What Is a PET Scan? - Definition, Uses & Side Effects

Instructor: Virginia Rawls

Virginia has a master' degree in Education and a bachelors in Sports Medicine/athletic Training

Have you ever wondered how doctors are able to diagnose diseases of the internal organs? How are they able to see what the organs look like? A PET scan is a diagnostic procedure that allows doctors to see if your organs are functioning like they should be. This lesson discusses what a PET scan is, why it is used and potential side effects of having this procedure done.

What Is a PET Scan?

A PET scan is an imaging test that shows how well your tissues and organs are working, especially metabolism, oxygen use, and blood flow to the organs. PET stands for positron emission tomography. The picture below shows what a PET scan machine looks like.

PET scan machine

This type of scan requires that a small amount of radiation be delivered into the patient's bloodstream through an IV (intravenous) catheter. This radioactive material is called a tracer. Once the tracer has time to work through the body, the patient will be taken back to the scanning machine to have the procedure done.

The PET scan itself is a large machine that looks like a tunnel. The patient lies on a hard table that will move their body into the tunnel. Once the body enters the tunnel, the PET reads signals sent from the tracer. The machine changes these signals into 3D pictures. These pictures are read by a radiologist, a doctor who specializes in the study and diagnosis of disease and conditions through radiology images or pictures. This rotating picture shows what a PET scan looks like.

PET scan

The tracer will only be active in the body for two to ten hours after it was injected. The radiation will eventually lose potency and will leave the body in your urine. Patients are advised to drink plenty of water after the procedure to help speed up this process.

Why Is a PET Scan Performed?

Since PET scans can show how your internal organs are working, it is a great test to look for diseases and functionality of the organs. These include:

  • Cancer, including detection, showing whether cancer treatments have been effective, and if cancer has returned
  • Brain disorders, such as tumors, seizures, and Alzheimer's disease
  • Heart disease, including weakened heart muscles, blockages, and decreased blood flow
  • Detection of abnormalities or masses throughout the whole body

What Will the Patient Experience?

Your doctor will give you specific instructions on how to prepare before a PET scan, but there are some general guidelines to follow. Most patients are advised to not eat or drink four to six hours before the scan. Eating or drinking can give misleading information about metabolism in the organs and give false positives or negatives.

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