Radiation Biology and Radiation Protection

Abstract

Modern radiotherapy and radiology would be unimaginable without knowledge of the fundamental effects of ionising radiation. All radiologists must be aware of the dangers and risks of the uncritical application of X-rays to diagnosis; this ensures the safety of both the patients and the radiologist. Because of CT and interventional radiological procedures, the patient and the physician are subjected to increased exposure to radiation. Knowledge of radio-biological principles and the use of ionising radiation is necessary.

Upon entering material or the body, ionising radiation loses part of its energy because of absorption. Energy transfer occurs via excitation and ionisation (primary processes). In biological tissue, only the absorbed radiation energy is effective; this can lead to cell damage. Biomolecules can be modified through chemical and biological processes (secondary processes). The effect of ionising radiation can be divided into phases. The changes in biomolecules are caused by the direct or indirect transfer of radiation energy to biomolecules (direct or indirect radiation effect).

Energy absorbed by the tissue can lead to ionisation, excitation of the molecule, and the generation of heat. The ionisation of water molecules leads to H₂O⁺ and a free electron; in subsequent reactions, H and OH radicals are generated. Hydrated electrons also arise. The reaction products directly attack biomolecules and react with oxygen to generate peroxide radicals, which can further attack biomolecules.