1. X-ray Production and Machines
X-rays, first discovered by Rontgen in 1895, are produced when high energy electrons are decelerated. 100KeV electrons lose their kinetic energy in the form of X-ray photons, with a characteristic spread of wavelengths appearing to look a bit like a whale (with a bit of imagination).
2. X-ray Absorption and Attenuation
X-rays are used in medical imaging because they are absorbed by the various tissues in the body. This is called attenuation and the coefficient that determines how much energy is absorbed is related to the proton number of the atoms within the body.
3. X-ray interactions (Photoelectric, Compton and Pair Production)
There are a number of ways that X-rays interact with matter. Low energy X-rays and the kind that are used for most medical imaging are absorbed through the photoelectric effect. Higher energy X-rays undergo Compton scattering while really high energy X-rays can create matter.
4. X-ray image intensifiers
Most X-rays pass straight through the camera film that can be used to detect them. To limit exposure of the patient to excess radiation, image intensifiers are used to turn this signal into visible light. This can then be used to view inside the body.