Design and fabrication of an integrated convex ultrasound endoscope for digestive tract imaging

Endoscopic ultrasound (EUS) goes one step further by combining high-frequency ultrasound with endoscopy. We have developed an 8 MHz, 64-element curvilinear array transducer integrated with a 5-million-pixel CMOS camera module for EUS application. A novel voice coil motor (VCM) for lens focus adjustments was used. This device can not only change the focus position of the lens but can also adjust the tilting angle of the lens to extend the depth of field (DOF). With this new technology, we have improved the image quality of the endoscope. For the ultrasonic transducer part, the measured center frequency and -6 dB fractional bandwidth are 7.9 MHz and 83.5%, respectively. A two-way insertion loss of -42 dB was obtained at the average central frequency. A cross-talk of less than -36 dB was achieved for the adjacent columns at the center frequency. The results show a desirable ultrasonic imaging performance.