22.3 - Using Radiation in Medicine
Five uses of radioactivity
In every application, the type of radiation is chosen for how penetrating it is and how strongly it ionises.
The five uses
- Smoke alarms - An alpha source ionises air between two electrodes so a current flows. Smoke entering binds to the ions, reducing the current and setting off the alarm. Alpha can't escape the alarm casing.
- Irradiating food - Gamma rays kill bacteria and mould without heating the food, helping it stay fresh longer.
- Sterilising equipment - Gamma rays sterilise medical instruments through sealed plastic packaging without heat damage.
- Thickness control - A beta source and detector monitor materials like paper or aluminium foil. If the material thickens, less beta penetrates, signalling the rollers to adjust.
- Cancer diagnosis and treatment - Gamma emitters act as tracers to highlight tumours on scans, and focused beams of gamma rays destroy cancer cells in radiotherapy.