Updated Aug 25, 2006

PET, CT, and PET/CT

Positron Emission Tomography (PET) is a new imaging procedure that, when combined with Computed Tomography (CT), enables physicians to more accurately diagnose and manage disease, especially cancer.

PET detects changes in cellular metabolism (how active a cell is), often indicating the presence of disease. CT detects changes in physical size and/or shape of a lesion as well as shows where in the body the lesion is located. With PET's ability to show a lesion's level of cellular activity and CT's ability to show a lesion's detailed structure and location, combining these two scanners has created a new very powerful diagnostic cancer imaging tool.

Together, PET/CT can be very helpful, for example, in the preoperative staging of some cancer types and in localizing suspected cancer recurrence when standard tests are inconclusive. This type of information can help physicians improve treatment planning for individual patients.

Normal PET Scan	Normal CT Scan	Fused PET/CT Scan

How PET/CT Works

Active cells such as malignant cancer cells will use sugar as an energy source. Inactive cells such as benign cells and scar tissue (both noncancerous) will not use sugar as an energy source. 
     
In PET, a special type of sugar is combined with a safe radioactive component to produce the radioactive tracer called FDG (Fluorodeoxyglucose). Once injected into a vein, the tracer, which emits signals detected by the scanner, will be absorbed by malignant cells but will not be absorbed by benign cells and scar tissue. This will indicate whether or not a lesion could be cancerous.

Before The Scan

Upon arrival to the Functional Imaging Department, you will be asked to complete a brief questionnaire and review the procedure consent form. Once you feel you have been adequately informed and have consented to the procedure, you will receive the tracer injection. Then you will be asked to relax in a private exam room for approximately 60 minutes. This provides adequate body distribution time for the tracer. When this "uptake" period is complete, we will take you to the scan room to begin imaging.

Scanning Procedure

You will lie on a comfortable imaging table that will slowly move you through the scanner while data is collected. For most procedures, you will be able to listen to music during the scan. The scan itself will last approximately 30-45 minutes.

Once the scan has been completed and reviewed for technical quality, the appointment concludes and you will be free to leave. The entire procedure, from the time you arrive at the BC Cancer Agency until the time you leave, will last approximately 2.5 hours. A report will be sent to your physician once the scan has been read.

Risks

A PET/CT scan is considered a diagnostic procedure similar to those done in Radiology and Nuclear Medicine. With over 2 million PET scans having been performed worldwide to date, there have been no reports of any adverse reaction to the tracer. Although there is a small amount of radiation exposure involved in your PET/CT scan, the exposure level is small and not considered harmful.

Also, tracers used in PET/CT have very short half-lives meaning they don't remain in your body very long. 24 hours after your PET/CT scan, we would not be able to take any more images because the tracer will have completely left your body.