Positron Emission Tomography/Computed Tomography (PET/CT)

Exam Forms

By logging in to Weill Cornell Connect, eCheck-In makes it easy to save time and complete all safety forms required for your upcoming appointment. 

Exam Preparation

Please notify our staff when scheduling and checking in for your appointment if any of the following apply to you:

  • If there is any possibility that you are pregnant.
  • If you are diabetic.
  • If you are allergic to contrast.
  • If you need an interpreter to assist you with your native language

Please plan to stay a minimum of two (2) hours.

What should I wear to my appointment?

Wearing the right clothing may eliminate the need for you to change into a gown prior to your exam. Suggestions for appropriate clothing include:

  • Wear loungewear, pajamas, or loose-fitting cotton or linen clothing without metal embellishment.
  • Do not wear clothing or undergarments with metal fasteners, zippers, hooks, under wires or other metal components.
  • Please leave items such as watches and jewelry at home.

Do I need to fast before my exam?

Yes, for all patients:

  • No food four (4) hours prior to the exam. 
  • Do not chew gum of any kind while fasting.
  • No sugar-containing drinks while fasting. Do not drink sodas, fruit juices, shakes of any kind; No iced tea, coffee or tea if they contain sugar. You may drink water.
  • Diabetic Patients: Blood sugar levels should be under control before arrival for PET scan. If you are on blood sugar medication, please contact us to coordinate medication and diet prior to exam.

What should I bring with me on the day of my appointment?

  • A copy of the prescription for your examination if it was given to you.
  • Your insurance information.
  • A list of your current medications.

What can I expect on the day of my appointment?

Patient verification is an important part of your safety and you will be asked to verify your identification and your exam several times during your appointment. Our check-in staff will review your completed registration forms with you.

For many exams you will not have to change into a gown unless you are wearing something that contains metal (see guidelines above).  Some exams do require that you are in a gown. You will be asked to remove and place your electronic devices, wallet, credit cards, metro card, watch, jewelry, belt, hairpins, eyeglasses, hearing aid, or any removable dental pieces into the provided lockers. It is best to keep valuables at home.

A skilled nurse or technologist will start an intravenous (IV) line will be started in the hand or arm for injection of the radionuclide, which is the medication that allows us to see different body structures and function. After the injection, you will be required to rest comfortably and quietly for approximately one (1) hour in order to allow the radionuclide to concentrate in the organ or tissue. You will not be hazardous to other people, as the radionuclide emits less radiation than a standard x-ray.

How is a PET/CT performed?

  • After the radionuclide has been absorbed for the appropriate length of time, you will be positioned on a padded table inside the scanner.
  • The scanner will move slowly over the body part being studied. During this period, both CT and PET images will be obtained which will later be fused together to provide further detailed information.
  • When the scan has been completed, the IV line will be removed the technologist will escort you outside of the scanning room where you will retrieve your personal belongings and proceed to check-out.
  • Once you leave the imaging center, you may resume normal activities.
Our staff is available to address any questions or concerns that you might have before, during, or after your appointment. Please call (212) 746-6000 if you wish to speak with us.


Health Library

Positron Emission Tomography (PET)

What is Positron Emission Tomography (PET)?

Positron emission tomography (PET) is a type of nuclear medicine procedure that measures metabolic activity of the cells of body tissues. PET is actually a combination of nuclear medicine and biochemical analysis. Used mostly in patients with brain or heart conditions and cancer, PET helps to visualize the biochemical changes taking place in the body, such as the metabolism (the process by which cells change food into energy after food is digested and absorbed into the blood) of the heart muscle.

PET differs from other nuclear medicine examinations in that PET detects metabolism within body tissues, whereas other types of nuclear medicine examinations detect the amount of a radioactive substance collected in body tissue in a certain location to examine the tissue’s function.

Since PET is a type of nuclear medicine procedure, this means that a tiny amount of a radioactive substance, called a radiopharmaceutical (radionuclide or radioactive tracer), is used during the procedure to assist in the examination of the tissue under study. Specifically, PET studies evaluate the metabolism of a particular organ or tissue, so that information about the physiology (functionality) and anatomy (structure) of the organ or tissue is evaluated, as well as its biochemical properties. Thus, PET may detect biochemical changes in an organ or tissue that can identify the onset of a disease process before anatomical changes related to the disease can be seen with other imaging processes such as computed tomography (CT).

PET is most often used by oncologists (physicians specializing in cancer treatment), neurologists and neurosurgeons (physicians specializing in treatment and surgery of the brain and nervous system), and cardiologists (physicians specializing in the treatment of the heart). However, as advances in PET technologies continue, this procedure is beginning to be used more widely in other areas.

PET may also be used in conjunction with other diagnostic tests such as computed tomography (CT) to provide more definitive information about malignant (cancerous) tumors and other lesions. This technology combines PET and CT into one scanner, known as PET/CT. PET/CT shows particular promise in the diagnosis and treatment of certain cancers, evaluating epilepsy, Alzheimer's disease and coronary artery disease.

How does a PET scan work? 

PET works by using a scanning device (a machine with a large hole at its center) to detect positrons (subatomic particles) emitted by a radionuclide in the organ or tissue being examined. The radionuclides used in PET scans are chemical substances such as glucose, carbon, or oxygen used naturally by the particular organ or tissue during its metabolic process. A radioactive substance is attached to the chemical required for the specific tests. For example, in PET scans of the brain, a radioactive substance is applied to glucose (blood sugar) to create a radionuclide called fluorodeoxyglucose (FDG), because the brain uses glucose for its metabolism. FDG is widely used in PET scanning.

Other substances may be used for PET scanning, depending on the purpose of the scan. If blood flow and perfusion of an organ or tissue is of interest, the radionuclide may be a type of radioactive oxygen, carbon, nitrogen, or gallium.

The radionuclide is administered either into a vein through an intravenous (IV) line or inhaled as a gas. Next, the PET scanner slowly moves over the part of the body being examined. Positrons are emitted by the breakdown of the radionuclide. Gamma rays are created during the emission of positrons, and the scanner then detects the gamma rays. A computer analyzes the gamma rays and uses the information to create an image map of the organ or tissue being studied. The amount of the radionuclide collected in the tissue affects how brightly the tissue appears on the image and indicates the level of organ or tissue function.

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