Pediatric emergency medicine trisk 1972 1972

Radiation is a very general term used to describe energy emitted from a source (
Fig. 90.10 ). Ionizing radiation, for example x-ray radiation, deposits a large
amount of energy in a small volume of tissue, and energy is sufficient to strip
electrons from atoms. Nonionizing radiation, for example visible light and
microwave radiation, is less energetic, of longer wavelength, and primarily
deposits heat in tissue.
Ionizing radiation can be further subdivided into types of radiation that have no
associated mass (nonparticulate ) and those that have mass (particulate ). X-rays
and gamma rays are nonparticulate types of radiation and can penetrate deeply
into the body and affect radiation-sensitive tissues, for example, bone marrow and
the lining of the GI tract. X-rays are emitted by excited electrons, whereas gamma
rays are emitted by excited or unstable nuclei (radioisotopes or radionuclides).
Once x-rays or gamma rays have been emitted, they are indistinguishable.
Particulate radiation can be further divided into charged and uncharged
particles. Neutrons, a type of uncharged particulate radiation, can penetrate the
body to depths similar to x-rays and gamma rays. Because neutrons deposit their
energy in a more concentrated area, they cause more biologic damage than x-rays
or gamma rays.