The word « scanner » designates the apparatus used to carry out the examination.
It is made up of a mobile table on which the patient lies and an x-ray tube which moves around the patient.
Detectors measure the intensity of the rays emitted by the tube.
Opposite these, receptors, made up of digital detectors, register received intensities, after the rays have passed through the patient's body.
This device is linked to a computer which analyzes the digital data. The intensity difference between the incident rays and those emerging from the patient's body, calculated for different angles, enables us to produce an image in grayscale (a more complex form of "black and white".)
Even though the rays penetrate the patient's body perpendicular to that body's main axis, the images obtained are horizontal sections.