No, a PET scan cannot provide a conclusive diagnosis regarding whether a tumour is benign or malignant.
PET scans detect the rate at which cells are using sugar. When the scan lights up brightly, it means there is metabolic activity. Most aggressive cancers light up brightly, but the caveat is inflammation in the body also lights up because inflammatory cells are also metabolically active.
Positron emission tomography (PET) is a medical imaging procedure that provides unique information about how an organ or system in the body is working. PET scans are mainly used to assess cancers, neurological (brain) diseases and cardiovascular (heart-related) disease.
PET scans may play a role in determining whether a mass is cancerous. However, PET scans are more accurate in detecting larger and more aggressive tumors than they are in locating tumors that are smaller than 8 mm a pinky nail (or half of a thumb nail) and/or less aggressive cancers.
Positron Emission Tomography (PET) is a method of functional imaging which can be merged or co-registered with traditional studies such as CT or MRI to improve diagnosis of benign versus malignant disease or extent of malignant disease.
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 diagnostic accuracy of PET-CT was 93.5%, and the false positive rate was 6.50%.
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.
Since most cancer cells are highly metabolically active, they will show up bright on a PET scan. Physicians can use PET scans to detect cancer cells at the primary site, in lymph nodes, and in distant sites of the body.
PET scans can show the difference between tissues that are actively growing (like cancer) and an old injury or scar. So it can also show if swollen lymph nodes after treatment are scar tissue or lymphoma that has not responded to treatment.
In PET, a small amount of radioactive glucose is injected into a vein, and a scanner makes a picture of where the glucose is being used in the body. Cancer cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.
A computer uses the absorption data to show the levels of activity as a color-coded brain map, with one color (usually red) indicating more active brain areas, and another color (usually blue) indicating the less active areas.
Discussion: The detection limit of PET is in the magnitude of 10(5) to 10(6) malignant cells.
How is the PET scan done? Before the scan you will have a small amount of mildly radioactive glucose solution injected through a small plastic tube (cannula) in your arm. Cancer cells absorb more of the solution than normal cells and will show up brighter on the scan.
F-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) is considered a potentially useful imaging technique for detecting cyst infection.
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.
Tumors with low activity are well-known major causes of false negative findings. This can be easily understood considering the FDG PET is metabolic imaging using the activity of lesion. Another major cause of false negative findings for malignancy is tumor size.
Sites of infection and inflammation can be misleading in oncology PET/CT imaging because these areas commonly show 18F-FDG activity. Caution in the interpretation must be taken to avoid the misdiagnosis of malignancy.
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.
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 amount of the radionuclide collected in the tissue affects how brightly the tissue appears on the image. It also indicates the level of sugar uptake or cell activity in that organ or tissue. For example, cancer cells use a lot of sugar and will show up as bright spots (called “hot spots”) on a PET scan.
PET/ CT was more sensitive (94 vs 24%; p < 0.001), demonstrated a higher negative predictive value (98 vs 80%) and was more accurate (98 vs 81%) than the biopsy procedure.
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.
Tissue that has a high rate of metabolism and a high consumption of sugar appears as especially dark spots on black-and-white PET images, and on color images as especially bright spots.