Flexible piezo film intravascular ultrasound arrays on guidewires and catheters

Coronary heart disease and peripheral artery disease are the leading causes of atherosclerotic morbidity along with stroke. More than a million percutaneous coronary and peripheral interventions such as balloon angioplasty and stent deployment are performed in the US alone every year. A thin guidewire and catheter are used in all of

these procedures while current IVUS imaging probes are infrequently used because of size and complexity. Our aim is to integrate intravascular ultrasound capability to regular guidewires and catheters so that interventionalists can use this technique as a routine in-situ imaging and measurement tool before, during and

after interventions without prolonging the procedure time by providing easy to interpret simple metrics such as lumen size, calcification arc and length, for procedure planning and evaluation. The proposed application aims to explore and demonstrate the critical steps to build such systems. It uses a novel flexible thin film piezoelectric

material (PiezoPaint) to form conformal linear and interlaced arrays of transducers operating in the 10-30MHz range on flexible cylindrical structures. It exploits recent advances in application specific integrated circuits (ASICs) by the Degertekin group for front end electronics that would fit on guidewires and catheters.

Furthermore, an optical encoding scheme is proposed to accurately determine axial distances during pullback or insertion to implement a simplified method to generate 3D maps of arteries as opposed to additional pullback hardware or complex angiography and software-based registration. Specifically, we will modify the current

process we use to coat and pattern PiezoPaint on optical fibers to form arrays on guidewires and catheters with electrical interconnect. Arrays will be fabricated on sections of guidewires and catheter samples with polyimide substrates including patterned electrodes and wiring. Different array geometries will be evaluated through

simulations and experiments in terms of SNR, measurement resolution and imaging performance to guide fabrication. To couple the optical encoder to the hemostatis valve and to the guidewire/catheter, a mechanical design will be developed and implemented. The arrays and ASICs will be electrically connected and the axial

distance encoding system and front end electronics will be synchronized to complete the setup. For experimental evaluation, 3D phantoms will be designed with guidance from interventional cardiologist collaborators from Emory University and experiments will be performed assess performance on lumen sizing, echo amplitude

mapping and imaging before moving to experiments on ex-vivo samples. The potential impact of this project is manifold. Just the demonstration of “ultrasound active” guidewire with simple metrology capability can lead to applications in coronary and neurovascular interventions. Integration of ultrasound measurement capability on

guidewires and balloon catheters along with simplified position tracking and data interpretation can make this much more widely used modality in percutaneous coronary and peripheral interventions.