FDG uptake on PET indicates clinically?

• A. Decreased glucose metabolism
• B. No metabolic activity
• C. Increased lipid metabolism
• D. Increased glucose uptake often associated with malignancy or inflammation

Answer: (D)

FDG-PET measures how much glucose tissues take up, using a glucose analog labeled with a radioactive tracer. Cells that rely heavily on glycolysis will take up more FDG and trap it, producing a signal on the scan. Many cancers show increased glycolysis even in the presence of oxygen, so they often appear as areas of high FDG uptake. Inflammation and infection also recruit metabolically active immune cells that consume lots of glucose, leading to similar increased uptake.

So, FDG uptake on PET is best interpreted as increased glucose uptake and metabolic activity, which is commonly seen with malignancy or inflammation. Low uptake would indicate decreased glycolytic activity, and uptake driven by lipid metabolism isn’t what FDG tracks.