In vivo DTI of the healthy and injured cat spinal cord at high spatial and angular resolution

Spinal cord diffusion tensor imaging (DTI) is challenging in many ways: the small size of the cord, physiological motion and susceptibility artifacts pose daunting obstacles to the acquisition of high-quality data. Here, we present DTI results computed from in vivo studies of the healthy and injured spinal cord of five cats. Both high spatial (1.1 mm3) and angular (55 directions) resolutions were used to optimise modelling of the diffusion process. Also, particular effort was directed towards a strategy that limits susceptibility artifacts. For validation purposes, acquisitions were repeated in two cats before and after making a spinal lesion. As a result, various axonal trajectories were identified by tractography including dorsal and ventral columns as well as lateral tracts. Also, fibre bundles showed robust disruption at the site of spinal cord injuries (partial and complete) via tractography, accompanied with significantly lower fractional anisotropy values at the site of lesions. Important outcomes of this work are (i) tractography-based localisation of anatomical tracts in the thoraco-lumbar spinal cord and (ii) in vivo assessment of axonal integrity following experimental spinal cord injury.