The  technique of Tomodensitometry  (TDM) is often referred to as a “scanner” because of confusion between the process itself and  the apparatus employed in that process. This imaging technique depends of the use of x-rays. It is particularly useful for observing the brain.
The x-ray beam is emitted by an x-ray tube and is then transformed by a detector into an electrical message that is sent to a computer.
The system emitter/detector is moved around the patient and computer analysis of received signals, from different angles, enables the creation of images in section