High Intensity Piezoelectric Sources for Medical Applications: Technical Aspects
D.Cathignol (INSERM Unite 556, Lyon, France)
Therapeutic ultrasound has received increasing interest during the past few years. However, the development of this technique depends on the availability of high performance transducers adapted to power generation constraints allowing to focus and or steer the ultrasonic energy within the volume to be treated. Roughly, one may consider two different fields where the constraints are totally different. In the case of generating CW or long burst wave, problems to be solved are mainly thermal ones while generating very high pulsed pressure wave demands to solve electrical breakdown and mechanical problems. We will give some examples of transducers or generator allowing to generate intensity of about thirty to forty watts per cm2 during several ten of seconds. In the field of high pulsed pressure generation some new concepts either in the material or the electrical driving circuit allow to obtain pressures up to 8 MPa at the surface of the transducer. Finally, it is pointed out that piezo-composite material plays a more and more important role due to its exceptional properties as for example; high efficiency, large bandwidth, predictable beam pattern and high flexibility in term of shaping and definition of sampling in annular arrays, linear arrays or matrix arrays.
Section : 5