Diffusion tractography of post-mortem human brains: optimization and comparison of spin echo and steady-state free precession techniques.
Diffusion imaging of post-mortem brains could provide valuable data for validation of diffusion tractography of white matter pathways. Long scans (e.g., overnight) may also enable high-resolution diffusion images for visualization of fine structures. However, alterations to post-mortem tissue (T2 and diffusion coefficient) present significant challenges to diffusion imaging with conventional diffusion-weighted spin echo (DW-SE) acquisitions, particularly for imaging human brains on clinical scanners. Diffusion-weighted steady-state free precession (DW-SSFP) has been proposed as an alternative acquisition technique to ameliorate this tradeoff in large-bore clinical scanners. In this study, both DWSE and DW-SSFP are optimized for use in fixed white matter on a clinical 3-Tesla scanner. Signal calculations predict superior performance from DW-SSFP across a broad range of protocols and conditions. DW-SE and DW-SSFP data in a whole, post-mortem human brain are compared for 6- and 12-hour scan durations. Tractography is performed in major projection, commissural and association tracts (corticospinal tract, corpus callosum, superior longitudinal fasciculus and cingulum bundle). The results demonstrate superior tract-tracing from DW-SSFP data, with 6-hour DW-SSFP data performing as well as or better than 12-hour DW-SE scans. These results suggest that DW-SSFP may be a preferred method for diffusion imaging of post-mortem human brains. The ability to estimate multiple fibers in imaging voxels is also demonstrated, again with greater success in DW-SSFP data.
FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK. karla@fmrib.ox.ac.uk
Karla L
KL
Miller
Jennifer A
JA
McNab
Saad
S
Jbabdi
Gwenaëlle
G
Douaud
D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology*; D002021:Buffers; D002102:Cadaver; D003337:Corpus Callosum / Q000033:anatomy & histology; D003627:Data Interpretation, Statistical; D056324:Diffusion Tensor Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods*; D006179:Gyrus Cinguli / Q000033:anatomy & histology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D015233:Models, Statistical; D009412:Nerve Fibers / Q000502:physiology; D009434:Neural Pathways / Q000033:anatomy & histology; D011712:Pyramidal Tracts / Q000033:anatomy & histology; D011786:Quality Control; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio; D016707:Tissue Fixation
D002021:Buffers