Miniature high frequency focused ultrasonic transducers for minimally invasive imaging procedures

Spherically focused, high frequency (30–50 MHz) ultrasonic imaging transducers are fabricated using poly(vinylidene) difluoride (PVDF) film and a membrane deflection technique that is compatible with CMOS microelectronics fabrication. Micromachined ultrasonic transducers with 0.75–2.00 mm-diameter apertures and f-numbers of 1.30–2.45 are fabricated and characterized. The transducers exhibit focused radiation patterns with 50 μm axial resolution and 51–92 μm lateral resolution and bandwidths of 80–110% around center frequency values. A miniature preamplifier hybrid circuit, which is designed to be mounted within the transducer housing, is fabricated and characterized to reveal a low noise level of 5.3 nV/ H z . Tissue imaging capabilities of the micromachined ultrasonic transducers are demonstrated through successful imaging of human cadaveric aorta.