Meeting Abstract

P1.126  Saturday, Jan. 4 15:30  High Resolution Functional Imaging of Fish Endocrine Glands and Target Tissues Using Positron Emission Tomography-Computed Tomography WILKES, AA*; BROWNING, Z; LENOX, M; JAQUES, J; MACKENZIE, DS; Texas A and M, College Station; Texas A and M, College Station; Texas A and M Institute of Preclinical Studies; Texas Veterinary Medical Diagnostic Laboratories awilkes@bio.tamu.edu

Positron Emission Tomography-Computed Tomography (PET/CT) is a sophisticated imaging technique combining high resolution functional images of PET with anatomical three-dimensional imaging of CT. Our objective was to determine whether PET/CT imaging would be applicable to studies of endocrine function in fish. To determine whether PET/CT could effectively image endocrine organs, we injected eight individuals of two fish species with 135.2 microcuries I¹²⁴ and performed whole body PET/CT on anesthetized animals. Four fish per species were imaged six and 24 hours after injection. Although most teleosts are believed to have dispersed thyroid tissue, our images found a localized region of iodine concentration in the lower jaw. CT imaging enabled identification of anatomical coordinates allowing for histological confirmation that radiolabelled tissue was thyroid. PET/CT should thus be useful to characterize the structure of thyroid glands across diverse species. To evaluate potential uses of PET/CT for characterizing hormonal actions at target tissues, we imaged several species of fish following injection of F-fluorodeoxyglucose (FDG). FDG uptake was readily detectable in all species. Standard uptake values were similar to reported values for the same tissues in mammals. Our results suggest that it may be practical to utilize PET/CT to investigate the effects of hormones on tissue-specific glucose utilization. Overall, our results indicate that this PET/CT instrument has sufficient sensitivity and precision to be applicable to structural and functional endocrine studies in diverse fish species.