What is an FDG PET-CT Scan – Oncology?

The most common type of PET-CT scan uses radioactively labelled glucose known as FDG (FluoroDeoxyGlucose) to provide detailed images of glucose metabolism throughout the body. This is particularly important in the staging and management of many cancers. It has long been known that many cancer cells use glucose as a fuel source and that they use it at a much higher rate than normal cells. If a fasting patient is injected with this radioactively labelled glucose, cancer cells will be revealed as more radioactive areas or “hot spots” on the scan. This information will allow your specialist to say if a cancer is localised to one area or has spread elsewhere. It also allows your specialist to monitor the effectiveness of treatments such as chemotherapy and radiotherapy.

FDG PET-CT Scan – Oncology

What happens during an FDG PET-CT Scan – Oncology?

A. Before your scan

What to bring

  • Any relevant previous imaging
  • Your Medicare card

To help us get an optimal FDG PET-CT scan it is important that you read the following instructions prior to your appointment.

Preparation – The day before the scan

  • Avoid any strenuous exercise for at least 24 hours prior to your PET-CT scan
  • If you have either Type 1 or Type 2 diabetes please contact Envision on 6382 3888 to discuss your preparation
  • If you think you may be pregnant, please inform our Nuclear Medicine team before your examination commences

Preparation – On the day of the scan


No food or liquids, except water. Be aware that fasting also includes avoiding the following:

  • Flavoured water
  • Chewing gum and cough lozenges
  • Black tea and coffee

Drink at least 1 litre of water prior to your PET-CT appointment.


Take all medications except those for diabetes as normal. Use only water to take medications.

What to wear

Avoid wearing jewelry and wear warm comfortable clothing without metallic zippers, buttons or labels. If you don’t have access to clothing without metal zippers etc, a gown will be provided.

Appointment duration

A PET-CT scan will take approximately 2 hours from the time you arrive until completion. Most of that time you will be relaxing in a comfortable room while the radioactive tracer accumulates in the body. The PET-CT scan itself will take about half an hour.

B. During your FDG PET-CT Scan – Oncology

Upon arrival, you will be asked to fill in a questionnaire prior to being escorted to the PET-CT department. You will then have your weight and height measured before a brief interview with a nuclear medicine technologist who will then escort you to an uptake room. This room is a small area which contains a comfortable chair where the technologist will perform a test to measure your Blood Sugar Level (BSL) prior to the injection of radioactive glucose. Your BSL may be elevated if you have recently eaten or have poorly controlled diabetes. If your BSL is too high you may be asked to reschedule your test to another day as a high BSL may lead to an undiagnostic scan.

After your blood sugar measurement, a cannula (a small tube) will be inserted into a vein in your arm and this will be connected to a specialised pump which contains the radioactive glucose (FDG). You will then be made comfortable and the lights will be dimmed prior to the injection of tracer.

Don’t expect to feel anything from the injection, as the tracer causes no side effects. Once the injection has been given, you will be left to relax for at least one hour prior to being taken through for your scan. During this “uptake” period it is important that you avoid any activities such as reading, texting or excessive movement as this may lead to abnormal tracer distribution in the body.

After the uptake period, you will be asked to empty your bladder prior to being escorted into the PET-CT scanner room and positioned on the scanner bed. A low dose CT scan is acquired first. This involves two planning or scout x-rays which are acquired so that the technologist can accurately plan which area of the body will be covered by the PET-CT scan. The low dose CT is then acquired. This takes approximately one minute to complete and then the scanner bed will move into position for the PET part of the scan. This takes longer to acquire than the CT and will typically take from 10 to 25 minutes depending on your size and the type of PET-CT required.

Once the PET-CT scan is finished you may also have a diagnostic CT performed but this will depend on what your specialist has requested.

Once finished you are required to wait for about 15 minutes so that your images can be checked for diagnostic quality.

Risks and side effects

Nuclear medicine examinations including PET-CT are considered safe with almost no reported adverse reactions attributable to the radiopharmaceuticals used in these examinations.

PET-CT scans expose the patient to gamma radiation that is injected (the radioactive tracer) as well as x-rays which are generated by the CT component of the test. The level of radiation exposure from a PET-CT scan is minimal and Envision Medical Imaging has invested in the latest technology and employs professionals trained in radiation reduction techniques so that any radiation exposure is kept as low as possible.

It is not uncommon for a diagnostic CT scan to be performed at the same appointment as the PET-CT scan. Diagnostic CT is usually performed after the injection of a contrast agent which contains iodine. When a CT or an x-ray of the body is performed many areas appear as a similar shade of gray. Contrast agents are used to highlight blood flow, lymph nodes and organs.
There is a small risk of an allergic reaction from contrast agents and you will be asked to fill in a questionnaire to determine any potential risk prior to the test. In the unlikely event that you have a reaction to contrast, Envision staff are trained in emergency procedures and have all the necessary equipment and medications to deal with any problems.

If you are worried or concerned about the test or the radiation exposure involved please speak with the nuclear medicine technologist when you go through for your appointment.

Who will perform my scan?

At Envision Medical Imaging, your PET-CT scan will be performed by a Nuclear Medicine Technologist, who has a degree in Medical Imaging, is accredited with the Australian Health Practitioner Regulation Agency (AHPRA) and holds a specialised license to practice Nuclear Medicine and CT from the Radiation Council of Western Australia.

FDG PET-CT Scan – Oncology

What happens after an FDG PET-CT Scan – Oncology?

How do I get my results?

Immediately after the PET-CT scan you may be asked to wait till your images are checked for diagnostic quality. If you have moved during the scan you may be asked to stay until an additional image of the affected body part can be taken.

If the scan is deemed to be of good quality you may then leave the department and resume your daily activities. There are no residual effects from the tracer or the PET-CT scan.

Your images will be reviewed along with your relevant medical history, and any other imaging, and be reported on by our Nuclear Medicine Radiologist.

If your results are needed urgently, or you have an appointment straight after your scan with you referring doctor or health care provider, Envision Medical Imaging will arrange to have your results available immediately. Otherwise your referring doctor will receive your report within 48 hours of your examination. Please ensure that you make a follow up appointment with your referring doctor to discuss the results.

Post procedural information

After your scan you will be able to return to your normal daily activities. If you have received contrast as part of a diagnostic CT, you should continue to drink a reasonable amount of water for the rest of the day. This will help clear the contrast from your kidneys.

FDG PET-CT Scan – Oncology

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