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Low frequency oscillating gradient spin-echo sequences improve sensitivity to axon diameter: An experimental study in viable nerve tissue
2017
NeuroImage
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Overall, these results suggest, quantitatively and in in vivo conditions, that low-frequency OGSE sequences may provide improved accuracy of axon diameter mapping compared to standard SDE sequences. ...
However, a growing number of studies show that oscillating gradient spin echo (OGSE) sequences can provide additional advantages over conventional SDE sequences. ...
Acknowledgements This work was funded by: EPSRC (EP/K502959/1, EP/J500331/1), the EPSRC-funded UCL Centre for Doctoral Training in Medical Imaging (EP/L016478/1) and the NIHR-funded Biomedical Research ...
doi:10.1016/j.neuroimage.2017.07.060
pmid:28774648
fatcat:654kgpjszfejfpeav53fsx2bau
Time-dependent diffusion in undulating thin fibers: Impact on axon diameter estimation
2019
NMR in Biomedicine
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We study time-dependent diffusion in the frequency domain and characterize the diffusion spectrum by its height, width, and low-frequency behavior (power law exponent). ...
If the straight-cylinder assumption is used to interpret data from undulating thin axons, the diameter is overestimated by an amount proportional to the undulation amplitude and microscopic orientation ...
ACKNOWLEDGEMENTS We would like to thank Dr Sune Jespersen, Björn Lampinen, and Dr Filip Szczepankiewicz for providing feedback that improved this manuscript.
FUNDING INFORMATION ...
doi:10.1002/nbm.4187
pmid:31868995
pmcid:PMC7027526
fatcat:f7jxi3legrg5fmjnks42k7fcx4
Quantification of cell size using temporal diffusion spectroscopy
2015
Magnetic Resonance in Medicine
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By combining measurements made using oscillating gradient spin echo (OGSE) and a conventional pulsed gradient spin echo (PGSE) acquisition with a single, relatively long diffusion time, we can accurately ...
Oscillating gradients have been used previously to probe variations on cellular and subcellular scales, but their ability to accurately measure cell sizes larger than 10 μm is limited. ...
Oscillating gradient spin echo (OGSE) sequences have emerged as a novel means to obtain much shorter effective diffusion times by replacing bipolar diffusion-sensitizing gradients in PGSE methods with ...
doi:10.1002/mrm.25684
pmid:25845851
pmcid:PMC4592783
fatcat:r763qqrl7betbmis363mird67e
MRI with ultrahigh field strength and high-performance gradients: challenges and opportunities for clinical neuroimaging at 7 T and beyond
2021
European Radiology Experimental
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Research in ultrahigh magnetic field strength combined with ultrahigh and ultrafast gradient technology has provided enormous gains in sensitivity, resolution, and contrast for neuroimaging. ...
This article provides an overview of the technical advantages and challenges of performing clinical neuroimaging studies at ultrahigh magnetic field strength combined with ultrahigh and ultrafast gradient ...
Augusto Lio Goncalves Filho for sharing the images used in Fig. 7 . ...
doi:10.1186/s41747-021-00216-2
pmid:34435246
pmcid:PMC8387544
fatcat:75bnubdt2rhhzg3tng5syb26oa
Imaging brain microstructure with diffusion MRI: practicality and applications
2017
NMR in Biomedicine
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J-L, Axon diameter indices from the monkey brain using ActiveAx (J), 11 ex vivo spinal cord (K) 12 and in vivo spinal cord using 300 mT/m gradients (L). 13 M-P, Imaging cell shape indices. ...
I, Estimated axon diameter distributions from diffusion MRI using AxCaliber in Reference 10 of the in vivo rat-brain cluster into groups reflecting corresponding diameter histograms from histology. ...
[99] [100] [101] [102] Oscillating diffusion encoding (ODE) can be achieved with the oscillating gradient spin echo (OGSE) sequence, which replaces the constant gradient pulses in SDE with pulses that ...
doi:10.1002/nbm.3841
pmid:29193413
fatcat:43pukyiwubb6bhsaey5gs3sizy
The sensitivity of diffusion MRI to microstructural properties and experimental factors
2020
Journal of Neuroscience Methods
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This work reviews the state-of-the-art methods for studying brain microstructure using diffusion MRI and their sensitivity to microstructural differences and various experimental factors. ...
The sensitivity of the diffusion MRI signal to the microstructural components and the effects of curvedness of axonal trajectories on the diffusion signal are reviewed. ...
There are clear benefits to using special sequences. For example, the OGSE improves the sensitivity to axon diameter in the presence of orientation dispersion . ...
doi:10.1016/j.jneumeth.2020.108951
pmid:33017644
pmcid:PMC7762827
fatcat:oi3x6utivvh6pbqalmbg3zr5tm
Impact of transcytolemmal water exchange on estimates of tissue microstructural properties derived from diffusion MRI
2016
Magnetic Resonance in Medicine
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Conclusion-For the sequences and models considered in this study, transcytolemmal water exchange has minor impacts on fittings of d and D in with physiologically relevant membrane permeabilities if SNR ...
Methods-Computer simulations were performed to incorporate a broad range of intracellular water life times τ in (50 -∞ ms), cell diameters d (5 -15 μm), and intrinsic diffusion coefficient D in (0.6 -2 ...
When diffusion times are short enough (such as those obtained using oscillating gradient spin echo (OGSE) sequences at moderately high gradient frequencies (6) ), ADC can be sensitive to intracellular ...
doi:10.1002/mrm.26309
pmid:27342260
pmcid:PMC5183568
fatcat:ar7yg2tvn5addpxzeizj7oxc2u
Double diffusion encoding and applications for biomedical imaging
2020
Journal of Neuroscience Methods
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Note that this fulltext copy is not of the "primary" version of this work. The version it corresponds to is:
2020 pre-print arXiv:2011.02913v1 fatcat:w7jjqtzsxndmxnfat3qq6jpaba
DDE measurements can also be used to improve the robustness of biophysical models (Section 5) and study intra-cellular diffusion via magnetic resonance spectroscopy of metabolites (Section 7). ...
These enhanced contrasts can play important roles in characterizing biological tissues, for instance upon diseases (e.g. neurodegenerative, cancer, stroke), aging, learning, and development. ...
Acknowledgements The authors would like to acknowledge the following sources of financial support. ...
doi:10.1016/j.jneumeth.2020.108989
pmid:33144100
fatcat:qqjbwghlmngbzctpi2cs37gz4m
MRI-Guided Focused Ultrasound Surgery
2009
Annual Review of Medicine
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Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequence of their ...
Gradient and Spin Echo (GRASE) Sequence A gradient and spin echo (GRASE) sequence is a combination of FSE and EPI. A series of 180° RF pulses is applied to generate several spin echoes (as in FSE). ...
Gradient Echo (GRE) Sequences Gradient echo sequences are also known as gradient-recalled echo or fastfield echo (FFE) sequences. ...
doi:10.1146/annurev.med.60.041707.170303
pmid:19630579
pmcid:PMC4005559
fatcat:7ojh6xtfc5ckvloxhnfb5dxtmi
Challenges for biophysical modeling of microstructure
2020
Journal of Neuroscience Methods
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First, we describe the critical initial task of selecting which features of tissue microstructure can be estimated using a model and which acquisition protocol needs to be implemented to make the estimation ...
The model performance should necessarily be tested in realistic numerical simulations and in experimental data - adapting the fitting strategy accordingly, and parameter estimates should be validated against ...
R01EB017230 and T32EB001628 (to KGS). ...
doi:10.1016/j.jneumeth.2020.108861
pmid:32692999
fatcat:bapfiafyqvcbtky3qggqibefsu
Review: magnetic resonance imaging techniques in ophthalmology
2012
Molecular Vision
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This review aims to classify the MRI techniques used to date in clinical and preclinical ophthalmologic studies, describing the qualitative and quantitative information that may be extracted and how this ...
Imaging the eye with magnetic resonance imaging (MRI) has proved difficult due to the eye's propensity to move involuntarily over typical imaging timescales, obscuring the fine structure in the eye due ...
Spin-echo, gradientrecalled echo, steady-state free precession, and echo planar imaging-based pulse sequences can be designed to be sensitive to motion with a specific frequency, a particular multiple ...
pmid:23112569
pmcid:PMC3482169
fatcat:7hxwr7gp5rbsvp77r4gu4bycsu
Segmentation of neuroanatomy in magnetic resonance images
1992
Medical Imaging VI: Image Processing
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In the unlikely e v e n t that the a u thor did not send a c o m p le te m anuscript and there are missing pages, these will be noted. ...
Also, if m aterial had to be rem oved, a n o te will ind ica te the deletion. ...
The second possible improvement is the use of either an inversion recovery sequence, or an inversion pre-pulse prior to a fast spin echo pulse sequence to null the signal from CSF [WHITE92]. ...
doi:10.1117/12.59406
fatcat:rbchl46uffcj5cysrho2pr2ewy
Pushing spatial and temporal resolution for functional and diffusion MRI in the Human Connectome Project
2013
NeuroImage
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These are: 1) resting state functional MR imaging (rfMRI) which uses correlations in the temporal fluctuations in an fMRI time series to deduce 'functional connectivity'; 2) diffusion imaging (dMRI), which ...
in the human brain in order to assist analyses of data obtained with the first two methods. ...
Acknowledgments The work reported in this article was supported by the Human Connectome Project (1U54MH091657) from the 16 Institutes and Centers of the National Institutes of Health that support the NIH ...
doi:10.1016/j.neuroimage.2013.05.012
pmid:23702417
pmcid:PMC3740184
fatcat:wajdgqkztvg43eyxxovlxlshky
International Society for Therapeutic Ultrasound Conference 2016
2017
Journal of Therapeutic Ultrasound
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Conclusions X-ray CT HU are sensitive to thermal changes, indicating their potential to serve as a tool for thermal monitoring. ...
In conclusion, assuming that radiation dose can be reduced to an acceptable level, Xray CT may be a valuable modality for non-invasive monitoring of HIFU thermal procedures. ...
The Sequence consisted of two echoes a gradient echo (TE = 4 ms) and a spin echo (TE = 46 ms). ...
doi:10.1186/s40349-016-0079-2
fatcat:wjrvxyhd5bappjipymenn5swwq
Proton Magnetic Resonance Spectroscopy of the Central Nervous System
[chapter]
2013
Novel Frontiers of Advanced Neuroimaging
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SVS is based on the stimulated echo acquisition mode (STEAM) [52] or the point resolved spectroscopy (PRESS) [53] pulse sequences while MRSI uses a variety of pulse sequences (Spin Echo, PRESS etc ...
The pulse sequence is designed to collect only the echo signal from the point where all three slices intersect [53] . ...
doi:10.5772/53892
fatcat:trfmtqcmdbflrb5qvkl5tadmze
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