MRS glucose mapping and PET joining forces: re-evaluation of the lumped constant in the rat brain under isoflurane anaesthesia.
Although numerous positron emission tomography (PET) studies with (18) F-fluoro-deoxyglucose (FDG) have reported quantitative results on cerebral glucose kinetics and consumption, there is a large variation between the absolute values found in the literature. One of the underlying causes is the inconsistent use of the lumped constants (LCs), the derivation of which is often based on multiple assumptions that render absolute numbers imprecise and errors hard to quantify. We combined a kinetic FDG-PET study with magnetic resonance spectroscopic imaging (MRSI) of glucose dynamics in Sprague-Dawley rats to obtain a more comprehensive view of brain glucose kinetics and determine a reliable value for the LC under isoflurane anaesthesia. Maps of Tmax /CMRglc derived from MRSI data and Tmax determined from PET kinetic modelling allowed to obtain an LC-independent CMRglc . The LC was estimated to range from 0.33 ± 0.07 in retrosplenial cortex to 0.44 ± 0.05 in hippocampus, yielding CMRglc between 62 ± 14 and 54 ± 11 μmol/min/100 g, respectively. These newly determined LCs for four distinct areas in the rat brain under isoflurane anaesthesia provide means of comparing the growing amount of FDG-PET data available from translational studies.
Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; Center for Radiopharmaceutical Sciences of ETH Zurich, Zurich, Switzerland.
Malte F
MF
Alf
João M N
JM
Duarte
Hongxia
H
Lei
Stefanie D
SD
Krämer
Vladimir
V
Mlynarik
Roger
R
Schibli
Rolf
R
Gruetter
D000465:Algorithms; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001692:Biological Transport; D001921:Brain / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism*; D001923:Brain Chemistry / Q000187:drug effects*; D002540:Cerebral Cortex / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism; D005462:Fluorine Radioisotopes / Q000032:analysis / Q000493:pharmacokinetics; D019788:Fluorodeoxyglucose F18 / Q000032:analysis / Q000493:pharmacokinetics; D005947:Glucose / Q000378:metabolism*; D006624:Hippocampus / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism; D007530:Isoflurane / Q000494:pharmacology*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008954:Models, Biological; D064847:Multimodal Imaging / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000032:analysis / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D013788:Thalamus / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism
D018685:Anesthetics, Inhalation; D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D007530:Isoflurane; D005947:Glucose
CMR

glc; glucose transport; isoflurane; lumped constant; magnetic resonance spectroscopic imaging; positron emission tomography