What is PET-CT scan?
Positron Emission Tomography (PET) is an imaging procedure which detects the activity in your body showing the chemical function of an organ or tissue
The PET-CT scanner is a very specialized medical imaging device which combines in a single gantry system both a Positron Emission Tomography (PET) and an x-ray Computed Tomography (CT). The combination of the two scans has been proven to be extremely sensitive for detecting the early stages of disease and abnormalities, even in the absence of structural change. PET-CT enable both imaging exams to be performed at the same time. The combined PET-CT scans provide images that pinpoint the anatomic locations of abnormal metabolic activity within the body. By combining these two scanning technologies (PET Scan & CT Scan), it allows morphological and functional imaging to be carried out in a single imaging procedure. Small tumours may be found even if they are undetectable by other imaging procedures, which can be a major impact on early health screening and choosing the best treatment option.
18-F Fluorodeoxyglucose (FDG) PET-CT Scan
For this scan, you receive an injection of a small amount of radioactive material in a form of radioactive sugar, which is called a tracer. The tracer flows in your bloodstream and collects in certain tissues or organs. Body cells take in different amounts of the sugar, depending on how fast they are growing. Cancer cells, which grow quickly, are more likely to take up larger amounts of the sugar than normal cells. Then, the PET-CT Scanner detects and makes 3D pictures that show where the tracer collects in the body.
In clinical practice, FDG PET-CT Scan is commonly used in the evaluation and management of many types of cancer, including but not limited to:
- Tumour Diagnosis
- Staging and Restaging
- Treatment Monitoring to access the effectiveness of a treatment plan
- Radiation Therapy Planning
Oncology imaging with PET has recently gained particular importance in the quest to identify new and effective therapies and to understand the role of molecular biomarkers in treating cancer.
How Should I Get Ready for the Scan?
You will be given an appointment and receive specific instructions about some preparations that you must follow strictly before your scan. You should inform your doctor of the following before going for the scan:
- Is there any possibility that you may be pregnant.
- What medications that you are currently taking, including over the counter drugs, vitamins and herbal supplements, recent illnesses and other medical conditions.
- If you are breastfeeding at the time of your scan, you should ask your doctor ordering the exam how to proceed. It may need to pump breast milk ahead of time and keep it on hand for use after PET radio-pharmaceutical and CT contrast material are no longer in your body.
- If you are diabetic and what type of diabetic medications you are on.
- If you have any history of asthma or allergies, especially to contrast material, medications, iodine or seafood.
- If you are claustrophobic.
How Should I Prepare for the Scan?
- No food or drink (other than water) for 6 hours prior to scan (including gum, breath mints, cough drops, alcohol, hard candy or anything that may contain sugar).
- You may drink ONLY water up to the time of your scan. It must be plain, unflavored water, no tea or coffee. Anything other than plain water could alter the results of your scan.
- It is highly recommended that you follow a high protein, low carbohydrate diet for 24 hours prior to your test to increase the quality of your PET/CT images.
- No strenuous exercise 24 hours prior to your scan.
- Take medications as scheduled prior to your scan as long as they are tolerated on an empty stomach.
- Wear warm, loose-fitting clothing; scanning room tends to be quite cool.
- Avoid wearing any metal or jewelleries on the day of your scan.
- Do not bring children or pregnant woman with you on the day.
How is the Scan Performed?
- Register at our front Registration Counter and you will be guided to the PET-CT Centre.
- You will be asked to change into our hospital gown and to keep your belongings in the locker provided.
- Your blood glucose level will be tested to see if the levels are acceptable.
- A thin plastic tube (cannula) or needle will be inserted into your vein to administer the radioactive material (tracer)
- After the administration, you will have to rest for 45 to 60 minutes inside a room in order to get sufficient FDG distribution in your body. During this period, you are advised to rest and minimize your movement as much as possible.
- You will then be asked to drink a cup of water and empty your bladder before commencing the scan.
- You will then be directed to the scanner room and lie on a padded table which moves back and forth through the hole in the scanner.
- You will need to be very still while the scans are done to avoid image blurring.
- You will be closely monitored at all times through a CCTV to ensure your safety and comfort. If you have any discomfort during the scan, you can communicate with the technologist through the mounted intercom.
- Sometimes CT Scan contrast material might be administered into your bloodstream through your IV line. The CT scan with or without contrast will be done first, followed by the PET scan.
- Total scanning time is approximately 25-30 minutes.
After the PET-CT scan
- After the scan, you will have to wait in the rest room until the technologist and physician check the images in case additional images are needed. Occasionally, some delayed scan for a specific part of the body may be needed for better visualization of certain areas of structures.
- If a delayed scan is needed, you may need to wait for another 2-3 hours for the delayed scan to commence.
- The thin plastic tube (cannula) will usually be removed unless you are scheduled for other procedure on the same day.
- You may resume your normal diet and activities after your scan.
- Radio-tracer that has been injected in your body will lose its radioactivity over time. It will be passed out of your body through your urine and stool during the first few hours following the scan.
- To reduce the risk of being exposed to the radioactive material in your urine after the scan, you should put the lid down and flush the toilet right after you use it. Flush the toilet twice and wash your hands thoroughly.
- Avoid close contact with small children and pregnant women for 24 hours following the scan.
- You will need to discuss your scan results with your physician who referred you for the exam according to your appointment.