Automated kinetic analysis of FDG uptake in living rat brain slices from dynamic positron autoradiography

Changes in regional cerebral glucose metabolism were investigated for varying levels of tissue oxygenation using a dynamic positron autoradiography technique. While incubating fresh rat brain slices with [18F]FDG in an oxygenated solution, serial images of the tissue slices were obtained over a time period of up to 300 min and archived onto over 20 phosphorous imaging plate exposures. In order to properly create time activity curves of the uptake levels, images of the individual tissue samples were automatically located, digitally extracted, and registered with the later images of the same tissue samples. After applying image processing techniques for aligning tissue sample images, time activity curves were extracted for individual substructures in the rat brain and quantitative results were reported using Patlak plots. Since the levels of oxygenation can be controlled for these experiments, [18F]FDG uptakes can be reported representing states of hypoxia, pseudoischemia, and reoxygenation. The image processing techniques developed for this application have enabled more experiments and tissue samples to be acquired and analyzed than would otherwise be possible using manual ROI techniques. The objective spatial registration of tissue samples and automated extraction of data has increased the analysis accuracy and decreased the operator error associated with the interactive handling of the image data. This supports improved kinetic modeling of FDG uptake in animal studies, and can be used for more accurate dosimetry calculations in humans.