Radiology

PET Scans

At Mount Sinai, we use nuclear medicine imaging called positron emission testing (PET) scans for diagnosis. This noninvasive and painless scan helps us develop a treatment plan. PET scans use a small amount of radioactive tracer that is injected into your vein. Tracers give off radiation in the form of gamma rays, which a special camera called a PET camera uses to create images of your internal organs. The PET camera does not give off radiation. The test is especially helpful in evaluating:

  • Cardiovascular system
  • Cancer imaging
  • Central nervous system
  • Certain types of infections

PET scans are combined with other types of imaging scans:

A PET/CT combines two types of scans into one. The CT (computed tomography) scan shows the anatomical structures of organs, bones, and tissues in greater detail than regular X-rays. It produces images and shows any abnormal cell activity.

  • PET/FDG scans can show the abnormal cell activity even when an abnormal growth is not yet visible on a CT scan. They combine fluorodeoxyglucose (FDG), a type of radiotracer, with PET scans.
  • PET/MRI scans show the soft tissues of the body very clearly. MRI stans for magnetic resonance imaging and uses magnetism and radio waves to create cross-sectional images of the body. 

Preparing for a PET/CT Scan

To prepare for a PET/CT scan, do not exercise, chew gum, or perform any strenuous physical activity the day before. Wear comfortable clothing, and leave your jewelry at home.

  • Do not eat or drink anything except water for 6 hours before the test.
  • Do not have anything that contains caffeine for 24 hours before the test. This includes coffee, tea, cola and other sodas, chocolate, and strawberries (these contain a small amount of caffeine). It also includes products labeled decaffeinated and caffeine-free (these contain small amounts of caffeine). Caffeine affects the test results.
  • Do not take any over-the-counter medication that contains caffeine, such as Excedrin®, Anacin®, diet pills, and NoDoz® for 24 hours before the test. Talk to your doctor, pharmacist, or nurse if you have questions about other medications that may contain caffeine.
  • Do not smoke on the day of the test—nicotine affects the test results.
  • If you are having a PET/CT test for sarcoidosis to detect infection/inflammation, you will need to strictly follow a special high-fat, no-carbohydrate diet the day before your test, followed by a longer period of time with no food. Please access the instructions for this study here.

For most tests, you can drink water and take medications up until the time for the exam. We will contact you a day or two before the exam to go over the procedure details.

It is very important that you arrive on time for your appointment. Please plan to arrive at least one hour before your scheduled appointment time.  The entire duration of the test is about one hour to 90 minutes.

A radiotracer is ordered specifically for your test, so please avoid cancelling and/or rescheduling at the last minute. If you need to reschedule, please call 212-636-4809 at least 48 hours before your appointment time.

Bring this information to the PET scan:

  • Any medications you are taking
  • Bone marrow stimulant medications taken, including date last received
  • Chemotherapy treatments, including date of the last therapy
  • History of contrast reaction
  • Recent imaging studies (CT, PET/CT, MRI, etc.), including where and when performed
  • Other types of cancer treatments received
  • Previous surgeries or other major medical procedures performed, including dates
  • Radiation therapy treatments, including dates, and area of body treated

Please let your technologist know beforehand whether you:

  • Are afraid of small spaces (claustrophobic)
  • Have had any problems with a prior nuclear medicine procedure
  • Are pregnant or breastfeeding
  • Have diabetes

If you are claustrophobic, your doctor may give you a mild sedative to take right before the scan. The technologist can keep in constant contact with you during the examination. Different procedures take different amounts of time. If you have any questions, ask the scheduler when you make your appointment.

Taking Medications the Day of the Test

Please bring a list of all medications and supplements you take, including those that are non-prescription or over-the-counter.

  • If you have asthma: DO NOT take theophylline, brand name Theo-dur, for 48 hours before the test. Please bring your asthma inhaler to the test.
  • If you have diabetes and you take insulin: ask your doctor how much you should take the day of the test. If you take pills to control your blood sugar, do not take your medication before the test. Bring your diabetes medication with you so you can take it after you finish the test. Do not take your diabetes medication and skip a meal before the test.
  • If you take heart medications: ask your doctor about changes you need to make to your medications before the test. DO NOT stop taking any medication unless your doctor tells you to do so. 
  • If you take medication for chest pain or discomfort, do not take the following medications on the day of the test unless your physician tells you otherwise or if you have chest discomfort:
    • Isosorbide dinitrate, brand names Dilatrate®, Isordil®
    • Isosorbide mononitrate, brand names Imdur®, ISMO®, Monoket®
    • Nitroglycerin, brand names Minitran®, Nitropatches®, Nitrostat®)
    • Dipyridamole, brand name Persantine®.  Stop taking this medication 48 hours before the test.
  • If you take Aggrenox® for stroke: do not take it for 48 hours before the test.

Please let your technologist know beforehand whether you:

  • Are afraid of small spaces (claustrophobic)
  • Have had any problems with a prior nuclear medicine procedure
  • Are pregnant or breastfeeding
  • Have diabetes

If you are claustrophobic, your doctor may give you a mild sedative to take right before the scan. The technologist can keep in constant contact with you during the examination. Different procedures take different amounts of time. If you have any questions, ask the scheduler when you make your appointment.

During the Scan. PET scans use a machine that resembles a large donut. You lie on a table that slides in and out of the center of the machine. Your technologist will be in an adjoining room the entire time. You can communicate by intercom. Your technologist may ask you to hold your breath for a minute or two so the images do not come back blurry. PET scans typically take about a half hour. You shouldn’t feel any pain during this process.

We may need you to wait after the procedure while the doctor reviews the scans. This does not mean there is a problem, just that we need a clearer or additional picture. Your doctor will get the results of the scans and discuss them with you. To request a copy of your images or your report, call the Radiology Medical Records at 212-241-3146.

After the Scan. After PET/CT and PET/MRI scans, there is almost no radiation left in the body at the end of the test. Drink plenty of fluids after the exam to completely flush the tracer out of your body. With a PT/FDG scan, there may still be a bit of radioactive material in your body after the exam. Try not to spend a lot of time near pregnant women or small children for 20 hours. Like the other tests, make sure to drink plenty of fluids to flush the tracer out of your body. You may resume your normal diet. If you need to travel, let us know. With a PET/FDG scan, there may be very small amounts of radiation in your body that a very sensitive detector at an airport, ferry port, and train station can detect. We can give you a card identifying the procedure done and the length of time that sensitive detectors can detect any radiation.