The basic physics of X-ray generation has not changed.
X-rays are photons (a type of electromagnetic radiation) and are generated from a complex X-ray tube, which is a type of cathode ray tube (See Figure). The X-rays are then collimated (i.e., directed through lead-lined shutters to stop them from fanning out) to the appropriate area, as determined by the radiographic technician. As the X-rays pass through the body they are attenuated (reduced in energy) by the tissues. Those X-rays that pass through the tissues interact with the photographic film.
In the body:
- air attenuates X-rays a little;
- fat attenuates X-rays more than air but less than water; and
- bone attenuates X-rays the most.
