Determination of Kinetic Rate Constants for 2-[18F]fluoro-2-deoxy-d-glucose and Partition Coefficient of Water in Conscious Macaques and Alterations in Aging or Anesthesia Examined on Parametric Images with an Anatomic Standardization Technique

Abstract

Kinetic rate constants for 2-[18F]fluoro-2-deoxy-d-glucose (FDG) and the tissue-blood partition coefficient of water were determined using dynamic positron emission tomography in conscious macaques, and alterations in these parameters in aging or anesthesia were also examined. The parameters were estimated on a pixel-by-pixel basis using an anatomic standardization technique; group differences were then examined on the parametric images from the young, aged, and anesthesia groups. For the conscious condition, seven young and seven aged male rhesus macaques were used; six young male rhesus macaques were used for the isoflurane anesthesia condition. H215O and FDG were used as tracers. The kinetic parameters were estimated by a nonlinear least-square fitting procedure with compartment models including terms for the cerebral blood volume (CBV) and time delay of the input function. Cerebral blood flow (CBF) and cerebral metabolic rate of glucose (CMRglc) were also calculated from the estimated parameters. In the aged group, glucose phosphorylation was decreased more than glucose transport, and the occipital cortex was the most affected region where reduction in CBV, CMRglc, and CBF were also observed. In the anesthesia group, glucose transport was decreased; however, glucose phosphorylation was not affected except for the occipital pole. The occipital cortex was also the most affected region. The tissue-blood partition coefficient of water was decreased globally.