scholarly journals Mapping magnetic susceptibility anisotropies of white matter in vivo in the human brain at 7T

NeuroImage ◽  
2012 ◽  
Vol 62 (1) ◽  
pp. 314-330 ◽  
Author(s):  
Xu Li ◽  
Deepti S. Vikram ◽  
Issel Anne L. Lim ◽  
Craig K. Jones ◽  
Jonathan A.D. Farrell ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
White Matter ◽  
Human Brain

scholarly journals Studying magnetic susceptibility, microstructural compartmentalisation and chemical exchange in a formalin-fixed ex vivo human brain specimen

2021 ◽  
Author(s):  
Kwok-Shing Chan ◽  
Renaud Hedouin ◽  
Jeroen Mollink ◽  
Anne-Marie van Cappellen van Walsum ◽  
Jose P Marques
Keyword(s):  
Magnetic Susceptibility ◽  
White Matter ◽  
Human Brain ◽  
In Vivo Imaging ◽  
Chemical Exchange ◽  
Ex Vivo ◽  
Signal Phase ◽  
Brain Specimen ◽  
Formalin Fixed

Purpose: Ex vivo imaging is a preferable method to study the biophysical mechanism of white matter orientation-dependent signal phase evolution. Yet, how formalin fixation, commonly used for tissue preservation, affects the phase measurement is not fully known. We, therefore, study the impacts of formalin fixation on magnetic susceptibility, microstructural compartmentalisation and chemical exchange measurement on human brain tissue. Methods: A formalin-fixed, post-mortem human brain specimen was scanned with multiple orientations with respect to the main magnetic field direction for robust bulk magnetic susceptibility measurement with conventional quantitative susceptibility imaging models. Homogeneous white matter tissues were subsequently excised from the whole-brain specimen and scanned in multiple rotations on an MRI scanner to measure the anisotropic magnetic susceptibility and microstructure-related contributions in the signal phase. Electron microscopy was used to validate the MRI findings. Results: The bulk isotropic magnetic susceptibility of ex vivo whole-brain imaging is comparable to in vivo imaging, with noticeable enhanced non-susceptibility contributions. The excised specimen experiment reveals that anisotropic magnetic susceptibility and compartmentalisation phase effect were considerably reduced in formalin-fixed white matter tissue. Conclusions: Despite formalin-fixed white matter tissue has comparable bulk isotropic magnetic susceptibility to those measured via in vivo imaging, its orientation-dependent components in the signal phase related to the tissue microstructure is substantially weaker, making it less favourable in white matter microstructure studies using phase imaging.

scholarly journals Measurement of GABA and contaminants in gray and white matter in human brain in vivo

2007 ◽  
Vol 58 (1) ◽  
pp. 27-33 ◽  
Author(s):  
Changho Choi ◽  
Paramjit P. Bhardwaj ◽  
Sanjay Kalra ◽  
Colin A. Casault ◽  
Umme S. Yasmin ◽  
...  
Keyword(s):  
White Matter ◽  
Human Brain

scholarly journals Virtual in Vivo Interactive Dissection of White Matter Fasciculi in the Human Brain

NeuroImage ◽  
2002 ◽  
Vol 17 (1) ◽  
pp. 77-94 ◽  
Author(s):  
Marco Catani ◽  
Robert J. Howard ◽  
Sinisa Pajevic ◽  
Derek K. Jones
Keyword(s):  
White Matter ◽  
Human Brain

scholarly journals Euclidean distance as a measure to distinguish ventral and dorsal white matter connectivity in the human brain

2016 ◽  
Author(s):  
Philipp Kellmeyer ◽  
Magnus-Sebastian Vry
Keyword(s):  
White Matter ◽  
Human Brain ◽  
Cognitive Processing ◽  
Euclidean Distance ◽  
Large Scale ◽  
Diffusion Tensor ◽  
Large Body ◽  
Coordinate Space ◽  
Fiber Tractography

AbstractFiber tractography based on diffusion tensor imaging (DTI) has become an important research tool for investigating the anatomical connectivity between brain regions in vivo. Combining DTI with functional magnetic resonance imaging (fMRI) allows for the mapping of structural and functional architecture of large-scale networks for cognitive processing. This line of research has shown that ventral and dorsal fiber pathways subserve different aspects of bottom-up- and top-down processing in the human brain.Here, we investigate the feasibility and applicability of Euclidean distance as a simple geometric measure to differentiate ventral and dorsal long-range white matter fiber pathways tween parietal and inferior frontal cortical regions, employing a body of studies that used probabilistic tractography.We show that ventral pathways between parietal and inferior frontal cortex have on average a significantly longer Euclidean distance in 3D-coordinate space than dorsal pathways. We argue that Euclidean distance could provide a simple measure and potentially a boundary value to assess patterns of connectivity in fMRI studies. This would allow for a much broader assessment of general patterns of ventral and dorsal large-scale fiber connectivity for different cognitive operations in the large body of existing fMRI studies lacking additional DTI data.

scholarly journals In situ impedance measurements on postmortem porcine brain

2020 ◽  
Author(s):  
Lucas Poßner ◽  
Matthias Laukner ◽  
Florian Wilhelmy ◽  
Dirk Lindner ◽  
Uwe Pliquett ◽  
...  
Keyword(s):  
Experimental Study ◽  
White Matter ◽  
Human Brain ◽  
Brain Tissue ◽  
Human Brain Tissue ◽  
Experimental Conditions ◽  
Impedance Measurements ◽  
Porcine Brain

AbstractThe paper presents an experimental study where the distinctness of grey and white matter of an in situ postmortem porcine brain by impedance measurements is investigated. Experimental conditions that would allow to conduct the same experiment on in vivo human brain tissue are replicated.https://doi.org/10.1515/cdbme-2019-XXXX

Rapid Communication: Response of the Human Brain to a Hypercapnic Acid Load in Vivo

1990 ◽  
Vol 79 (1) ◽  
pp. 1-3 ◽  
Author(s):  
T. A. D. Cadoux-Hudson ◽  
B. Rajagopalan ◽  
J. G. G. Ledingham ◽  
G. K. Radda
Keyword(s):  
White Matter ◽  
Human Brain ◽  
Intracellular Ph ◽  
Grey Matter ◽  
Resonance Spectroscopy ◽  
Rotating Frame ◽  
End Tidal ◽  
End Tidal Co2 ◽  
Deep Brain

1. The aim of this investigation was to measure the change in intracellular pH of human brain in vivo in response to hypercapnia. 2. Five healthy male subjects inspired air for 20 min and then 5% CO2/95% O2 for 30 min, of which the first 10 min was used to achieve a steady-state end-tidal CO2 measurement. 3. 31P nuclear magnetic resonance spectroscopy was used to measure intracellular pH while breathing air and during hypercapnia. Simultaneous localization between superficial and deep brain was achieved by using the phase-modulated rotating frame imaging technique. One subject volunteered to breath air for a further phase-modulated rotating frame imaging study while recovering from hypercapnia. 4. End-tidal CO2 increased when breathing 5% CO2/95% O2 (on air, 5.57 ± 0.21%; on 5% CO2/95% O2, 6.41 ± 0.16%; rise = +0.84 ± 0.09%; means ± sem) causing a reduction in brain intracellular pH, which was more pronounced in deep brain (5 cm = mainly white matter, from 7.02 ± 0.006 pH units to 6.96 ± 0.001 pH units, mean ± sem) than in superficial brain (2 cm = mainly grey matter, from 7.02 ± 0.006 pH units to 7.00 ± 0.006 pH units, mean ± sem). 5. The white matter responded to hypercapnia with a greater fall in intracellular pH than the grey matter. This could either be due to differences in blood flow between grey and white matter in response to hypercapnia or to differences in intracellular pH regulation/buffering between these two tissues.

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