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Some uses of radioactivity: in medicine

Sterilisation surgical instruments

Gamma rays are high energy which are only stopped by thick lead.

This means they can easily pass through medical equipment, such as syringes.

As gamma rays pass through the packaging and syringe, they will kill viruses and bacteria which contaminate the syringe.

As long as the equipment remains in a sealed plastic pack it will remain free of viruses and bacteria and be safe for use with patients.

The gamma ray source used should have a long so that the hospital does not have to replace it too frequently

Advantages

  • sterilisation can be done without high temperatures;
  • it can be used to kill bacteria on things that would melt e.g. plastic syringes.

Disadvantages

  • it may not kill all bacteria on an object;
  • it can be very harmful - standing in the environment where objects are being treated by radiation could expose people’s cells to damage and possibly cancer.

Radiotherapy: killing cancerous tumours

A patient undergoing radiotherapy.
Image caption,
A patient undergoing radiotherapy

Although can cause cancer, high doses can be directed at cancerous cells to kill them.

This is called radiotherapy.

About 40 per cent of people with cancer undergo radiotherapy as part of their treatment.

It is administered in two main ways:

  • from outside the body using X-rays or gamma rays from radioactive cobalt;
  • from inside the body by putting radioactive materials into the tumour, or close to it.

Gamma knife

  • beams of gamma rays, called a gamma knife, can be used to kill the cancerous tumour deep inside the body;
  • these beams are aimed at the tumour from many different directions to maximise the dose on the tumour but to minimise the dose on the surrounding soft tissue. This technique can damage healthy tissue, so careful calculations are done to establish the best dose - enough to kill the tumour, but not so much so that the healthy tissue is damaged.
Person receiving gamma treatment for cancer, with rays being directed to the head.

The gamma ray source used should have a long half-life so that the hospital does not have to replace it too frequently

Radioactive Tracers

In some cases, injected radioactive sources (such as technetium-99) can be used as tracers to make soft tissues, such as blood vessels or the kidneys, show up through medical imaging processes.

Iodine-131 is used as a radioactive tracer to investigate the thyroid gland.

The radioactive source emits gamma rays that easily pass through the body to a detector outside the body, for example a ‘gamma camera’.

In this way, the radioactive source can be followed as it flows through a particular organ in the body.

Changes in the amount of gamma rays emitted from different parts would indicate how well the isotope is flowing, or if there is a blockage.

The source used must:

  • be a source of gamma rays so that they pass out through the body to be detected by the gamma camera or GM tube;
  • have very short half-lives - sources used typically have half-lives of hours so after a couple of days there will hardly be any radioactive material left in a person’s body;
  • not be poisonous.

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