Stefan Sommer

Stefan Sommer
ETH Zurich | ETH Zürich · Institute for Biomedical Engineering

PhD

About

18
Publications
1,619
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64
Citations

Publications

Publications (18)
Article
Full-text available
Background The anteroposterior (ap) radiograph of the pelvis is decisive in the diagnosis of different pathologies of the hip joint. Technical advantages have reduced the radiation dose of pelvic CT to levels comparable to radiographs. The purpose of this study was to validate if standard radiographic parameters (lateral center edge angle, medial c...
Article
Background Widespread white matter abnormalities are a frequent finding in chronic schizophrenia patients. More inconsistent results have been provided by the sparser literature on at-risk states for psychosis, i.e., emerging subclinical symptoms. However, considering risk as a homogenous construct, as characteristic of earlier studies, may impede...
Article
Purpose To demonstrate direct imaging of the white matter ultrashort T2∗ components at 7 Tesla using inversion recovery (IR)-enhanced ultrashort echo time (UTE) MRI. To investigate its characteristics, potentials and limitations, and to establish a clinical protocol. Material and methods The IR UTE technique suppresses long T2∗ signals within whit...
Article
Full-text available
Myelin insulates neuronal axons and enables fast signal transmission, constituting a key component of brain development, aging and disease. Yet, myelin-specific imaging of macroscopic samples remains a challenge. Here, we exploit myelin’s nanostructural periodicity, and use small-angle X-ray scattering tensor tomography (SAXS-TT) to simultaneously...
Article
Full-text available
Objectives To compare ultra-low-dose CT (ULD-CT) of the osseous pelvis with tin filtration to standard clinical CT (CT), and to assess the quality of computed virtual pelvic radiographs (VRs). Methods CT protocols were optimized in a phantom and three pelvic cadavers. Thirty prospectively included patients received both standard CT (automated tube...
Article
Objectives: Through-slice chemical shift artifacts in state-of-the-art turbo-spin-echo (TSE) images can be significantly more severe at 7 T than at lower field strengths. In musculoskeletal applications, these artifacts appear similar to bone fractures or neoplastic bone marrow disease. The objective of this work was to explore and reduce through-...
Article
Full-text available
The detection and assessment of cerebral lesions and traumatic brain injuries are of particular interest in forensic investigations in order to differentiate between natural and traumatic deaths and to reconstruct the course of events in case of traumatic deaths. For this purpose, computed tomography (CT) and magnetic resonance imaging (MRI) are ap...
Article
Full-text available
Compared to computed tomography (CT), magnetic resonance imaging (MRI) provides superior visualization of the soft tissue. Recently, the first 7 Tesla (7 T) MRI scanner was approved for clinical use, which will facilitate access to these ultra-high-field MRI scanners for noninvasive examinations and scientific studies on decedents. 7 T MRI has the...
Article
Full-text available
In the current work two novel parameters, fiber density (FD) and mean diffusion signal (MDS) are investigated for evaluating neurodegenerative processes in amyotrophic lateral sclerosis (ALS). The MDS provides a measure of the FD but is derived directly from the diffusion signal. Using tract-based spatial statistics (TBSS), pathological changes acr...
Article
Full-text available
Altered cerebral connectivity is one of the core pathophysiological mechanism underlying the development and progression of information-processing deficits in schizophrenia. To date, most diffusion tensor imaging (DTI) studies used fractional anisotropy (FA) to investigate disrupted white matter connections. However, a quantitative interpretation o...
Article
Full-text available
Diffusion magnetic resonance imaging (dMRI) is a compelling tool for investigating the structure and geometry of brain tissue based on indirect measurement of the diffusion anisotropy of water. Recent developments in global top-down tractogram optimizations enable the estimation of streamline weights, which characterize the connection between gray...
Thesis
The emergence of new neuroimaging techniques com- bined with sophisticated computational models and al- gorithms allows to non-invasively probe the structure of the brain in-vivo. Diffusion magnetic resonance imaging (dMRI) is a compelling tool for investigating the structure and geometry of brain tissue based on indirect measure- ment of the diffu...
Article
Full-text available
Background and purpose: Diffusion MRI tractography enables to investigate white matter pathways noninvasively by reconstructing estimated fiber pathways. However, such tractograms remain biased and nonquantitative. Several techniques have been proposed to reestablish the link between tractography and tissue microstructure by modeling the diffusion...
Conference Paper
Full-text available
In the last few years, tract base spatial statistics (TBSS) become prominent tools for analyzing diffusion data in group studies. In this study, we introduce optimized high-resolution tract density (optTD) images based on tractograms. In order to avoid tractography bias, the tractograms are optimized using the convex-optimization modeling for micro...
Conference Paper
Full-text available
In the last few years, tract base spatial statistics (TBSS) and automating fiber-tract quantification (AFQ) have become prominent tools for analyzing diffusion data in group studies. In this study, we introduce optimized high-resolution tract density (optTD) images and analyze these maps using TBSS and AFQ in patients with major depressive disorder...
Conference Paper
Diffusion magnetic resonance imaging provides a useful tool to examine structural white matter changes in health and disease. Tract-based spatial statistics (TBSS) (Smith, 2006) is a popular tool for the evaluation of diffusion data in group studies. As a quantitative measure, TBSS typically analyses the fractional anisotropy (FA) to find statistic...
Conference Paper
High angular resolution diffusion techniques including diffusion spectrum imaging [1] and q-ball imaging [2] have been developed to resolve complex intra-voxel fiber structures. Thereby, the entire diffusion profile is captured in the so-called orientation distribution function (ODF). Various tracking algorithms have been proposed to reconstruct vi...

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