First In Vivo Use of a Capacitive Micromachined Ultrasound Transducer Array–Based Imaging and Ablation Catheter

Abstract

Objectives The primary objective was to test in vivo for the first time the general operation of a new multifunctional intracardiac echocardiography (ICE) catheter constructed with a microlinear capacitive micromachined ultrasound transducer (ML-CMUT) imaging array. Secondarily, we examined the compatibility of this catheter with electroanatomic mapping (EAM) guidance and also as a radiofrequency ablation (RFA) catheter. Preliminary thermal strain imaging (TSI)-derived temperature data were obtained from within the endocardium simultaneously during RFA to show the feasibility of direct ablation guidance procedures. Methods The new 9F forward-looking ICE catheter was constructed with 3 complementary technologies: a CMUT imaging array with a custom electronic array buffer, catheter surface electrodes for EAM guidance, and a special ablation tip, that permits simultaneous TSI and RFA. In vivo imaging studies of 5 anesthetized porcine models with 5 CMUT catheters were performed. Results The ML-CMUT ICE catheter provided high-resolution real-time wideband 2-dimensional (2D) images at greater than 8 MHz and is capable of both RFA and EAM guidance. Although the 24-element array aperture dimension is only 1.5 mm, the imaging depth of penetration is greater than 30 mm. The specially designed ultrasound-compatible metalized plastic tip allowed simultaneous imaging during ablation and direct acquisition of TSI data for tissue ablation temperatures. Postprocessing analysis showed a first-order correlation between TSI and temperature, permitting early development temperature-time relationships at specific myocardial ablation sites. Conclusions Multifunctional forward-looking ML-CMUT ICE catheters, with simultaneous intracardiac guidance, ultrasound imaging, and RFA, may offer a new means to improve interventional ablation procedures.

Image-guided ultrasound phased arrays are a disruptive technology for non-invasive therapy

“…The main advantages of ultrasound devices compared to RF or laser-based devices are that thermal coagulation is more predictable, and it can be induced at greater depths using acoustic energy [287]. Small catheter-mounted, high-frequency CMUT phased arrays have been developed for this purpose and have shown to be capable of inducing thermal ablation [288]. Phased arrays may offer a less invasive approach via the trans-esophageal route routinely used for cardiac imaging.…”

New Endoscopic Imaging Technology Based on MEMS Sensors and Actuators

“…As a novel MEMS based US transducer in the research field, CMUT performs the energy transduction due to the tiny capacitance changes. In principle, while a small cavity is formed in a substrate, a thin-film layer suspended on the top of the cavity serves as a membrane on which a metalized layer acts as a conductive electrode, integrated with the lower substrate that serves as a bottom electrode [ 24 , 25 , 26 , 27 , 28 ]. Silicon wafer based micromachining techniques are usually used for CMUT development.…”

Single-chip CMUT-on-CMOS front-end system for real-time volumetric IVUS and ICE imaging

“…More recent piezo based ring arrays may have similar issues [7]. Capacitive micromachined ultrasonic transducer (CMUT) technology has potential to overcome most of these limitations as it offers flexibility to fabricate arrays of different shapes and sizes [4, 5, 8–10]. In addition, it enables monolithic or flip-chip-bonding-based electronics integration [11–14].…”

“…Single-ring 64-element annular CMUT arrays operating at 15.5 MHz, 19 MHz and 13.5 MHz have been demonstrated for FL-IVUS [4, 5, 15]. A 64–element 10 MHz single-ring CMUT array was integrated in a multi-chip, flip-chip-bonded package for FL-ICE [10, 16]. More recently, a single ring array was connected to a commercial ultrasound system to demonstrate and compare its imaging capabilities in different modes including full phased array and synthetic aperture processing with spatially coded excitation for high frame rate imaging with improved SNR, respectively [17].…”