Getting Ready for Your PET/CT Scan

  • Do not eat or drink except for plain water for 6 hours before your test. No gum or candy.

  • You may take your non-diabetic medicines as long as they do not contain sugar or glucose.

  • If you have been told not to take your medicines on an empty stomach, please do not eat more than 2 or 3 soda crackers within 4-6 hours of your exam.

  • If you have diabetes, do not take your diabetic medicines for 6 hours before your test. Your glucose should be less than 200. Let us know in advance if we need to work with your doctor to find a safe way for you to prepare for the test.

  • If you have an insulin pump, please contact us so we can discuss your prep.

  • If you are afraid of small spaces or pain, your doctor may prescribe medicine to help you relax during your exam. You must then have someone drive you home.

  • No strenuous exercise for 24 hours before your test.

  • Do not wear jewelry or clothing that contains metal.

  • If you are pregnant or breast feeding, please contact us.

  • Please bring your MRI or CT films with you if they were taken at an outside hospital or clinic.

Planning for Your Visit

Plan to spend 2-3 hours here. The length of the actual exam varies.

Reasons for a PET/CT Scan

A CT or MRI scan tells the doctor what an organ looks like or where a tumor is. A PET/CT scan shows how cells and organs in your body are working. A PET/CT scan can measure how much energy a tumor is using. Scar tissue and tumors that have responded to chemo or radiotherapy do not use much energy and are not seen on the PET/CT scan. Cells and tumors that are growing or active use a lot of energy and are seen as a bright area on the PET/CT scan. A PET/CT scan can help tell the difference between these types of cells. It is often able to find cancer that has spread to other parts of the body.


Our PET and CT scanners are combined as one scanner. A PET/CT scanner is a camera that can take pictures of the inside of your body by sensing a radioactive tracer. For most studies, this tracer is a radioactive glucose (sugar). Before your PET/CT scan, we will inject you with a small amount of the tracer. Cells in the body absorb glucose at different rates. The PET/CT scan can measure how much of this glucose is being used. This reflects how active the cells are. A PET/CT scan may find disease before it shows up on other tests. It can tell doctors how a disease responds to treatment.

When a PET/CT May Be Used

  • Epilepsy: to show where the seizures are coming from.

  • Alzheimer’s disease: to show areas of reduced activity.

  • Parkinson’s disease: to show areas of reduced function.

  • Brain tumors: to see if recurrent tumor is present.

  • Cancer: to show active areas for staging.

  • Heart problems: to show blood flow and metabolism.

What to Expect During the Scan

We will inject you with a tracer. The time between the injection and the scan depends on how long it takes the tracer to get to the part of your body being scanned. Most often, this will be 45 minutes to an hour. If you are having a heart study, you may not need to wait at all. While you wait, you may not read, talk or listen to music. For some exams we may ask you to wait in a quiet dimly lit room to keep your brain less active.

You will lie on a table that moves slowly through the ring-like scanner. You must lie very still because movement can affect the test. You should feel normal during the test. The CT scan part is first and takes about 5 minutes. The PET scan part is second and takes about 35 minutes. The total exam time from injection through scan can take 30 minutes to 2 hours.


After the Scan

You may leave right after the scan is done. You can eat and drink right away unless you have been told not to. Drink a lot of fluids the day of the test to help clear the tracer from your system.


The radiation you receive from a PET/CT scan is about the same as what you would get from a bone scan. The tracer does not stay in your body for very long. You do not need to avoid being around other people. But, to be extra safe, avoid being around infants or pregnant women for a couple of hours after the scan.

When to Call

Call if you have any questions about these instructions or about the PET/CT.

Who to Call

Monday through Friday, 8 am – 4 pm