Uses of Radioactive Material

Section 1 of 6Medical tracers

What a tracer is

• What a tracer is A tracer is a radioactive isotope given to a patient, by injection or swallowing,
  • so that its movement through the body can be followed.
• A detector outside the body picks up the radiation and builds an image of where the substance has gone, for example blood flow or the thyroid gland.
  • Iodine-131 is one example.

Why gamma emitters

• Why gamma emitters Gamma rays are highly penetrating so they pass out of the body and can be detected.
• Gamma radiation is less ionising than alpha, so it does less harm to cells inside the body.

Why a short half-life

• Why a short half-life The half-life should be a few hours: long enough to carry out the scan but short enough that the activity quickly drops and does not harm the patient later.
• The smallest possible quantity is used to keep exposure low.

Section 2 of 6Radiotherapy

Treating cancer with radiation

Why it works

• Why it works Radiation kills living cells, and cancer cells are more susceptible than many healthy cells.

External treatment

• External treatment Beams of gamma rays are directed at the tumour from several angles,
  • so the dose is high at the tumour but spread out in the surrounding healthy tissue.

Internal treatment

• Internal treatment Small radioactive pellets or seeds are placed in or next to the tumour, delivering radiation directly to it.

Risks

• Risks Healthy cells can also be damaged, so doses are carefully controlled and healthy tissue is shielded where possible.

Section 3 of 6Sterilising equipment

1Gamma rays are the most penetrating

• Gamma rays are the most penetrating Gamma radiation can pass through packaging and through the equipment itself.

2All surfaces are irradiated

• All surfaces are irradiated Radiation reaches every side of the instrument, including places that are hard to clean.

3Microbes are killed

• Microbes are killed The radiation destroys bacteria and other microorganisms on the instruments.

4Sealed and ready to use

• Sealed and ready to use Items can be sterilised after being sealed in packaging, so they stay sterile until opened.

Section 4 of 6Choosing an isotope

Property needed	Reason	Rule out
Gamma emitter	Must penetrate out of the body to be detected	Alpha emitters, which are stopped by skin and a few centimetres of air
Half-life of hours	Long enough to move around the body, short enough to leave little activity afterwards	Half-lives of seconds or minutes (too short) and of years (too long)
Small quantity	Reduces the radiation dose to the patient	Large amounts used for no reason

Section 5 of 6Key terms

Term	Meaning
Tracer	A radioactive isotope used to follow the path of a substance through the body or a system.
Radiotherapy	The treatment of cancer using ionising radiation to kill cancer cells.
Gamma radiation	High-frequency, highly penetrating electromagnetic radiation from the nucleus.
Sterilise	To kill all microorganisms on an object.
Half-life	The time taken for the activity of a radioactive isotope to halve.

Section 6 of 6Exam technique

1

Choosing an alpha emitter as a tracer. It cannot get out of the body, so it cannot be detected externally.

2

Choosing an isotope with a very long half-life, which would leave the patient radioactive for too long.

3

Choosing an isotope with a half-life that is too short, which would decay before the scan is complete.

4

Saying radiotherapy removes the tumour. It kills the cancer cells using radiation.

5

Thinking sterilising with gamma rays makes the equipment radioactive. The radiation passes through and does not stay in the instruments.