Correlation in dog hearts between Fick-derived (x-axis) measurements of the rate of myocardial glucose utilization (rMGU) and PET-derived (y-axis) rMGU using (A)1-11C-glucose, (B) FDG before correcting PET values for the lumped constant (LC), (C) FDG after correcting PET values by the LC, and (D) FDG after correcting PET values by a variable LC (LCv) that accounts for varying substrate, hormonal and work environments. Correlation with Fick-derived values was significantly close when 1-11C-glucose (panel A), as opposed to 18F-FDG was used, regardless of whether an LC was used or the type of LC used (panels B-D). Reproduced with permission reference 27.