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.
PET scans can be used to determine how much cancer is in a person's body and how far the cancer has spread, which is called staging. Since PET scans can detect more cancerous sites than CT scans alone, they are often used in the initial staging and follow-up testing.
Detection Of Cancer Cells
PET scan is best known for detecting abnormal changes in the human body on the cellular level. The cancer cells appear as big spots in the PET scan. It is because the cancer cells have a higher metabolic rate and appear as large dark-colored spots in the PET scan report.
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. The size of smallest tumor mass that can be found at PET is constantly improving.
The diagnostic accuracy of PET-CT was 93.5%, and the false positive rate was 6.50%.
PET imaging can be useful to determine whether a tumor is malignant (cancerous) or benign (not cancerous). Unlike other imaging tests like CT or MRI that show anatomy, the PET scan looks at the physiological changes and cellular activity, so cancer may be diagnosed much earlier.
Cancer cells tend to be more active than normal cells because they are growing and multiplying faster than normal, so they take in more sugar and give off more positrons and gamma rays. This causes them to glow brighter than normal cells on a PET-CT scan.
Descriptively, we define SUV < 5 as “low intensity”, 5–10 as “moderate”, 10–15 as “intense” and >15 as “very intense”.
Discussion: The detection limit of PET is in the magnitude of 10(5) to 10(6) malignant cells.
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.
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.
It's possible to have cancer even if the PET scan is negative. That's because cancer cells may not be emitting enough of the radioactive substance for the PET scan to detect them. In addition, other conditions can cause false positive PET results.
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.
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).
[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.
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.
In the PET image to the right, darker areas represent those that are using more sugar, and so have more of the radioactive substance in them. For example, because healthy tissue uses glucose for energy, it accumulates some of the tagged glucose, which will show up on the PET images.
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.
PET scans are most commonly used to detect: Cancer-Cancer cells have a higher metabolic rate than non-cancerous cells. Because of this high level of chemical activity, cancer cells show up as bright spots on PET scans.
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.
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.
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.
This type of scan help determine whether a smaller spot is cancerous or benign, as cancerous lesions are much more likely to light up on a PET scan than benign spots or scar tissue.