10C-6 Fully Integrated CMUT-Based Forward-Looking Intracardiac Imaging for Electrophysiology

Abstract

Minimally invasive percutaneous electrophysiological mapping of the heart chambers is becoming a standard procedure to diagnose and treat cardiac arrhythmias. Due to advances in technology that enable small feature sizes and a high level of integration, non-fluoroscopic intracardiac imaging is attracting more attention to better guide electrophysiologal (EP) interventions. In this effort, we are developing a forward-looking intracardiac ultrasound imaging catheter, which is also equipped with several EP electrode sensor bands and a metal RF ablation tip enclosure. A 24-element fine-pitch (63 mum) 1-D array, based on capacitive micromachined ultrasonic transducer (CMUT) technology, has been fabricated for high-frame-rate imaging. Through-wafer vias are incorporated in the device to connect the signal and ground electrodes to the flip-chip bond pads on the backside of the array. The total footprint of the array measures 1.73 mm x 1.27 mm. Also a custom-designed integrated circuit (IC) has been fabricated to be closely integrated with the CMUT array for improved SNR. This IC comprises some of the important front- end electronics of an ultrasound imaging system. It measures 2 mm x 2 mm and is composed of 24 individual transmit/receive blocks. The transmit circuitry is capable of delivering 25 -V unipolar pulses. The receive circuitry includes a transimpedance preamplifier followed by a line driver buffer. A CMUT array was flip-chip bonded directly on to the IC for initial testing. All of the 24 elements of the array and the IC are functional. Array uniformity was tested by measuring the resonant frequency in air. A standard deviation of 0.37 percent was measured around the mean value of 17.9 MHz. The same array operates at 9.2 MHz in immersion with a 104 percent fractional bandwidth. Imaging performance of the described front-end was tested on a commercial phantom and also in ex- vivo environment on an isolated perfused rabbit heart (Langendorfl). The final goal is to integrate the CMUT array and the front-end electronics at the tip of a 10 -F catheter. A flexible printed circuit board (PCB) has been designed and the first sub-assembly is ready for cable attachment and final catheter integration.