Forward-viewing, robotically-steerable guidewire system for peripheral chronic total occlusions: Transducer and imaging system development

Although minimally-invasive approaches such as stenting, atherectomy, and angioplasty represent more desirable alternatives to many open surgical procedures for restoring blood flow to ischemic tissues, tortuous vasculature and chronic total occlusions may lead to iatrogenic injury and failure of endovascular procedures, largely due to the problem of navigating complex environments using only side-viewing images from fluoroscopy. A forward-viewing steerable guidewire is proposed that could allow visualization of possible paths and controlled steering through complex lesions. To this end, a custom 0.035” guidewire-compatible transducer was designed and fabricated with a center frequency of 17 MHz and 37% fractional bandwidth. By acquiring pulse-echo imaging data while the guidewire tip is moved mechanically using the steerable guidewire, images can be formed using a synthetic aperture approach with a single element transducer mounted on the end of the robotically-steerable guidewire. In imaging experiments with 20 μm wire targets at a depth of 6 mm, lateral resolution was 0.25 mm. Additionally, proof of concept visualization of vessel morphology and a patent lumen was demonstrated in an ex vivo porcine artery. The integrated system could allow navigation of chronic occlusions in peripheral arteries that are currently impassable.