scholarly journals High-gradient diffusion MRI reveals distinct estimates of axon diameter index within different white matter tracts in the in vivo human brain

2019 ◽  
Vol 225 (4) ◽  
pp. 1277-1291 ◽  
Author(s):  
Susie Y. Huang ◽  
Qiyuan Tian ◽  
Qiuyun Fan ◽  
Thomas Witzel ◽  
Barbara Wichtmann ◽  
...  
Keyword(s):  
White Matter ◽  
Human Brain ◽  
Diffusion Mri ◽  
Axon Diameter ◽  
White Matter Tracts ◽  
High Gradient ◽  
Gradient Diffusion

scholarly journals Does powder averaging remove dispersion bias in diffusion MRI diameter estimates within real 3D axonal architectures?

2021 ◽  
Author(s):  
Mariam Andersson ◽  
Marco Pizzolato ◽  
Hans Martin Kjer ◽  
Katrine Forum Skodborg ◽  
Henrik Lundell ◽  
...  
Keyword(s):  
White Matter ◽  
Diffusion Mri ◽  
Ex Vivo ◽  
Dynamic Properties ◽  
High Signal ◽  
Axon Diameter ◽  
Signal To Noise ◽  
B Values ◽  
Wide Range

Noninvasive estimation of axon diameter with diffusion MRI holds potential to investigate the dynamic properties of the brain network and pathology of neurodegenerative diseases. Recent methods use powder averaging to account for complex white matter architectures, such as fibre crossing regions, but these have not been validated for real axonal geometries. Here, we present 120-313 μm long segmented axons from X-ray nano-holotomography volumes of a splenium and crossing fibre region of a vervet monkey brain. We show that the axons in the complex crossing fibre region, which contains callosal, association, and corticospinal connections, are larger and exhibit a wider distribution than those of the splenium region. To accurately estimate the axon diameter in these regions, therefore, sensitivity to a wide range of diameters is required. We demonstrate how the q-value, b-value, signal-to-noise ratio and the assumed intra-axonal parallel diffusivity influence the range of measurable diameters with powder average approaches. Furthermore, we show how Gaussian distributed noise results in a wider range of measurable diameter at high b-values than with Rician distributed noise, even at high signal-to-noise ratios of 100. The number of gradient directions is also shown to impose a lower bound on measurable diameter. Our results indicate that axon diameter estimation can be performed with only few b-shells, and that additional shells do not improve the accuracy of the estimate. Through Monte Carlo simulations of diffusion, we show that powder averaging techniques succeed in providing accurate estimates of axon diameter across a range of sequence parameters and diffusion times, even in complex white matter architectures. At sufficiently low b-values, the acquisition becomes sensitive to axonal microdispersion and the intra-axonal parallel diffusivity shows time dependency at both in vivo and ex vivo intrinsic diffusivities.

In vivo waveguide elastography of white matter tracts in the human brain

2012 ◽  
Vol 68 (5) ◽  
pp. 1410-1422 ◽  
Author(s):  
Anthony Romano ◽  
Michael Scheel ◽  
Sebastian Hirsch ◽  
Jürgen Braun ◽  
Ingolf Sack
Keyword(s):  
White Matter ◽  
Human Brain ◽  
White Matter Tracts

scholarly journals Axon diameter index estimation independent of fiber orientation distribution using high-gradient diffusion MRI

NeuroImage ◽  
2020 ◽  
Vol 222 ◽  
pp. 117197 ◽  
Author(s):  
Qiuyun Fan ◽  
Aapo Nummenmaa ◽  
Thomas Witzel ◽  
Ned Ohringer ◽  
Qiyuan Tian ◽  
...  
Keyword(s):  
Fiber Orientation ◽  
Diffusion Mri ◽  
Orientation Distribution ◽  
Axon Diameter ◽  
High Gradient ◽  
Gradient Diffusion ◽  
Fiber Orientation Distribution ◽  
Index Estimation

scholarly journals Diffusion MRI microstructure models with in vivo human brain Connectome data: results from a multi-group comparison

2017 ◽  
Vol 30 (9) ◽  
pp. e3734 ◽  
Author(s):  
Uran Ferizi ◽  
Benoit Scherrer ◽  
Torben Schneider ◽  
Mohammad Alipoor ◽  
Odin Eufracio ◽  
...  
Keyword(s):  
Human Brain ◽  
Diffusion Mri ◽  
Group Comparison ◽  
Brain Connectome

scholarly journals In vivo DTI evaluation of white matter tracts in rat spinal cord

2006 ◽  
Vol 24 (1) ◽  
pp. 231-234 ◽  
Author(s):  
Jayaroop Gullapalli ◽  
Jaroslaw Krejza ◽  
Eric D. Schwartz
Keyword(s):  
Spinal Cord ◽  
White Matter ◽  
Rat Spinal Cord ◽  
White Matter Tracts

Characterizing glioma microenvironment with ultra-high gradient diffusion MRI.

2017 ◽  
Vol 35 (15_suppl) ◽  
pp. 2050-2050
Author(s):  
Ina Ly ◽  
Barbara Wichtmann ◽  
Susie Yi Huang ◽  
Aapo Nummenmaa ◽  
Ovidiu Andronesi ◽  
...  
Keyword(s):  
Diffusion Model ◽  
Diffusion Mri ◽  
Volume Fraction ◽  
Response To Treatment ◽  
Imaging Biomarker ◽  
Normal Brain ◽  
Post Contrast ◽  
Major Barrier ◽  
High Gradient ◽  
Gradient Diffusion

2050 Background: The infiltrating nature of gliomas, particularly into the peritumoral area, is a major barrier to improving clinical outcome as microscopic disease remains even after apparent gross total resection. Conventional T1 post-contrast and T2/FLAIR MRI do not capture full tumor extent. A better imaging biomarker is needed to improve differentiation between tumor, peritumoral area and normal brain. Methods: 4 pre-surgical patients with non-enhancing, FLAIR-hyperintense lesions suspicious for glioma underwent ultra-high gradient diffusion MRI on the Connectome MRI scanner, a unique scanner with maximum gradient strength of 300 mT/m enabling mapping of cellular microstructures on a micron-level scale. The FLAIR area was defined as the tumor region of interest (ROI). Radiographically normal appearing brain up to 1 cm around the FLAIR area was defined as the peritumoral ROI. Using a novel 3 compartment diffusion model (Linear Multiscale Model), the volume fraction of water (VFW) was calculated within restricted (intracellular), hindered (extracellular) and free (CSF) spaces. VFW in the tumor, peritumoral ROI, contralateral normal white matter (WM) and cortex were compared. Results: Within the tumor ROI, the median VFW in the restricted compartment was decreased vs. the peritumoral ROI (↓ 34%), WM (↓ 46%) and cortex (↓ 18%) while median VFW in the hindered compartment was increased vs. the peritumoral ROI (↑ 26%), WM (↑ 54%) and cortex (↑ 25%). Within the peritumoral ROI, median VFW in the hindered compartment was increased compared to WM (↑ 23%). 3 patients had available histopathology revealing isocitrate dehydrogenase-mutant gliomas. Conclusions: Using ultra-high gradient diffusion MRI and a novel diffusion model, we detected distinct diffusion patterns in the tumor and peritumoral area not seen on conventional MRI. Lower VFW in the restricted compartment within the tumor may reflect decreased intracellular water mobility due to enlarged nuclei. Higher VFW in the hindered compartment in the tumor and peritumoral area may reflect higher degree of tissue permeability and edema. MRI-pathology and larger cohort validation studies are underway to elucidate microenvironment changes in response to treatment.

scholarly journals Representing Diffusion MRI in 5-D Simplifies Regularization and Segmentation of White Matter Tracts

2007 ◽  
Vol 26 (11) ◽  
pp. 1547-1554 ◽  
Author(s):  
Lisa Jonasson ◽  
Xavier Bresson ◽  
Jean-Philippe Thiran ◽  
Van J. Wedeen ◽  
Patric Hagmann
Keyword(s):  
White Matter ◽  
Diffusion Mri ◽  
White Matter Tracts

scholarly journals Functional Diffusion Tensor Imaging: Measuring Task-Related Fractional Anisotropy Changes in the Human Brain along White Matter Tracts

PLoS ONE ◽  
2008 ◽  
Vol 3 (11) ◽  
pp. e3631 ◽  
Author(s):  
René C. W. Mandl ◽  
Hugo G. Schnack ◽  
Marcel P. Zwiers ◽  
Arjen van der Schaaf ◽  
René S. Kahn ◽  
...  
Keyword(s):  
Diffusion Tensor Imaging ◽  
White Matter ◽  
Human Brain ◽  
Fractional Anisotropy ◽  
Diffusion Tensor ◽  
White Matter Tracts
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