Application of positron emission tomography to determine cerebral glucose utilization in conscious infant monkeys

Cerebral glucose metabolism has been used as a marker of cerebral maturatio n and neuroplasticity. In studies addressing these issues in young non-huma n primates, investigators have used positron emission tomography (PET) and [F-18]2-fluoro-2-deoxy-D-glucose (FDG) to calculate local cerebral metaboli c rates of glucose (ICMRGlc). Unfortunately, these values were influenced b y anesthesia. In order to avoid this confounding factor, we have establishe d a method that permits reliable measurements in young conscious vervet mon keys using FDG-PET. Immature animals remained in a conscious, resting state during the initial 42 min of FDG uptake as they were allowed to cling to t heir anesthetized mothers. After FDG uptake, animals were anesthetized and placed in the PET scanner with data acquisition beginning at 60 min post-FD G injection. FDG image sets consisted of 30 planes separated by 1.69 mm, pa rameters sufficient to image the entire monkey brain. Our method of region- of-interest (ROI) analysis was assessed within and between raters and demon strated high reliability (P < 0.001). To illustrate that our method was sen sitive to developmental changes in cerebral glucose metabolism, quantitativ e studies of young conscious monkeys revealed that infant monkeys 6-8 month s of age exhibited significantly higher ICMRGlc values (P < 0.05) in all re gions examined, except sensorimotor cortex and thalamus, compared to monkey s younger than 4 months of age. This method provided high resolution images and ICMRGlc values that were reliable within age group. These results supp ort the application of FDG-PET to investigate questions related to cerebral glucose metabolism in young conscious non-human primates. (C) 1999 Elsevie r Science B.V. All rights reserved.