Photoelastic Stress Analysis Error Quantification in Vasculature Models for Robot Feedback Control

Abstract

Real-time and accurate stress calculation in walls of vasculature is a desired goal in order to provide feedback control for catheter insertion robots without changing catheter stiffness and lumen. This feedback source also has applications in endovascular surgery simulation. In order to address this need, we consider photoelastic effect, as birefringence produced by light retardation relates to the stress inside photoelastic materials. In this research, a polariscope was designed for urethane elastomer vasculature models, the photoelastic coefficient of urethane elastomer was measured, and a camera system was calibrated to quantify and reduce error in the measurement system. An average error of 3.9% was found in stress measurements for the pressure range of 60-189 mmHg inside the urethane elastomer model. This result was applied to correct stress distribution images, using the average stress value as a reference and preserving local maxima and minima of stress. This enabled us to accurately calculate stress in vasculature models during human blood pressure simulation (HBPS), and enables the comparison, in a closed loop, of stress produced by HBPS and by catheter motion when driven by a robot, as well as to measure the stress produced by medical tools on the vascular model wall.