Medical Imaging: Molecular Imaging and Theranostics (Nuclear Medicine, PET/CT) - What To Expect

Before your PET/CT scan

  • tell your doctor if you are pregnant or might be pregnant
  • you may be asked to sign a consent form authorizing this procedure. Use this opportunity to ask any questions you may have about the need for this test or how it will be done.
  • depending on the part of the body being examined, you may be asked to undress and put on a hospital gown. Please wear loose-fitting, comfortable clothing and no jewelry or other metallic objects.
  • do not drink a lot of fluid before the test as you will have to lie still for an extended period of time. For your own comfort, you should empty your bladder before the test begins.

Depending on the PET/CT scan you are having, you will receive specific instructions with your appointment notice. You may be asked to:

  • not smoke or drink any beverages containing alcohol or caffeine for 24 hours before the test
  • stop taking any medications for 24 hours before the test. If you take insulin to control diabetes, you should take your insulin before your test.
  • avoid eating or drinking for 8 to 12 hours before the test
  • if you are having a PET/CT scan of your abdomen, you may need to take a laxative the evening before the test and possibly have an enema the morning of the test. However, this is rare.

What will happen during my appointment?

Depending on the imaging you are having done, the radioactive materials required for imaging will be injected or you will take it by mouth.

You may feel nothing at all from the needle when the tracer is injected, or you may feel a brief sting or pinch as the needle goes through the skin. It will take anywhere from a few minutes to several hours for the radioactive material to accumulate in the areas of your body being scanned. After the appropriate interval, you will be asked to lie on the exam table for your imaging to begin. The scanning procedure itself is painless.

The time required for the actual scan will vary from several minutes up to an hour. You will need to lie absolutely still during the imaging test. 

You may be uncomfortable lying still for an extended period of time on the table during the scan and you may feel claustrophobic when you are placed in the scanner.  The care team can help support you. 

How long will my appointment take?

The length of your appointment will depend on the type of imaging being done.  You should plan on your appointment taking most of the day. You may also be asked to return for additional pictures on the same day or on a different day. This information will be given to you when you make your appointment. 

Is it safe to nurse my baby after the exam?

It is best to stop nursing for a period of time after your exam. The technologist or radiologist will let you know how long you should stop. The recommendation is usually to stop for 24-hours or longer depending on the radiopharmaceutical used for your test. It is important to inform the technologist if you are breast-feeding.

Can I have a molecular imaging and theranostics study if I am pregnant?

Generally, molecular imaging and theranostics (nuclear medicine) studies are not recommended for pregnant women. Some molecular imaging and theranostics studies can be safely performed during pregnancy when medically indicated and with no risk to the fetus, such as lung scans for pulmonary embolus.  You and your doctor must decide if the information gained from having the test is of more benefit versus the potential effect on your unborn child.