Efficiency in colonoscopy

Global trends, including demographic changes, are significantly increasing the demand and cost of healthcare. Endoscopy services are no exception and, even before the Covid-19 pandemic, significant pressure resulted in many units failing to meet cancer wait targets. The need to improve efficiency has never been greater and particularly so for colonoscopy which significantly reduces morbidity and mortality from colorectal cancer. Today, advances in colonoscope technologies and emergence of artificial intelligence offer the potential for improved colonoscopy practice. The aim of this thesis is to explore how efficiency in colonoscopy can be enhanced throughout the patient pathway. Five major studies were performed evaluating bowel preparation (CLEANSE), polyp detection (AI-DETECT), optical diagnosis (DISCARD3), insertion technique (WAVE) and post-colonoscopy colorectal cancer (AI-DETECT). CLEANSE is an evaluation of a novel low-volume same-day bowel preparation regime (Plenvu) and showed this offers a more efficient bowel cleansing option than standard regimens. AI-DETECT is a randomised study evaluating a computer-aided detection (CADe) system (GI Genius) and showed a borderline significant improvement in polyp detection is achieved amongst high performing endoscopists. DISCARD3 is a major evaluation of optical diagnosis with a “resect and discard” strategy exploring the learning curve, quality assurance process, causes of error and economic impact. This study shows such a strategy is feasible and safe and could potentially be implemented with a quality assurance process in place within the English Bowel Cancer Screening Progamme (BCSP). WAVE is a randomised study evaluating colonoscopy insertion technique. This showed a ‘hybrid’ insertion technique is more efficient than a water-exchange colonoscopy technique. REFLECT is a retrospective evaluation of post-colonoscopy colorectal cancer cases identified at national level and showed after local root cause analysis a significant proportion were in fact detected cancers. These studies provide valuable insights that we hope will ultimately lead to more efficient colonoscopy whilst maintaining quality and enhancing patient care.Open Acces

Remote access computed tomography colonography

This thesis presents a novel framework for remote access Computed Tomography Colonography (CTC). The proposed framework consists of several integrated components: medical image data delivery, 2D image processing, 3D visualisation, and feedback provision. Medical image data sets are notoriously large and preserving the integrity of the patient data is essential. This makes real-time delivery and visualisation a key challenge. The main contribution of this work is the development of an efficient, lossless compression scheme to minimise the size of the data to be transmitted, thereby alleviating transmission time delays. The scheme utilises prior knowledge of anatomical information to divide the data into specific regions. An optimised compression method for each anatomical region is then applied. An evaluation of this compression technique shows that the proposed ‘divide and conquer’ approach significantly improves upon the level of compression achieved using more traditional global compression schemes. Another contribution of this work resides in the development of an improved volume rendering technique that provides real-time 3D visualisations of regions within CTC data sets. Unlike previous hardware acceleration methods which rely on dedicated devices, this approach employs a series of software acceleration techniques based on the characteristic properties of CTC data. A quantitative and qualitative evaluation indicates that the proposed method achieves real-time performance on a low-cost PC platform without sacrificing any image quality. Fast data delivery and real-time volume rendering represent the key features that are required for remote access CTC. These features are ultimately combined with other relevant CTC functionality to create a comprehensive, high-performance CTC framework, which makes remote access CTC feasible, even in the case of standard Web clients with low-speed data connections

Eye-tracking the moving medical image: Development and investigation of a novel investigational tool for CT Colonography

Colorectal cancer remains the third most common cancer in the UK but the second leading cause of cancer death with >16,000 dying per year. Many advances have been made in recent years in all areas of investigation for colorectal cancer, one of the more notable being the widespread introduction of CT Colonography (CTC). CTC has rapidly established itself as a cornerstone of diagnosis for colonic neoplasia and much work has been done to standardise and assure quality in practice in both the acquisition and interpretation of the technique. A novel feature of CTC is the presentation of imaging in both traditional 2D and the ‘virtual’ 3D endoluminal formats. This thesis looks at expanding our understanding of and improving our performance in utilizing the endoluminal 3D view. We present and develop novel metrics applicable to eye-tracking the moving image, so that the complex dynamic nature of 3D endoluminal fly-through interpretation can be captured. These metrics are then applied to assess the effect of important elements of image interpretation, namely, reader experience, the effect of the use Computer Aided Detection (CAD) and the influence of the expected prevalence of abnormality. We review our findings with reference to the literature of eye tracking within medical imaging. In the co-registration section we apply our validated computer-assisted registration algorithm to the matching of 3D endoluminal colonic locations between temporally separate datasets, assessing its accuracy as an aid to colonic polyp surveillance with CTC

A roadmap for the clinical implementation of optical-imaging biomarkers

Clinical workflows for the non-invasive detection and characterization of disease states could benefit from optical-imaging biomarkers. In this Perspective, we discuss opportunities and challenges towards the clinical implementation of optical-imaging biomarkers for the early detection of cancer by analysing two case studies: the assessment of skin lesions in primary care, and the surveillance of patients with Barrett’s oesophagus in specialist care. We stress the importance of technical and biological validations and clinical-utility assessments, and the need to address implementation bottlenecks. In addition, we define a translational roadmap for the widespread clinical implementation of optical imaging-technologies

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

Visualisation of curved tubular structures in medical databases: An application to virtual colonoscopy

Medical conditions affecting the colon are problematic to diagnose due to the difficulty in examining this particular internal organ. To date, the most widely used approach is to perform a colonoscopy; a procedure in which a small camera is inserted into the colon to examine its surface. This procedure is unpleasant and potentially dangerous for the patient, and is expensive and time consuming for the hospital. As a result, patients at risk of developing the conditions are not always screened as often as would be desirable. Over the last few years a new approach known as virtual colonoscopy has been gaining popularity. The method uses information from a CT scan to reconstruct a 3D model of the colon which can then be examined without the patient needing to undergo a colonoscopy. This approach is now commonly used when screening for polyps (an indication of colon cancer) but can not be so easily used on conditions such as Inflammatory Bowel Disease (IBD) where information beyond the shape of the surface is required. This thesis forms part of a larger project which aims to diagnose conditions such as IBD by using image processing algorithms on CT data and presenting the results to the user in an easy to interpret way. Specifically we are concerned with this visualisation stage of the system and so have developed a new visualisation approach which we call Volumetric CPR. This can be used to supplement the more traditional virtual flythrough visualisation and is applicable to IBD detection as well as screening for polyps. Our technique builds on the concept of Curved Planar Reformation (CPR), which has proved to be a practical and widely used tool for the visualisation of curved tubular structures within the human body. It has been useful in medical procedures involving the examination of blood vessels and the spine. However, it is more difficult to use it for structures such as the colon because abnormalities are smaller relative to the size of the structure and may not have such distinct density and shape characteristics. Our new approach improves on this situation by using volume rendering for hollow regions of the structure and standard CPR, for the surrounding tissue. This effectively combines grey scale contextual information with detailed colour information from the area of interest. The approach is successfully used with each of the standard CPR types and the resulting images are promising as an alternative for virtual colonoscopy. We also demonstrate how systems can effectively utilize this new visualisation in order to convey maximum information to the user. We show how overlays can be used to present surface coverage data and how sophisticated lighting models can improve the users understanding of the 3D structure. We also present details of how to integrate our visualisation into existing systems and work flows

Developing and evaluating expertise in colonoscopy

The quality and safety of colonoscopy have become of paramount importance with the worldwide expansion in the utilisation of this procedure, especially with the introduction of colorectal cancer screening in many countries. It is well known that colonoscopic performance varies significantly between practitioners. This thesis explores the effects of assessment in colonoscopy and polypectomy on performance and practice as well as trying to define the factors which differentiate the very best practitioners from the clinically competent. Until 2011, there was no formalised way of certifying polypectomy competence. We looked at the effects of the introduction of mandatory polypectomy assessment on trainee endoscopists applying for certification of competency in the United Kingdom. This work showed that documentation of polypectomy competence significantly improved after these changes were introduced. A global survey of polypectomy practice was undertaken to evaluate international guidance on polypectomy skills training and how trainers deliver teaching on polypectomy around the world, as well as trainees’ experience of gaining polypectomy skills. Significant variability in endoscopists’ experience of polypectomy training was found with few formal national guidelines published. This led to an evaluation of expert endoscopists who underwent an accreditation process with some similarities before commencing Bowel Cancer Screening (BCS). We examined whether it was possible to predict future performance from a single assessment and found that criteria used to assess whether candidates were competent could not predict the best performers from those who passed. Several hundred expert BCS colonoscopists were then monitored over a three year period to determine changes in performance over time and whether long-term performance could be predicted. The best predictors of performance over time for all metrics were initial performance. In order to identify key features of expertise in endoscopy, experienced colonoscopists were interviewed to distinguish characteristics of true endoscopic experts. These interviews revealed the importance of both technical and non-technical skills in defining expertise.Open Acces

Appearance Modelling and Reconstruction for Navigation in Minimally Invasive Surgery

Minimally invasive surgery is playing an increasingly important role for patient care. Whilst its direct patient benefit in terms of reduced trauma, improved recovery and shortened hospitalisation has been well established, there is a sustained need for improved training of the existing procedures and the development of new smart instruments to tackle the issue of visualisation, ergonomic control, haptic and tactile feedback. For endoscopic intervention, the small field of view in the presence of a complex anatomy can easily introduce disorientation to the operator as the tortuous access pathway is not always easy to predict and control with standard endoscopes. Effective training through simulation devices, based on either virtual reality or mixed-reality simulators, can help to improve the spatial awareness, consistency and safety of these procedures. This thesis examines the use of endoscopic videos for both simulation and navigation purposes. More specifically, it addresses the challenging problem of how to build high-fidelity subject-specific simulation environments for improved training and skills assessment. Issues related to mesh parameterisation and texture blending are investigated. With the maturity of computer vision in terms of both 3D shape reconstruction and localisation and mapping, vision-based techniques have enjoyed significant interest in recent years for surgical navigation. The thesis also tackles the problem of how to use vision-based techniques for providing a detailed 3D map and dynamically expanded field of view to improve spatial awareness and avoid operator disorientation. The key advantage of this approach is that it does not require additional hardware, and thus introduces minimal interference to the existing surgical workflow. The derived 3D map can be effectively integrated with pre-operative data, allowing both global and local 3D navigation by taking into account tissue structural and appearance changes. Both simulation and laboratory-based experiments are conducted throughout this research to assess the practical value of the method proposed