Don't drink caffeine for 24 hours before a PET scan of your heart. Don't do any exercise or other strenuous activity for at least 48 hours before this test. Tell your doctor if: you have diabetes.
Avoid exercising 24 hours before the scan. Follow a special diet for 12 to 24 hours before the scan. Don't drink or eat anything, except water, for 6 hours before the scan.
Can I brush my teeth before a PET/CT scan? Normal brushing without swallowing mouthwash or toothpaste within the four hour preparation timeframe will have no effect on the outcome of your PET/CT scan.
Do not eat or drink anything, except water, for 6 hours before the exam. You may drink water, as much water as you can would be helpful, until arrival. Routine medications may be taken, unless you have been instructed otherwise.
The radioactive tracer gives off very small levels of radiation that go away very quickly. As a precaution, you should avoid close contact with pregnant women, babies and young children for 6 hours after the scan. You need someone to take you home and stay overnight if you've had medicine to help you relax (sedative).
If you're having a brain PET-CT, it is important to limit brain activity before your scan. Your nurse may tell you not to read or listen to music while you're waiting for your scan. Your care team will ask you to urinate (pee) just before your scan.
We prefer that you avoid anything with caffeine (coffee, tea, chocolate, or soda) within 24 hours of the test. Caffeine alters the distribution of the radiopharmaceutical throughout your body, specifically to your heart.
24 HOURS PRIOR TO TEST: No strenuous exercise. No alcohol, nicotine, caffeine, coffee or tea.
During the procedure
It takes about 30 minutes to complete a PET-CT scan and 45 minutes for a PET-MRI scan. The machine makes buzzing and clicking sounds. The test is painless. If you're afraid of enclosed spaces, you may feel some anxiety while in the scanner.
The radioisotope that is used in PET imaging, fluorine 18 fluorodeoxyglucose or 18F-FDG, is a glucose transporter. This radioisotope will go to any metabolically active areas in the body. If the glucose levels are elevated from food or drink the patient consumed prior to the test, the level of insulin will increase.
You should have nothing to eat or drink except water for at least 4 hours before your appointment time. This includes chewing gum, hard candy, breath mints and tobacco products.
Recommended foods:
Vegetables: you may eat low-carbohydrate vegetables such as asparagus, cabbage, cauliflower, celery, chilies, cucumbers, green or wax beans, green peppers, lettuce, mushrooms, olives, onion, tomatoes, summer squash, spinach and turnips.
Complications of a PET scan
The injected radioactive chemicals have a very short lifespan and are removed from the body fairly quickly. Sometimes, you will be advised to avoid close contact with babies or pregnant women in the few hours after your scan.
Then, the patient will be asked to lie on a table that passes slowly through the scanner. The scanner resembles a CT scanner, but has a much larger opening. Some people fall asleep during the scan.
Though most cancers are picked up on PET CT, there are a few which do not. The most important of these would be cancer of stomach (signet cell type). In such cases performing this test would be waste. However, there are cancers which are very sensitively detected which include lymphoma, GIST, etc.
PET-CT Precautions
If undergoing a combination PET-CT scan, the iodine-based contrast dye used for the CT component can cause side effects, including nausea, vomiting, headache, itching, flushing, and mild rash. In rare cases, a serious, all-body allergic reaction known as anaphylaxis may occur.
After the PET-CT scan
You can do normal activities after the scan. This includes driving. The staff will tell you to drink several glasses of water. This helps wash the radioactive substance and dye out of your body.
As a precaution, you may be advised to avoid prolonged close contact with pregnant women, babies or young children for a few hours after a PET scan, as you will be slightly radioactive during this time.
You may be asked to drink water before a CT urogram and not to urinate until after the procedure. This expands your bladder.
The major drawback to standard PET is that the images are of substantially lower resolution than, for example, those of CT and MRI, and PET is generally poor at delineating anatomic detail.