Diffusion imaging of whole, post-mortem human brains on a clinical MRI scanner

Karla L Miller,Charlotte J Stagg,Gwenaëlle Douaud,Saad Jbabdi,Stephen M Smith,Timothy E.J Behrens,Mark Jenkinson,Steven A Chance,Margaret M Esiri,Natalie L Voets,Ned Jenkinson,Tipu Z Aziz,Martin R Turner,Heidi Johansen-Berg,Jennifer A Mcnab

doi:10.1016/j.neuroimage.2011.03.070

Abstract

Diffusion imaging of post mortem brains has great potential both as a reference for brain specimens that undergo sectioning, and as a link between in vivo diffusion studies and “gold standard” histology/dissection. While there is a relatively mature literature on post mortem diffusion imaging of animals, human brains have proven more challenging due to their incompatibility with high-performance scanners. This study presents a method for post mortem diffusion imaging of whole, human brains using a clinical 3-Tesla scanner with a 3D segmented EPI spin-echo sequence. Results in eleven brains at 0.94×0.94×0.94mm resolution are presented, and in a single brain at 0.73×0.73×0.73mm resolution. Region-of-interest analysis of diffusion tensor parameters indicate that these properties are altered compared to in vivo (reduced diffusivity and anisotropy), with significant dependence on post mortem interval (time from death to fixation). Despite these alterations, diffusion tractography of several major tracts is successfully demonstrated at both resolutions. We also report novel findings of cortical anisotropy and partial volume effects.

Highlights

Diffusion-weighted MRI has become a popular method for investigating white matter non-invasively
The diffusivity is reduced by 0.01–0.02 × 10− 3 mm2/s/h; extrapolating the regression curves to a PMI of zero hours does not yield common in vivo values, indicating either a non-linear dependence on PMI, or that additional factors may contribute to these changes
The one white-matter region that is essentially independent of PMI is the posterior limb of the internal capsule, but this region does have a trend toward correlation with SI

Summary

Introduction

Diffusion-weighted MRI has become a popular method for investigating white matter non-invasively. A number of studies have demonstrated the feasibility and utility of diffusion imaging of ex vivo animal brains (Guilfoyle et al, 2003; Verma et al, 2005; Kroenke et al, 2005; D'Arceuil et al, 2007, 2008; Dyrby et al, 2007; Tyszka and Frank, 2009), spinal cord (Schwartz et al, 2005; Kim et al, 2009) and brain tissue sections (Guilfoyle et al, 2003; D'Arceuil et al, 2005) These studies have utilized small-bore, high-field scanners, typically with a maximum gradient amplitude of 400 mT/m or greater (10 times that available on most clinical systems). We explore the possibility of post mortem diffusion imaging with a steady-state free precession sequence (McNab et al, 2009a), which has potential to overcome this problem

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Conclusion