Abstract: Objective To explore the applicability of magnetic resonance diffusion tensor imaging（DTI） for diagnosis of pyramidal tract damage in rats. Methods Marmarou’s model was set up, followed by DTI scanning at 3, 12, 24 and 72 h post trauma to acquire the dispersion parameter of bilateral pyramidal tracts. Moreover, axonal varicosities per square millimeter and the percentage of positive area of axons demonstrated by β-amyloid precursor protein（β-APP） immunostaining were obtained, as well as the mean density and sum density of neurofilament（NF） 68 immunostaining. Results Axial diffusivity（AD）, fraction anisotropy（FA） and relative anisotropy（RA） in the pyramidal tract were significantly and continuously reduced and reached to the bottom at 72 h post trauma（P<0.05） in accord with the gradient of axonal damage verified by β-APP and NF68 immunostaining. Furthermore, the changes of AD, FA and RA showed a significant negative correlation with the β-APP immunohistochemical results. Conclusion DTI has important value for early diagnosis in pyramidal tract damage.

Key words: forensic pathology, craniocerebral trauma, pyramidal tracts, diffusion magnetic resonance imaging, rats