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.
The diagnostic accuracy of PET-CT was 93.5%, and the false positive rate was 6.50%.
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.
FDG is not only a cancer specific imaging agent, false positive results may be observed with benign diseases. False positive results are commonly observed in areas of active inflammation or infection (Gupta et al., 20000), with a reported false positive rate of 13% and false negative rate of 9% (Alavi et al., 2002).
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.
Not all cancers show up on a PET scan. PET scan results are often used with other imaging and lab test results. Other tests are often needed to find out whether an area that collected a lot of radioactive material is non-cancerous (benign) or cancerous (malignant).
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.
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.
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.
A PET scan can help to: show up a cancer. find out how big it is and whether it has spread (stage a cancer) show whether a lump is cancer or not.
Cancer cells show up as bright spots on PET scans because they have a higher metabolic rate than do typical cells. PET scans may be useful in: Detecting cancer. Revealing whether your cancer has spread.
I very often have patients who ask me “is there a test that can detect cancer cells in the body?” or “shall we do PET CT and confirm the presence of cancer and then give next treatment?” Well, the answer is NO! The PET scan can only detect cancer when it is at least larger than 5mm in size in a given place.
Discussion: The detection limit of PET is in the magnitude of 10(5) to 10(6) malignant cells.
When should I get my PET scan results? A radiologist with specialized training in PET scans will review the images, write a report and send it to your healthcare provider. This process usually takes 24 hours.
[13] showed that PET/CT scan can identify more bone marrow involvement in DLBCL and Hodgkin's lymphoma as compared to bone marrow biopsy with sensitivity, specificity, accuracy, and positive and negative predictive values of 95%, 86%, 87%, and 54% and 99%, respectively.
A PET or PET-CT scan may be helpful if your doctor suspects your cancer has returned, based on your symptoms, a physical exam, or other tests. A scan may also be recommended if you were treated for advanced cancer and your doctor needs to find out if your most recent treatment was effective.
In general, PET scans may be used to evaluate organs and/or tissues for the presence of disease or other conditions. PET may also be used to evaluate the function of organs, such as the heart or brain. The most common use of PET is in the detection of cancer and the evaluation of cancer treatment.
It's because of this location, surrounded and obscured by internal organs, that pancreatic tumors are impossible to see or feel during a routine medical exam. Making diagnosis even more difficult is the fact that in its early stages, pancreatic cancer is usually a so-called “silent” disease and causes no symptoms.
While even the most advanced imaging technology doesn't allow radiologists to identify cancer with certainty, it does give them some strong clues about what deserves a closer look.
Melanoma is a cancer of the skin, and it has a high survival rate because it is easy to detect in this part of the body.
If a lesion is identified by a PET scan, it may need to undergo a biopsy to determine benign nature versus malignancy. The reported sensitivity and specificity varies greatly among studies, and, in many instances, there is a lack of histologic confirmation.
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.
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.