PET scanning can give false results if chemical balances within the body are not normal. Specifically, test results of diabetic patients or patients who have eaten within a few hours prior to the examination can be adversely affected because of altered blood sugar or blood insulin levels.
Disadvantages of PET/CT Scans
Because the radioactive material is combined with glucose and then injected into the patient, this can be a concern for some diabetic patients. Before having a PET/CT scan, a diabetic patient's blood sugar level will be evaluated, and a glucose serum blood test might be administered.
The radioactive tracer gives off very small levels of radiation that go away very quickly. As a precaution, you should avoid close contact with pregnant women, babies and young children for 6 hours after the scan. You need someone to take you home and stay overnight if you've had medicine to help you relax (sedative).
Why PET scans are used. An advantage of a PET scan is that it can show how well certain parts of your body are working, rather than showing what it looks like. They're particularly helpful for investigating confirmed cases of cancer, to determine how far the cancer has spread and how well it's responding to treatment.
In cancer cells, there is an overproduction of glucose transporters and, as a result, increased FDG uptake. However, not all PET-positive lesions are cancer, and in many instances, PET findings can be false positive."
In general, PET scans are safe and rarely cause problems. The amount of radiation in the radioactive tracer is very low. It doesn't stay in your body for long. You should drink lots of water after a PET scan to help flush the radioactive drug from your body.
PET/CT is the most useful test for determining the stage of cancer. It is more accurate than any other test in finding local or metastatic tumors. Although PET can't detect microscopic cells, it can detect clusters of tumor cells that metastasized, or spread, to other tissues or organs.
Why do I need a PET scan? You may need a PET scan to find out if you have cancer. If you've already been diagnosed with cancer, you may need this test to see if your cancer treatment is working. A PET scan also helps diagnose and monitor heart and brain diseases.
The most common use for a PET scan is for cancer, when it may be done: To see how far cancer has spread. This helps to select the best treatment approach. To check how well your cancer is responding, either during treatment or after treatment is completed.
A CT scan shows detailed pictures of the organs and tissues inside your body. A PET scan can find abnormal activity and it can be more sensitive than other imaging tests. It may also show changes to your body sooner. Doctors use PET-CT scans to provide more information about the cancer.
PET scans are very safe. There are no side effects associated with the radioactive tracers, which only remain in your body for a short time. In addition, the dose of radiation is very small — similar to several years' worth of natural radiation from the environment. Allergic reactions are very rare and usually minor.
After your PET scan, you can go on with your normal activities straight away. The injection of the radioactive material does not make you feel any different or drowsy. There are no sedative drugs or anaesthesia used during this procedure. Your scan results will not be available immediately.
Avoid exercising 24 hours before the scan. Follow a special diet for 12 to 24 hours before the scan. Don't drink or eat anything, except water, for 6 hours before the scan.
PET has been reported to have a sensitivity of 97–100% and a specificity of 62–100% in the detection of recurrent tumours. Scans are most reliable 6 months to 1 year after completion of therapy. Before that time, hypermetabolic inflammatory changes may result in false-positive studies.
Weaknesses of PET/MR imaging tool
Technical challenges in building PET/MR systems include: The addition of PET components to the system in the presence of strong magnetic field from MR. Working with long optical fibers. Use of semiconductor light detectors for counting photons.
Because PET scans read your sugar metabolism, eating sugar could affect the results of your scan. It's also important that you don't exercise for 24 hours before your PET scan. That's because exercise affects the radiotracer's reading and could cause the results to be inaccurate.
PET scans can help detect cancer and how far it has spread. PET scans can show solid tumors in the brain, prostate, thyroid, lungs, and cervix. The scans can also evaluate the occurrence of colorectal, lymphoma, melanoma, and pancreatic tumors.
Avoid food and drinks that contain sugar or carbohydrates for at least 24 hours before your scan. This will help to make sure that your images are of the best quality and help prevent having to reschedule your scan because of a blood sugar that is too high.
Do I have to pay for a PET scan? There is no cost for most PET scans if you are a citizen or permanent resident of Australia and covered by Medicare. For a limited number of indications that are not approved by Medicare, there can be a charge to the patient.
CT scans are more accurate than PET scans, but PET scans can be used to diagnose cancer at an early stage. Both scans are painless and take about 30 minutes to complete. If you're unsure which scan is right for you, be sure to talk to your doctor about PET and CT protocols.
The main difference in a PET scan vs. MRI or CT scan is that it can show cellular-level changes and issues with oxygen use, glucose metabolism and blood flow that reveal medical problems at a very early stage.
18F-Fluorodeoxy glucose positron emission tomography‒computed tomography (18F-FDG-PET) can detect malignant lymph nodes of even normal size, thus overcoming one of the major limitations of CT.
1. Computed Tomography (CT) Scan. The doctor uses a CT scan to take images of the inside of your body from various angles using x-rays. Then, a computer combines the pictures into a three-dimensional, detailed image to reveal any tumors or abnormalities.
Not all that lights up on a PET scan can or should be considered malignancy, and clinical context can become even more pertinent. Inflammatory cells, sarcoidosis, and other thoracic etiologies such as silicone-induced granuloma, can cause PET scans to light up, giving false positives [3,4,5].