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Sterilisation surgical instruments

Gamma rays are high energy electromagnetic waves 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 half-life 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

Although ionising radiation 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.

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