scholarly journals Quantifying nerve decussation abnormalities in the optic chiasm

2019 ◽  
Author(s):  
Robert J. Puzniak ◽  
Khazar Ahmadi ◽  
Jörn Kaufmann ◽  
Andre Gouws ◽  
Antony B. Morland ◽  
...  
Keyword(s):  
Diffusion Mri ◽  
Diffusion Tensor ◽  
Area Under The Curve ◽  
Optic Chiasm ◽  
List Type ◽  
Test Model ◽  
Discriminative Power ◽  
Significant Group ◽  
Structural Abnormalities

AbstractObjectiveThe human optic chiasm comprises partially crossing optic nerve fibres. Here we used diffusion MRI (dMRI) for the in-vivo identification of the abnormally high proportion of crossing fibres found in the optic chiasm of people with albinism.MethodsIn 9 individuals with albinism and 8 controls high-resolution 3T dMRI data was acquired and analyzed with a set of methods for signal modeling [Diffusion Tensor (DT) and Constrained Spherical Deconvolution (CSD)], tractography, and streamline filtering (LiFE, COMMIT, and SIFT2). The number of crossing and non-crossing streamlines and their weights after filtering entered ROC-analyses to compare the discriminative power of the methods based on the area under the curve (AUC). The dMRI results were cross-validated with fMRI estimates of misrouting in a subset of 6 albinotic individuals.ResultsWe detected significant group differences in chiasmal crossing for both unfiltered DT (p=0.014) and CSD tractograms (p=0.0009) also reflected by AUC measures (for DT and CSD: 0.61 and 0.75, respectively), underlining the discriminative power of the approach. Estimates of crossing strengths obtained with dMRI and fMRI were significantly correlated for CSD (R2=0.83, p=0.012). The results show that streamline filtering methods in combination with probabilistic tracking, both optimized for the data at hand, can improve the detection of crossing in the human optic chiasm.ConclusionsEspecially CSD-based tractography provides an efficient approach to detect structural abnormalities in the optic chiasm. The most realistic results were obtained with filtering methods with parameters optimized for the data at hand.SignificanceOur findings demonstrate a novel anatomy-driven approach for the individualized diagnostics of optic chiasm abnormalities.HighlightsDiffusion MRI is capable of detecting structural abnormalities of the optic chiasm.Quantification of crossing strength in optic chiasm is of promise for albinism diagnostics.Optic chiasm is a powerful test model for neuroimaging methods resolving crossing fibers.

Diffusion tensor characteristics of gyrencephaly using high resolution diffusion MRI in vivo at 7T

NeuroImage ◽  
2015 ◽  
Vol 109 ◽  
pp. 378-387 ◽  
Author(s):  
Michiel Kleinnijenhuis ◽  
Tim van Mourik ◽  
David G. Norris ◽  
Dirk J. Ruiter ◽  
Anne-Marie van Cappellen van Walsum ◽  
...  
Keyword(s):  
High Resolution ◽  
Diffusion Mri ◽  
Diffusion Tensor

scholarly journals Perivascular space fluid contributes to diffusion tensor imaging changes in white matter

2018 ◽  
Author(s):  
Farshid Sepehrband ◽  
Ryan P Cabeen ◽  
Jeiran Choupan ◽  
Giuseppe Barisano ◽  
Meng Law ◽  
...  
Keyword(s):  
Diffusion Tensor Imaging ◽  
White Matter ◽  
Fractional Anisotropy ◽  
Diffusion Mri ◽  
Diffusion Tensor ◽  
Diffusion Imaging ◽  
Mean Diffusivity ◽  
Brain Parenchyma ◽  
Perivascular Space ◽  
List Type

AbstractDiffusion tensor imaging (DTI) has been extensively used to map changes in brain tissue related to neurological disorders. Among the most widespread DTI findings are increased mean diffusivity and decreased fractional anisotropy of white matter tissue in neurodegenerative diseases. Here we utilize multi-shell diffusion imaging to separate diffusion signal of the brain parenchyma from fluid within the white matter. We show that unincorporated anisotropic water in perivascular space (PVS) significantly, and systematically, biases DTI measures, casting new light on the biological validity of many previously reported findings. Despite the challenge this poses for interpreting these past findings, our results suggest that multi-shell diffusion MRI provides a new opportunity for incorporating the PVS contribution, ultimately strengthening the clinical and scientific value of diffusion MRI.HighlightsPerivascular space (PVS) fluid significantly contributes to diffusion tensor imaging metricsIncreased PVS fluid results in increased mean diffusivity and decreased fractional anisotropyPVS contribution to diffusion signal is overlooked and demands further investigation

scholarly journals Diffusion MRI Changes in the Healthy Aging Canine Brain

2020 ◽  
Author(s):  
Erica F. Barry ◽  
John P. Loftus ◽  
Wen-Ming Luh ◽  
Mony J. de Leon ◽  
Sumit N. Niogi ◽  
...  
Keyword(s):  
White Matter ◽  
Diffusion Mri ◽  
Healthy Aging ◽  
Parietal Lobe ◽  
Diffusion Tensor ◽  
Mean Diffusivity ◽  
Human Aging ◽  
Age Related ◽  
Age Related Changes

AbstractWhite matter dysfunction and degeneration have been a topic of great interest in healthy and pathological aging. While ex vivo studies have investigated age-related changes in canines, little in vivo canine aging research exists. Quantitative diffusion MRI such as diffusion tensor imaging (DTI) has demonstrated aging and neurodegenerative white matter changes in humans. However, this method has not been applied and adapted in vivo to canine populations. This study aimed to test the hypothesis that white matter diffusion changes frequently reported in human aging are also found in aged canines. The study used Tract Based Spatial Statistics (TBSS) and a region of interest (ROI) approach to investigate age related changes in fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AxD) and radial diffusivity (RD). The results show that, compared to younger animals, aged canines have significant decreases in FA in parietal and temporal regions as well as the corpus callosum and fornix. Additionally, AxD decreases were observed in parietal, frontal and midbrain regions. Similarly, an age-related increase in RD was observed in the right parietal lobe while MD decreases were found in the midbrain. These findings suggest that canine samples offer a model for healthy human aging as they exhibit similar white matter diffusion tensor changes with age.

scholarly journals Neurite orientation and dispersion density imaging (NODDI) detects cortical and corticospinal tract degeneration in ALS

2018 ◽  
Vol 90 (4) ◽  
pp. 404-411 ◽  
Author(s):  
Rebecca J Broad ◽  
Matt C Gabel ◽  
Nicholas G Dowell ◽  
David J Schwartzman ◽  
Anil K Seth ◽  
...  
Keyword(s):  
Diffusion Mri ◽  
Corticospinal Tract ◽  
Diffusion Tensor ◽  
Free Water ◽  
Cortical Atrophy ◽  
Precentral Gyrus ◽  
Water Fraction ◽  
Sporadic Als ◽  
The Right

BackgroundCorticospinal tract (CST) degeneration and cortical atrophy are consistent features of amyotrophic lateral sclerosis (ALS). We hypothesised that neurite orientation dispersion and density imaging (NODDI), a multicompartment model of diffusion MRI, would reveal microstructural changes associated with ALS within the CST and precentral gyrus (PCG) ‘in vivo’.Methods23 participants with sporadic ALS and 23 healthy controls underwent diffusion MRI. Neurite density index (NDI), orientation dispersion index (ODI) and free water fraction (isotropic compartment (ISO)) were derived. Whole brain voxel-wise analysis was performed to assess for group differences. Standard diffusion tensor imaging (DTI) parameters were computed for comparison. Subgroup analysis was performed to investigate for NODDI parameter differences relating to bulbar involvement. Correlation of NODDI parameters with clinical variables were also explored. The results were accepted as significant where p<0.05 after family-wise error correction at the cluster level, clusters formed with p<0.001.ResultsIn the ALS group NDI was reduced in the extensive regions of the CST, the corpus callosum and the right PCG. ODI was reduced in the right anterior internal capsule and the right PCG. Significant differences in NDI were detected between subgroups stratified according to the presence or absence of bulbar involvement. ODI and ISO correlated with disease duration.ConclusionsNODDI demonstrates that axonal loss within the CST is a core feature of degeneration in ALS. This is the main factor contributing to the altered diffusivity profile detected using DTI. NODDI also identified dendritic alterations within the PCG, suggesting microstructural cortical dendritic changes occur together with CST axonal damage.

scholarly journals A data-driven approach to optimising the encoding for multi-shell diffusion MRI with application to neonatal imaging

2019 ◽  
Author(s):  
J-Donald Tournier ◽  
Daan Christiaens ◽  
Jana Hutter ◽  
Anthony N. Price ◽  
Lucilio Cordero-Grande ◽  
...  
Keyword(s):  
Information Content ◽  
Diffusion Mri ◽  
Data Driven ◽  
Abnormal Development ◽  
Quality Data ◽  
List Type ◽  
Reconstruction Methods ◽  
Human Connectome Project ◽  
Data Driven Approach

AbstractDiffusion MRI has the potential to provide important information about the connectivity and microstructure of the human brain during normal and abnormal development, non-invasively and in vivo. Recent developments in MRI hardware and reconstruction methods now permit the acquisition of large amounts of data within relatively short scan times. This makes it possible to acquire more informative multi-shell data, with diffusion-sensitisation applied along many directions over multiple b-value shells. Such schemes are characterised by the number of shells acquired, and the specific b-value and number of directions sampled for each shell. However, there is currently no clear consensus as to how to optimise these parameters. In this work, we propose a means of optimising multi-shell acquisition schemes by estimating the information content of the diffusion MRI signal, and optimising the acquisition parameters for sensitivity to the observed effects, in a manner agnostic to any particular diffusion analysis method that might subsequently be applied to the data. This method was used to design the acquisition scheme for the neonatal diffusion MRI sequence used in the developing Human Connectome Project, which aims to acquire high quality data and make it freely available to the research community. The final protocol selected by the algorithm, and currently in use within the dHCP, consists of b = 0, 400, 1000, 2600 s/mm2 with 20, 64, 88 & 128 DW directions per shell respectively.HighlightsA data driven method is presented to design multi-shell diffusion MRI acquisition schemes (b-values and no. directions).This method optimises the multi-shell scheme for maximum sensitivity to the information content in the signal.When applied in neonates, the data suggest that a b=0 + 3 shell strategy is appropriate

scholarly journals Enabling constrained spherical deconvolution and diffusional variance decomposition with tensor-valued diffusion MRI

2021 ◽  
Author(s):  
Philippe Karan ◽  
Alexis Reymbaut ◽  
Guillaume Gilbert ◽  
Maxime Descoteaux
Keyword(s):  
Diffusion Mri ◽  
Diffusion Tensor ◽  
Simulated Data ◽  
Orientation Distribution ◽  
Variance Decomposition ◽  
Distribution Functions ◽  
Constrained Spherical Deconvolution ◽  
Spherical Deconvolution ◽  
Fiber Orientation Distribution

Diffusion tensor imaging (DTI) is widely used to extract valuable tissue measurements and white matter (WM) fiber orientations, even though its lack of specificity is now well-known, especially for WM fiber crossings. Models such as constrained spherical deconvolution (CSD) take advantage of HARDI data to compute fiber orientation distribution functions (fODF) and tackle the orientational part of the DTI limitations. Furthermore, the recent introduction of tensor-valued diffusion MRI allows for diffusional variance decomposition (DIVIDE), opening the door to the computation of measures more specific to microstructure than DTI measures, such as microscopic fractional anisotropy (μFA). However, tensor-valued diffusion MRI data is not compatible with latest versions of CSD and the impacts of such atypical data on fODF reconstruction with CSD are yet to be studied. In this work, we lay down the mathematical and computational foundations of a tensor-valued CSD and use simulated data to explore the effects of various combinations of diffusion encodings on the angular resolution of extracted fOFDs. We also compare the combinations with regards to their performance at producing accurate and precise μFA with DIVIDE, and present an optimised protocol for both methods. We show that our proposed protocol enables the reconstruction of both fODFs and μFA on in vivo data.

scholarly journals Dorsal White Matter Integrity and Name Retrieval in Midlife

2019 ◽  
Vol 12 (1) ◽  
pp. 55-61 ◽  
Author(s):  
Vanja Kljajevic ◽  
Asier Erramuzpe
Keyword(s):  
White Matter ◽  
Diffusion Tensor ◽  
Mean Diffusivity ◽  
White Matter Integrity ◽  
Middle Aged ◽  
Significant Group ◽  
Proper Name ◽  
The Right ◽  
Name Retrieval

Background: Recent findings on retrieval of proper names in cognitively healthy middle- aged persons indicate that Tip-Of-The-Tongue (TOT) states occurring during proper name retrieval implicate inferior frontal (BA 44) and parietal (BA 40) cortical areas. Such findings give rise to the possibility that anatomical connectivity via dorsal white matter may be associated with difficulties in name retrieval in midlife. Objectives & Method: Using Diffusion Tensor Imaging, we examined in vivo microstructural properties of white matter in 72 cognitively healthy Middle-Aged (MA) and 59 Young Adults (YA), comparing their naming abilities as well as testing, for possible associations between dorsal white matter integrity and naming abilities in the MA group. Results: The MA group was better in retrieving correct names (U = 1525.5, p = .006), but they also retrieved more incorrect names than YA believing they had retrieved the correct ones (U = 1265.5, p < .001). Furthermore, despite being more familiar with the tested names than YA (U = 930, p < .001), MA experienced significantly more TOTs relative to YA (U = 1498.5, p = .004). Tract-based spatial statistics showed significant group differences in values of fractional anisotropy (FA), mean diffusivity, axial diffusivity, radial diffusivity, and mode of anisotropy in a range of white matter tracts. In the MA group, FA values in the right Superior Longitudinal Fasciculus (SLF) were positively correlated with “don’t know” scores (rs = .287, p = .014). Conclusion: The association of SLF integrity and name retrieval ability in midlife indicates a need to revisit the models of name retrieval that posit no role for dorsal white matter in proper name retrieval.

In vivo diffusion tensor imaging of the neonatal rat brain development

2013 ◽  
Vol 44 (S 01) ◽  
Author(s):  
M Breu ◽  
D Reisinger ◽  
D Wu ◽  
Y Zhang ◽  
A Fatemi ◽  
...  
Keyword(s):  
Diffusion Tensor Imaging ◽  
Brain Development ◽  
Rat Brain ◽  
Diffusion Tensor ◽  
Neonatal Rat ◽  
Neonatal Rat Brain

LACK OF EFFECT OF CORTICOSTEROIDS ON THE IN VIVO DISAPPEARANCE OF SULFHYDRYL-INHIBITED AND ANTIBODY-COATED ERYTHROCYTES

1964 ◽  
Vol 47 (3_Suppl) ◽  
pp. S28-S36
Author(s):  
Kailash N. Agarwal
Keyword(s):  
Red Cells ◽  
List Type ◽  
Red Cell

ABSTRACT Red cells were incubated in vitro with sulfhydryl inhibitors and Rhantibody with and without prior incubation with prednisolone-hemisuccinate. These erythrocytes were labelled with Cr51 and P32 and their disappearance in vivo after autotransfusion was measured. Prior incubation with prednisolone-hemisuccinate had no effect on the rate of red cell disappearance. The disappearance of the cells was shown to take place without appreciable intravascular destruction.

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