Super-resolution track-density imaging of thalamic substructures: Comparison with high-resolution anatomical magnetic resonance imaging at 7.0T

Abstract

The thalamus is one of the most important brain structures, with strong connections between subcortical and cortical areas of the brain. Most of the incoming information to the cortex passes through the thalamus. Accurate identification of substructures of the thalamus is therefore of great importance for the understanding of human brain connectivity. Direct visualization of thalamic substructures, however, is not easily achieved with currently available magnetic resonance imaging (MRI), including ultra-high field MRI such as 7.0T, mainly due to the limited contrast between the relevant structures. Recently, improvements in ultra-high field 7.0T MRI have opened the possibility of observing thalamic substructures by well-adjusted high-resolution T1 -weighted imaging. Moreover, the recently developed super-resolution track-density imaging (TDI) technique, based on results from whole-brain fiber-tracking, produces images with sub-millimeter resolution. These two methods enable us to show markedly improved anatomical detail of the substructures of the thalamus, including their detailed locations and directionality. In this study, we demonstrate the role of TDI for the visualization of the substructures of the thalamic nuclei, and relate these images to T1-weighted imaging at 7.0T MRI.

Enhanced characterization of the zebrafish brain as revealed by super-resolution track-density imaging

“…We compared DEC stTDI maps with conventional T 2 * images, diffusion tensor based images (DEC FA), and histological sections to demonstrate the efficacy of DEC stTDI maps for neuroanatomical characterization of the zebrafish brain. The structures visualized in the DEC stTDI maps were consistent with our histological analysis, supporting the veracity of the anatomical contrast in these maps, which is in agreement with previous TDI studies in the mouse (Calamante et al 2012b) and human (Calamante et al 2012a) brains. Moreover the super-resolution property and the local-directional information provided by DEC stTDI, combined with the high signal to noise ratio provided by ultra-high MRI at 16.4T, enabled enhanced examination of the zebrafish brain.…”

“…Previous studies have demonstrated the utility of DEC stTDI for visualization of small brain structures, such as the thalamic nuclei (Calamante et al 2012a), the cerebellar peduncles , and other structures in the human brain (Cho et al 2013). By registering the TDI data to other MR images and histology, more detailed highresolution atlases could be created, due to the complementary information of all these imaging modalities.…”

Mapping somatosensory connectivity in adult mice using diffusion MRI tractography and super-resolution track density imaging

“…Our TDI maps for adult barreloids were consistent with that seen in early rodent brain development, and highlight the advantage of the 3D TDI method to allow "virtual" slicing, overcoming the constraints of irreversible tissue sectioning used in histology. Overall, the MRI diffusion micro-imaging was necessary to resolve thalamic structures in mice (20μm spatial resolution for mice) compared to 200μm spatial resolution for humans (Calamante et al, 2012a); future studies are warranted to create detailed parcellation of thalamic sub-structures in mice based on connectivity pattern (Behrens et al, 2003;Calamante et al, 2012a).…”

“…Diffusion MRI is an important mapping tool for tissue structure and connectivity, including information about fibre orientation and integrity and has been used to visualize tissue microstructure in humans and animal models (Behrens et al, 2003;Calamante et al, 2012a;Calamante et al, 2010;Jiang and Johnson, 2011;Kim et al, 2012;Moldrich et al, 2010).…”

Collaborative patch-based super-resolution for diffusion-weighted images

“…Finally, in a different way, a new concept of the SR problem for DW imaging has been proposed in (Calamante et al, 2012a;Calamante et al, 2010;Calamante et al, 2012b;Nedjati-Gilani et al, 2008). Instead of increasing image resolution, the authors proposed to reconstruct a HR density map by using the extra information resulting from tractography.…”