PIEZOELECTRIC POLYMER COMPOSITE ARRAYS FOR ULTRASONIC MEDICAL IMAGINGAPPLICATIONS

The predominant sensor materials used in medical acoustic imaging have traditionally been piezoelectric ceramics (PZT, LaNbO3, etc.) More re cently piezoelectric polymers (PVDF) have been used in this area. Poly mers present several advantages over ceramics (very flexible, easy to process, good acoustic matching to tissue, good reception constant), b ut also have some major drawbacks (poor emission constant, low couplin g coefficient). Composite piezoelectric materials aim to incorporate t he most advantageous properties of ceramics and polymers. This paper i nvestigates the electrical and mechanical properties of two different piezoelectric polymer composite materials (Piezoflex1 and Piezel) to a ssess their performance for medical imaging applications. Practical tr ansducer constructions with corona-poled, PCB-backed and diced-array a rchitectures have been manufactured with the composites, and their per formance evaluated in pulse-echo mode. The results obtained, using a s imple object as target, confirm the potential use of the composite mat erials in medical imaging applications.