What is A PET/CT Scan?
PET/CT combines the functional information from a Positron Emission Tomography (PET) exam with anatomical information from a Computed Tomography (CT) exam in one single exam.
A PET scan detects changes in cellular function specifically, how your cells are utilizing nutrients like sugar and oxygen. Since these functional changes take place before physical changes occur, PET can provide information that enables your physician to make an early diagnosis.
The advantage of CT is its ability to take cross-sectional images of your body. These are combined with the information from the PET scan to provide more anatomic details of the metabolic changes in your body.
The PET exam pinpoints metabolic activity in cells and the CT exam provides an anatomical reference. When these two scans are fused together, your physician can view metabolic changes in the proper anatomical context of your body.
- No food 6 hours prior to study.
- May have water only, right up to time of exam but no other liquids allowed
- Wear warm, loose fitting clothing with as little metal as possible (sweat suits are ideal).
- Rings and watches are okay but other jewelry and piercings need to be removed.
- No exercise or repetitive/vigorous activity 24 hours prior to exam. This includes yard work, sports, hunting, etc.
- You may take regularly scheduled medications if able to tolerate on an empty stomach.
- To get best results, completely avoid sugar, chewing gum (even sugarless) and caffeine the day of the exam and limit sweets and starches for 24 hours (NO sugar, potatoes, bread, rice, pasta).
- Must be able to lie flat on back for at least 20 minutes (A melanoma patient may be required to lie on his/her back for 30 minutes)
- Day prior to exam follow low-carb, high-protein diet (see reverse side for sample diet).
- No strenuous activity for 24 hours prior to exam.
- The day of exam: No food, caffeine or chewing gum even sugarless) 4-6 hours prior to exam.
- Water ONLY 4-6 hours prior to exam.
- Take medications as usual morning of exam.
- Goal is blood sugar level less than 200 at time of exam.
- Day prior avoid sweets and starches (see reverse side of form for sample diet).
- Day prior avoid strenuous activity.
- MUST have light, low-carb meal 4-6 hours prior to exam.
- Take insulin with meal at least 4 hours prior to exam.
- May have water ONLY right up to exam.
- No food, caffeine or gum (including sugarless) until after exam.
- If using an insulin pump, PET/CT technologist will consult with you for best protocol.
- Note: Other factors affecting PET/CT Scans: No oral barium contrast studies within 48 hours of PET/CT (i.e. CT with oral contrast, UGI, video swallow)
- Eggs any style, sausage or bacon, low-fat plain yogurt (without fruit)
- Scrambled eggs, bacon, tomato juice
- Cheese omelet with chopped bacon and mushrooms, milk (fat-free or 1%)
- Grilled chicken salad or chicken Caesar salad (without croutons), Cobb or Greek salad
- Grilled hamburger steak (no bun), sliced cucumbers or tomatoes
- Sliced grilled chicken breast on romaine with balsamic vinaigrette
- Grilled/broiled salmon, steamed asparagus, tossed salad (mixed greens, cucumbers, green peppers, cherry tomatoes); use only balsamic vinaigrette dressing
- Baked chicken/Cornish hen, steamed broccoli or asparagus, mashed cauliflower, oven-roasted vegetables
- Grilled sirloin, steamed spinach or green beans, roasted eggplant
- Crystal Light
- Caffeine-free, sugar-free soda
- Club soda
- V-8 juice or similar vegetable juice
- Milk (fat-free or 1%)
- Turkey roll-ups
- Hummus and celery
- Mixed nuts
- Hard-boiled eggs
Drinks to Avoid
- Coffee or tea, including decaf
- Alcoholic beverages (including beer)
- Fruit juices
- Caffeinated sodas
Foods to Avoid
- Chewing gum
- Fresh fruit
- Grains (white rice)
- Hard candies
Frequently Asked Questions
Your PET/CT exam results may have a major impact on your diagnosis, and course of treatment selected by your physician.
A PET/CT study not only helps your physician diagnose a problem, but it also helps your physician predict the likely outcome of various therapeutic alternatives, pinpoint the best approach to treatment, and monitor your progress. If you are not responding as well as expected, you may be switched to alternative therapy.
Ask your physician what he or she hopes to learn from your PET/CT exam.
When you arrive, we will review your history and any past exams.
For the PET portion of the exam, you will receive an injection of radioactive material similar to what is used for bone scans and other nuclear medicine exams. This is a radioactive tracer that must pass multiple quality control measures before it is used for any patient injection. PET radiopharmaceuticals lose their radioactivity very quickly (two hours) and only very small amounts are injected. In all cases, the majority of radioactivity will be eliminated from the body approximately 6 hours after injection.
After Your injection, you will be asked to wait in our injection suite for one hour while the radiopharmaceutical distributes. During this time you will be asked to relax.
During the exam, you will lie very still on a comfortable table that will move slowly through the scanner as it acquires the information needed to generate diagnostic images.
The PET/CT scan should last between 20 and 45 minutes. The exam can vary depending on what we are looking for and what we discover along the way. Plan to spend two to three hours with us.
You may return to the designated area as soon as the exam is complete. Unless you’ve received special instructions, you will be able to eat and drink immediately. Drinking lots of fluids soon after the exam will help remove any of the radiopharmaceuticals that may still be in your system.
In the meantime, we’ll begin preparing the results for review by our interpreting physician, and then by your physician, who will tell you what we’ve learned.
Be assured that PET/CT exams are a safe and effective diagnostic procedure. The radiopharmaceuticals used in PET do not remain in your system long, so there’s no reason to avoid interacting with other people once you’ve left. To be extra safe, wait for a few hours before getting too close to an infant or anyone who is pregnant.