Doctor of Philosophy
Electrical and Computer Engineering
Patel, Rajni V.
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.
Summary for Lay Audience
Colon cancer is one of the leading causes of death due to cancer worldwide. Colonoscopy is a commonly used procedure for screening and diagnosing colon cancers, leading to more colonoscopies being performed annually. Thus, there is an increasing demand for clinicians (endoscopists) with sufficient expertise who can perform colonoscopies well. Learning colonoscopy is technically challenging and requires substantial training to acquire the skills necessary for performing a successful procedure. The insufficient experience of an endoscopist can result in incomplete colonoscopies due to twisting of the colon or application of excessive force, which can cause pain and discomfort to patients. In extreme but rare cases, the colon could experience serious injuries such as tearing, which might require extensive surgery to repair. The present teaching methods predominantly focus on visualizing the inner walls of the colon without monitoring the pressure applied by the colonoscope on the colon.
This thesis introduces a novel flexible pressure-sensing sleeve that senses pressure along the full length of a colonoscope. The sleeve uses a special flexible carbon-filled polymer whose conductivity changes with applied pressure. The sensor has a high accuracy and is capable of measuring pressures reliably up to a safe limit. The thesis also describes the development of a training setup using a physical simulator. This uses information from the pressure sensor and electromagnetic position trackers to create a 3D shape of the colonoscope which displays the applied pressure at each location by appropriate changes in color. This setup helps a trainee to acquire the necessary skills in a safe environment. Evaluation measures based on applied pressure, time to completion, movement of the colon, and efficient navigation of the colonoscope have been developed to assess the skills of the trainees in comparison with those of experts. Experts and trainees were asked to use this system to collect data on the efficiency of the training environment and the usefulness of the measures. All participants were positive about the benefits of the system. It was noted that the expert endoscopists, on average, applied significantly less pressure, completed the procedure faster, moved the colon less, and navigated more efficiently.
Vajpeyi, Anirudh, "Development of a Novel Flexible Pressure Sensor for Colonoscopes and a Multi-Modal Colonoscopy Training Environment" (2023). Electronic Thesis and Dissertation Repository. 9825.
Available for download on Wednesday, January 01, 2025