Radiation safety concerns the safe use of ionizing radiation. The radiation exposure has to be controlled to protect people and the environment from unnecessary exposure and the damaging effect to the health. Legal regulations require that radiation exposure (individual radiation exposure as well as collective dose) must be kept as low as reasonably achievable.
The electromagnetic spectrum includes x-rays, gamma rays, ultraviolet radiation, visible light, infrared radiation, and radio waves. Additionally, there are several types of particulate radiation e.g., alpha and beta particles. All types of radiation are used in a wide range of medicine, industry, research and communication. Radiation risks can occur due to either long-term low level exposure or short-term high level exposure. A well-functioning dosimetry program is essential for a safe use and for compliance with federal and state regulations.

Three basic rules have to be observed for a safe use of ionizing radiation.

See also Inverse Square Law, Administrative Dose Guidelines and Annual Dose Limit.

(ALARA) 'As low as reasonably achievable' is a precautionary principle that should be part of basic radiation safety considerations in protection to the exposure as well as in other technologies of the medical, the nuclear and the industrial fields.
ALARA is based on three principles: Justification means that possible exposure to humans should yield a sufficient benefit to society to justify the risks of the radiation exposure. The ICRP in 1977 states that 'all exposures shall be kept as low as reasonably achievable, economic and social factors being taken into account'. The radiation exposure must be reduced to the lowest level possible, considering the costs of such a limitation in dose.

Dosage is an important factor in the use of ionization radiation as well as in application of contrast agents or radiopharmaceuticals and the dosage should be comply with the ALARA principle (As Low As Reasonably Achievable).
Ionizing radiation comes from natural and artificial sources. Radiation effects depend on the type of radiation, and various units are used for measurement of dosages including gray, sievert, radiation absorbed dose (RAD), roentgen equivalent in man (REM), and roentgen. The amount of radiopharmaceutical given to a patient is measured in becquerels (Bq).
The dosage of contrast media in radiographic or computer-tomographic procedures should be tailored according to the diagnostic indications, the iodine concentration, and the patient's body size and age.

See also Administrative Dose Guidelines.

The dose limit is the highest value of an applied or allowed radiation exposure. The radiation dose is limited in order to prevent the occurrence of radiation-induced deterministic effects or to limit the probability of radiation-related stochastic effects to an acceptable level.

See also Whole Body Counter, Thermoluminescent Dosimeter, Dosimetrist, Annual Limit On Intake, Committed Effective Dose Equivalent, Computed Tomography Dose Index, Directional Dose Equivalent, Doubling Dose.

The administrative dose guidelines are the predetermined value of radiation dose to workers, below the dose limit (administrative level), which triggers a specific course of action when the dose value is exceeded, or is expected to be exceeded.

See also Medical Internal Radiation Dose Committee, Food and Drug Administration, Material Safety Data Sheet, Annual Dose Limit, Air Kerma, Supervised Area and Drug Development and Approval Process USA.