What is a PET/CT Scan?

PET is an acronym for Positron Emission Tomography. A positron camera (tomography) is used to produce cross-sectional tomographic images, which are obtained from positron emitting radioactive tracer substances (radiopharmaceuticals) such as F18 fluorodeoxyglucose (FDG) that are administered intravenously to the patient. The tracer is very safe. Adverse reactions are essentially non-existent.

  • Surgeons can use PET/CT to determine the optimal location to perform an invasive procedure
  • Radiation Oncologists can use PET/CT to tailor radiation fields reaching all the cancer cells without damaging the surrounding healthy cells
  • Medical Oncologists can use PET/CT to monitor response to treatment


What to Expect During a PET/CT Scan:

Before the scan, you will receive a small injection of FDG (sugar water with a radioactive tracer).  You will sit or lie down on a comfortable chair or bed for 30-90 minutes while the FDG travels throughout your body.

The technologist will then assist you to the scanner and position you appropriately on the table, based on what part of the body is being scanned. The CT portion of the exam is completed first, followed by the PET portion. You will be asked to lie perfectly still. You may also be asked to hold your breath for a few seconds while the CT scan is performed, as any movement may require the exam to be repeated.

The length of the exam is determined by your height and area of the body being scanned. When the total scan in finished, the computer will produce images for the radiologist to review.

How should I prepare for my PET/CT?

There are strict patient preparation guidelines for all PET/CT patients, especially diabetic patients, regarding what you can eat or drink before your exam. If you have questions regarding your preparation, please contact us for specific instructions.

General preparation guidelines for all patients include:

  • Do not eat or drink anything except water for four to six hours prior to your exam
  • Take any regularly scheduled medicine before arriving (if you can tolerate it on an empty stomach)
  • Avoid rigorous activity for 24 hours before your exam
  • Dress warmly and comfortably
  • If you are diabetic, eat a small meal four hours prior to your exam and take your insulin, if necessary. It is critical that you follow all patient preparation guidelines and ensure that your glucose levels are within normal limits, or the exam will need to be rescheduled.

Please make every effort to keep your appointment. If you must cancel or reschedule, please notify our office at least 24 hours in advance. The FDG (sugar water with a radioactive tracer) used for your scan is prepared specifically for you and will have to be discarded if you fail to keep your appointment.

CT stands for Computed Tomography. CT is an X-ray test that generates a detailed view of the anatomy or structure of organs and tissues in the body. The CT scan can show the dimension of vessels, lymph nodes and organ systems.

A PET/CT is one continuous full-body scan (usually about 20-30 minutes), PET captures images of miniscule changes in the body’s metabolism caused by the growth of abnormal cells, while CT images simultaneously allow physicians to pinpoint the exact location, size, and shape of the diseased tissue or tumor.

Essentially, small lesions or tumors are detected with PET and then precisely located with CT.

A PET/CT scan depicts both technologies using a single machine. It provides a picture of function (PET), a picture of anatomy (CT) and a merged picture of both the body’s metabolism and structure.

Why a PET/CT?

PET/CT helps physicians diagnose, stage and treat cancer with more accuracy than ever before. The exam can provide answers to the following critical questions:

  • Where is the tumor?
  • Is it spreading?
  • How large is it?
  • What is the optimal therapy?
  • Is the therapy working?
  • Is there a recurrence?

Benefits for Patients who get a PET/CT scan:

  • Detailed diagnostic information not available from other tests like CT and MR
  • Shorter time for definitive diagnosis
  • Enhanced ability to detect disease with fewer invasive diagnostic procedures
  • Improved staging of the disease and better monitoring of cancer recurrences
  • More effective tracking of the results of treatment therapy
  • Less extensive surgeries and avoidance of some surgeries
  • Lower overall cost of care