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Positron emission tomography (PET) examines organ and tissue functioning down to the cellular level. This nuclear medicine imaging procedure involves small amounts of radioactive materials that are usually injected, inhaled or given through an IV. As the material gives off energy, a camera and computer use this data to generate images.

With computed tomography (CT) or magnetic resonance imaging (MRI) also utilized, the procedure incorporates image fusion or co-registration, providing information from two different exams within a single image. This information allows for a more accurate diagnosis.

What is PET/CT?

Nuclear medicine imaging like PET zeroes in on molecular activity, allowing radiologists to identify certain diseases in their early stages and determine if a patient is responding to treatment. These noninvasive, relatively painless procedures are ideal for detecting and monitoring certain cancers, heart disease, gastrointestinal and endocrine issues, neurological disorders and other abnormalities.

One key factor delivering this level of detail, radiotracers contain miniscule amounts of radioactive materials that a PET scan can pick up and most procedures use F-18 fluorodeoxyglucose (FDG), a radiotracer that behaves similarly to glucose. After it’s in the body, radiotracers gather in areas with high levels of inflammation, chemical activity or metabolic activity, including where cancer cells are concentrated. The scan identifies these “hot spots” and can pick up on metabolic activity or other abnormalities far sooner than other imaging procedures.

As the radiotracers move to these areas, a gamma camera examines the radioactive emissions or energy they generate and translates this data down to the molecular level to create images displayed on a monitor.

When CT technology is also utilized, a single photon emission computed tomography/computed tomography (SPECT/CT) or a positron emission tomography/computed tomography (PET/CT) unit may perform the procedure. CT technology alone operates much like an X-ray, although patients may need to consume a contrast dye beforehand.

Both types of devices are tunnel shaped, with a hole going through the unit. At the center, the camera or scanner is located on a gantry and the patient lies down on a table that passes through. The camera or scanner rotates around you as the procedure begins, while the radiologist guides you through the procedure via speaker and microphone in a separate room.

Collectively, these technologies offer helpful, detailed information for diagnosing many diseases, may preclude the need for exploratory surgery and eliminate the patient having to schedule multiple imaging procedure, thus reducing the percentage of error. While PET/CT scans are fairly convenient, they still have a few risks:

  • Low radiation exposure, due to the radiotracers used.
  • Allergic reactions, which are rare and tend to be mild.
  • Pain and redness at the injection site.

Who Should Have This Procedure?

Doctors may request the combined PET/CT scan to:

  • Detect and diagnose certain cancers, including if it has spread throughout the body or returned after remission.
  • Examine the effectiveness of a prescribed treatment plan.
  • Determine a prognosis.
  • Examine tissue metabolism and viability.
  • Assess the effects of a heart attack on specific areas of the heart.
  • Determine which areas of the heart muscle could benefit from angioplasty or coronary artery bypass surgery, in conjunction with a myocardial perfusion scan.
  • Examine brain abnormalities, including tumors, central nervous system disorders and sources of seizures and memory issues.
  • Map brain and heart functioning.


Prior to the procedure, patients should tell their doctor if they may be or are pregnant, or are currently breastfeeding to avoid radiation exposure risks. Also disclose any medical conditions, recent illnesses, medications you currently take, if you’re claustrophobic and any allergic reactions, especially if you reacted negatively to a contrast material in the past.

Patients may be told to refrain from eating and should drink only water several hours before the scan is scheduled. Failing to do so may alter image quality and you’ll be asked to return another day. On the day of the procedure, you should arrive in comfortable, loose clothing and leave anything metal outside, including jewelry, eyeglasses, hair accessories and removable dental instruments.

PET/CT scans are done on an outpatient basis or in a hospitalized setting. As the procedure begins, you will lie down on the examination table and an IV catheter will be inserted to inject the radiotracers. You’ll then wait 30 to 60 minutes for the radiotracers to travel through and be absorbed by your body. Patients may also be asked to drink a liquid containing contrast material, which will gather in the intestines. As this occurs, patients should remain still throughout the procedure.

Once the radiologist is ready to begin taking images, the table will slide into the scanner. Throughout the procedure, patients should remain still. The CT scan occurs first, followed by the PET scan. A second CT scan, this time with contrast material, may follow. For certain heart conditions, additional drugs and tracers used may extend the length of the procedure.

Afterward, the radiologist will ensure all images have been taken. The IV will then be removed and the patient can resume day-to-day activities. From here, the radiologist and your doctor will review the results. You may be asked to come in for a follow-up appointment or schedule additional imaging.
Has your doctor recommended a PET/CT scan? Contact us to make an appointment today!