Magnetic Resonance Characterization of Axonal Response to Spinal Cord Injury.

摘要

Assessment of axon health in spinal cord injury (SCI) is vital for proper diagnosis and treatment. Magnetic resonance imaging (MRI) is routinely performed in patients and provides valuable information about cord edema and hemorrhage. However, comprehensive prediction of axonal changes from in vivo MR imaging remains elusive. At the U. Penn site, we are applying two novel MRI methods to the problem of assessment of axonal loss, axonal diameter distribution, and myelin loss (q-space imaging (QSI) and ultra-short echo-time (UTE) MRI) first on animal specimens and then on human subjects. During the final period of the project the focus of the research was on the core aim, which was to study Wallerian degeneration of spinal cord axons in a mouse injury model. Injury was induced by hemisection of the spinal cord (i.e. sectioning of only one hemisphere of the spinal cord, leaving the contralateral side intact, thereby providing an internal control). Spinal cords were examined after perfusion fixation by means of a quantitative magnetic resonance technique, called Q=space imaging or QSI, that provides indirect information on axonal structure by measuring diffusion of tissue water perpendicular to the spinal cord axis. Spinal cords were studied 3 weeks and 3 months post injury. Spinal cord degeneration was clearly evident and quantifiable at locations distant to the injury site in conformance with hypothesis. Finally, histologic images were obtained, which allow for direct visualization of axons. This portion of the project could not be completed yet but it is planned to finish the project provided funds can be obtained from other sources.