Download MS Word - Wonderstruck

KS5 Physics
Lesson Plan 5 – Nuclear Medicine
Science at Work in Healthcare
Post – 16 Science Education Pack
Resource Sheet 5.3 – Isotope Testing
You are part of a team of medical physicists working at Curie General Hospital. One
of the consultant radiographers you regularly work with at the hospital recently
attended a medical imaging conference. At the conference one of the other
delegates told her about a new radioactive tracer that they were thinking about using
with their gamma camera and SPECT imaging machines.
The radiographer has asked you to visit the other hospital and carry out some tests
on the tracer to see if it will be of use within your own department.
Your task is to analyse the sample and make a recommendation about its use.
The steps outlined below will help you through the analysis.
Safety
Remember that you will be using a radioactive source in this experiment. Follow the
general safety procedures for working with radioactive materials:

Do not touch the source directly – use tongs or tweezers.

Handle the source for as short a time as possible.

Wear gloves, safety glasses and a lab coat.

Keep the time you are working with the source to a minimum.
Make sure that you read any safety instructions that come with the source.
Analysis Step 1 – Where does it come from?
For a tracer to be really useful it needs to be readily accessible in hospitals. Most of
the tracers already used with gamma cameras and SPECT (Single Photon Emission
Computed Tomography) scanners are produced by on site generators.
In comparison fluorine-18, one of the main tracers used with PET (Positron Emission
Tomography) scanners, has to be produced from a medical cyclotron. These are
expensive to buy and run and there are only a few in the UK. Because of the short
half life of F-18 any PET scanner must be located close to one of these cyclotrons.
KS5 Physics
Lesson Plan 5 – Nuclear Medicine
Science at Work in Healthcare
Post – 16 Science Education Pack
How is this new tracer produced?
Write down a nuclear equation which shows how the tracer is produced.
Analysis Step 2 – What is the half life of the tracer?
The half life of a tracer is very important. It needs to relate to the particular
processes that it is being used to image. For example, a tracer with a half life of a
few minutes will not be of much use in imaging processes such as liver function
which might take place over a number of hours.
Use Resource Sheet 5.4 – Measuring Half Life to help with this step.
Write down the measured half life in the box below.
Write down the calculated half life in the box below.
Is there a difference between your two values? If so, explain why you think this might
be.
KS5 Physics
Lesson Plan 5 – Nuclear Medicine
Science at Work in Healthcare
Post – 16 Science Education Pack
Analysis Step 3 – What type of radiation does the tracer emit?
Gamma radiation is the best type of radiation for this type of imaging as it is
penetrating and not heavily ionising. Beta radiation can also be useful in certain
circumstances but has limited penetrating power and causes more ionisation in body
tissues.
Alpha radiation is not used for imaging as it has very low penetrating power and is
highly ionising, causing great damage to living tissue.
What type of radiation does the tracer emit?
Write down a nuclear equation showing how this radiation is emitted.
Analysis Step 4 – Chemical Properties
You may have found the ideal tracer, but it won’t be much use if it is highly toxic or it
isn’t chemically compatible with type of imaging you want to carry out. For example,
strontium-85 is very useful for looking at skeletal conditions because it is taken up by
the skeleton in place of calcium. However, it gives a very high radiation dose
because of its long half life. Technetium-99m labelled with a phosphate, which will
also ensure that it is taken up by the skeleton has a short radioactive and biological
half life so is routinely used to image the skeleton.
Carry out some research into your chemical to see if it is going to be usable.
Remember that the different isotopes of a given element will have exactly the same
chemical properties regardless of whether they are radioactive or not.
Write down your findings in the box below.
KS5 Physics
Lesson Plan 5 – Nuclear Medicine
Science at Work in Healthcare
Post – 16 Science Education Pack
Analysis Step 5 – Making a Recommendation
You have now completed your preliminary research and its time to make a
recommendation back to the radiographer about the use of this new tracer.
Using the evidence you have collected consider the following points:

Is the type of radiation the tracer emits useful for imaging?

Is the tracer likely to be easily available to hospitals and medical centres?

What types of imaging does its half life make it suitable for?

Is it toxic? If the tracer is toxic it may still be given in very small doses as the
benefits of the imaging may outweigh the side effects.

How will it react in a patient’s body and is this compatible with the type of
imaging you want to use it for? For example, if you want to use it to look at
blood flow, do you think it will bind with red or white blood cells?

What other tests do you think should now be carried out?
Write down the key points of your recommendation as you may be asked to present it
back to the rest of the group.