Dr. Monserrat Ribas; Hospital de la Santa Creu i Sant Pau, Barcelona

ABSTRACT: Medical practice involving the use of ionizing radiation (hereinafter referred to as radiation) is by far the largest contributor to human exposure from human-made sources of radiation. The radiation is used in both diagnostic and therapeutic purposes. Diagnostic radiology, nuclear medicine and radiation therapy have evolved from the original crude practices to advanced techniques that form an essential tool for all branches and specialities of medicine. The most common ionizing radiations used in hospitals are X ray, gamma rays, beta particles and electrons. The three important principles, which are the foundation of radiation protection, are justification, optimisation, and limitation. The principles of justification and optimisation apply to all exposed individuals, while dose limitation is applicable to employees and the public, but not to patients. Adequate restriction of exposure to radiation for the hospital staff and members of the public can be achieved by seeking suitable compromises between the three basic elements of shielding, distance, and time and also to include systems of work and procedures.