CT Colonography: Defining Performance and Interventions to Improve Interpretation

CT colonography is now widely regarded as the optimal radiological technique for colonic examination. However, performance characteristics, particularly relating to interpretation accuracy, interpretation times and polyp measurement have been derived primarily from academic centres in the USA. For successful implementation of CT colonography, such performance characteristics must be generalisable to non-academic centres, different patient populations in different geographical locations, and different clinical environments. This thesis aims to investigate current UK implementation and to determine the interpretative performance of observers across the UK and Europe, focussing on those interventions influencing reader accuracy and polyp measurement. The first chapter reviews the technique, diagnostic performance and clinical role of CT colonography. It is followed by two surveys revealing CT colonography is widely available across the UK NHS, and that hitherto unsuspected complications do occur, although CT colonography appears relatively safe in routine clinical practice when compared to alternatives. The effect of directed training on reader performance is investigated in a multi-centre European study and shows that experienced radiologists are significantly more accurate and time-efficient when reporting CT colonography compared to specifically trained but less experienced radiologists and radiographers. A subsequent study also shows they are more accurate than radiologists offering CT colonography in UK clinical practice routinely. Trained radiographers can perform as well as their radiologist counterparts. The accuracy of polyp measurement is investigated and the effect of different visualisation displays determined. Results suggest that an optimised 2D display utilising a 'colon CT window' should be recommended. Finally, we show that an automatic measurement software tool improves inter and intra-observer agreement for polyp measurement 'in vitro' although the benefit for in-vivo measurement is less clear.