Abstract:

Objective To observe the changes of diffusion weighted imaging (DWI) after diffuse axonal injury (DAI) in rats. Methods Models of various degrees of DAI (mild, moderate, and severe) were established in 135 SD rats by Marmarou method, and MRI examinations were performed 4, 8 and 24 h after injury. Another 8 rats were served as control group. The findings of MRI were analysed, and the apparent diffusion coefficient (ADC) values were compared among each group. Results No clear traumatic lesion was found from MRI in rats after injury. Four hours after injury, ADC values decreased in each DAI group, and there were significant differences between moderate DAI group and control group, and between severe DAI group and control group (P<0.05). Eight hours after injury, ADC values increased in each DAI group, and there was no significant difference between DAI groups and control group (P>0.05). There were significant differences in ADC values between 8 h after injury and 4 h after injury in severe DAI group (P<0.05), while there was no significant difference in moderate and mild DAI groups (P>0.05). Twenty-four hours after injury, ADC values continuously increased, especially in severe trauma group. Conclusion ADC values may reveal traumatic changes that can not be demonstrated by MRI. ADC values decrease in acute phase of DAI in rats, then increased, and the degree of variation may be related to the severity of DAI.

Key words: diffuse axonal injury, magnetic resonance imaging, diffusion weighted imaging, apparent diffusion coefficient