A 120-MHZ ULTRASOUND PROBE FOR TISSUE IMAGING

Ultrasound transducers with center frequency above 100 MHz are expecte d to be used for future diagnostic tissue characterization because of their high lateral resolution. We have fabricated a 120-MHz transducer that consists of a ZnO piezoelectric film on a sapphire substrate tha t has a concave acoustic lens. The lateral resolution was calculated a s 13 mu m. The insertion loss of the transducer, defined as the differ ence between the received voltage and. the transmitted one, was -45 dB . The 6-dB bandwidth of the received signal was approximately 40 MHz. The transducer was mounted in a rod-shaped probe to ensure contact wit h in vivo tissue, because of the low penetration of ultrasound in the high frequency region. While the probe is rotated and moved along its axis mechanically, the transducer receives backscattered ultrasound fr om the surrounding tissue on a cylindrical plane that is kept a consta nt distance from the probe surface. The feasibility of this high-frequ ency tissue imaging probe has been demonstrated by obtaining prelimina ry images of an in vitro bovine kidney. (C) 1996 Academic Press.