Tissue standardized uptake value is a closer surrogate of blood fluorine-18 fluorodeoxyglucose clearance after division by blood standardized uptake value, illustrated in brain and liver

摘要

The numerator and denominator of the left-hand side of the Gjedde-Patlak-Rutland (GPR) equation for measurement of blood fluorine-18 fluorodeoxyglucose (F-18-FDG) clearance into tissue (K-i) are the standardized uptake values (SUVs) of tissue and blood, respectively. The extent to which normalized time (NT) in the GPR equation exceeds real time depends on half-time of clearance of F-18-FDG from blood. A literature review shows that NT is fairly constant, about 100 min at 60 min postinjection of F-18-FDG, in keeping with our own finding of no significant difference in maximum SUV in blood 60 min postinjection of F-18-FDG between 39 patients with F-18-FDG-avid malignancy on routine PET/CT (1.74 +/- 0.31) and 21 patients with normal PET/CT (1.79 +/- 0.32), and similar blood glucose levels (BGLs). Volume of distribution (V-0) in the GPR equation is similar to 0.4 ml/ml for brain and similar to 0.9 ml/ml for lean liver. Using these values of V-0 and an NT of 100 min, we used the GPR equation to calculate K-i from our own published values of SUVliver/SUVblood and SUVbrain/SUVblood at 60 min postinjection, obtaining 0.0045 ml/min/ml for liver and 0.036 ml/min/ml for brain at BGL of 5 mmol/l. These values for K-i at this BGL are close to literature values of K-i, which for liver and brain are similar to 0.0033 and similar to 0.035 ml/min/ml, respectively. We conclude, therefore, that following division with blood pool SUV, tissue SUV becomes a closer surrogate of K-i. This division also eliminates the controversy over which whole body metric to use in the calculation of SUV.