  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.
