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Diagnostic Methods

PET scan

What is a PET scan? 

A PET (positron emission tomography) scan is a type of imaging test that is used to diagnose certain diseases including cancer.  

When is a PET scan used? 

PET scans can be used to: 

  • find tumours 
  • determine if a lump is cancer, where it is, how big it is and if it has spread 
  • diagnose brain disorders 
  • diagnose heart disease 
  • help diagnose and manage central nervous system disorders such as depression, epilepsy, Alzheimer’s and Parkinson’s disease. 

For cancer patients it can also help your doctors determine the best course of treatment, to see how well you are responding to treatment or to check if there is a recurrence.  

How do I prepare for a PET scan? 

A PET scan usually takes about 15-20 minutes but expect to be in the imaging department for 2-3 hours.  

Before your scan: 

  • let your treatment team know if you are (or could be) pregnant or if you are breastfeeding 
  • tell your treatment team if you are anxious about being in a confined/closed space (claustrophobic) 
  • let your treatment team know if you have diabetes  
  • ask if there are any food or drink restrictions. 

How is the PET scan done?  

Before the scan you will have a small amount of mildly radioactive glucose solution injected through a small plastic tube (cannula) in your arm. Cancer cells absorb more of the solution than normal cells and will show up brighter on the scan. 

You will be asked to sit for 30-90 minutes so that the solution can move around your body. The scan itself will take about 30 minutes.  

What are the risks with a PET scan? 


A PET scan is considered a safe medical procedure. The scan exposes you to about the same amount of radiation you would receive in the general environment over approximately three years.  

The injected radioactive materials are removed quickly from the body. You may be advised to avoid close contact with pregnant women or babies in the hours after your scan.  

Allergic reaction  

Some people have an allergic reaction to the radioactive material used. Let your doctor know if you are allergic to iodine, aspartame or saccharine.  


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