PET/CT

At Columbia Radiology, we perform and interpret more than 4,000 PET/CT scans each year, providing expert diagnosis of common and rare diseases. We offer state-of-the-art exams at our PET Center in northern Manhattan and our midtown Manhattan location, interpreted by our board-certified radiologists for expert results. We know that a PET/CT scan can be stressful, and our staff of nurses and technologists will make sure you are as comfortable as possible while you are with us. 

What is a PET scan?

A positron emission tomography (PET) scan allows doctors to evaluate how well your organs and tissues are working. A safe radioactive chemical called a radiotracer is injected into your body before the imaging test. A PET scanner then detects cells that absorb large amounts of the radiotracer, which indicates a possible health problem.

You may be referred for a PET scan to check for signs of:

  • cancer, including breast cancer, prostate cancer, thyroid cancer, and others.
  • heart problems, such as coronary artery disease or a heart attack.
  • brain disorders, such as brain tumors, Alzheimer's disease, and seizures.

PET scans are combined with computed tomography (CT) in a dual-purpose PET/CT imaging device. PET/CT scans provide information that is often unattainable with other imaging procedures.

Why do I need a PET/CT scan?

PET/CT scans are most commonly used to:

  • detect early onset of diseases.
  • check whether a cancer treatment is working.
  • gauge whether cancer has spread or recurred.
  • evaluate vital functions, such as blood flow, oxygen use, and blood sugar (glucose) metabolism.

How does a PET/CT scan work?

Before the exam, you receive an intravenous (IV) injection of a radioactive drug called a radiotracer. Diseased cells in your body absorb more of the radiotracer than healthy ones do. The PET scanner detects the radiation in your body and produces images of the affected tissue. A PET/CT scan combines X-ray images from a CT scan with PET scan images to show both the structure and function of organs and tissues.

How do I prepare for the exam? 

Preparation For Scans Using 18F-FDG

  • Do not eat anything for six hours before you arrive for your scan.
  • Drink only water, preferably between 32 and 64 oz. two hours prior to your appointment.
  • Do not chew gum or suck on hard candy, mints, or cough drops.
  • If you take medications, take them with water only.
  • Don't exercise for 24 hours before your PET scan.
  • Please bring copies of previous diagnostic scans with you on the day or your PET scan, unless your previous tests were done at Columbia.

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 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.

Information for 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) or 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 four hours prior to the appointment.
  • You can have breakfast after the study and switch on continuous insulin infusion.

Preparation For Scans Using 18-F NaF, F-18 beta amyloid imaging (18F-florbetapir, 18F-flutemetamol, 18F-florbetaben)

  • Please drink water, preferably between 32 adn 64 oz. two hours prior to your appointment.
  • Please bring copies of previous diagnostic scans with you on the day or your PET scan, unless your previous tests were done at Columbia.
  • No other preparation is required.

Preparation For Scans Using 18-F fluciclovine

  • Do not to eat or drink for at least four hours (other than small amounts of water for taking medications) before you arrive for your scan.
  • Please bring copies of previous diagnostic scans with you on the day or your PET scan, unless your previous tests were done at Columbia.
  • No other preparation is required.

Preparation For Scans Using Ga-68 dotatate

  • Please consult with your physician if you are receiving octreotide therapy.
  • Please drink water, preferably between 32 and 64 oz. two hours prior to your appointment.
  • Please bring copies of previous diagnostic scans with you on the day or your PET scan, unless your previous tests were done at Columbia.
  • No other preparation is required.

What will happen during the exam?

  • Depending on your type of scan, your finger may be pricked or blood will be drawn from your arm to measure your blood sugar level. If your level is 200 mg/dL or above, your procedure may need to be rescheduled. Your nurse will speak with you about this.
  • You will be given a radioactive medication called a tracer through an intravenous (IV) line in your arm. Some tracers require you to wait in a room for 40 to 60 minutes.
  • You may need to drink a contrast dye for your scan. This dye helps improve the overall image on a CT scan. You will start drinking the oral contrast 45 to 60 minutes before your scan. This will allow time for the solution to move into your intestines.
  • Please relax and limit your movement during this time and stay warm. You can sleep, listen to music, or watch videos in the area provided for you. However, if you are receiving a brain scan, do not watch videos or listen to music. These activities stimulate certain areas of your brain and may interfere with the results of your scan.
  • When you are ready, you'll lie on a narrow, padded table that slides into the scanner. During the scan you'll need to lie very still so that the images aren't blurred because movement could affect the results of the PET/CT scan.
  • The scan itself will take 20 to 40 minutes. The entire process will take about two hours.

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. But the tracer might:

  • cause an allergic reaction, in rare instances.
  • expose your unborn baby to radiation if you are pregnant.
  • expose your child to radiation if you are breastfeeding.

After the exam

Most people can return to their normal activities immediately after a PET/CT scan. A very small amount of radioactive sugar will remain in your body, so be sure to drink plenty of water to help flush it out your system. Our physicians will review and compare your PET/CT 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/CT findings with you.