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Stefan Skare

Bio: Stefan Skare is an academic researcher from Karolinska University Hospital. The author has contributed to research in topics: Diffusion MRI & Image quality. The author has an hindex of 29, co-authored 66 publications receiving 6033 citations. Previous affiliations of Stefan Skare include Karolinska Institutet & Stanford University.


Papers
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TL;DR: This work suggests acquiring two images for each diffusion gradient; one with bottom-up and one with top-down traversal of k-space in the phase-encode direction, which achieves the simultaneous goals of providing information on the underlying displacement field and intensity maps with adequate spatial sampling density even in distorted areas.

2,409 citations

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TL;DR: Positive correlations between practicing and fiber tract organization in different regions for each age period are found, and long-term training within critical developmental periods may induce regionally specific plasticity in myelinating tracts.
Abstract: Using diffusion tensor imaging, we investigated effects of piano practicing in childhood, adolescence and adulthood on white matter, and found positive correlations between practicing and fiber tract organization in different regions for each age period. For childhood, practicing correlations were extensive and included the pyramidal tract, which was more structured in pianists than in non-musicians. Long-term training within critical developmental periods may thus induce regionally specific plasticity in myelinating tracts.

1,004 citations

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TL;DR: Numerical algorithms are applied to optimize a DTI scheme by minimizing the condition number, hence improving the robustness to experimental noise and avoiding rotational variances of eigenvalues and anisotropy.

308 citations

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TL;DR: This paper suggests and implements a method for retrospective correction of geometric distortion firmly based on a physical model for the diffusion-weighted images and suggests models for how distortions vary with slice position and gradient direction that allow us to substantially reduce the dimensionality of the parameter space.

283 citations

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TL;DR: The findings support the view that global and regional white matter abnormalities occur in chronic schizophrenia.
Abstract: Fractional anisotropy and the mean diffusion coefficient were measured in the cerebral volume in 20 schizophrenic and 24 healthy subjects, men and women, using diffusion tensor imaging. In addition, 3D SPGR was used for segmentation of brain tissue into grey and white matter and cerebrospinal fluid. In schizophrenic patients, fractional anisotropy was reduced in the splenium of the corpus callosum and in adjacent occipital white matter. The segmentation revealed no tissue deficits in the volume of reduced fractional anisotropy. The mean diffusion was increased in the total white and grey matter volume of the schizophrenic patients compared with the healthy subjects. The findings support the view that global and regional white matter abnormalities occur in chronic schizophrenia.

234 citations


Cited by
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Journal ArticleDOI
TL;DR: The minimal preprocessing pipelines for structural, functional, and diffusion MRI that were developed by the HCP to accomplish many low level tasks, including spatial artifact/distortion removal, surface generation, cross-modal registration, and alignment to standard space are described.

3,992 citations

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TL;DR: The method is based on registering the individual volumes to a model free prediction of what each volume should look like, thereby enabling its use on high b-value data where the contrast is vastly different in different volumes.

2,431 citations

Journal ArticleDOI
TL;DR: This work suggests acquiring two images for each diffusion gradient; one with bottom-up and one with top-down traversal of k-space in the phase-encode direction, which achieves the simultaneous goals of providing information on the underlying displacement field and intensity maps with adequate spatial sampling density even in distorted areas.

2,409 citations

Journal ArticleDOI
TL;DR: Diffusion tensor imaging (DTI) is a promising method for characterizing microstructural changes or differences with neuropathology and treatment and the biological mechanisms, acquisition, and analysis of DTI measurements are addressed.

2,315 citations

Journal ArticleDOI
TL;DR: It is demonstrated that brain hubs form a so-called “rich club,” characterized by a tendency for high-degree nodes to be more densely connected among themselves than nodes of a lower degree, providing important information on the higher-level topology of the brain network.
Abstract: The human brain is a complex network of interlinked regions. Recent studies have demonstrated the existence of a number of highly connected and highly central neocortical hub regions, regions that play a key role in global information integration between different parts of the network. The potential functional importance of these “brain hubs” is underscored by recent studies showing that disturbances of their structural and functional connectivity profile are linked to neuropathology. This study aims to map out both the subcortical and neocortical hubs of the brain and examine their mutual relationship, particularly their structural linkages. Here, we demonstrate that brain hubs form a so-called “rich club,” characterized by a tendency for high-degree nodes to be more densely connected among themselves than nodes of a lower degree, providing important information on the higher-level topology of the brain network. Whole-brain structural networks of 21 subjects were reconstructed using diffusion tensor imaging data. Examining the connectivity profile of these networks revealed a group of 12 strongly interconnected bihemispheric hub regions, comprising the precuneus, superior frontal and superior parietal cortex, as well as the subcortical hippocampus, putamen, and thalamus. Importantly, these hub regions were found to be more densely interconnected than would be expected based solely on their degree, together forming a rich club. We discuss the potential functional implications of the rich-club organization of the human connectome, particularly in light of its role in information integration and in conferring robustness to its structural core.

2,089 citations