X-ray apparatus having a composite field of view

Medical radiography requires specialist control of radiography equipment to achieve good imaging results. Typical errors that can occur consist of an inappropriate field of view being accidentally applied. This results in a "cropping effect" in which portions of the region of interest of a patient which would be of clinical use are omitted from the image. Conventionally, the only solution is to re-take the entire image with a more appropriate (and inevitably larger) field of view selected. This is undesirable, because it might require recall of the patient from another location, and the patient will be subject to two exposures, thus undesirably increasing their X-ray dosage. The present application proposes to use an anatomical atlas to analyse an X-ray image output from an initial exposure, in particular to assess whether significant anatomical elements are missing from the image. If elements are missing, the field of view of the X-ray imager is recalibrated, using collimation or pan/tilt adjustments, for example. A subsequent X-ray image is obtained, and combined with the initial image, to provide an output image. Because only a small area of the region of interest may subsequently need to be exposed, a smaller additional dose results.