A mathematical model for the distribution of fluorodeoxyglucose in humans.
The goals of this study were to define the total body distribution kinetics of 18F-fluorodeoxyglucose (FDG), to contribute to its radiation dosimetry and to define a suitable proxy for arterial cannulation in human FDG studies.


METHODS
Time-activity FDG heart, lung, liver and blood data from paired fasting and glucose-loaded sessions in five adult human volunteers, together with published brain parameters, were incorporated into a multicompartmental model for whole-body FDG kinetics. Tau values were calculated from this model. We also compared the usefulness of activity in the left ventricle (LV), right ventricle (RV), left lung and right lung as proxy for arterial blood FDG sampling.


RESULTS
No systematic difference was found in model parameters between the fasting and glucose-fed sessions, even for the parameter for transfer of FDG into the myocardium. Myocardial PET data fitted well to a model in which there is very rapid exchange indistinguishable from blood kinetics and transfer into an intracellular "sink." The lung data fitted to a simple sink representing the lung cells. The liver data required an additional intermediate exchange compartment between the plasma and a hepatic sink. In terms of total body distribution kinetics, unmeasured organs and tissues (probably the skeletal muscle and gut) become increasingly important with time and account for a mean of 76% of the decay-corrected FDG activity at infinity. Right lung activity, corrected to venous blood, represents the whole arterial blood curve better than the LV or RV. The tau values for radiation dosimetry of FDG in the heart, lungs, liver and bladder calculated from our model do not differ significantly from published results using other methods. Bladder tau decreased with voiding frequency and was markedly decreased with early voiding.


CONCLUSIONS
Glucose loading state is not a good predictor of myocardial FDG uptake. The majority of FDG distribution at 90 min is in tissues other than the blood, brain, heart and liver. Bladder radiation will be much reduced if the patient voids early after FDG administration. Summed large volume right lung activity, normalized to venous blood activity, is a good proxy for arterial blood FDG sampling. The model presented may be expanded to include other FDG kinetics as studies become available.
Hays
M T
MT
Nuclear Medicine Service, Veterans Affairs Palo Alto Health Care System, California 94304, USA.
Segall
G M
GM
D000328:Adult; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006321:Heart / Q000000981:diagnostic imaging; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008297:Male; D008954:Models, Biological; D008962:Models, Theoretical; D009206:Myocardium / Q000378:metabolism; D012016:Reference Values; D014018:Tissue Distribution; D014055:Tomography, Emission-Computed; D001743:Urinary Bladder / Q000000981:diagnostic imaging / Q000378:metabolism
D019788:Fluorodeoxyglucose F18