ABSTRACT
In medicine, ionising radiation plays an important role in imaging internal anatomy as well as in therapeutic applications. This is because of the attenuation properties of tissues and the capacity of ionising radiation to produce damage in biological structures, respectively. This chapter describes different types of radiation used clinically and the ways in which their interaction with tissues is understood, and introduces elements of radiation dosimetry. Dependence of photoelectric effect absorption on atomic number of the medium is the major reason for the clear contrast between bones and other tissues in diagnostic radiographs since the calcium and phosphates in the bones result in a higher effective atomic number, than muscle and fat which are mainly water. Compton effect is an example of incoherent scattering where a photon interacts with an electron, is scattered and loses energy which is transferred to the electron in the form of kinetic energy.
