Using Radiation in Medicine

Two important ways in which radiation is used in medicine are:

  • Radiotherapy
  • Radioactive tracers


Ionising radiation can cause cancer by damaging DNA. This is because they ionise the atoms and molecules in our cells, causing the DNA to mutate. However, radiation can also be effective at getting rid of unwanted cells, such as cancer cells, because they are more susceptible to radiation than other cells.

The treatment of cancer using radiation is called radiotherapy. Radiotherapy can be administered in two main ways: internally and externally.

Internal radiotherapy

Internal radiotherapy involves placing radioactive material inside the body, close to or within the cancer.

The internal method tends to use beta radiation instead of gamma radiation because it causes more damage without being as penetrating.

External radiotherapy

Radiation beams are aimed at the cancer site in high doses to destroy the cancer cells and shrink the tumours.

The external method often uses gamma rays because they penetrate the body more effectively to reach the cancer site.

However, there are downsides to using radiotherapy to treat cancer. Healthy cells will also be damaged or destroyed in the process. This is why many cancer patients experience side effects.

Radioactive Tracers

Tracers are radioactive isotopes introduced into the patient’s body either by injection or ingestion. They can be used to assess bodily functions and for the diagnosis and treatment of disease.

We can use the emitted radiation to track the movement of the isotopes around the body. This means we can check if different organs are functioning as they should be, by checking if they absorb the correct amount of the substance.

Gamma or beta radiation is typically used for radioactive tracers for two main reasons:

  • They are less ionising than alpha radiation – This minimises damage to body tissue
  • They exit the body more readily than alpha radiation

We tend to use isotopes with the shortest half-life possible. This approach minimises the amount of time they emit radiation, ensuring they decay before causing severe damage.

As radiation can be both beneficial and harmful, it is important to weigh the risks against the benefits when using it.

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