PET Scan: About This Test

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PET machine

What is it?

A PET scan is a test that uses a special type of camera and a radioactive substance called a "tracer" to look at organs in the body. PET stands for positron emission tomography.

During the test, the tracer liquid is put into a vein in your arm. It moves through your body and collects in the specific organ or tissue, where it gives off tiny positively charged particles (positrons). The camera records the positrons and turns the recording into pictures on a computer.

A computed tomography (CT) scan is often done at the same time as a PET scan.

Why is this test done?

A PET scan is often used to:

  • Look for cancer.
  • Find heart problems.
  • Find brain disorders.

How can you prepare for the test?

  • Tell your doctor if:
    • You have diabetes.
    • You are or might be pregnant, or you are breastfeeding.
    • You get nervous in confined spaces. You may need medicine to help you relax.
  • Don't drink caffeine for 24 hours before a PET scan of your heart.
  • Don't do any exercise or other strenuous activity for at least 48 hours before this test.
  • Don't eat or drink (except water) for at least 6 hours before this test (e.g., no coffee, tea, juice, milk, gum, or candies).
  • Take your regular medicines with water.
  • Limit the amount of carbohydrates you eat the day before your test (e.g., bread, pasta, cereal, potatoes, rice, sugary foods).
  • Drink 1 to 1.5 litres (4 to 6 cups) of water before your test.

What happens during the test?

  • You will be asked about your medical history.
  • Your blood sugar will be tested. If your blood sugar is normal, an intravenous (IV) will be started.
  • A radioactive tracer will be given in a vein (IV). You will need to wait 30 to 60 minutes for the tracer to move through your body. During this time, you will need to avoid moving and talking.
  • You will lie on your back on a table that is attached to a PET scanner.
  • The table will pass slowly through the PET scanner, which is shaped like a doughnut. The scanner picks up signals from the tracer in your body. It is very important to lie still while each scan is being done. The test usually takes between 30 and 60 minutes.

What else should you know about the test?

  • You may feel a quick sting or pinch when the IV is put in your arm. The tracer is not likely to cause side effects.If you don't feel well, tell your doctor.

How long does the test take?

  • The entire test (appointment) will take 2 to 3 hours.

What happens after the test?

  • You will probably be able to go home right away.
  • You can go back to your usual activities right away.
  • After the test:
    • Drink lots of fluids for the next 24 hours to help flush the tracer out of your body. Most of the tracer willbe flushed from your body within 6 to 24 hours. Allergic reactions to the tracer are very rare.
    • There is always a slight chance of damage to cells or tissue from radiation, including the low levels ofradiation used for this test. But the chance of damage is usually very low compared with the benefits ofthe test.
    • In rare cases, some soreness or swelling may develop at the IV site where the radioactive tracer was putin. Apply a moist, warm compress to your arm.
  • If you are breastfeeding, you will need to use saved breast milk or formula for 2 days after the PET scan. This is so you won't pass the tracer to your baby.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if you are having problems. It's also a good idea to keep a list of the medicines you take. Ask your doctor when you can expect to have your test results.

Where can you learn more?

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