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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.

Datortomografiundersökning av tjocktarmen har blivit en vanlig undersökning som utförs på röntgenavdelningar. Inför denna undersökning krävs förberedelser i form av laxering och födorestriktioner. Information till patienter inför denna undersökning är av stor vikt för förberedelsernas resultat och därmed även för en optimal undersökning.                       Syftet med denna studie var att beskriva om patienterna upplever att de fått tillräcklig information om laxeringsförberedelserna inför en DT-undersökning av tjocktarmen. Ett annat syfte med studien var att studera om patienterna förstått den information de fått.                       Tio patienter med en ålder mellan 62-81 år intervjuades efter DT-kolografiundersökningen på en röntgenavdelning i mellansverige under en period på två veckor. Det insamlade materialet analyserades sedan genom kvalitativ innehållsanalys.                       De intervjuade patienterna upplevde att informationen om förberedelserna inför DT-kolografiundersökningen var tillräcklig. Patienterna kunde ordagrant återberätta den information som de erhållit men det fanns en bristande förståelse av informationen som behandlade definitionen klar dryck och tillvägagångssättet med vissa mediciner. De flesta patienterna förstod syftet med de tarmförberedelser som utförs innan undersökningen.                       Studien visade att det fanns oklarheter i den skriftliga informationen inför DT-kolografiundersökningar som patienterna inte förstod, trots att de bedömde att informationen var tillräcklig. Genom att ta i beaktanden de brister i informationen om de tarmförberedelser som studiens resultat visar finns det förutsättning att undersökningens förberedelser och genomförande utförs på bästa möjliga sätt. / Computed tomography (CT) scan of the colon has become a common investigation in radiology departments. Prior to this examination preparation in form of purgation and food restrictions are required. Information to patients facing this examination are of great importance for the results of preparations and thus for optimal investigation.                The aim of this studie was describe whether patients feel that they received sufficient information about the bowel preparations before a CT scan of the colon. Another purpose of the study was to see whether patients understood the information they receive before the examination.                              Ten patients with an age between 62-81 years were interviewed after the CT colography examination at the radiology department in a hospital in the middle of Sweden for a period of two weeks. The collected material was then analyzed by qualitative content analysis.                              The interviewed patients felt that information on preparations for the CT colonography examination was sufficient. Patients can literally retell the information received but there is a lack of understanding of the information that deals with the definition of clear liquids and the approach of certain medications. Most patients understood the purpose of the bowel preparations performance before the examination.                The study showed that there were unclarities in the written infomrmation given before the CT colonography examination that the patients did not understand, even though they considered that the information was sufficient. By taking into considerations the lack of information about bowel preparation that the studies results show there are subject to examination, preparation and implementation is carried out in the best manner.

About half of million deaths caused by colorectal cancer (CRC) has been reported worldwide every year. Programmes for early diagnosis of CRC has reduced mortality due to this disease, as the cancer is diagnosed in earlier stages which can be treated more successfully. Programme for early CRC diagnosis in Lithuania has been based on the faeces occult blood test (FOBT). If positive FOBT result is obtained, patients should be referred for colonoscopy (CS) examination. Based on the data from the National Health Fund, during the first three years CS examination was carried out for a little bit more than half of the patients participating in the programme and presenting with positive FOBT result. Aiming to improve accuracy of CRC diagnostics we have suggested alternative CS examination – computed tomography colonography (CTC). The aim of our study was to establish diagnostic value of CTC examination in the identification of neoplastic alterations in the patients with positive FOBT result and to specify factors having influence on the examination quality. CTC examinations were carried out and their results were compared with the findings of CS. We discovered that CTC is of high diagnostic value for detection of lesions sized ≥ 6 mm and of very high diagnostic value for detection of large ( ≥ 10 mm) polyps in a colon. We found out that the length of colon had no influence on how patients tolerated this examination and on patients well-being during CTC procedure, and colon cleaning... [to full text] / Pasaulyje kasmet nuo storosios žarnos vėžio (SŽV) miršta apie pusė milijono žmonių. SŽV ankstyvosios diagnostikos programos sumažina mirtingumą nuo šios ligos, nes vėžys tada yra aptinkamas anksčiau ir galima jį lengviau išgydyti. Lietuvoje SŽV ankstyvosios diagnostikos programa yra paremta slapto kraujo išmatose nustatymo testu (FOBT). Po teigiamo FOBT atsakymo pacientai yra nukreipiami kolonoskopijai (KS). Valstybinės ligonių kasos duomenimis per pirmuosius trejus metus iš pacientų, dalyvavusių programoje, kuriems nustatytas teigiamas FOBT, iš jų tik kiek daugiau nei pusei pacientų atlikta KS. Norint dažniau diagnozuoti SŽV, pasiūlėme alternatyvų KS tyrimą - kompiuterinės tomografijos kolonografiją (KTK). Taikydami KTK ir lygindami jos rezultatus su KS, norėjome išsiaiškinti KTK tyrimo diagnostinę vertę nustatant neoplastinius pakitimus pacientams su teigiamu FOBT bei nustatyti tyrimo kokybei darančius įtaką faktorius. Nustatėme, kad KTK pasižymi didele diagnostine verte nustatant ≥6 mm dydžio pakitimus bei labai didele diagnostine verte nustatant didelius (≥10 mm) polipus, storojoje žarnoje. Nustatėme, kad storosios žarnos ilgis neturi įtakos KTK tyrimo tolerancijai ir paciento savijautai KTK metu, o žarnos išsivalymo kokybė prieš KTK tyrimą nepriklauso nuo anatominių storosios žarnos savybių – tokių, kaip ilgis. Išsiaiškinome, kad KTK tyrimas yra jautrus nustatant storosios žarnos neoplastines adenomas ir vėžį, bet nesiekia KS tyrimo jautrumo, todėl KTK taikyti... [toliau žr. visą tekstą]