An X-ray scanner comprises an array 12 of X-ray detectors 16 arranged in cylindrical configuration around an imaging volume 28, and a multi-focus X-ray source 20 which extends in a helical configuration around the outside of the detector array 12. A helical gap 24 in the detector array 12 allows X-rays from the source 20 to pass through the patient 26 in the imaging volume 28, and onto the detectors 16 on the opposite side of the scanner. The source 20 is controlled so that the X-rays are produced from a number of source points along the helical locus 23 to produce a tomographic image. As the patient is stationary and the source point varied electrically, the scanning rate is sufficient to produce a series of images which can be displayed as a real time three-dimensional video image.
