What is a PET scan?

Positron emission tomography (also called PET imaging or a PET scan) is a way to gather medical information that would otherwise require surgery or more expensive diagnostic tests. PET scan imaging acquires images based on the detection of radiation emitted from a radioactive solution administered before the scan. PET scan images are used to evaluate and treat a variety of diseases.

When is a PET scan used?

PET scans are used most often to detect cancer and to see how well cancer therapy is working. These scans can be performed on the whole body using a PET scan machine.

PET scans of the brain are used as part of PET diagnostic imaging to evaluate patients who have memory disorders of an undetermined cause, suspected or proven brain tumors, or seizure disorders that are not responsive to medical therapy and may be helped by surgery.

When used to evaluate the heart, PET scans show details about blood supply and oxygen use.

What does a PET scan show?

PET scans show how your body is working on a molecular and cellular level. Different colors or degrees of brightness on a PET image represent different levels of tissue or organ function.

For example, cancer cells absorb more of the radioactive substance than healthy cells. So if a tumor doesn't absorb more radioactivity than surrounding cells, it's a sign that it may not be cancerous or that chemotherapy has worked to remove the cancer.

In the heart, PET scans can identify where there is decreased blood flow and determine where there is healthy heart muscle or damaged heart muscle.

What's a CT scan vs. a PET scan?

CT scans provide X-ray images that can tell the size of organs or size and location of tumors. PET scans provide information on a molecular and cellular level to help doctors see changes on a smaller scale. It's kind of like the difference between examining a tumor by looking at it during a surgery vs. extracting DNA from one of the tumor's cells to see if it has any mutations. Both tests are valuable. They just look at different details.

How do I prepare for a PET scan?

PET is usually done on an outpatient basis. Your doctor will give you detailed instructions for PET scan prep. You should wear comfortable, loose-fitting clothes. You should not eat for four hours before the scan. You'll be encouraged to drink water. Your doctor will instruct you regarding the use of medications before the test.

Note: Diabetic patients should ask for any specific diet guidelines regarding their PET scan preparation to control glucose levels during the day of the test. Don't take your diabetic medication before the PET scan procedure.

Please bring your physician's orders, insurance card and picture I.D. with you on the day of the exam. Family members are invited to stay in our waiting area for the duration of your PET scan procedure.

How is a PET scan performed?

A technologist will take you into a special injection room. In this room, blood will be drawn to check your glucose levels. A radioactive substance will be administered through a vein. The wait time before your scan is approximately 30 to 90 minutes. During this time, you'll be asked to rest quietly and avoid significant movement or talking.

Usually, there are no restrictions after the test, although you should drink plenty of fluids to flush the radioactive substance from your body.

What can I expect during the PET scan?

The administration of the radioactive substance will feel like a slight pinprick when given by intravenous injection. You won't feel anything related to the radioactive substance in your body.

You'll then be made as comfortable as possible before you are positioned in the PET scanner for the test. We'll ask you to remain still for the duration of the examination.

Patients who are claustrophobic may feel some anxiety while positioned in the scanner. While you'll be alone in the exam room, the technologist will be able to see you and communicate with you throughout the exam.

If you have difficulty lying down or remaining still because of pain, talk to your physician about medication to help you relax during the exam. It's important to remain as still as possible during the PET exam because any movement will affect the quality of the image produced.

When can I expect results of my PET scan?

After the PET scan procedure is complete, a nuclear medicine physician will study the pictures along with your medical history to make an assessment of what the photos show. They'll prepare a report that will be forwarded to your physician within three business days. If results are needed sooner, your doctor may contact the nuclear medicine physician on the day of the exam.

Can I schedule my PET scan with a CT scan?

Yes, a PET scan and CT scan can be done in the same appointment and they're often done together. A combined study with CT and PET will take about two hours.

How long does a PET scan take?

A PET scan usually takes about 30 minutes, but it can take up to 60 minutes for your body to absorb the injected radioactive substance. During this time, you'll need to sit quietly and limit your movements. You can expect to be in the PET imaging department for between two and three hours.