Volumetric Intracardiac Imaging Using a Fully Integrated CMUT Ring Array: Recent Developments

Atrial fibrillation, the most common type of cardiac arrhythmia, now affects more than 2.2 million adults in the US alone. Currently, electrophysiological interventions are performed under fluoroscopy guidance, a procedure that introduces harmful ionizing radiation without providing adequate soft-tissue resolution. Intracardiac echocardiography (ICE) provides real-time, high-resolution anatomical information, reduces fluoroscopy time, and enhances procedural success. We have previously developed a forward-looking, volumetric ICE catheter using a ring-shaped, 64-element capacitive micromachined ultrasonic transducer (CMUT) array with a 10MHz center frequency. The Ring array was flip-chip bonded to a flexible PCB along with 8 identical custom ASICs providing a total of 64 dedicated preamplifiers. The flex was then reshaped for integration with the catheter shaft. In the second-generation catheter, 72 micro-coaxial cables (reduced from 100) are terminated on a newly designed flex to provide the connection between the array electronics and the imaging system. The reduced number of cables enhances the catheter's steerability. Furthermore, the new flex allows grounding of the top CMUT electrode through proper level-shifting of the ASIC supplies without additional circuitry. This feature enables complete ground shielding of the catheter, which improves its noise susceptibility and is an important safety measure for its clinical use. Beyond real-time, forward-looking imaging capability, the Ring catheter provides a continuous central lumen, enabling convenient delivery of other devices such as HIFU transducers, RF ablation catheters, etc. Using a PC-based imaging platform from Verasonics and a commercial Vivid7 imaging system from GE, we have demonstrated the in vivo, volumetric, real-time imaging capability of the finalized Ring catheter in a pig heart.