State-of-the-art three-dimensional endo-luminal virtual colonoscopy (VC) or CT colonography (CTC) is a minimally invasive medical procedure that examines the entire colon in order to detect polyps and colorectal cancer. Most colon cancers malignantly transform from polyps, which are extra growths on the surface of the mucous membrane. Three dimensional endoscopic colon lumen interior images offered by CTC allow physicians to examine the colon interactively. Thus, CTC has several advantages over conventional optical colonoscopy including reduced risk. One of the challenging problems that prevent practical use in clinical situations is the complexity of the human colon. The colon's deformation by peristalsis and the diverse shapes of polyps make it difficult to distinguish polyps from other non-threatening entities in the colon. Hence, most CTC protocols acquire both prone and supine images to improve the visualization of the lumen wall, reduce false positives, and improve sensitivity. Comparisons between the prone and supine images can be facilitated by computerized registration between the scans. In this dissertation, two algorithms for registering colons segmented from prone and supine images are presented. First is an algorithm for three dimensional registration of the prone and supine colon when both are well distended and there is a single connected lumen. Second is another registration algorithm between colons with topological differences caused by inadequate bowel preparation or peristalsis. Such topological changes make deformable registrations of the colons difficult, and at present there are no registration algorithms which can accommodate them. The first algorithm uses feature matching of the colon centerline and a modified version of the demons deformable registration algorithm to define a deformation field between the prone and supine lumen surface. The second method utilizes embedded map representation of colon volume. The two proposed colon registration methods will contribute to improving the accuracy of the computerized registration process and increasing the versatility of the clinical use of CT colonoscopy. / Ph. D.

BackgroundIn this study, we describe a Quality Improvement (QI) intervention in three radiology departments within the Swedish health care system, with a special focus on access and methodology. AimThe goals for the QI-intervention were to implement best practice for patients with suspected colon cancer, and reduce the Turn Around Time (TAT).The aim of the study was to identify relevant factors for successful QI in order to further develop the organisation to create a system of continuous QI (CQI) for the radiological service. MethodsInitially, a multiprofessional QI-team was formed. To identify waste and areas for improvement, process mapping and lead time analysis were conducted during a collaborative learning approach. A focus group interview was carried out with the participants in the QI-intervention and the local managers, and a qualitative content analysis of the focus group transcript was performed. ResultsBest practise was gradually introduced, and overall access was improved, but TAT was not changed. Four key factors for CQI were revealed; Communication, Engagement, Context, and Patient- and Customer focus. Moreover, the impact of providing useful and reliable measurements to the frontline staff was found to be high DiscussionThe lack of decreased TAT indicates that further redesign of the radiology process is needed. As the impact of measurements was considered high, an improved system for obtaining and providing useful information to all parts in the organization is essential. Moreover, the infrastructure for CQI needs to be developed further, e.g. by clarifying roles, educating in improvement knowledge, and developing multiprofessional meetings. Finally, motivating and engaging staff is crucial to improve healthcare. It is important with a deeper understanding what triggers this, patient centeredness could be one.