Long period changes of hippocampal diffusion kurtosis imaging and its correlation with cognitive dysfunction after incomplete cerebral ischemia-reperfusion in rats.

This study aims to summarize the changes of functional diffusion kurtosis imaging (DKI) parameters in the bilateral hippocampal CA1 region of the hemorrhagic shock reperfusion (HSR) model of rats and their correlation with cognitive dysfunction. Adult male Sprague-Dawley rats (9-10 weeks of age, weighing 350-400 g) were randomized into the HSR group (n = 30) and the sham-operated group (Sham) (n = 30). Rats in the HSR group and the Sham group were subdivided into five time points (1, 2, 4, 8, and 12 weeks) for examination. Diffusion kurtosis imaging (DKI) was performed. Cognitive dysfunction was analyzed by the Morris Water Maze. The correlation between the DKI parameters and cognitive dysfunction was analyzed by the Spearman correlation. In the HSR group, the values of axial kurtosis (Ka), radial kurtosis (Kr), and mean kurtosis (MK) in the bilateral hippocampal CA1 of rats at 1, 2, 4, 8 and 12 weeks after the surgery were significantly higher. The rats in the HSR group had significantly longer escape latency than in the Sham group. The rats in the HSR group had significantly shorter time and shorter distance in target quadrant than those in the Sham group. The escape latency had positive correlation with MK, Ka, and Kr. The distance and the time in target quadrant had negative correlation with MK, Ka, and Kr. The parameters get from the DKI could accurately evaluate the abnormal blood perfusion and microstructure changes in hippocampal CA1 area of the incomplete cerebral ischemia reperfusion rats induced by HSR. MK, Ka, and Kr values could reflect the decreased learning and memory ability in HSR rat model.

Advanced MRI to assess hippocampal injury after incomplete cerebral ischemia-reperfusion in rats.

BACKGROUND AND PURPOSE: The purpose of this study was to evaluate advanced MRI findings in the bilateral hippocampus CA1 region of rats with hemorrhagic shock reperfusion (HSR) and their correlation with histopathological results. Additionally, this study aimed to identify effective MRI examination methods and detection indexes for assessing HSR. METHODS: Rats were randomized into the HSR and the Sham groups with 24 rats in each group. MRI examination included diffusion kurtosis imaging (DKI) and 3-dimensional arterial spin labeling (3D-ASL). Apoptosis and pyroptosis were evaluated directly from tissue. RESULTS: In the HSR group, cerebral blood flow (CBF) was significantly lower than that of the Sham group, while radial kurtosis (Kr), axial kurtosis (Ka), and mean kurtosis (MK) were all higher. In the HSR group, fractional anisotropy (FA) at 12 and 24 hours and radial diffusivity, axial diffusivity (Da), and mean diffusivity (MD) at 3 and 6 hours were lower than in the Sham group. MD and Da at 24 hours in the HSR group were significantly higher. The apoptosis rate and pyroptosis rate were also enhanced in the HSR group. CBF, FA, MK, Ka, and Kr values in the early stage were strongly correlated with apoptosis rate and pyroptosis rate. The metrics were obtained from DKI and 3D-ASL. CONCLUSIONS: Advanced MRI metrics from DKI and 3D-ASL, including CBF, FA, Ka, Kr, and MK values, are useful to evaluate abnormal blood perfusion and microstructural changes in the hippocampus CA1 area in the setting of incomplete cerebral ischemia-reperfusion in rats induced by HSR.