Describe and evaluate the uses of nuclear radiations for exploration of internal organs, and for control or destruction of unwanted tissue.
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GCSE Physics Revision
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GCSE Physics revision
Uses of nuclear radiation
Hazards and uses of radioactive emissions and of background radiation
Your specification
AQA student objectives
Learning pathway
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Apply the scientific explanation of uses of nuclear radiation to a relevant example.
Analyse a new situation involving uses of nuclear radiation and explain the scientific reasoning.
Revision summary
Key knowledge
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How Ionising Radiation Affects Cells
- Ionising radiation damages cells by ionising the atoms and molecules within them, which can mutate DNA and potentially cause cancer.
- If cells receive a large enough dose of radiation, they are killed off completely rather than just damaged.
- Large doses of radiation across the whole body cause radiation sickness, with symptoms including vomiting, tiredness, and hair loss.
What is Radiotherapy?
- Radiotherapy is the medical use of radiation to deliberately destroy unwanted cells, such as cancer cells.
- Although radiation can cause cancer, it can also treat cancer — making radiotherapy a key example of radiation's dual nature.
- Radiation is effective at killing cancer cells because a sufficiently large dose destroys cells completely.
External Radiotherapy
- External radiotherapy uses a source outside the body that emits gamma rays targeted at the cancer site.
- Gamma rays are directed from multiple different angles so that only the cancer site receives the highest cumulative dose.
- This technique minimises damage to surrounding healthy tissue by spreading the entry points of the radiation beams.
Internal Radiotherapy
- Internal radiotherapy involves placing a radioactive source directly inside or next to the tumour within the body.
- Beta radiation is typically used for internal radiotherapy because it is more damaging to nearby tissue than gamma rays but cannot penetrate as far through the body.
- Both external and internal radiotherapy cause side effects because healthy cells surrounding the cancer site are also damaged or destroyed in the process.
Medical Tracers: How They Work
- Medical tracers involve introducing radioactive isotopes into the body, either by injection or by swallowing, and then tracking the radiation they emit.
- By monitoring where the tracer travels, doctors can assess whether particular organs are absorbing the correct amount of a substance and functioning properly.
- A well-known example is iodine-123, a gamma-emitting isotope used to check whether the thyroid gland is absorbing iodine as it should.
Choosing the Right Isotope for Medical Tracers
- Gamma radiation is preferred for medical tracers because it is less harmful to the body than alpha or beta radiation, though beta is occasionally used.
- Isotopes with as short a half-life as possible are chosen so that radiation is only emitted during the measurement period, reducing the patient's overall exposure.
- A short half-life ensures the isotope quickly becomes harmless after the diagnostic procedure is complete.
Weighing Up Risks and Benefits
- Every use of radiation in medicine requires a careful comparison of the risks of radiation exposure against the potential medical benefits.
- Medical tracers are generally considered worthwhile when a disease is already suspected, as the diagnostic benefit outweighs the low radiation risk.
- Radiotherapy can be life-saving for cancer patients, but some individuals may choose not to undergo it if it would only extend life by a short period rather than providing a full cure.
- Risk is minimised in medical procedures by using the lowest effective dose and isotopes with the shortest suitable half-life.