CT scanning. Head of a patient seen through the central hole of a computed tomography (CT) scanner that will be scanning his head. The patient's head is being held still to improve the quality of the scan. Markers (red lights) are used to ensure correct alignment. The patient will pass through the CT scanner's central hole. CT scanning sends small doses of X-rays through the body at different angles, and a computer produces a cross- sectional image of the area scanned. CT scans are widely used to locate tumours, as they are good at distinguishing soft tissue from bone. Photographed at the American Hospital of Paris, France.