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PET/CT Scan (Positron Emission Tomography)

What is this test?

A positron emission tomography (PET) scan is an imaging test that allows your doctor to check for diseases in your body.

The scan uses a special dye that has radioactive tracers.

These tracers are injected into a vein in your arm. Your organs and tissues then absorb the tracer.

When highlighted under a PET scanner, the tracers help your doctor to see how well your organs and tissues are working.

The PET scan can measure blood flow, oxygen use, glucose metabolism (how your body uses sugar), and much more.

How the test is performed

Before the scan, you’ll get tracers through a vein in your arm, through a solution you drink, or in a gas you inhale. Your body needs time to absorb the tracers, so you’ll wait about an hour before the scan begins.

Next, you’ll undergo the scan. This involves lying on a narrow table attached to a PET machine, which looks like a giant letter “O.”

The table glides slowly into the machine so that the scan can be conducted.

You’ll need to lie still during the scan. The technician will let you know when it is that you need to remain still. You may be asked to hold your breath for short periods. You’ll hear buzzing and clicking noises during the test.

When all the necessary images have been recorded, you will slide out of the machine. The test is then complete.

How to prepare for the test

Your doctor will provide you with complete instructions for how to prepare for your PET scan. Tell your doctor about any prescription, over-the-counter, or supplemental medications you’re taking.

You may be instructed not to eat anything for up to eight hours before your procedure. You’ll be able to drink water, however.

If you’re pregnant or believe you could be pregnant, tell your doctor. The test may be unsafe for your baby. You should also tell your doctor about any medical conditions you have.

If you have diabetes, you’ll get special instructions for test preparation because fasting beforehand could affect your blood sugar levels.

You may be asked to change into a hospital gown. You’ll also need to remove all of your jewelry and body piercings because metal can interfere with the testing equipment.

How the test will feel

You may feel a sharp sting when the needle with the tracer is placed into your vein.

A PET scan causes no pain. The table may be hard or cold, but you can request a blanket or pillow.

An intercom in the room allows you to speak to someone at any time.

There is no recovery time, unless you were given a medicine to relax.

Why the test is performed

Your doctor may order a PET scan to inspect the blood flow, oxygen intake, and metabolism of your organs and tissues. PET scans are most commonly used to detect:

  • cancer
  • heart problems
  • brain disorders
  • problems with the central nervous system

Unlike other imaging tests, such as CT or MRI, PET scans show problems at the cellular level. This gives your doctor the best view of complex systemic diseases, such as:

  • coronary artery disease
  • brain tumors
  • memory disorders
  • seizures

When PET is used to detect cancer, it allows your doctor to see how the cancer metabolizes, and whether it has spread, or metastasized, to new areas. PET also shows how the tumor is responding to chemotherapy.

After the scan

After the test, you can go about your day unless your doctor gives you other instructions. Drink plenty of fluids after the test to help flush the tracers out of your system. Generally, all tracers leave your body after two days.

Meanwhile, a trained specialist will interpret the PET images and share the information with your doctor. Your doctor will go over the results with you at your follow-up appointment.

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Positron emission tomography

It’s called a positron emission tomography scan or PET scan for short. “We tend to use them commonly in things like lung cancer, head and neck cancer, lymphomas,” explained Dr. Kristina Mirabeau-Beale, a radiation oncologist on the medical staff of Lee Health. PET scans are used to help doctors find where the cancer is located. During cancer treatment, patients may undergo additional PET scans to determine how well their body is responding to treatment. “Sometimes a patient is getting a PET scan after they’ve had a certain constellation of symptoms and if we see a mass somewhere that has a lot of pet uptick we will divert that patient to get a biopsy,” she said. Using a radioactive tracer, a PET scan will clearly show physicians any abnormal cells in the body. “We’re able to look at the patient’s whole body globally and really see if there’s any cancer hiding somewhere,” said Dr. Mirabeau-Beale. PET scans can also be used for cardiology or neurology patients—but if doctors are searching for brain cancer or slow-growing cancer, they may decide to use an MRI instead. “PET dye doesn’t necessarily show us detailed brain images of the brain to identify a primary brain cancer, so we will often have to get an MRI,” she explained. If a patient is experiencing symptoms, doctors will determine the best test to help find the problem and get patients the right treatment.