The FDG lumped constant in normal human brain

Abstract

The lumped constant (LC) is a correction factor used to infer glucose metabolic rate (MR(glc)) from FDG metabolic rate (MR(FDG)).

Methods: LC was determined in normal brain in 10 subjects (4 male, 6 female) by measuring regional MR(glc) and MR(FDG) independently using 1-(11)C-glucose and (18)F-FDG with dynamic positron tomographic imaging, arterial blood sampling, and region-of-interest time-activity curve analysis with appropriate compartmental models.

Results: The mean LC (+/-SD) for normal brain was found to be 0.89 +/- 0.08. The value for cerebellum was slightly lower, 0.78 +/- 0.11 (P = 0.006; 2-tailed paired t test).

Conclusion: The LC values determined in this study are considerably higher than older values in the literature, probably because of methodologic differences, but agree with a recent study by Hasselbalch.