Positron emission tomography (PET) uses a small amount of radioactive material called, a radiotracer, to form an image of the metabolic state of your cells. The radiotracer is injected intravenously and is taken up by the cells of your body. The PET camera can pick up the radiotracer from your body and convert the information into an image. It is a molecular image. When it is combined with a CT (computed tomography) it is called a PET/CT.
PET/CT is a dual-modality. (PET + CT) This means that we image the cellular/metabolic function (how does the cell WORK) AND the anatomy (what does it LOOK like) of the human body in one investigation.
The PET/CT scan has a specific place in the management of your disease and cannot replace a CT, MRI or other scan. One scan is not better than the other. Some information can only be seen on a PET/CT scan, but other information can only be seen on a MRI scan. Your referring doctor will know when a PET/CT scan is the best imaging modality.
The advantage of PET is that it may detect the early onset of disease before it is evident on other imaging tests. For example a PET scan can distinguish between dead scar tissue and active tumour tissues. The PET scan can evaluate if your current treatment regime (eg chemotherapy) is effective.
It is a whole-body imaging modality and we can therefore look at the entire body with one investigation. Routinely the scans are done from “eyes to thighs”, but in certain diseases we do a total-body scan where we scan the patient from head to toe (eg melanoma).