A 1-D CMUT transducer with front-end ASIC in a 9 French catheter for Intracardiac Echocardiography: Acoustic and Imaging evaluation

In this work, we report the acoustical characterization of a 9 French (Fr) CMUT-based 1D catheter tip (2.5×12.8 mm2 - 64 elements - 7.5 MHz) embedding a 64 channels analog transceiver ASIC (180 nm HV BCD technology) dedicated to Intra-cardiac Echocardiography. To this end, a Through-Silicon-Via process has been integrated in the CMUT process flow to ensure suitable vertical integration level needed to accommodate with the catheter's form factor. Good overall functioning of essential ASIC functionalities with the CMUT, i.e. transmit, beamforming, and receive, is first reported, starting from elementary characterization up to imaging. Additionally, a comparison with a custom discrete solution based on Commercial Off-The-Shelf components (COTS) to provide suitable CMUT preamplification in receive is performed. Using the same CMUT chip either with the ASIC, either with the COTS, allowed to quantify the benefit brought by the ASIC compared to a more straightforward but less integrated solution. Main results highlight that CMUT-on-ASIC allows to recover a much wider bandwidth (BW), increasing by 3 MHz the -6dB upper limit, and therefore getting closer the theoretical BW of the CMUT itself. Moreover, lower element crosstalk is measured on CMUT-on-ASIC device, showing that the ASIC decreases the electrical coupling compared to the COTS. Finally, noise equivalent pressure measurements in comparison with simulations in realistic ICE configuration promise much higher receive sensitivity with the ASIC solution, hence, confirming its great interest for the CMUT technology compared to less integrated solution, especially for catheter application.