This is the focus of a Collaborative Award in Science and Engineering (CASE) studentship funded by the Economic and Social Research Council and the University Hospitals of Morecambe Bay NHS Trust. Our PhD student, Irene Swarbrick, is being co-supervised by Professor Andrew Smith and Dr Maggie Mort of the Institute for Health Research at Lancaster University. Using an ethnographic approach drawing on theories of the sociology of science and technology, observational data are being collected in Accident and Emergency, Radiology and within the Clinical Governance team. The work is illuminating how practitioners learn to make sense of medical images and how they make sense of incidents that affect patient safety. We expect that the findings will help shape the training of junior doctors and other professionals.