Positron Emission Tomography (PET)

Human diseases change how the cells affected by disease behave and interact. These “biochemical” changes are what enable doctors to diagnose certain conditions using an imaging test called positron emission tomography (PET). This powerful non-invasive imaging tool can reveal abnormal molecular activity caused by many forms of cancer and diseases and disorders of the brain and heart. PET can show these changes before they become visible on imaging tests such as CT and MRI, which show structural but not biochemical changes.

PET is a type of “nuclear imaging” test. In this group of imaging procedures, doctors administer to patients small amounts radioactive materials linked to specific, biologically active molecules such as glucose. The biologically active molecules migrate to and accumulate in tumors and other diseased tissues, carrying the radioactive tracer along with them. During the imaging procedure, the scanner detects the location and amount of the radioactive isotope in different areas in the body and can help identify diseases in their earliest stages as well patients’ responses to therapies.

PET is often combined with CT (computed tomography) in a dual-purpose PET-CT imaging device. The scans are done simultaneously and can be viewed separately or as a single, overlapping "fused" PET-CT image. The two individual techniques present different types of information:

  • PET shows metabolic or chemical activity in the body
  • CT shows the body's anatomical structures

A PET scan, for example, highlights a tumor's level of activity such as increased glucose consumption, while a CT scan shows its physical characteristics including size, shape, and precise location.

ColumbiaDoctors radiologists are board certified in nuclear medicine and radiology, performing more than 4,000 PET and PET-CT scans each year at our state-of-the-art PET Center in Northern Manhattan, our 51st Street location, and at our affiliate NewYork-Presbyterian Lawrence Hospital in Bronxville, NY.

Our clinical PET service offers FDG PET/CT for both oncological and neurological indications, NaF PET/CT for prostate cancer, and Amyvid for Alzheimer’s disease. Working collaboratively with physicians at the Irving Cancer Center, we help diagnose, stage, gauge treatment response, and manage a broad range of cancers, including common cancers such as lung and breast to uncommon cancers such as mesothelioma, GIST, and sarcomas.

How do I prepare for the test? 

Download PDF Instructions/Information here.

In order to interpret a PET scan accurately, our radiologists need to compare their findings with the results of your previous diagnostic tests. Please bring copies of the relevant scans with you on the day or your PET scan, unless your previous tests were done at Columbia. 

You should prepare for your PET scan by following the instructions below:

For scans using 18F-FDG:

  • Do not eat anything for 6 hours before you arrive for your scan. You may drink only water.
  • Do not chew gum or suck on hard candy, mints, or cough drops.
  • You may drink only water , preferably 32-64 oz. 2 hours prior to your appointment
  • If you take medications, take them with water only.

Your last meal before the scan should include high protein foods and plenty of water. Avoid carbohydrates and foods with sugar. Because PET scans read your sugar metabolism, eating sugar/carbohydrates could affect the results of your scan.

Stay warm - It is important that you stay warm the day before and the day of your scan. This prevents a special type of fat from becoming active, which can make it hard for the physician to read your PET scan. 

  • In the winter, dress extra warmly. Wear hats, scarves, gloves, and extra layers.
  • In the summer, avoid turning on your air conditioner to very high. You should not feel cold, or have cold hands or feet.

It's also important that you don't exercise for 24 hours before your PET scan. That's because exercise affects the radiotracer's reading and could cause the results to be inaccurate.

Diabetic Patients:

Insulin can affect the results of your scan. Please follow the guidelines below.

  • Type II diabetes mellitus (controlled by oral medication)
    • The study should preferably be performed in the late morning.
    • Continue to take oral medication to control your blood sugar.
  • Type I diabetes mellitus and insulin-dependent type II diabetes mellitus
    • The study should preferably be performed late morning or midday:
      • 6 hours after injection of rapid-acting insulin (Humalog, Novolog, and Apidra) or short acting insulin (regular, novolin, or velosulin).
  • 12 hours after the subcutaneous injection of intermediate-acting (NPH) and/or long-acting insulin, such as Lantus, Toujeo, Basaglar, Levemir, and Tresiba.
    • The study is not recommended on the same day after injection of intermediate-acting (NPH) and/or long-acting insulin
  • For rapid and short acting insulin: Eat a normal breakfast by early morning (around 7.00 a.m.) and inject the normal amount of insulin. Do not consume any more food or fluids, apart from the prescribed amount of water.
  • Patients on continuous insulin infusion
    • The study should be scheduled for early in the morning.
    • The insulin pump should be switched off for at least 4 h prior to the appointment.
    • You can have breakfast after the study and switch on continuous insulin infusion.

For scans using 18-F NaF, F-18 beta amyloid imaging (18F-florbetapir, 18F-flutemetamol, 18F-florbetaben):

  • Please drink water, preferably 32-64 oz. 2 hours prior to your appointment.
  • No other preparation is required.

For scans using 18-F fluciclovine:

  • Do not to eat or drink for at least 4 hours (other than small amounts of water for taking medications) before you arrive for your scan.
  • No other preparation is required.

For scans using Ga-68 dotatate:

  • Please consult with your physician if you are receiving octreotide therapy.
  • Please drink water, preferably 32-64 oz. 2 hours prior to your appointment.
  • No other preparation is required.

What will happen during the test?

Before undergoing a PET scan, you will receive an injection of the radiotracer, which your body will easily absorb and eliminate. You will wait in an exam room for an hour to allow the radiotracer to circulate throughout your body. You will lie on a table that slides slowly through the scanner, a large, ring-shaped device. The PET scanner will detect the tracer and create a color-coded image of your body's chemical function. PET scans typically take about half an hour. (Cardiac cases often take longer.)

Are there any risks?

Doctors have used nuclear medicine procedures to diagnose disease for more than five decades, and there are no known long-term adverse effects of these procedures. The doses of radiotracer used in a PET scan are small, so your radiation exposure is very low compared with the potential benefits.

After the test

Most people can return to their normal activities immediately after a PET scan. Our physicians will review and compare your PET scan with your other imaging tests, and write up a detailed report explaining their findings. We will share this with your referring physician, who will discuss the PET findings with you.