MODEL RELEASED. CT scanning. Patient undergoing a CT scan. Computed tomography (CT) is a diagnostic technique that sends small doses of X-rays through the body at different angles to produce cross-sectional images of the area scanned. The red laser lines are used to align the patient. A computer compiles the X-ray data into multiple image slices. CT scans are widely used to locate tumours, as they are good at distinguishing soft tissue from bone.