Site Map

PET scan

Positron emission tomography; Tumor imaging - PET; PET/CT

A positron emission tomography (PET) scan is a type of imaging test. It uses a radioactive substance called a tracer to look for disease in the body.

A PET scan shows how organs and tissues are working.

I Would Like to Learn About:

How the Test is Performed

A PET scan uses a small amount of radioactive tracer. The tracer is given through a vein (IV). The needle is most often inserted on the inside of your elbow. The tracer travels through your blood and collects in organs and tissues. This helps the radiologist see certain areas more clearly.

You will need to wait as the tracer is absorbed by your body. This takes about 1 hour.

Then, you will lie on a narrow table that slides into a large tunnel-shaped scanner. The PET detects signals from the tracer. A computer changes the signals into 3D pictures. The images are displayed on a monitor for your health care provider to read.

You must lie still during the test. Too much movement can blur images and cause errors.

How long the test takes depends on what part of the body is being scanned.

How to Prepare for the Test

You may be asked not to eat anything for 4 to 6 hours before the scan. You will be able to drink water but no other beverages including coffee. If you have diabetes, your provider will tell you not to take your diabetes medicine before the test. These medicines will interfere with the results.

Tell your provider if:

Always tell your provider about the medicines you are taking. Let your provider know about the medicines you bought without a prescription. Sometimes, medicines may interfere with the test results.

How the Test will Feel

You may feel a sharp sting when the needle with the tracer is placed into your vein.

A PET scan causes no pain. The table may be hard or cold, but you can request a blanket or pillow.

An intercom in the room allows you to speak to someone at any time.

There is no recovery time, unless you were given a medicine to relax.

Why the Test is Performed

The most common use for a PET scan is for cancer, when it may be done:

This test can also be used to:

Normal Results

A normal result means there were no problems seen in the size, shape, or position of an organ. There are no areas in which the tracer has abnormally collected.

What Abnormal Results Mean

Abnormal results depend on the part of the body being studied. Abnormal results may be due to:

Risks

The amount of radiation used in a PET scan is about the same amount as used in most CT scans. These scans use short-lived tracers, so the radiation is gone from your body in about 2 to 10 hours. Having many x-rays, CT or PET scans over time may increase your risk for cancer. However, the risk from any one scan is small. You and your provider should weigh this risk against the benefits of getting a correct diagnosis for a medical problem.

Tell your provider before having this test if you are pregnant or breastfeeding. Infants and babies developing in the womb are more sensitive to radiation because their organs are still growing.

Rarely, people may have an allergic reaction to the tracer material. Some people have pain, redness, or swelling at the injection site.

Considerations

It is possible to have false results on a PET scan. Blood sugar or insulin levels may affect the test results in people with diabetes.

Most PET scans are now performed along with a CT scan. This combination scan is called a PET/CT. This helps find the exact location of the tumor.

Related Information

PET scan
Bone scan
Nuclear ventriculography
Pulmonary ventilation/perfusion scan
Thyroid scan
Lung gallium scan
Renal scan
Cancer
Abscess
Arthritis
Broken bone
Acute
Blood clots
Cyst
Anaplastic thyroid cancer
Autonomic neuropathy
Gastroparesis
Huntington disease
Hydronephrosis of one kidney

References

Deroose CM, Dooms C. Positron emission tomography. In: Broaddus VC, Ernst JD, King TE, et al, eds. Murray & Nadel's Textbook of Respiratory Medicine. 7th ed. Philadelphia, PA: Elsevier; 2022:chap 25.

Glaudemans AWJM, Israel O, Slart RHJA, Ben-Haim S, Slart RHJA. Vascular PET/CT and SPECT/CT. In: Sidawy AN, Perler BA, eds. Rutherford's Vascular Surgery and Endovascular Therapy. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 31.

Herholz K, Teipel S, Hellwig S, et al. Functional and molecular neuroimaging. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 42.

Nair A, Barnett JL, Semple TR. Current status of thoracic imaging. In: Adam A, Dixon AK, Gillard JH, Schaefer-Prokop CM, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 1.

BACK TO TOP

Review Date: 7/5/2022  

Reviewed By: Jason Levy, MD, FSIR, Northside Radiology Associates, Atlanta, GA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

ADAM Quality Logo
Health Content Provider
06/01/2025

A.D.A.M., Inc. is accredited by URAC, for Health Content Provider (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics. This site complied with the HONcode standard for trustworthy health information from 1995 to 2022, after which HON (Health On the Net, a not-for-profit organization that promoted transparent and reliable health information online) was discontinued.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- 2024 A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

A.D.A.M. content is best viewed in IE9 or above, Firefox and Google Chrome browser.