CT scanning. Patient undergoing a CT (computed tomography) scan, seen from the scanner control room. CT scanning is a diagnostic technique in which X-rays are passed through the body at different angles. A computer then produces a cross-sectional image or images of the body tissues (lower frame, on screen), which are used by a radiographer for diagnosing a medical condition. Also known as CAT (computed axial tomography) scanning, this technique provides clearer and more detailed information about body tissues than X-rays used by themselves. It also reduces the amount of dangerous radiation to which the patient is exposed.