Closed-loop Control of Steerable Balloon Endoscopes for Robot-assisted Transcatheter Intracardiac Procedures

TL;DR

This work introduces a steerable balloon cardioscope that enables direct cardioscopic visualization and tool delivery inside the beating heart while remaining compatible with vascular delivery. By tuning balloon-wall thickness, the device decouples the deployed optical window diameter $D_2$ from the steering angle $α$, controlled by a single inflation input, and validates this with image-based closed-loop control. The authors show independent control of $D_2$ and $α$, develop a calibration-based image feedback loop achieving near-ideal steering (|$α(t)$−$α_c$| ≤ 2°) during tool manipulation, and demonstrate high-quality imaging including 0.14 mm feature resolution and visualization of calcified leaflet tissue. This platform promises improved navigation, reduced radiation exposure, and straightforward integration with robotic catheter systems across various intracardiac applications.

Abstract

To move away from open-heart surgery towards safer transcatheter procedures, there is a growing need for improved imaging techniques and robotic solutions to enable simple, accurate tool navigation. Common imaging modalities, such as fluoroscopy and ultrasound, have limitations that can be overcome using cardioscopy, i.e., direct optical visualization inside the beating heart. We present a cardioscope designed as a steerable balloon. As a balloon, it can be collapsed to pass through the vasculature and subsequently inflated inside the heart for visualization and tool delivery through an integrated working channel. Through careful design of balloon wall thickness, a single input, balloon inflation pressure, is used to independently control two outputs, balloon diameter (corresponding to field of view diameter) and balloon bending angle (enabling precise working channel positioning). This balloon technology can be tuned to produce cardioscopes designed for a range of intracardiac tasks. To illustrate this approach, a balloon design is presented for the specific task of aortic leaflet laceration. Image-based closed-loop control of bending angle is also demonstrated as a means of enabling stable orientation control during tool insertion and removal.

Figures (11)

• Figure 1: Steerable robotic balloon cardioscope. (a) Balloon cardioscope with camera and LED in balloon interior and separate working channel terminating in the face of the optical window. For this image, in order to see the transparent working channel, an orange tube was placed within it. (b) Target pattern. (c) Target pattern viewed through cardioscope with working channel centered over target. (d) Example clinical application of aortic leaflet laceration. Laceration is initiated by extending an electrosurgical wire through the leaflet. Balloon steerability is used to ensure that the wire is oriented into the ventricle to avoid perforating the heart wall.
• Figure 2: Balloon design and parameter definitions. (a) Cross section schematic showing design parameters. (b) Cardioscope schematic showing camera, working channel, and proximal tubing inserted through a steerable sheath. (c) Trumpet-shaped cardioscope workspace achieved via combined steering and rotation about its axis. (d) Section view highlighting steering adjuster clip angle for camera alignment with optical face.
• Figure 3: Cardioscope fabrication. (a) Balloon casting. (b) Ballon demolding. (c) Post-processing and bonding of tubing connections. (d) Assembly of complete cardioscope. (e) Insertion through a steerable sheath.
• Figure 4: Steering angle control. (a) Computer-controlled infusion pump. (b) Controller block diagram. (c) Image processing pipeline for estimating steering angle.
• Figure 5: Experimental platform. Cardioscope is suspended in saline tank with external camera used to record balloon size and steering angle.