Computed Axial Tomography, also known as a CT scan, uses computers to generate a three-dimensional image from flat, two-dimensional x-ray pictures. The patient lies on a table and is centered into the CT machine. The CT machine is open on both ends and looks like a large mechanical donut. The CT machine scans the body in sections and then puts all the scans together to show a three-dimensional area of the body. Physicians use CT scans to see into the human body and to diagnose disease, internal problems or trauma. Learn more about CT scans.