Abstract

El-Shanshoury H.*

ABSTRACT

Whenever ionizing radiation falls on human body, it produces ionization and excitation in the tissues and impairs the normal function of the cells. Thus human body will be subjected to biological damage and severity of this damage depends upon various factors mainly, nature and energy of the radiation, total dose & dose rate, the extent and part of the body exposed, age of the person exposed to radiation, radiation sensitivity of the organ exposed. The energy transmitted by radiation may act directly causing ionization of the biological molecule or may act indirectly through the free radicals resulting from the ionization of the water molecules that surround the cell. Risk refers to the potential for a radiation hazard to cause harm. Irradiation can cause two classes of harmful; deterministic and stochastic. Deterministic effects of radiation are those whose severity is dependent on the dose of radiation received. These effects can be acute, occurring within hours or days, or delayed for months or years. Stochastic radiation effects are those whose probability of occurring is related to dose, but whose severity when they do occur is not dependent on the initial dose of radiation. As quantifying radiation-induced cancer risks with radiological examinations is not an easy task, the ICRP proposed three different risk categories depending on effective dose to the subjects, and added a corresponding classification in terms of benefits.