Postmortem delay does not change regional diffusion anisotropy characteristics in mouse spinal cord white matter

It has been demonstrated previously that water diffusion anisotropy in vivo is equivalent to that observed ex vivo after perfusion fixation in the mouse brain. This finding supports the practice of ex vivo diffusion tensor imaging (DTI) measurement on perfusion-fixed tissues. However, the validity of extrapolating ex vivo DTI measurements from immersion-fixed autopsy specimens to the in vivo state is questionable because of variable postmortem delays often encountered before fixation. In this study, we investigated the effect of postmortem delay on the water diffusion anisotropy of ventrolateral spinal cord white matter from mice. Mouse spinal cords, each from the same animal, were examined using DTI in vivo, in situ after death before fixation, and ex vivo immersion fixed 10h after death. Our results suggest that diffusion anisotropy in mouse spinal cord is preserved up to 10h after death. Regional characteristics of diffusion anisotropy in mouse spinal cord white matter are equivalent in vivo, in situ after death (up to 10h before fixation), and ex vivo 15 weeks after immersion fixation.