Registration of prone and supine CT colonography images and its clinical application

Computed tomographic (CT) colonography is a technique for detecting bowel cancer and potentially precancerous polyps. CT imaging is performed on the cleansed and insufflated bowel in order to produce a virtual endoluminal representation similar to optical colonoscopy. Because fluids and stool can mimic pathology, images are acquired with the patient in both prone and supine positions. Radiologists then match endoluminal locations visually between the two acquisitions in order to determine whether pathology is real or not. This process is hindered by the fact that the colon can undergo considerable deformation between acquisitions. Robust and accurate automated registration between prone and supine data acquisitions is therefore pivotal for medical interpretation, but a challenging problem. The method proposed in this thesis reduces the complexity of the registration task of aligning the prone and supine CT colonography acquisitions. This is done by utilising cylindrical representations of the colonic surface which reflect the colon's specific anatomy. Automated alignment in the cylindrical domain is achieved by non-rigid image registration using surface curvatures, applicable even when cases exhibit local luminal collapses. It is furthermore shown that landmark matches for initialisation improve the registration's accuracy and robustness. Additional performance improvements are achieved by symmetric and inverse-consistent registration and iteratively deforming the surface in order to compensate for differences in distension and bowel preparation. Manually identified reference points in human data and fiducial markers in a porcine phantom are used to validate the registration accuracy. The potential clinical impact of the method has been evaluated using data that reflects clinical practise. Furthermore, correspondence between follow-up CT colonography acquisitions is established in order to facilitate the clinical need to investigate polyp growth over time. Accurate registration has the potential to both improve the diagnostic process and decrease the radiologist's interpretation time. Furthermore, its result could be integrated into algorithms for improved computer-aided detection of colonic polyps

New Techniques in Gastrointestinal Endoscopy

As result of progress, endoscopy has became more complex, using more sophisticated devices and has claimed a special form. In this moment, the gastroenterologist performing endoscopy has to be an expert in macroscopic view of the lesions in the gut, with good skills for using standard endoscopes, with good experience in ultrasound (for performing endoscopic ultrasound), with pathology experience for confocal examination. It is compulsory to get experience and to have patience and attention for the follow-up of thousands of images transmitted during capsule endoscopy or to have knowledge in physics necessary for autofluorescence imaging endoscopy. Therefore, the idea of an endoscopist has changed. Examinations mentioned need a special formation, a superior level of instruction, accessible to those who have already gained enough experience in basic diagnostic endoscopy. This is the reason for what these new issues of endoscopy are presented in this book of New techniques in Gastrointestinal Endoscopy

Optimization and acceptance of enteric MRI in inflammatory bowel disease

Inflammatory bowel disease is a chronic inflammatory condition of bowel. CT and barium fluoroscopy are main stay of radiological investigation but impart high radiation dose. MRI is a safe and less invasive technique to assess bowel. The thesis examines the use of magnetic resonance Imaging in enteric inflammatory bowel disease. A discussion on inflammatory bowel disease and overview of MRI techniques, diagnostic features and review of literature is described. A national survey about the uptake of MRI for the investigation of IBD showed that 38% of radiology departments offered enteric MRI and barium studies remaining the main imaging investigation performed. A proforma administered to clinicians in OPD showed significant increase in their diagnostic confidence for small bowel disease after MRE, which had positive impact on therapeutic strategy of 61% of patients. The results of a prospective studies investigating MR colonography as a biomarker of disease activity are then presented. Quantitative measurements of contrast enhancement in normal colon have shown intersegmental differences. Three proposed qualitative MRI scores of disease activity correlated with endoscopic disease activity, but correlation with histopathological scores was less apparent. The use of unprepared colonic MRI in assessment of acute colitis is then investigated. A qualitative total colonic inflammation score (TCIS) proposed and validated against clinical standards including stool frequency and CRP. It also has prognostic ability for length of hospital stay. Region of interest derived quantitative measurements from the colon wall including T2 signal and contrast enhancement are then compared to a validated clinical score of colitis activity. Quantitative markers seemed less robust then qualitative scores, although quantified contrast enhancement is correlated with disease severity. Patient experiences of MR Colonography and colonoscopy are investigated by using face-to-face qualitative interviews, together with a quantitative questionnaire. Patient preference is highly complex but patients expressed overall preference for MRC

Diseases of the Abdomen and Pelvis 2018-2021: Diagnostic Imaging - IDKD Book

Gastrointestinal disease; PET/CT; Radiology; X-ray; IDKD; Davo

Enhanced computer assisted detection of polyps in CT colonography

This thesis presents a novel technique for automatically detecting colorectal polyps in computed tomography colonography (CTC). The objective of the documented computer assisted diagnosis (CAD) technique is to deal with the issue of false positive detections without adversely affecting polyp detection sensitivity. The thesis begins with an overview of CTC and a review of the associated research areas, with particular attention given to CAD-CTC. This review identifies excessive false positive detections as a common problem associated with current CAD-CTC techniques. Addressing this problem constitutes the major contribution of this thesis. The documented CAD-CTC technique is trained with, and evaluated using, a series of clinical CTC data sets These data sets contain polyps with a range of different sizes and morphologies. The results presented m this thesis indicate the validity of the developed CAD-CTC technique and demonstrate its effectiveness m accurately detecting colorectal polyps while significantly reducing the number of false positive detections