Radiation Hazard Evaluation and Control in Nuclear Medicine

Abstract

The use of radioisotopes in unsealed form has potential radiation hazards to the person handling the radiation sources, the people around and the environment. Radiation hazards are classified into two categories such as ‘external’ and ‘internal’. External radiation hazards can be controlled by using one or a combination of factors such as time, distance and shielding. The lesser the ‘time’ spent in the radiation field, the lesser is the radiation dose received by an individual. Increasing the distance is a very effective method of reducing the dose rate as isotropic emission of radiation follows the ‘inverse square law’. The concepts of ‘half-value layer (HVL)’ and ‘tenth-value layer (TVL)’ are widely used in designing shielding and depend on the composition of the material used for shielding and the energy of the radiation. When radioactive material gets into the person’s body through any means such as ingestion, inhalation or subcutaneous absorption (through wounds), it gives rise to an internal radiation hazard. The effective half-life, annual limit of intake (ALI) and derived air concentration (DAC) are different terms used to estimate internal hazards.