PET/CT

Positron Emission Tomography (PET) is an imaging test that can be useful in the management of patients with certain cancers. Conventional radiography, such as CT or MR, provides exquisite detail of a patient’s anatomy, while PET depicts the metabolic activity of tissues in the body. With an imaging resolution as low as 5 —10 mm in very active disease, PET provides valuable additional information to assist in the management of patients with many types of disease. For example, PET assists clinicians with the:

  • Early detection of lesions not visible by CT or MR
  • Evaluation of lesions treated with chemo- or radiotherapy
  • Differentiation between inactive necrotic tissue or scar and lesions
  • Characterization of lesions that are indeterminate on x-ray images


PET/CT combines the functional information from a positron emission tomography (PET) exam with the anatomical information from a computed tomography (CT) exam into one single exam. A PET scan detects changes in cellular function — how your cells are utilizing nutrients like sugar and oxygen. Since these functional changes take place before physical changes occur, PET can provide information that enables your physician to make an early diagnosis.

A CT scan uses a combination of x-rays and computers to give the radiologist a non-invasive way to see inside your body. One advantage of CT is its ability to rapidly acquire two-dimensional pictures of your anatomy. Using a computer, these 2-D images can be presented in 3-D for in-depth clinical evaluation.

The PET exam pinpoints metabolic activity in cells and the CT exam provides an anatomical reference. When these two scans are fused together, your physician can view metabolic changes in the proper anatomical context of your body.

Why do I need this exam?
Your PET/CT exam results may have a major impact on your physician’s diagnosis of a potential health problem and how a treatment plan is developed and managed.

A PET/CT exam not only helps your physician diagnose a problem, it also helps predict the likely outcome of various therapeutic alternatives, pinpoint the best approach to treatment and monitor your progress. If you are not responding as well as expected, you can be switched immediately to a more effective therapy.

Preparing for your visit
PET is usually done on an outpatient basis. Your doctor will give you detailed instructions on how to prepare for your examination. You should wear comfortable, loose-fitting clothes. You should not eat for four hours before the scan. You will be encouraged to drink water. Your doctor will instruct you regarding the use of medications before the test.

Note: Diabetic patients should ask for any specific diet guidelines to control glucose levels during the day of the test.

When you arrive, we will take a review of your medical history and any past exams.

For the PET portion of the exam you will receive a radiopharmaceutical injection. The amount of radiation you will receive is about the same as any other nuclear medicine procedure. You should not feel any side effects from the material. In all cases, little or no radioactivity will remain in your body approximately 6 hours after injection.

For most studies, you will have to wait for the radiopharmaceutical to distribute itself — typically 30 minutes to an hour. During this time you will be asked to relax.

There are no additional preparations for the CT portion of your exam.