High-frequency CMUT arrays for high-resolution medical imaging

Applications of ultrasonic imaging in fields such as dermatology, ophthalmology, and cardiovascular medicine require very high resolution. Limitations in existing transducer technologies inhibit the development of highfrequency arrays, which would allow the use of dynamic focusing and enable higher frame rates. As an alternative, capacitive micromachined ultrasonic transducer (CMUT) technology, using integrated circuit fabrication techniques, can provide arrays with the small dimensions required for high-frequency operation. We have designed and fabricated several linear and ring arrays of CMUTs to operate in the 10 to 50 MHz range. These new arrays are made with the wafer bonding process. The ring arrays in particular demonstrate the feasibility of thinning the transducer to aid packaging in intravascular applications. This study shows that CMUTs can be made for high-frequency operation. Both transducers for use in conventional and collapse-mode operation have been designed and characterized. The results demonstrate that CMUT is an appropriate technology for building high-frequency arrays. A linear array of high-voltage pulser and amplifier circuits has also been designed for use with an array of CMUTs to enable real-time imaging applications. Pulse-echo results from the sixteen-channel array have been demonstrated.