3.7 - 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.

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.