Module 5: Radiation Biology - Introduction

BIOLOGICAL EFFECTS OF RADIATION:

The primary effect of radiation is mediated via:

1. Ionisation of molecules by the direct transfer of energy (LET).
2. Radiolysis of water - creation of free radicals.

Subcellular targets:

• Enzymes - probably not significant in few of the multitude of enzyme molecules present.
• Membranes - damage and changes in permeability - decrease cell viability.
• DNA - most common targets leading to clinical sequelae

DNA damage:

• Base damage - deamination/change in base - mutation.
• Strand breaks - double or single, depending of the stage of cell cycle - can repair abnormally resulting an aberrent chromosomes.

Radiation effects on subcellular elements can cause:

1. Cell death - if sufficient numbers of cells die, then organ systems will fail.
2. Alteration of function - alter differentiation and division - carcinogenesis/genetic mutations