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Thursday, 27 January 2011 12:51 |
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What is PET?
Positron Emision Tomography – or PET uses short lived radionuclides attached to tracers to look at metabolic processes in health and disease. The most common radionuclide used is fluorine -18 (F-18) which has a half life of 110mins. It can be attached to a molecule that mimics glucose metabolism, flurodeoxyglucose, to produce 18F-FDG.
Metabolic changes often precede changes that can be visualised by conventional imaging with CT or MRI.
Cancer cells have altered glucose metabolism, using glucose at a much faster rate than normal cells, so F18-FDG is the major tracer used to assess and detect early cancer.
New tracers are being developed continually, but short acting tracers need a nearby cyclotron to produce them eg C11 methionine for brain imaging in dementia
Combination of Anatomy and Function
Overlaying the PET images on an anatomical image – taken with Computed Tomography (CT) at the same time, allows accurate localisation of the increased FDG uptake
PET –CT is more accurate than PET or CT alone
What does it mean for the person having the scan?
A short cannula is placed in a vein in the arm
Blood sugar is checked if you are diabetic – and you may be given some insulin
The FDG is injected into the cannula
You have to rest quietly for 30 minutes
Pictures are taken of the whole body with a special camera, which picks up the radiation
 Printable Leaflet version of this page with Images |
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Thursday, 27 January 2011 11:52 |
What is a PET scan?
PET is short for Positron Emission Tomography. It uses a radioactive substance to look at the way organs work in a unique way. It involves an injection into a vein in your arm of FDG, a substance similar to glucose. The PET scanner then detects areas of high glucose concentration within the body.
Preparation for the Scan
Do not eat or drink anything but water for 6 hours before your scan. Please take any medicines as normal (unless your appointment letter says otherwise).
If you are diabetic it is really important to let the department know before your appointment
Please let us know if you are pregnant or breast feeding.
Is it safe for me to have a scan?
The small amount of radioactive tracer injected is used to take the pictures. The risk is outweighed by the information that is gained by taking the scan. A doctor will have checked the request to make sure this is the optimal test before we contact you.
If you have any concerns or would like further information, please contact the department where you will be having your scan.
The injection
The FDG is injected through a short cannula (needle) in your arm. It takes 60-90 minutes for the FDG to be taken up by the cells.
So that the scans are of the best quality, your sugar levels need to be tested. If you sugar is high, you may be asked to take a small amount of a drug, to reduce this. One of our doctors will prescribe this and you should not have any major side effects.
The injection will normally be in a vein in your arm
The pictures will be taken by a special camera and all you will have to do is to lie as still as you can.
One of the clinical staff will be watching all the time you to make sure everything is OK
Your Scan
Please do not be late, or you may not be able to have your scan that day
2 sets of scans are taken, one for the FDG and a CT scan, so that the anatomy can be seen. This lets the reporter see the exact location of any FDG uptake.
Your Results
Your scans will be looked at by 2 doctors, who will agree the report and this will be sent to the doctor who requested your scan. The reason it is done this way is because your doctor will have all the results from other tests and will be able to tell you how the results if your scans affect your care.
Printable Leaflet version of this page
Printable Leaflet version of this page with Images
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