Phase imaging of axonal integrity of cranial corticospinal tract in experimental spinal cord injury at 9.4T.

It was known that Spinal cord injury (SCI) leads to neuronal cell death, axonal damage and demyelination, and often results in severe functional loss. Noninvasive imaging of axonal integrity may hold great importance in clinic. This study evaluated the role of phase imaging in detection of axonal integrity of cranial corticospinal tract after spinal cord injury. Quantitative MR phase imaging and diffusion tensor imaging were performed on a group of rats prior to and after spinal cord injury at 9.4 T in this study. The phase contrast decreased mainly in contralateral white matter containing the corticospinal tract (CST), i.e., pyramid by 46%, two weeks postinjury compared to preinjury levels. Diffusion measurements further showed fractional anisotropy (FA) increased and radial diffusivity (λ⊥) decreased significantly, and axial diffusivity (λ∥) remained unchanged in these regions confirmed intact fiber tracts two weeks after injury, precluding the possibility of axonal damage and potential contribution to the shifted susceptibility. It was concluded that phase imaging is a potential endogenous biomarker for brain axonal integrity after spinal cord injury. This novel tool could potentially be applied to diagnose brain pathologies in patients who have spinal cord injury.