Michaelis-Menten constraints improved cerebral glucose metabolism and regional lumped constant measurements with ( sup 18 F)fluorodeoxyglucose

Journal Article · Thu Mar 01 04:00:00 EST 1990 · Journal of Cerebral Blood Flow and Metabolism; (USA)

DOI:https://doi.org/10.1038/jcbfm.1990.33· OSTI ID:6994158

Kuwabara, H; Evans, A C; Gjedde, A ^[1]

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1. Montreal Neurological Institute, Quebec (Canada)

In the three-compartment model of transfer of native glucose and (18F)fluorodeoxyglucose (FDG) into brain, both transport across the blood-brain barrier and phosphorylation by hexokinase can be described by the Michaelis-Menten equation. This permits the use of fixed transport (tau = K*1/K1) and phosphorylation (psi = k*3/k3) ratios and a common partition volume (Ve = K1/k2) for tracer and glucose. By substituting transfer constants of FDG for those of glucose, using tau and psi, the lumped constant was determined directly by positron tomography. The same constraints also eliminated k*2 and k*3 from the model, thus limiting the parameters to K* (equivalent to K*1k*3/(k*2 + k*3)), K*1, and the cerebral vascular volume (Vo). In six healthy elderly men (aged 61 +/- 5 years), time-activity records of cerebral cortical regions were analyzed with tau = 1.1 and psi = 0.3. The results were compared with those of the conventional FDG method. At 20 min, the goodness of fit by the new equation was as good as that of the conventional method at 45 min. The estimates obtained by the constrained method had stable coefficients of variation. After 20 min, regional differences between the estimates were independent of time, although we observed steady decreases of K* and (k*3). The decrease strongly suggested dephosphorylation of FDG-6-phosphate, particularly after 20 min. All estimates of variables with the constrained method were more accurate than those of the conventional method, including the cerebral glucose metabolic rate itself, as well as physiologically more meaningful, particularly with respect to k*2 and k*3.

• OSTI ID: 6994158
• Journal Information: Journal of Cerebral Blood Flow and Metabolism; (USA), Journal Name: Journal of Cerebral Blood Flow and Metabolism; (USA) Vol. 10:2; ISSN 0271-678X; ISSN JCBMD
• Country of Publication: United States
• Language: English

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550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
ALDEHYDES
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
BIOLOGICAL MODELS
BLOOD-BRAIN BARRIER
BODY
BRAIN
CARBOHYDRATES
CENTRAL NERVOUS SYSTEM
CHEMICAL REACTIONS
COMPUTERIZED TOMOGRAPHY
DIAGNOSTIC TECHNIQUES
EMISSION COMPUTED TOMOGRAPHY
ENZYMES
FLUORINE 18
FLUORINE ISOTOPES
GLUCOSE
HEXOSES
HOURS LIVING RADIOISOTOPES
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
LIGHT NUCLEI
MATHEMATICAL MODELS
MEMBRANE TRANSPORT
METABOLISM
MONOSACCHARIDES
NERVOUS SYSTEM
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANS
PHOSPHORUS-GROUP TRANSFERASES
PHOSPHORYLATION
PHOSPHOTRANSFERASES
POSITRON COMPUTED TOMOGRAPHY
RADIOISOTOPES
SACCHARIDES
TOMOGRAPHY
TRANSFERASES