Abstract
Post-mortem diffusion imaging of whole, human brains has potential to provide data for validation or high-resolution anatomical investigations. Previous work has demonstrated improvements in data acquired with diffusion-weighted steady-state free precession (DW-SSFP) compared with conventional diffusion-weighted spin echo at 3T. This is due to the ability of DW-SSFP to overcome signal-to-noise and diffusion contrast losses brought about by tissue fixation related decreases in T2 and ADC. In this work, data of four post-mortem human brains were acquired at 3T and 7T, using DW-SSFP with similar effective b-values (beff~5150s/mm2) for inter-field strength comparisons; in addition, DW-SSFP data were acquired at 7T with higher beff (~8550s/mm2) for intra-field strength comparisons. Results demonstrate that both datasets acquired at 7T had higher SNR and diffusion contrast than data acquired at 3T, and data acquired at higher beff had improved diffusion contrast than at lower beff at 7T. These results translate to improved estimates of secondary fiber orientations leading to higher fidelity tractography results compared with data acquired at 3T. Specifically, tractography streamlines of cortical projections originating from the corpus callosum, corticospinal tract, and superior longitudinal fasciculus were more successful at crossing the centrum semiovale and projected closer to the cortex. Results suggest that DW-SSFP at 7T is a preferential method for acquiring diffusion-weighted data of post-mortem human brain, specifically where the primary region of interest involves crossing white matter tracts.
Highlights
Diffusion tensor imaging (DTI) is an increasingly popular magnetic resonance imaging (MRI) technique for probing the microscopic architecture of white matter in the brain
Data acquired with a higher beff have more precise estimates of secondary fiber populations than lower beff, confirming that 7 T scanning supports the use of b-values that are more equivalent to those used in vivo. We investigated whether these gains improved tractography results through regions where tracts are known to interdigitate in the centrum semiovale (CS): the corpus callosum (CC), corticospinal tract and other related motor cortex projections (CST), and superior longitudinal fasciculus (SLF). 7 T data produced superior tractography results where dependence on secondary fiber populations through the CS is critical
Significant improvements in overall data quality and subsequent tractography indicate that diffusion-weighted steady-state free precession (DW-SSFP) is well suited for acquiring diffusion data in post-mortem brain
Summary
Diffusion tensor imaging (DTI) is an increasingly popular magnetic resonance imaging (MRI) technique for probing the microscopic architecture of white matter in the brain. The predominant confounding factor affecting tractography reconstruction from in vivo DTI data is the experimental time-scale. High-resolution imaging (with voxel sizes smaller than ~2 mm) generally requires long scan times as well as acquisition of a large number of diffusion-weighted (DW) image volumes to overcome the associated signal-to-noise ratio (SNR) losses. This puts an immediate strain on the subject/patient to remain still for unreasonable durations. Post-mortem tissue provides the advantage of having no time restrictions, thereby allowing for the long scan durations necessary to achieve high resolutions that are unfeasible in vivo. DTI data of post-mortem rat brain has been acquired with isotropic
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
