently fragment calcifications on an aortic valve to restore its functionality. Within the device, piezoelectric transducers (ultrasonic transducers) generate ultrasound at two different frequencies, creating a strong cavitation effect to break down calcifications both in the tissue and on the valve.

The video explains why new and disruptive medical applications are best driven by ultrasonic transducers. Piezoelectric transducers generate HIFU, high-intensity focused ultrasound, enabling contactless treatment and incisionless surgery,  for example treating tumors or neurodegenerative diseases.

More information on Carrying Out Contactless Therapies with Piezo-Based Catheter Instruments

Outside of ultrasonics, piezo transducers, actuators and piezoelectric motors also find may applications in medical engineering. 

Langevin Transducers
PI also provides custom power ultrasound Langevin Transducers for cell lysis, phacoemulsification, ultrasonic scalpels, tissue aspiration, tartar removal, ultrasonic mixing, cleaning, atomization, welding, drilling and cutting

Ultrasonic Transducers in Sensing Applications
Ultrasonic transducers also work well as sensors in medical applications such as patient monitoring, flow measurement and air bubble detection used in infusion systems, pharmaceutic devices or spirometry.  Piezoelectric transducer sensors are compact, low energy and very robust and reliable.

What is a Transducer?
A transducer is an electro-mechanical device that converts one form of energy or a physical quantity—such as pressure, sound, motion, temperature, or light—into another usable form, typically an electrical signal or mechanical action.  One very prominent class of transducer is based on piezo-technology. These piezo transducers are capable of high frequency energy conversion up to the MHz range.    

How do piezoelectric ultrasound transducers work?
Piezoelectrics are ideal for generating and detecting ultrasonic waves. Charge carriers in piezoelectric materials are moved by electric fields, leading macroscopic dimensional changes of the material (inverse piezoelectric effect). When an AC current is applied to the piezoelectric transducer, its shape starts to follow the AC signal and moves the particles in the medium, for example air or liquids, leading to pressure fluctuations. 
Rarefaction of the particles reduces pressure, and compression leads to higher pressure. The wavelength of the generated sound is equivalent to the distance between two rarefaction or compression areas.
The resulting sound waves propagate in the surrounding medium. The speed of the sound varies according to the density and the elastic properties of the medium.