Lumen Shape Reconstruction using a Soft Robotic Balloon Catheter and Electrical Impedance Tomography

TL;DR

This paper presents a novel method combining electrical impedance tomography and a soft robotic balloon catheter to accurately assess lumen shape and size during minimally invasive procedures, including detection of elliptical and occluded lumens.

Contribution

It extends previous impedance-based sizing methods by incorporating multiple electrodes and EIT imaging to detect complex lumen deformations and shapes.

Findings

Numerical simulations identified optimal electrode configurations.

Experimental results confirmed lumen occlusion localization.

EIT images visualized lumen dilation during angioplasty.

Abstract

Incorrectly sized balloon catheters can lead to increased post-surgical complications, yet even with preoperative imaging, correct selection remains a challenge. With limited feedback during surgery, it is difficult to verify correct deployment. We propose the use of integrated impedance measurements and Electrical Impedance Tomography (EIT) imaging to assess the deformation of the balloon and determine the size and shape of the surrounding lumen. Previous work using single impedance measurements, or pressure data and analytical models, whilst demonstrating high sizing accuracy, have assumed a circular cross section. Here we extend these methods by adding a multitude of electrodes to detect elliptical and occluded lumen and obtain EIT images to localise deformations. Using a 14 Fr (5.3 mm) catheter as an example, numerical simulations were performed to find the optimal electrode configuration of two rings of 8 electrodes spaced 10 mm apart. The simulations predicted that the maximum detectable aspect ratio decreased from 0.9 for a 14mm balloon to 0.5 at 30mm. The sizing and ellipticity detection results were verified experimentally. A prototype robotic balloon catheter was constructed to automatically inflate a compliant balloon while simultaneously recording EIT and pressure data. Data were collected in experiments replicating stenotic vessels with an elliptical and asymmetrical profile, and the widening of a lumen during angioplasty. After calibration, the system was able to correctly localise the occlusion and detect aspect ratios of 0.75. EIT images further localised the occlusion and visualised the dilation of the lumen during balloon inflation.