What is Positron Emission Tomography (PET-CT)?
Nuclear medicine is a type of medical imaging where our patient is given a very small amount of a radioactive peptide, and we image the pattern of that activity within the body with a gamma camera. It is a functional imaging modality, where we are looking at how the organs and tissues of the body are behaving. It is especially useful for the following body systems – skeletal, cardiac, neurological, gastrointestinal, endocrine, and lymphatic. These tests can go from 20 minutes to 5 days in length, depending on the body system we are evaluating.
Positron Emission Tomography is a special subtype of nuclear medicine which uses a PET-CT scanner to detect the activity of cells within your body. The scanner is very similar in size and appearance to a normal CT scanner, and the examination typically takes 30-40 minutes. Prior to the scan, we inject your veins with a radiotracer (usually 18F-FDG) which will gradually disperse throughout the body, accumulate in some of the body’s cells (including abnormal cells), and enable us to create a whole body picture of any potential disease process.
In Australia, the vast majority PET-CT scans use very small doses of 18-FDG (fluoro-deoxyglucose) which is radioactive sugar. Normal activity is seen in tissues and organs which require a lot of sugar for their day-to-day function (including the brain, heart, liver and bowel). Abnormally functioning cells (such as cancer cells and inflammatory cells) also accumulate the 18F-FDG molecules, and the location and intensity of this disease process can be accurately determined by the PET-CT scanner. A CT scan obtained at the same time to provide precise information on the structural changes to the affected tissues. The images are then interpreted by one of our nuclear radiologists who have had intense subspecialty training in PET-CT imaging.
A PET-CT scans are performed to:
- See how the tissues and organs in the body are working
- Find, diagnose and stage many disorders, including cancer
- Plan treatment, including surgery and radiotherapy
- Evaluate the effectiveness of treatment and exclude recurrence
What preparation is required?
Perfect preparation prior to PET-CT prevents poor performance. There are several important things to consider prior to undergoing a PET-CT scan. Our staff will assist you with this in the days before the scan as well as on the day of the scan.
- Tell our staff if you think you may be pregnant or are breast feeding
- Tell us if you have kidney failure or have diabetes (insulin dependent or non-insulin dependent)
- Tell us if you have had a previous adverse reaction to intravenous contrast (for CT scans)
- Let us know if you are severely claustrophobic – we can make things much easier for you
- Let us know what medications you are on and what allergies you may have
- Ideally, we need to know accurate dates of your most recent therapies (including surgery, radiotherapy, and chemotherapy).
Please confirm the time and date of your scan. The calculated dose of 18-FDG is based upon a specific time of injection, and this will rapidly decay after it is produced. We have an outstanding PET-CT scanner which can detect even the lowest levels of radioactivity but its best to scan your body 60 minutes after an optimised injected dose, based upon your body weight. If you’re really late for your appointment, it could potentially affect scan results. Please bring all relevant imaging that you’ve had performed elsewhere (ideally on CD). This can be uploaded onto our system for comparison. All prior imaging at South East Radiology will be electronically available to our radiologists. Also, refrain from strenuous exercise (including jogging, swimming, cycling) for 24 hrs prior to your scan.
On the day of your scan, don’t eat or drink anything 6 hours prior to your scan. Drinking water is ok up until 30 minute prior to the scan. If your scan is at 11am, perhaps a small 4:30am snack could be an idea. Don’t chew gum or suck on lollies for 1 hour prior to your scan. If you’re a diabetic, we will give you more specific information over the phone on how to optimise your glucose levels for best results. The use of insulin just prior to the scan will usually make for a very difficult scan interpretation.
What happens during your PET scan?
Our friendly staff will welcome you to our PET-CT imaging centre, and a cannula will be placed into one of your veins. At this time, you’ll have plenty of time to ask last minute questions. You’ll be guided to one of our uptake rooms, and the 18F-FDG will be administered. You get to sit comfortably in one of our recliner chairs for the next 60 minutes, and during this time, it is very important that you completely relax your body with no movement, no reading, no speaking, no eating/drinking. After 60 minutes, we will take you across the corridor to our PET-CT scanner and image your body for the next 30-40 minutes. The table is very comfortable and will slowly move you through the scanner. It is very important that you lie as still as possible. Then, you can head home. Our technicians will prepare the images for the radiologist, who will interpret the scans and provide a report for you and your treating doctor. This will be delivered in the 1-2 days after your scan.
How long will the scan take?
You’ll need to arrive 45 minutes prior to your injection time. Once injected with the radioactive peptides, there is a 60 minutes uptake phase which allows the radiotracer to access all cells in your body. The scan itself takes 30-40 minutes depending on what type of scan you are having. So, you can plan to be with us for around 2 hours. Our friendly South East Radiology Customer Service team will advise you of how long the appointment is scheduled for at the time of booking.
What is the radiation dose?
The risk of treatment is always weighed against the potential benefits for all radiology and nuclear medicine procedures. South East Radiology uses the latest generation of PET-CT scanner which is able to accurately detect the smallest doses of radioactivity. Thus, we can keep the administered radiation dose to a minimum. This radioactivity will clear your body within 24 hours.
18F-FDG has a half-life of just under 2 hours, which means that 8 hours after injection, more than 90% of the activity has disappeared. Typically, a patient will receive 5mSv from the radiotracer and approximately 9mSv from the CT component of the test. A total dose of 14mSv is a very safe level of radiation exposure, even if multiple scans are required over a period of time.
How much will the PET scan cost?
South East Radiology bulk bills all Medicare eligible PET-CT scans, but this requires a referral by a specialist doctor. A referral received from a general practitioner or another non-specialist health care provider will incur a gap payment. Some cancers and inflammatory disorders are not covered by a Medicare rebate, even if referred by a specialist, and these referrals will also incur a gap payment. For further clarification on expected costs associated with your examination, please call one of our friendly South East Radiology staff.
When can I get my results?
Images obtained from your scan are digitally recorded. At South East Radiology, a subspecialty trained Radiologist interprets the images obtained and provides a report for your doctor within 24 hours.
As soon as you are assisted off the scanner, our PET-CT technician will begin creating the images and uploading them onto our private electronic database. Our highly trained subspecialist PET Radiologists will interpret the images, produce a report, and send it to your referring doctor.
Our Radiologists have very close working relationships with many of the referring doctors and will contact them urgently when appropriate. Reports and images will be available electronically via the South East Radiology MyResults Patient Access app and web portal 7 days after your report has been processed. If required, films are available for collection or delivery to your referring practitioner.