What is a PET scan?

A positron emission tomography (PET) scan produces images of your organs and tissues at work. The test uses a safe injectable radioactive chemical called a radiotracer and a device called a PET scanner. The scanner detects diseased cells that absorb large amounts of the radiotracer, which indicates a potential health problem.

Why do healthcare providers use PET scans?

Your healthcare provider may order a PET scan to check for signs of:

What does a PET scan show?

A PET scan can:

  • Measure vital functions, such as blood flow, oxygen use and blood sugar (glucose) metabolism.
  • Identify organs and tissues that aren’t working as they should.
  • Detect cancerous tumor cells to help gauge cancer spread (metastasis).
  • Evaluate how well a treatment plan is working and help your healthcare provider adjust treatment, if needed.

How is a PET scan different from a CT or MRI scan?

Computed tomography (CT) scans use X-rays. Magnetic resonance imaging (MRI) scans use magnets and radio waves. Both produce still images of organs and body structures.

PET scans use a radioactive tracer to show how an organ is functioning in real time. PET scan images can detect cellular changes in organs and tissues earlier than CT and MRI scans. Your healthcare provider may perform a PET scan and CT scan at the same time (PET-CT). This combination test produces 3D images that allow for a more accurate diagnosis.

Some hospitals now use a hybrid PET/MRI scan. This new technology creates extremely high-contrast images and can primarily be used for diagnosing and monitoring cancers of the soft tissues (brain, head and neck, liver and pelvis).

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy