A novel forward-looking ultrasound catheter for treating vascular occlusions

TL;DR

This paper introduces a new forward-looking ultrasound catheter designed to treat large vessel occlusions by enabling precise cavitation and drug delivery, with promising experimental results demonstrating its potential clinical utility.

Contribution

The study presents a novel catheter design with a radially polarized transducer for forward-looking ultrasound therapy, combining simulation, fabrication, and proof-of-concept experiments.

Findings

Achieved forward-looking ultrasound pressures of 2.5 MPa at 0.5 mm

Demonstrated microbubble ejection and inertial cavitation in vessel phantoms

Validated the catheter's potential for treating vascular occlusions

Abstract

Thrombotic and chronic occlusions of large blood vessels are a major cause of mortality and morbidity, and so there is a need for improved treatments in many clinical circumstances. Endovascular ultrasound approaches have been shown to hold considerable potential to treat large vessel thrombotic occlusions. Here, we report the development of a novel forward-looking therapeutic ultrasound catheter approach. The design concept centers on the use of a radially polarized hollow cylindrical transducer situated at the distal tip. This approach enables a compact configuration where the central lumen can accommodate a guidewire during navigation as well as provide a route to release cavitation seeds and therapeutic agents adjacent to the site of occlusion. PZT-5H transducers with outer/inner diameters of 1.35/0.73 mm were evaluated using simulations and experiments for their capacity to project forward-looking ultrasound. A length of 2.5 mm operating in the 3rd harmonic of the length mode resonance (1.85 MHz) was selected. Catheters (1.55 mm outer diameter) were designed and fabricated with a liner, outer jacket, and braiding, where the transducers were incorporated with air-backing and a front-face matching layer. Forward-looking pressures of 2.5 MPa (peak negative) at 0.5 mm were achieved. Proof of principle vessel phantom experiments were performed demonstrating the ability to eject microbubbles in proximity to an occlusion and stimulate inertial cavitation. This approach holds potential for treating thrombotic and chronic total occlusions.