Development of hydraulic propulsion for colonoscopic devices
Colorectal cancer is the third most common type of cancer and is responsible for around 700 thousand deaths each year globally. Colonoscopy is the gold standard technique for diagnosing colorectal cancer and can greatly reduce incidence and mortality rates when used as part of a screening programme. While widely used and effective, colonoscopy has several drawbacks including patient discomfort, high operator skill requirement and cost. A range of alternative approaches to colonoscopy has been proposed, but none has yet overcome all these drawbacks. Hydro-colonoscopy is a development where colonoscopy is carried out with a warm liquid-filled colon, reducing patient discomfort. This thesis aims to explore whether an alternative colonoscope design can safely utilise liquid within the colon for its propulsion, and whether this approach has potential to address the drawbacks of colonoscopy. The thesis includes a review of the background to colonoscopy, its problems, and the devices that have been developed to overcome them. It examines the requirements for self-propelled colonoscopes, and the initial development of two novel approaches to the propulsion of devices for hydro-colonoscopy: hydraulic propulsion and hydro-jet propulsion. A hydraulic colonoscope is described, which utilises intraluminal water pressure to propel it through the colon. This approach was assessed in experiments using ex vivo porcine colons arranged to model human anatomy. The results suggest that a hydraulic colonoscope can successfully be propelled though a colon, including tight flexures, using anatomically tolerable levels of intraluminal pressure. Compared to a conventional colonoscope, the hydraulic colonoscope reduced loading on the mesenteries, indicative of probable reduction of patient discomfort. An automatic controller was also developed that was capable of controlling insertion of the hydraulic colonoscope. Colonoscope propulsion using thrust from hydro-jets was also explored. The safety of hydro-jets in the colon was assessed, principally with experimental evaluation tissue trauma due to hydro-jet impingement. The design and optimisation of a hydro-jet colonoscope were modelled, with a focus on thrust and manoeuvrability. Multiple hydro-jet prototypes were developed and used to assess a range of design options, including manoeuvring using on-board microvalves. A hydro-jet colonoscope system was constructed and tested in a synthetic human colon model. Results indicated that the hydro-jet colonoscope could navigate through various colonic layouts quickly and safely, suggesting that further development of this approach towards clinical translation will be worthwhile.
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