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Radiology Services


What is PET/CT?
Positron emission tomography (PET) and computed tomography (CT) are imaging tools that allow physicians to diagnose and pinpoint the location of cancer within the body before making treatment recommendations. The highly sensitive PET scan picks up actively growing cancer cells, and the CT scan provides a detailed picture of the inside of your body to reveal the size and shape of abnormal cancerous growths.

At this time, PET/CT is most often used in cancer diagnosis and staging. However, PET/CT can provide important information about some neurological conditions, including Alzheimer's disease, dementia, and refractory seizures.

Why do I need this scan?
A PET/CT scan not only helps your physician diagnose the problem, it also helps predict the likely outcome of various therapeutic alternatives, identify the best approach for treatment and monitor your progress. If the cancer is not responding to treatment, your physician may immediately switch to a different therapy.

What should I expect when I arrive?

  • Please arrive 15 minutes early; we will register you and review your medical history and any past exams.
  • Before the scan, a blood sugar test will be administered using a relatively painless skin stick.
  • For the PET portion of the scan, you will receive an injection of a small dose of radioactive glucose (sugar) called FDG. FDG is safe and will lose its radioactivity very quickly.
  • For most studies, you will have to wait an hour for the FDG to distribute itself. During this time, you will be asked to relax in a quiet area and refrain from talking.

What should I expect during the scan?

  • The PET/CT scan should last between 25 and 45 minutes. Typically, you will be at the facility for at least two hours.
  • You will lie on a comfortable, padded table. The table will move slowly through the donut-shaped PET/CT scanner as it acquires the information needed to generate diagnostic pictures.
  • You will be asked to lie very still and breathe normally during the scan because movement can interfere with the results.
  • A technologist will monitor you during the exam and answer your questions.

What happens after the scan?

  • You may leave as soon as the scan is complete.
  • Unless you have received special instructions, you will be able to eat and drink immediately. Drinking lots of fluids soon after the scan will help remove any of the FDG that may still be in your system.
  • When the scan is complete, a radiologist (a specially-trained medical imaging physician) will review your pictures. Your physician will receive a report detailing the findings of your scan and will follow up with you.

Preparing for the scan
Our goal is to provide you the best possible medical care for you and your family. Please take a few minutes to read this general information on PET/CT to help you understand and prepare for your scan.


Please follow these instructions:

  • It is very important to arrive on time due to the short time the FDG can be used.
  • Please bring with you all of your previous films/radiology studies (i.e., CT, MRI, bone scan, ultrasound or PET) with you, if not performed at St. Luke's Hospital or CDI.
  • Restrain from strenuous exercise 24 hours before your scan.
  • Drink plenty of fluids the day before your scan; try to drink 48 ounces or six full glasses of fluid.
  • Do not eat or drink anything except for water for six hours before your scan. Also, please do not chew gum.
  • Continue to take your medications, with water, unless instructed not to do so by your physician.
  • If you are diabetic, inform your physician who may give you special instructions to prepare for your scan.
  • Feel free to bring CDs or a cassette tape of relaxing music to listen to during your scan.
  • Wear comfortable clothing.
  • Let us know, prior to your scan, if you might be pregnant or are currently breastfeeding.

Safety of PET/CT scans
Be assured that PET/CT scans are a safe and effective diagnostic procedure. The FDG used in the PET will not remain in your system long, so there is no reason to avoid interacting with other people once you leave the center.

If you have any additional questions, please call and ask for a technologist at St. Luke's Hospital at 314-205-6518 or St. Luke's Center for Diagnostic Imaging (CDI) at 636-519-7865.