Positron Emission Tomography (PET/CT)

What is Positron Emission Tomography (PET/CT)?

Positron Emission Tomography or PET/CT scan is a diagnostic nuclear medicine examination that combines anatomic images obtained by computed tomography (CT) with physiologic imaging of the body based on the detection of subatomic particles (positrons).

What are some of the common uses for the procedure?

PET/CT scans are most often used to detect and stage cancer and to evaluate the response of the tumor to chemotherapy or radiation. These scans are usually performed on the whole body. PET/CT scans of the heart can be used to determine blood flow to the heart muscle and help evaluate signs of coronary artery disease. PET/CT scans can help differentiate non-functioning heart muscle from viable heart muscle that would benefit from angioplasty or coronary artery bypass surgery to re-establish adequate blood flow. PET/CT scans of the brain are used to evaluate patients with Alzheimer’s disease or memory disorders of an undetermined cause, those with suspected or proven brain tumors, and those who have seizure disorders and are candidates for surgical therapy.

How should I prepare for the procedure?

Patients should not eat or drink for 6 hours prior to the exam, except for water and medications. Diabetic patients should discuss specific diet and glycemic medication guidelines with their physician to control glucose levels the day of the test. Patients should avoid heavy physical activity, alcohol, caffeine, nicotine and other stimulants for 24 hours prior to the exam. One should wear comfortable, loose-fitting clothes without metal for the examination. Female patients should be certain they are not pregnant for the examination, even if it requires having a pregnancy test. All patients should bring any pertinent outside imaging studies to MDR at the time of the PET/CT scan to ensure the most accurate interpretation possible.

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

What should I expect during the procedure?

Whole body oncology and brain PET/CT scans are performed at MDR. Prior to the actual scanning, a radioactive compound, 18-fluorodeoxyglucose or 18-FDG, will be injected intravenously. There is no risk of allergic reaction or side effects of the radioactive substance. The compound is similar to glucose, or normal blood sugar, and will be taken up by both normal and abnormal tissues according to their metabolic rate. More metabolically active tissues, such as tumors, will accumulate more radioactivity and will appear as a “hot spot” on the scan. It takes approximately 45 minutes for the 18-FDG to be adequately taken up by the body. During this time, the patient is instructed to remain still, so as to avoid any excessive muscle uptake, which may make interpretation of the scan difficult. Once the scan begins, the patient will lie still on a cushioned examination table and advance through the bore of the scanner as the data is acquired. The entire scan takes approximately 30 minutes. The images are then processed and displayed on a computer for evaluation by the radiologist. There are no restrictions on daily routine after the test, although you should drink plenty of fluids to flush the radioactive substance from your body.