Medical Uses of Radiation Flashcards

All 6 cards in this deck

How is nuclear radiation used to explore internal organs?

A radioactive tracer is injected or swallowed; it collects in the organ and the gamma radiation it emits is detected outside the body to give an image.

What type of emitter and what sort of half-life should a medical tracer have?

A gamma (or beta) emitter with a short half-life — long enough to complete the scan but short enough that the patient is not radioactive for long.

How is nuclear radiation used to destroy unwanted tissue from outside the body?

External radiotherapy: a beam of high-energy gamma rays (or X-rays) is aimed at the tumour from several directions, so the tumour gets the highest dose and healthy tissue less.

How is nuclear radiation used to control or destroy unwanted tissue from inside the body?

A radioactive source is placed in or next to the tumour (implanted seeds), or an isotope is swallowed or injected so it collects in the tissue and destroys it.

True or false? An alpha emitter is a good choice for a tracer injected to image an internal organ.

False. Alpha radiation cannot pass out of the body to be detected and is strongly ionising inside it; a gamma emitter is used.

When judging whether the risk of a medical scan or treatment is acceptable, what should the patient's radiation dose be weighed against?

The benefit (diagnosis or destroying a tumour) and the risk of the radiation damaging healthy cells and causing cancer; the dose can be compared with the background dose received over the same time.