PET Positron Emission Tomography
About the Examination
A Positron Emission Tomography (PET) scan is a three dimensional diagnostic imaging procedure used to image the function of our internal organs and skeleton. PET scans can also be combined with CT scans and MRIs to produce more detailed results.
It involves the injection of a small amount of radioisotopes or radiopharmaceuticals known as tracers, which are designed to target and image a specific area/organ of the body. Because PET images the functions of the body, it can also be used to assess the response to treatment.
While PET studies do use radiation, the dose is very low and is rapidly excreted from the body. Radioisotopes have a “half life” which means they will decay by half over a period of time. The most commonly used tracer in PET is Fluorine-18 and its half life is less than 2 hours.
What is a PET scan?
PET scans detect the radiation emitted by an injected substance called a radiotracer to produce images of internal organs and soft tissue. Unlike CT scans and x-rays, which allow doctors to see the structure of internal parts of the body, PET scans allow doctors to test and monitor the function of internal organs. The information gathered from a PET scan is used in conjunction with other imaging techniques to produce more comprehensive results.
What part of the anatomy is examined during a PET scan?
PET scans can be used to examine the soft tissues and internal organs of the body.
What conditions can be diagnosed by a PET scan?
PET scans are used to diagnose a number of conditions including:
- Some cancers
- Conditions of the nervous system (Parkinson's, multiple sclerosis, etc.)
- Brain disorders
- Alzheimer's disease
- Issues with blood flow
- Cardiac viability
What are the risks of a PET scan?
A PET scan is a low risk procedure. Patients who undergo PET procedures are exposed to a small dose of radiation, following the ALARA (As Low As Reasonably Achievable) principle. Administration of radiation to patients is highly regulated and exposure is well within the published guidelines from public health authorities. Your doctor will have taken into consideration the benefit of having this procedure and the radiation exposure from these procedures before requesting any PET scan.
Side effects or allergic reactions are extremely rare, as the radioactive tracers are usually based on water and not iodine like X-ray contrast. Patients can eat, drink, and drive a car after having a PET scan, and will not feel sick or dizzy.
Although the tracer contains a low dose of radiation, it may pose a risk to patients who are pregnant or breastfeeding. Please notify our staff if there is any chance of pregnancy before the procedure begins. Patients are advised to avoid contact with anyone who is pregnant, breastfeeding or very young children for a few hours after the procedure.
About the Equipment
What equipment is used for the scan?
The following equipment is used during a PET scan:
- A large tube like scanner
- A narrow flat bed
- Computers and monitors
Are there alternatives to a PET scan?
PET scans are usually combined with CT and MRI scans to produce a more detailed image. The information gathered from a PET scan is used in conjunction with other imaging techniques to produce more comprehensive results.
Preparation for the PET scan
Is a special diet required before a PET scan?
You will need to fast for 6 hours before the test but you can drink plain water.
Diabetic patients require specific preparation depending on their type of diabetes. Please notify our friendly staff at the time of booking if you are diabetic.
What should a patient tell the Technologist before a PET scan?
Before undergoing a PET scan you should tell your doctor if you:
- Are pregnant or suspect that may be pregnant
- Suffer from diabetes
- Take any regular medications or supplements
- Are claustrophobic
- Have had any previous PET scan
What do you need to bring for the PET scan?
Please bring your referral, any previous scans or x-rays to the procedure, along with a list of medications you’re currently taking.
Non-english speaking patients are welcome to bring a suitable relative/friend who can interpret for them.
What should you wear for the PET scan?
Please wear comfortable clothing that has no metal zippers, buttons or clips. Please remove all jewellery prior to your appointment.
How long will the PET scan take?
The total procedure takes 2 hours.
PET Scan Procedure Description
What does a PET scan involve?
The PET scan procedure involves injecting a radiotracer into a vein in the arm. The PET scanner, a large circular machine, then detects the signals from the tracer and transmits them to a monitor, building a 3D image of the body. Most PET procedures take 2 hours to complete.
This image is used by specialists and doctors to determine whether the organs and tissues being examined are functioning normally.
Specific steps during the PET scan
You will be instructed to arrive at least 10 minutes before your appointment so that you can fill out any paperwork
Before the test begins, a Nuclear Medicine Technologist will give you an explanation about the procedure.
The technologist will take a brief history of why you are having the scan, check you are correctly prepared for the test and confirm the pregnancy/breastfeeding status of female patients. The technologist will be able to answer any of your questions before the procedure begins.
Most PET procedures will require patients to have their blood sugar tested either by finger prick or by removing a small drop of blood from the inserted cannula. Blood sugar levels need to be within a specific range for the test to go ahead. It is very important that diabetic patients follow their specific instructions.
An intravenous cannula will be inserted into a vein in the arm and a radioactive tracer will be injected. You will be asked to remain quiet and calm for 60 minutes so that the tracer is absorbed correctly.
You will be asked to empty your bladder before being taken into the procedure room.
The technologist will instruct the patient to lie down on a flat bed, with your head pointed towards the machine. Most scans will require you to raise your arms above your head.
During the scan, it is normal for the machine to make buzzing and clicking noises. The procedure itself causes no pain and should only take 30 minutes.
Post PET Scan Instructions
What are the recovery details?
After the procedure you will be able to resume normal activities immediately.
Drinking plenty of fluids will help to flush the remainder of the radiotracer from your body and patients are advised to avoid contact with anyone who is pregnant, breastfeeding or very young children for a few hours after the procedure. The technologist performing your scan can give a more detailed explanation.
The results of the scan will be sent to your doctor, who will discuss them with you during your next appointment.
Can I Drive Home?
Patients are well enough to drive home after the procedure. The radioactive tracer will not make you feel any different and you will be able to resume normal activities such as eating, drinking and driving.