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PET (Positron Emission Tomography) and CT (Computed Tomography) scans are both standard imaging tools that physicians use to pinpoint disease states in the body. A PET scan images the cellular activity of the body at a very early stage, often before anatomical changes take place. The CT scan provides information about the body’s anatomy such as size, shape and location. By combining these two scanning technologies, a PET/CT scan enables physicians to more accurately diagnose and identify cancer, heart disease and brain disorders.
CT and MRI scans are anatomic imaging modalities, which means that they look at the size and shape of organs and body structures. A PET scan is a metabolic imaging modality, which means it looks at cellular activity. The information collected from a PET scan is different from any other test that is available.
A single PET or PET/CT exam can provide information that once would have required several medical studies and possibly surgery. PET scans are most often used to help the physician detect cancer and monitor response to treatment. PET scans are also used to evaluate heart disease, neurological conditions and other physiological problems.
PET scans provide the physician with valuable information. For cancer patients it may help diagnose the extent of disease, guide the most effective therapy, and then help evaluate if the treatment is effective. PET scans aid in the diagnosis of heart disease and neurological diseases. This type of imaging can show changes much earlier than other imaging tests like CT or MRI.
The risks associated with a PET scan are very minimal. The quantity of radiation is low and the radiopharmaceutical degrades quickly so that no detectable radioactivity is present after several hours. In addition to the radioactive decomposition, the remaining radiopharmaceutical is eliminated from the body through urine. Family members are not at risk for exposure since most of the radioactivity has left the body or decomposed before the patient has left the center.
If you are having a PET scan for an oncologic application you will usually be scheduled for your scan at an outpatient imaging facility. Upon arrival you will receive an injection of radioactive glucose (FDG), which will take approximately 60 minutes to distribute throughout your body. You will be asked to empty your bladder and then lie down on the scanner bed. The scan takes approximately 15-35 minutes, depending upon the type of scan you are having and the type of scanner being used. It is important that you lie still during this process. If you need pain medication please bring it with you. You should plan on being at the imaging facility for approximately 2 to 3 hours.
A radiopharmaceutical is a radioactive drug. The most commonly used PET radiopharmaceutical is F 18 Fluorodeoxyglucose, or FDG, which is a radioactive form of glucose (sugar).
F-18 Fluorodeoxyglucose or FDG, is a type of glucose (sugar) and is the most common radiopharmaceutical used in PET imaging. To begin the PET procedure, a small amount of glucose is injected into your bloodstream. There is no danger to you from this injection. Glucose is a common substance that every cell in your body needs in order to function. Diabetic patients do not need to worry; it would take 1,000,000 doses of FDG to equal the glucose in 1 teaspoon of sugar. FDG has a half-life of approximately 110 minutes, so it is quickly expelled from your body. FDG must pass multiple quality control measures before it is used for any patient injection.
Once the PET scan is complete, you will be able to leave the imaging facility. Make sure you drink plenty of water or other fluids throughout the day to help flush the FDG from your body.
There are no side effects to having a PET scan. Make sure you drink plenty of water and check with your physician if you have any concerns.
The PET scan is interpreted by a trained nuclear medicine physician or radiologist and results are usually sent to the referring physician within 24-48 hours. You should contact your doctor to discuss the results.
If you are under a physician’s care, you should follow your physician’s recommendations for frequency of PET scans.
Yes and no. There are examinations that can be performed. However, there is no other metabolic (biological) scanning technique other than PET at this time. CT and MRI, for example, both examine the anatomical (physical) structure. Therefore, they can be useful in determining the size and location of a tumor. However, neither of them can determine whether a tumor is still metabolically active.
PET has been around for years, but originally was used only in research. As the technology grew, PET procedures were performed only in dedicated imaging facilities that had ready access to a cyclotron and a radiochemistry lab to make the radiopharmaceutical. Now, companies are producing radiopharmaceuticals in many areas for distribution to imaging facilities across the country making it feasible for more medical facilities to offer PET scanning.
Approximately 1.5 to 1.7 million PET scans were performed last year. The number of PET scans performed increases dramatically every year.
The only pain involved is the needle prick when you receive the radiopharmaceutical injection, which does not differ from any other type of injection.
Many PET scans are covered by private insurance and Medicare; pre-authorization may be needed and is advised.
