Wire guided endoscopy with a finite element analysis of planar electrodes
As an alternative to conventional colonoscopy, which is time-consuming, requires considerable operator skill, and is often painful and hazardous to the patient, this thesis proposes a new method of examining the colon. It involves using a guide wire, which helps the endoscopist advance the colonoscope with a reduced risk of loop formation. It does this by ensuring that it follows a path along the lumen of the colon and by acting as an anchor against which a motor attached to the tip of the colonoscope pulls the colonoscope forward. Clinical measurements show that use of a conventional colonoscope exceeds the human pain threshold 17% of the time, whilst use of the guide wire assisted colonoscope exceeds the human pain threshold only 4% of the time. It is concluded that guide wire assisted colonoscopy is likely to reduce pain and make the procedure easier for both the patient and the endoscopist. In addition to the guide wire assisted colonoscope, the thesis proposes and assesses the 'planar electrode', an instrument designed to treat colorectal cancer in a more precise and controlled manner than conventional, endoscopic, electrosurgical methods. The planar electrode is assessed using tissue studies and a finite element model. When optimally configured, the planar electrode is shown to coagulate only the tissue between the electrode pair, thereby allowing the endoscopist to oversee the coagulation process as it happens. The finite element model is shown to predict the depth of tissue coagulation within 15% of the depth of coagulation measured in the tissue studies. It is concluded that the planar electrode coagulates tissue in a predictable and controlled manner, and the finite element model is likely to be a useful tool when designing planar electrode configurations for specific tasks.