P7.6 Nuclear radiation in medicine

Question 1

How does a radioactive tracer work?

Answer 1

Tracer contains a radioactive isotope that emits gamma radiation as it be can detected outside the system - for example, doctors use radioactive iodine to find out if a patient’s kidney is blocked

Question 2

How does the tracer work in real life conditions?

Answer 2

The patient drinks water containing the tracer - a detector is placed on the kidney

Radioactive substance flows in and out of a normal kidney - so the detector reading goes up then down

For a blocked kidney the reading goes up and stays up - because the radioactive substance goes into the kidney but doesn’t flow out again

Question 3

Why is radioactive iodide used for a tracer?

Answer 3

Its half life is eight days - so it last long enough for the test to be done but decays almost completely after weeks

Emits gamma radiation so can be detected

It decays into a stable product

Question 4

How can gamma cameras take images of internal body organs?

Answer 4

Before image is taken patient is injected with a solution that contains a gamma emitting radioactive isotope

Solution is absorbed by the organ and nearby gamma camera detects it

Gamm rays pass through holes in the thick lead grid in front of the detector

Gamma rays only detects gamma rays from the nuclei directly in front of it

Detector signals are used to build up an image of where the radioactive isotope is located in the organ

Question 5

What must a key feature of the radioactive isotope be?

Answer 5

Must be a gamma emitter with a half-life long enough to give a useful image, but short enough so that its nuclei have mostly decayed after the image has been taken

Question 6

How can gamma radiation be used to destroy cancerous tumours?

Answer 6

Radiation can be emitted from a radioactive isotope of cobalt down a narrow beam.
Cobalt has a half-life of 5 years
Gamma radiation is used as it can penetrate deeper into the body than beta radiation and alpha radiation

Question 7

How do radioactive implants work?

Answer 7

Beta or gamma emitting isotopes are used in the form of small seeds or tiny rods
Permanent implants use isotopes with half-lives long enough to irradiate the tumour over a given time - but short enough so that most of unstable nuclei will have decayed

Question 8

What is a film badge?

Answer 8

Shows whether the person is in at-risk areas