Searching in axial and 3D CT visualisations

Traditional diagnostic modalities have been, for the most part, static two-dimensional images displayed on film or computer screen. More recent diagnostic modalities are solely computer-based and consist of large data-sets of multiple images. Image perception and visual search using these new modalities are complicated by the need to interact with the computer in order to navigate through the data. This paper reports the late-breaking results from two small studies into visual search within two types of CT Colonography (CTC) visualisations. The twelve novice observers in the study were taking part in a week-long course in CTC and were tested at the beginning and end of the course. A number of expert observers were also recorded. The two visualisations used in the study were 2D axial view and 3D colon fly-through. In both cases, searching was performed by inspecting the colon wall, but by two distinct mechanisms. The first study recorded observer eye-gaze and image navigation in a CTC axial view. The search strategy was to follow the lumen of the colon and detect abnormalities in the colon wall. The observer used the physical computer interface to navigate through the set of axial images to perform this task. The 3D fly-through study recorded observer eye-gaze whilst watching a recording of a computed flight through the colon lumen. Unlike the axial view there was no computer control, so inspection of the colon surface was dictated by the speed of flight through the colon.