The maximum (not average) activity in the region of interest (ROI) should be used, because small ROIs can result in higher average SUVs. In addition, because obese patients generally have higher SUVs in both normal and malignant tissue, lean body mass is preferred in the nominator. Finally, administered activity, the denominator of the equation, is affected by technical factors like extravasation and the amount of FDG remaining in the syringe following injection.
Specific uptake values for FDG in PET must be obtained from the attenuation corrected data. An SUV of 1 g/mL means that the FDG is uniformly distributed throughout the body.
SUVmax of Liver: 2.5 g/mL
SUVmax of Blood: 2.3 g/mL
SUVmax of Spleen: 1.9 g/mL
SUVmax of Bone marrow: 1.0 g/mL
SUVmax of Lung: 0.7 g/mL
Minor changes in scan technique can change SUVs by up to 30%. Delaying image acquisition following injection can also increase SUVs, since FDG continues to accumulate in tumors for up to two hours.
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