ABSTRACT
The effects of radiation can be categorised into stochastic effects and tissue reactions. This chapter explains the terms stochastic effects and tissue reactions, and presents two examples of each type of effect. It describes health risk models from radiation exposure, and provides the differences between cell damage by direct action and indirect action. In direct action, the radiation interacts directly with the target cell (DNA) and produces biological damage directly. In the indirect action of radiation, the radiation hits the water molecules, the major constituent of the cell, and other organic molecules in the cell, whereby free radicals such as hydroxyl and alkoxy are produced. A cell survival curve describes the relationship between the absorbed doses of radiation. The chapter explores the typical relationships between radiation dose with the tumour control probability and normal tissue complication probability expected from a radical course of radiotherapy.
