PET / CT Scan

A PET/CT scanner is used to detect cancer. It combines the technology of a PET scan with that of a CT scan to produce a more accurate depiction of what’s happening in the body. University of Tennessee Medical Center’s Cancer Institute installed its first PET/CT scanner in late 2003 and began scanning patients on March 18, 2004. On average University of Tennessee Medical Center scans 80 to 100 patients a day.

What is a PET/CT scan? PET stands for Positron Emission Tomography, and it uses a radioactive tracer to show organ and tissue function.¹ The tracer is administered intravenously, it moves through the body collecting in specific organs and tissues. As the tracer breaks down it gives off positrons that the camera records, these recordings are used to create a picture. However, these pictures are not very detailed because they only show the location of the tracer.²

CT scans, however, are much more detailed. It uses X-rays to create pictures of organs, blood vessels, bones and the spinal cord. Each picture that’s taken shows a slice of an organ or body area. CT scans require the use of a contrast material, an iodine dye, in order to make structures and organs easier to see. The contrast material can be given a number of ways such as IV, ingestion or injection.⁴

Before the evolution of a PET/CT scanner, these scans were performed at different times on different machines. The two images were then overlaid to give doctors a rough estimate about what was going on in the body and where the activity was happening.⁵ However, with a PET/CT scan the tests are performed simultaneously, and the machine compiles the images to create a more accurate depiction of what’s happening inside the body.

Tips for Your PET/CT Scan Below are some tips to help make the appointment go as quickly and smoothly as possible. Do not eat or drink anything, except plain water, for at least 6 hours before the exam Allow 2½ to 3 hours for the exam Wear comfortable clothes without metal on them Bring music to listen to or a book to read

What can PET/CT Scan Patients Expect?

The PET/CT Scan is painless and only takes a few minutes to perform. However, patients need to allow 2½ to 3 hours for their appointment because there is a lot of preparation that needs to be done. When the patient arrives for the scan he will need to register with the receptionist.

Once the patient is taken back, an IV will be started and the FDG contrast will be injected. FDG (2-Deoxy-2-[18F]fluoro-D-Glucose), a sugar solution, is given because cancer cells feed off of the sugar and create “hot spots” that the scan will pick up on.

Despite being a sugar solution, diabetics shouldn’t worry because it would take 1 million does of FDG to equal a teaspoon of sugar.⁶

The FDG decays quickly and should leave the patient’s body a few hours later. This contrast needs 1½ hours to work through the body before the scan can begin.

During the uptake period (90 min. wait after injection) the patient can sleep, listen to music, watch TV or read a book. However, during the scan, the patient must remain still. The table will move back and forth through a doughnut-looking apparatus.

Once the scan is over, the patient is free to leave. The images will be sent to a radiologist who will analyze them and send a report to the doctor in a few days.

The most important thing to remember when having a PET/CT Scan is that while the actual scan only takes 10 to 15 minutes, patients will need to allow 2½ to 3 hours for the appointment.

 

Resources
1. “Pet Scan.” (2007). A.D.A.M
2. “Information Resources: Positron Emission Tomography (PET).” (2007). www.webmd.com  
3. “CT Scan.” (2006). A.D.A.M
4. “Information Resources: Computed Tomography (CT) Scan of the Body.” (2007). www.webmd.com  
5. Interview with Chris Carr, nuclear medicine technologist. 3/5/08
6. “PET NET Solutions.” (200). www.petscaninfo.com