Using Radiation in Medicine

Two important ways 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. As they are more susceptible to radiation than other cells.

The treatment of cancer using radiation is called radiotherapy. The two main ways that radiotherapy is administered are internally and externally.

Internal radiotherapy

It is administered by putting radioactive material inside the body, close to or inside 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 tends to use gamma rays because they are more effective at penetrating the body 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 cancer patients experience many side effects.

Radioactive Tracers

Tracers are radioactive isotopes that are placed inside the patient’s body, either by injections or by swallowing it. They can be used to assess bodily functions and for the diagnosis and treatment of disease.

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

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

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

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

As radiation can be both useful and harmful, it is important to weigh up the risks against the benefits when we use it.