Objective:To establish stable and controllable brain injury with accurate degree and good repeatability in rat model.Methods:Controlled cortical impact(CCI) device was used to prepare for the rat brain injury model by the impact head of different model(Group A No.4.Group B No.5,Group C No.6) and the impact depth(Group A:1.5-2.0 mm.Group B:2.5-3.0 mm.Group C:3.5-4.0mm) with impact time of 0.1 s and impact velocity of 2.5 m/s.Twelve rats with three months of age were used in each group(the impact depth of every two rats was added 1 mm respectively).After modeling for 1 h,magnetic resonance imaging(MRI) was received and brain histopathology was observed to assess degree of injury by model parameter's of three groups.Results:After modeling of Group A,MRI showed that the cortex structure was damaged with a small amount of bleeding in center and mild edema around,and the total volume of injury was(28.69±4.94)mm^3.Pathology revealed the injury was confined to the superficial cortical with mild edema of nerve cell,which was assessed as mild cerebral contusion.While after modeling,MRI of Group B showed that the structure of cortex and medulla were damaged simultaneously and extended to cerebral nuclei zone,With 4 cases of hematoma in the center and larger edema range around,and the total volume of injury was(78.38±9.28) mm^3.Pathology revealed the injury range was reached nuclei zone,with swell of nerve cell and mitochondria,which was assessed to moderate cerebral contusion.After modeling of Group C,MRI showed that extensive tissue injury was appeared in cortex and medulla and deep nuclei,with 9 cases of hematoma and large edema signal of surrounding tissue T2W1,while in 5 cases,lateral nucleus of injury signal was increased,and the total volume of injury was(135.89±24.80)mm^3.Pathology revealed the deep cerebral nuclei was damaged,with the disappearance of neuronal structure and vacuolization of mitochondria,which was assessed as severe cerebral contusion.MRI changes were consistent with pathological changes in three
