PET scan images can detect cellular changes in organs and tissues earlier than CT and MRI scans. Your healthcare provider may perform a PET scan and CT scan at the same time (PET-CT). This combination test produces 3D images that allow for a more accurate diagnosis. Some hospitals now use a hybrid PET/MRI scan.
PET scans show metabolic changes that occur at a cellular level in your organ or tissue, which is where diseases can first be detected. MRIs cannot view the tissue at this scale, but rather are useful for detecting larger changes in the organ or tissues.
PET/CT is believed to be the most accurate imaging test available to evaluate lung cancer, colon cancer, breast cancer, melanoma, lymphoma, head and neck cancer, and esophageal cancer. In published research studies, PET has been shown to have an approximately 90% accuracy in many of these cancer types.
PET scans detect areas of activity (like cell growth) in the body. More radioactive material collects in cancer cells than normal cells and will appear brighter on the image. Not all cancers show up on a PET scan. PET scan results are often used with other imaging and lab test results.
Though most cancers are picked up on PET CT, there are a few which do not. The most important of these would be cancer of stomach (signet cell type). In such cases performing this test would be waste. However, there are cancers which are very sensitively detected which include lymphoma, GIST, etc.
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.
If it looks as though there are still swollen (enlarged) lymph nodes after treatment, a PET-CT scan can help show if this is due to scar tissue or there are still active lymphoma cells.
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).
A PET/MRI scan is a two-in-one test that combines images from a positron emission tomography (PET) scan and a magnetic resonance imaging (MRI) scan. This new hybrid technology harnesses the strengths of PET and MRI to produce some of the most highly detailed pictures of the inside of your body currently available.
A PET scan is an effective way to help discover a variety of conditions, including cancer, heart disease and brain disorders. Your health care provider can use this information to help diagnose, monitor or treat your condition.
While radiation exposure in a PET scan is safe for most adults, it can be harmful to an unborn baby. So be sure to tell your provider if you are pregnant or think you may be pregnant. Also, tell your provider if you are breastfeeding, because the tracer may contaminate your breast milk.
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.
Perhaps the main difference between a CT scan and a PET scan is their focus. A CT scan creates a detailed non-moving image of organs, bones and tissues. A PET scan, on the other hand, shows doctors how the tissues in your body work on a cellular level.
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.
A PET/CT scan can be more sensitive than other imaging tests and may find cancer sooner than other tests do. Not all tumors take up the radiotracer, but PET/CT is highly accurate in differentiating from the benign and malignant tumors it finds, particularly in some cancers such as lung and musculoskeletal tumors.
Therefore, PET is not specific for neoplastic states. If a lesion is identified by a PET scan, it may need to undergo a biopsy to determine benign nature versus malignancy.
PET scans reveal possible cancerous areas earlier than other forms of testing can, making them very valuable for early detection and treatment. Other imaging tests can provide more information on cancerous (malignant) tumors and the best treatment options.
Healthcare providers frequently use PET scans to help diagnose cancer and assess cancer treatment. They can also assess certain heart and brain issues with the scan.
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.
The specific amounts patients pay vary according to their insurance coverage. Medicare limits the number of PET scans following initial cancer treatment to three per patient. (More could be covered if deemed necessary by the doctor.) “These are good scans and appropriate in many situations,” Healy says.
For nodules that are not metabolically active during the PET/CT scan, it's not recommended to follow up with a biopsy. So patients avoid the risks of an unnecessary procedure. However, if the nodule positively reacts to the radiotracer, further investigation and a biopsy are strongly recommended.
Some masses can be watched over time with regular mammograms or ultrasound to see if they change, but others may need to be checked with a biopsy. The size, shape, and margins (edges) of the mass can help the radiologist decide how likely it is to be cancer.
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. That's why we need to verify the scan results with a needle biopsy.