Development of a Novel Flexible Pressure Sensor for Colonoscopes and a Multi-Modal Colonoscopy Training Environment
Abstract
Colorectal cancer is one of the leading cancers causing death worldwide, leading to an increasing number of colonoscopies performed each year. Performing a successful colonoscopy is technically challenging and requires substantial training. Some important factors that result in incomplete colonoscopies include lack of sufficient experience on the part of the endoscopist; pain and discomfort felt by patients due to excessive forces; and procedural complications such as looping of colon and colon perforation (rare but most feared). The existing training methods primarily focus on adequate visualization of the lumen of the colon without providing any feedback on the pressure applied by the colonoscope on the colon walls. Also, these methods require an expert to be present for direct observation of the trainee's performance.
This thesis describes the design and validation of a novel pressure-sensing sleeve for sensorizing the full length of a commercial colonoscope for use in a physical simulator. The sleeve utilizes flexible printed-circuit boards (flex PCBs) and the piezoresistive behavior of carbon-filled polymers to reliably measure the applied pressures up to a safe limit of 34 kPa with an accuracy and repeatability of ±4.8\% and ±2.7\%, respectively. The thesis also describes a custom training environment that utilizes the pressure data and position information from electro-magnetic tracking sensors to generate an informative color-mapped 3D pressure profile of the colonoscope. This serves as a training tool to acquire skills for safely and efficiently navigating through the colon. Objective metrics based on pressure, time, colonic displacements, and navigation are proposed to evaluate an endoscopist's performance. Results are provided from experiments performed by experts, trainees, and novices to validate the design of the training environment and the efficacy of specific evaluation metrics such as those based on pressure and colonic displacement, overall completion time, Colonoscope Advancement Score, etc.