Time-series atlases of the rat brain after middle cerebral artery occlusion using FDG-PET images

The middle cerebral artery occlusion (MCAO) procedure is widely used in ischemic stroke research. When using functional 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) images to study ischemic stroke, the difficulty in determining the region of interest (ROI) comes from two aspects: the large variations due to differences in uptake and reaction time and the consistency of different intensity normalization methods among subjects. Using the rat as a model animal, we propose time-series atlases of ischemic stroke after MCAO based on the PET images to annotate changes in ROIs. Concretely, we spatially align serial scans with a built PET template, use histograms of orientated gradient (HOG) features to detect lesion boundaries, and combine them with results from an intensity-based detection method to construct probability maps at different time points with the Bernoulli mixture model (BMM). Simulated PET images with known ground truth and triphenyl tetrazolium chloride (TTC) staining slices validate the correctness of the time-series atlases. We demonstrate that these atlases could provide references when tracking the spatial–temporal dynamic development of lesions in rat brains.