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The medical imaging test Positron Emission Tomography (PET) Scan uses radioactive tracer to highlight parts of a body that may have abnormal growth, such as cancers. More of the tracer tends to congregate in areas of rapid cell growth like cancers, and it is this high concentration of radiation compared to levels elsewhere in the body that pinpoint problem areas. The calculation of how much more intense the tracer is at this point compared to elsewhere is called the standardized uptake value (SUV.) Doctors calculate a PET Scan SUV to ensure that suspected problem areas under visual inspection are accurately identified.
A patient undergoing a PET scan receives an injection of radioactive tracer into the body. This tracer typically is an energy source such as glucose. Certain medical conditions like cancers require more energy than normal cells, as they grow more quickly. As a result, the cancers attract more of the radioactive glucose than most other parts of the body. This unequal distribution of radioactivity is visible in a PET scan of the patient.
Although areas of intense activity on a PET scan may indeed be a cancer or other undesirable medical condition, sometimes relatively normal cells can be highly radioactive under the scan. An example of one of these situations is tissue inflammation. If a patient does not follow pre-test instructions to fast, the body's cells, such as the muscle cells, may take up the radioactivity and cause a false positive result.
Doctors may be able to identify the presence of medical issues from a visual inspection. He or she can also employ a PET Scan SUV calculation to make the diagnosis more accurate. This calculation only takes into account the data from the scan and is unaffected by individual doctors' interpretations of results.
For this method of diagnosis, each medical condition has its own SUV. Individual SUVs state how much of the radioactivity gets absorbed by the medical problem compared to the rest of the body. As PET machines can all be different in the way they take the scanning image, an SUV also depends on individual brands of machine. Data from previous tests are necessary for a medical authority to calculate an appropriate range of SUV for each disease.
Normal parts of the body have an intensity of 1.0 in the PET Scan SUV. More intensely radioactive areas have higher readings, such as 2.3 and above, and less intense areas have a value of less than 1.0. Computer calculations of a PET Scan SUV can rule out many false positive identifications, and be more accurate at identifying disease, than a doctor may be able to. An increased level of detection, and decrease in false positives, helps patients get quicker treatment, or save patients from unnecessary treatments.
1.2 (total body) and 1.5 (chest) suv on a 1.5 x 1.0 cm nodule with central lucency found incidently on a chest CT done just as a screen on a smoker. Patient is not a candidate for percutaneous or endobronchial biopsy for at least 9 more months because of post cardiac stent placement, on anticoagulants. A right lower lobectomy was offered for diagnostic purposes. Patient is PPD positive, TB gold negative, and may have contracted valley fever two or three years ago. Chest x-rays have been negative until now.