PET-CT scans combine two different forms of imaging to help your doctor to understand what is going on inside your body. Using two different scanning techniques enables your doctor to look for both structural and functional abnormalities. The results can be used for diagnosis, to guide treatment, or to monitor how your condition is changing.
The CT Scan
The CT or computed tomography element of PET-CT scans uses X-rays to examine the structure of your organs, blood vessels, bones or other parts of your body. The scanner takes a series of X-ray images from different angles which will then be combined into a single image by the computer. You might be given a contrast dye before the procedure to help certain structures to stand out, but it depends on the part of your body that is being investigated. As the CT scan uses X-rays, you will also need to remove anything metallic that could block the scan, including any jewellery. The dose of X-rays you will receive during the scan will be safe, but you should not have a CT scan if you are pregnant.
The PET Scan
The other component of PET-CT scans is positron emission tomography. The PET scan is used to look at the function of particular body parts rather than their structure. You will be given a special radioactive drug in an injection about an hour before the procedure. It is the tiny amount of radiation from this drug that the scanner will actually be detecting. Since the drug accumulates in the most active cells, the pattern it produces will show your doctor whether there are any abnormalities or to pinpoint exactly where the problem is. The radiotracer is very safe as it only produces a very small amount of radiation that will leave your body within a few hours. You will be encouraged to drink plenty of fluids after the procedure to help this to happen.