The PET-CT Scan
PET (Positron Emission Tomography) and CT (Computed Tomography) are both important diagnostic tools that physicians use to determine the presence and severity of cancers, neurological conditions and cardiovascular disease. PET-CT scans have proven to be very effective in detecting cancer and determining how well cancer is responding to therapy.
The PET scan demonstrates the biological function of the body's tissues, while the CT scan provides information about the body's anatomy such as size, shape, and location. By combining these two state-of-the-art technologies, physicians can more accurately diagnose and monitor diseases such as cancer, heart disease, and certain brain disorders. Each imaging modality can be viewed independently of the other without compromise, or used in concert for complementary functional and anatomic diagnosis.
How the PET-CT Scan Works
PET stands for Positron Emission Tomography. It works by detecting gamma rays produced by radiopharmaceuticals injected into the body and making pictures of the location and amount of the injected radiopharmaceutical. Cancer cells use sugar (glucose) faster than healthy tissue, so PET scans can show the cancer based on the concentation of the glucose radiopharmaceutical. CT stands for Computed Tomography, which uses x-rays to make detailed pictures of the body's internal structure. By performing both a PET and CT scan together, the pictures of the body are lined up properly and can be used most effectively.
While PET-CT is useful in diagnosing certain cardiovascular and neurological diseases, it is particularly effective in early detection and staging of cancer. PET-CT can be very sensitive in determining the full extent of disease and can accurately characterize a tumor as benign or malignant, avoiding the need for surgical biopsy when the scan is negative. It is a very effective tool in treatment planning for the patient.
What to Expect During Your Procedure
To begin the procedure, a small amount of radioactive glucose is injected into your bloodstream through a small catheter (tube) in an arm or hand vein. There is no danger to you from this injection. Glucose (also known as sugar) is a common substance your body needs in order to function. After the injection, you will wait approximately 90 minutes in a private waiting room while the injected material is distributed throughout your body. You may be asked to drink water and oral contrast material during the waiting period.
After the distribution time is complete, you will be asked to lie on a table, which passes slowly through the scanner. The first part of the scan is the CT scan which shows the body's structure. There may be an injection of contrast material into the vein through the catheter that was previously placed. This is routine with most CT scans. The second part of the scan is the PET scan where you will continue to lie on the table which slowly moves through the scanner.
How to Prepare for Your Exam
Typically, you will be asked not to eat or drink anything after midnight the night before your scan except tap or bottled water. You should eat a meal low in carbohydrates the day before the exam. If you are diabetic, you may have special instructions.
For your comfort and peace of mind, please:
- tell your doctor if you are pregnant or think that you might be
- wear comfortable clothing with no metal buttons or buckles
- take any prescribed medication on the day or your exam, unless instructed not to do so
- ask your doctor if you can eat after midnight on the day, prior to your exam
- avoid all beverages with sugar the day before the exam
You can expect to be in the PET center for 3 to 3 ½ hours. The actual scan averages 30 - 60 minutes.
Re-Scheduling Your Exam
Twenty-four notice is required to re-schedule a procedure. The injection required for your exam is ordered specifically for you and expires very quickly.
Questions?
If you have additional questions, please contact the PET Medical Imaging Center at 616-391-6001.
