White matter tract-oriented deformation is dependent on real-time axonal fiber orientation

AbstractTraumatic axonal injury (TAI) is a critical public health issue with its pathogenesis remaining largely elusive. Finite element (FE) head models are promising tools to bridge the gap between mechanical insult, localized brain response, and resultant injury. In particular, the FE-derived deformation along the direction of white matter (WM) tracts (i.e., tract-oriented strain) has been shown to be an appropriate predictor for TAI. However, the evolution of fiber orientation in time during the impact and its potential influence on the tract-oriented strain remains unknown. To address this question, the present study leveraged an embedded element approach to track real-time fiber orientation during impacts. A new scheme to calculate the tract-oriented strain was proposed by projecting the strain tensors from pre-computed simulations along the temporal fiber direction instead of its static counterpart directly obtained from diffuse tensor imaging. The results revealed that incorporating the real-time fiber orientation not only altered the direction but also amplified the magnitude of the tract-oriented strain, resulting in a generally more extended distribution and a larger volume ratio of WM exposed to high deformation along fiber tracts. These effects were exacerbated with the impact severities characterized by the acceleration magnitudes. Results of this study provide insights into how best to incorporate fiber orientation in head injury models and derive the WM tract-oriented deformation from computational simulations, which is important for furthering our understanding of the underlying mechanisms of TAI.

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The impact of isolated lesions on white-matter fiber tracts in multiple sclerosis patients

NeuroImage Clinical ◽

10.1016/j.nicl.2015.03.003 ◽

2015 ◽

Vol 8 ◽

pp. 110-116 ◽

Cited By ~ 19

Author(s):

Amgad Droby ◽

Vinzenz Fleischer ◽

Marco Carnini ◽

Hilga Zimmermann ◽

Volker Siffrin ◽

...

Keyword(s):

Multiple Sclerosis ◽

White Matter ◽

Fiber Tracts ◽

White Matter Fiber Tracts ◽

Multiple Sclerosis Patients ◽

The Impact

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Influence of Fiber Orientation and Volume Fraction on Tensile Strength and Fatigue Life of CARALL Hybrid Composite

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.353-358.1455 ◽

2007 ◽

Vol 353-358 ◽

pp. 1455-1458 ◽

Cited By ~ 2

Author(s):

Han Ki Yoon

Keyword(s):

Tensile Strength ◽

Fatigue Life ◽

Carbon Fiber ◽

Hybrid Composite ◽

Fiber Orientation ◽

Small Volume ◽

Volume Fraction ◽

Volume Ratio ◽

Fiber Direction ◽

Life Tests

In this paper the tensile and fatigue life tests of carbon fiber-reinforced epoxy prepreg (CFRP) were conducted in order to investigate the influence of volume ratio and fiber orientation. CFRP/Al7075 laminate hybrid composite (CARALL) consists of alternating Al7075-T6 sheets and carbon epoxy prepreg (epoxy 121oC #2560). The fiber orientations of CFRP were applied to the extent of 0/90° and ±45°. The CFRP layers are 1ply, 3plies and 5plies in case of 0/90°, and 1ply and 2plies in case of ±45° of carbon fiber direction, respectively. The tensile strength decreased with the volume ratio of CFRP in both the cases of fiber orientation 0/90° and ±45°. The fatigue life is lower in large volume ratio of CFRP than in small volume ratio in both the cases of fiber orientation 0/90° and ±45°.

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Motor threshold in transcranial magnetic stimulation: The impact of white matter fiber orientation and skull-to-cortex distance

Human Brain Mapping ◽

10.1002/hbm.20649 ◽

2009 ◽

Vol 30 (7) ◽

pp. 2044-2055 ◽

Cited By ~ 62

Author(s):

Tal Herbsman ◽

Lauren Forster ◽

Christine Molnar ◽

Robert Dougherty ◽

Doug Christie ◽

...

Keyword(s):

Transcranial Magnetic Stimulation ◽

White Matter ◽

Fiber Orientation ◽

Magnetic Stimulation ◽

Motor Threshold ◽

The Impact

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The impact of real-time fMRI denoising on online evaluation of brain activity and functional connectivity

10.1101/2021.03.02.433573 ◽

2021 ◽

Author(s):

Masaya Misaki ◽

Jerzy Bodurka

Keyword(s):

White Matter ◽

Functional Connectivity ◽

Noise Reduction ◽

Real Time ◽

Brain Activity ◽

Time Estimation ◽

Blood Oxygenation ◽

Physiological Noise ◽

Global Signal ◽

The Impact

AbstractObjectiveComprehensive denoising is imperative in fMRI analysis to reliably evaluate neural activity from the blood oxygenation level dependent signal. In real-time fMRI, however, only a minimal denoising process has been applied and the impact of insufficient denoising on online brain activity estimation has not been assessed comprehensively. This study evaluated the noise reduction performance of online fMRI processes in a real-time estimation of regional brain activity and functional connectivity.ApproachWe performed a series of real-time processing simulations of online fMRI processing, including slice-timing correction, motion correction, spatial smoothing, signal scaling, and noise regression with high-pass filtering, motion parameters, motion derivatives, global signal, white matter/ventricle average signals, and physiological noise models with image-based retrospective correction of physiological motion effects (RETROICOR) and respiration volume per time (RVT).Main resultsAll the processing was completed in less than 400 ms for whole-brain voxels. Most processing had a benefit for noise reduction except for RVT that did not work due to the limitation of the online peak detection. The global signal regression, white matter/ventricle signal regression, and RETORICOR had a distinctive noise reduction effect, depending on the target signal, and could not substitute for each other. Global signal regression could eliminate the noise-associated bias in the mean dynamic functional connectivity across time.SignificanceThe results indicate that extensive real-time denoising is possible and highly recommended for real-time fMRI applications.

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Abstract 221: Regional Vulnerability within White Matter tracts to White Matter Hyperintensities: a Diffusion Tensor Imaging Tractography Study

Stroke ◽

10.1161/str.46.suppl_1.221 ◽

2015 ◽

Vol 46 (suppl_1) ◽

Author(s):

Pauline Maillard ◽

Sudha Seshadri ◽

Alexa Beiser ◽

Jayandra Himali ◽

Charles DeCarli

Keyword(s):

Diffusion Tensor Imaging ◽

White Matter ◽

Cognitive Decline ◽

White Matter Hyperintensities ◽

Diffusion Tensor ◽

Brain Mri ◽

Fiber Tracts ◽

Regional Vulnerability ◽

Increased Risk ◽

The Impact

Background: Characterizing the impact of cerebral white matter (WM) damage on age related cognitive decline is of growing interest. White matter hyperintensities (WMH) and reduced microstructural WM integrity, as expressed by diffusion tensor imaging (DTI), have been associated with increased risk of clinically cognitive decline in the elderly, but the regional vulnerability within certain WM tracts to WMH is not well understood. Characterizing the implication and interactions of microstructural integrity and WMH within specific WM tracts would further elucidate mechanisms of cognitive decline in normal aging. Methods: 410 cognitively normal individuals from the Offspring Framingham Heart Study, aged 72.5±7.5 ([54.2; 104.9]), received a comprehensive clinical evaluation and brain MRI including FLAIR and DTI sequences. WM tractography was performed from DTI using FSL tools, resulting in 27 fiber tracts maps for each subject. WMHs were detected on FLAIR scans using a standardized protocol and coregistered to the subject DTI space. The mean fractional anisotrophy (mFA) within each tract was computed. Superimposition of WMH masks onto fiber tracts maps was used to calculate the overlap ratio of WMH (WMHor) within each tract. For each tract, mFA was regressed against the age and tract size and resulting residuals related to WMHor using a linear regression model. Results: The highest rates of WMHor were found within the thalamic radiations (range: [0- 28%]) and the inferior longitudinal fasciculi ([0- 29%]). Lower mFA was independently associated with larger WMHor within almost all association and projection fibers (p values<0.05). Correcting for the overall WMH burden did not significantly alter the results. Discussion: Regional mean FA has been previously associated with the overall WMH burden. We extended this finding by showing that, independently of the overall WM injury, microstructural WM integrity was associated with WMH within specific fiber tracts. Further investigations are needed to detangle the impact of specific tract disruption from that of more generalized subtle WM injury on cognitive decline.

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