AQA GCSE Physics

Revision Notes

4.3.3 Medical Uses of Radiation

Medical Uses of Radiation

Medical Tracers

  • A tracer is a radioactive isotope that can be used to track the movement of substances, like blood, around the body
  • Gamma emitters are usually used for this purpose
    • Gamma rays are highly penetrating and so will be able to pass through the body and be detected outside the body
  • This allows an internal image of the body to be created

Iodine-131 is an example of a radioactive tracer

  • Since gamma rays are less ionising than some other forms of radiation, the harm caused to the patient is also minimised
  • As well as choosing a gamma emitter:
    • The amount of isotope used is kept to a minimum to reduce people’s exposure to radiation
    • Isotopes are chosen that have short half-lives of around a few hours: Long enough to carry out the procedure, but not so long that they cause long term harm


  • Radiotherapy is the name given to the treatment of cancer using radiation
  • Although radiation can cause cancer, it is also highly effective at treating it
  • Radiation can kill living cells
    • Some cells, such as bacteria and cancer cells, are more susceptible to radiation than others
  • During external radiotherapy, beams of gamma rays are directed at the cancerous tumour
    • Surrounding healthy tissue tends to be shielded to avoid causing any damage

Radiation Therapy 1, downloadable AS & A Level Physics revision notes

During radiotherapy, the beams are moved around to minimise harm to healthy tissue whilst still being aimed at the tumour

  • During internal radiotherapy, small pellets of radioactive materials can also be inserted into a tumour exposing it directly to radiation

Sterilising Medical Equipment

  • Gamma radiation is widely used to sterilise medical equipment
  • Gamma is most suited to this because:
    • It is the most penetrating out of all the types of radiation
    • It is penetrating enough to irradiate all sides of the instruments
    • Instruments can be sterilised without removing the packaging

Worked Example

A new medical tracer is required for investigating the absorption of a particular substance found in blood around the body.

Tracer examples, downloadable IGCSE & GCSE Physics revision notes

Which of the different isotopes in the table would be most suitable?


    • A suitable medical tracer must:
      • Be able to penetrate out of the body
      • Have a long enough half-life to move around the body before it decays away
      • Have a short enough half-life that it won’t remain in the body at dangerous levels for too long
    • The answer is not A because alpha radiation cannot penetrate out of the body
    • The answer is not B because the half-life is too short
    • The answer is not D because the half-life is too long

Risks of Nuclear Radiation

  • The use of radiation in medicine carries risk
  • Radiation can:
    • Kill or damage living cells
    • Cause cancer
    • Cause mutations
  • As a result, its use needs to be kept to a minimum
  • However, the benefits of using radiation in medicine can out way the potential risks
    • The risks posed by the radiation are smaller than the risks associated with leaving the condition untreated
  • For example, if a person has a cancerous tumour that is likely to kill them, then it is less of a risk to use radiotherapy than to leave the tumour

Exam Tip

You may be given data and asked to evaluate the risk of nuclear radiation in a particular example. Remember to compare the potential dangers with the benefits.

Author: Katie

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.

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