What Does an SUV of 8.3 Mean?
SUV stands for "standardized uptake value." It is a commonly used measure in positron emission tomography (PET) that indicates the uptake of radioactive material (radioactive fluorodeoxyglucose, or FDG) in the brain. It can be standardized against patient weight or background activity. The SUV is very useful in distinguishing scar tissue and normal cells from active lesions or tumors, and in tracking the progress of disease in cancer therapy.
SUV Significance and Definition
SUV is a measure of the concentration of a radiotracer in a defined region at time "t," divided by the dose at time of injection (t=0), normalized to the patient's body weight. Instead of body weight, the injected dose might also be corrected by the lean body mass or Body Surface Area (BSA). The SUV is calculated either pixelwise or over a single region of interest (ROI). Generally if the SUV of one tumor region is many times greater than in another (normal) region, this may be a cause for concern. A higher SUV number corresponds to higher metabolic activity, but is also related to the volume of the cells used in the calculation.
SUV of 8.3
SUVs range from 0 for no uptake to 15 for maximal uptake. SUV for most cancers are greater than 3, although sometimes normal tissues can have uptake greater than 3 as well. Inflammation and infection can cause higher-than-normal SUVs. A high SUV does not necessarily mean there is cancer. Breast cancer can have SUVs in the lower range (3-5), while aggressive lymphomas have high SUV values (>13). Overall, detailed reading and evaluation by the radiologist is most important since these values are subjective. A SUV of 8.3, however, will be deemed suspicious.
Noise in the PET image, poor resolution and ROI definition can affect the SUV. In addition, factors such as patient motion during the scan, recent chemotherapy treatments and high glucose levels prior to the scan can cause falsely high SUV readings.