Medical Uses of Radiation (OCR Gateway GCSE Physics)

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

• 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

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

Risks of Using Radioactivity

• 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

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

ANSWER:  C

• • 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