Optimizing experimental protocols for quantitative behavioral imaging with 18F-FDG in rodents.
Small-animal PET provides the opportunity to image brain activation during behavioral tasks in animal models of human conditions. The present studies aimed to simplify behavioral imaging procedures without a loss of quantitation by using an intraperitoneal route of administration (no cannulation, no anesthesia) and using a standardized uptake value (SUV) to reduce scan duration.


METHODS
Sixteen animals with carotid artery cannulations were studied with 18F-FDG small-animal PET accompanied by serial arterial blood sampling. Ten of these animals were anesthetized and were inside the tomograph during 18F-FDG uptake, whereas 6 animals were awake in their home cages and scanned after 60 min of uptake. Of the 10 anesthetized animals, 6 received intraperitoneal 18F-FDG, whereas 4 received intravenous 18F-FDG, and all 6 awake animals received intraperitoneal 18F-FDG. Intravenously injected animals were positioned far enough inside the tomograph to obtain region-of-interest-based measures from the heart and the brain. In all animals, a full arterial input function and plasma glucose levels were obtained. To establish the optimal time during 18F-FDG uptake for blood sampling when using an SUV, a Patlak kinetic model was used to derive absolute rates of glucose metabolism and compared with SUVs calculated using different plasma points from the arterial input function.


RESULTS
A single plasma point taken at 60 min after injection for intraperitoneal injections or 45 min after injection for intravenous injections provides a sensitive index of glucose metabolic rate with the highest correlation with data obtained from a fully quantitative input function.


CONCLUSIONS
These studies support an experimental protocol in which animals can receive the 18F-FDG tracer injection intraperitoneally, away from the small-animal tomograph and with minimal impact on behavior. Further, animals can occupy the tomograph bed for a 10- to 30-min scan with a consequent increase in animal throughput.
Schiffer
Wynne K
WK
Medical Department, Brookhaven National Laboratory, Upton, New York, New York 11973, USA. wynne@bnl.gov
Mirrione
Martine M
MM
Dewey
Stephen L
SL
D000465:Algorithms; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D001786:Blood Glucose / Q000378:metabolism; D001921:Brain / Q000000981:diagnostic imaging*; D002339:Carotid Arteries; D002404:Catheterization; D003627:Data Interpretation, Statistical; D019788:Fluorodeoxyglucose F18 / Q000008:administration & dosage*; D007091:Image Processing, Computer-Assisted; D007274:Injections, Intraperitoneal; D007275:Injections, Intravenous; D008297:Male; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000008:administration & dosage*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism
D001786:Blood Glucose; D019275:Radiopharmaceuticals; D018094:Receptors, Metabotropic Glutamate; D019788:Fluorodeoxyglucose F18