X-Rays (Oxford AQA IGCSE Combined Science Double Award)

Revision Note

Properties of X-Rays

Extension Tier only

  • X-rays are part of the electromagnetic spectrum

  • X-rays have:

    • a very short wavelength

    • a very high frequency

    • high energy

  • X-rays are ionising radiation

    • They can remove electrons from atoms

    • This means that they can damage the structure of DNA and therefore cause damage to cells

  • The properties of X-rays include:

    • They affect photographic film in the same way as light

    • They are absorbed strongly by metal and bone

    • they are transmitted by healthy tissue

  • These properties make X-rays very useful for medical imaging

Uses of X-Rays

Extension Tier only

  • X-rays are used in medicine for both diagnostics and treatments

X-ray imaging

  • X-ray images are used to diagnose medical and dental issues

    • X-rays are directed at the patient

    • The X-rays are absorbed by bone or teeth, but pass through tissue

    • The X-rays that pass through the patient are detected by a flat-panel detector or photographic film

    • An image is created showing the bones or teeth of the patient

  • Contrast mediums can be used to view organs using X-rays

    • A contrast medium is a substance that absorbs X-rays, for example, barium

    • The patient is given food or drink containing the contrast medium (for viewing the digestive or renal system)

    • Or the patient is injected with the contrast medium (for viewing arteries or blood vessels)

    • An X-ray image is conducted

    • The organ or structure containing the contrast medium will absorb the X-rays and can therefore be shown on the image

X-ray using barium as a contrast medium

X-ray image of large intestines for IGCSE & GCSE Physics revision notes
The large intestines can be seen as opaque on this x-ray image since the food containing the barium is now located in the large intestines

CT scans

  • X-rays are used in computerised tomography scanners (CT scanners) to create cross-sectional images through the body and three-dimensional (3D) images of organs

CT scan

CT scan for IGCSE & GCSE Physics revision notes
X-ray images are taken through different angles of the patient and compiled by a computer
  • The X-ray tube moves around the ring

  • The X-rays pass through the patient

  • The X-rays are detected by the ring of detectors

  • The computer produces an image of the scanned area

  • The CT scan can distinguish between different types of soft tissue

X-ray therapy

  • X-rays are also used to treat certain conditions

    • Such as killing cancer cells

  • Shorter wavelength X-rays are used for treatment

    • These have a higher frequency and a higher energy

  • Metal filters are used direct the correct wavelengths to the correct location

    • A thin sheet of metal is placed between the X-ray tube and the patient

    • The metal filter absorbs the X-rays at other wavelengths

    • This minimises the exposure to the patient's healthy tissues

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