1.7 - X-Rays & Gamma Rays

X-rays let us see inside the body

X-rays pass easily through soft tissue but are absorbed by denser material such as bone or metal.

Forming an X-ray image

• Radiation is directed through the body onto a detector plate.
• The result is a negative image: lighter areas show where X-rays were absorbed by dense material (such as bone), while darker areas show where they passed through soft tissue.

Uses of X-ray imaging

• Diagnosing broken bones and dental problems - Dense bone shows up clearly against surrounding tissue.
• CT scans - Use multiple X-rays taken from different angles to build a 3D image of the body.
• Airport security scanners - Detect hidden objects inside baggage.

Treating cancer and tracing the body

Radiotherapy

• High doses of X-rays and gamma rays kill living cells.
• In radiotherapy, beams of radiation are aimed precisely at a tumour to destroy cancer cells while minimising damage to surrounding healthy tissue.

Medical tracers

• A tracer containing a gamma-emitting source is injected or swallowed, and a gamma camera outside the body detects the emitted gamma rays to build an image.
• Gamma rays are used because they pass out through skin, soft tissue and bone without being fully absorbed.
• Tracers can be attached to molecules like glucose; cancerous tumours use more energy and take up more glucose, showing up as bright spots on the scan.

Sterilising with gamma rays

Medical instruments

• Gamma rays sterilise medical instruments by killing microbes (such as bacteria).
• They pass through packaging and reach into deep crevices.
• They can sterilise items that would melt or be damaged by heat, such as plastic instruments.

Food

• Gamma radiation kills microbes on food, keeping it fresh for longer without cooking or freezing.
• The treatment does not make the food radioactive, so it's safe to eat.

Staying safe around X-rays

• X-rays are ionising, so exposure can damage living cells.
• Exposure is kept as low as possible by:
  • Using lead aprons and shields to absorb stray radiation.
  • Keeping the exposure time to a minimum.

Weighing risks against benefits

• Using electromagnetic radiation brings benefits that must be weighed against the risks.
• Decisions about using radiation technologies should be justified using scientific evidence and data, rather than opinion.

Example - Airport body scanners

• Some airport body scanners used X-rays to improve security.
• Although the radiation dose was very low, concerns that repeated exposure increased cancer risk led to this type of scanner being banned in many countries.