X-Rays (Oxford AQA IGCSE Physics)

Properties of X-Rays

• 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

• 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

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

• 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