This thesis describes a cross-sectional behavioral and neuroimaging study in a sample of n=85 adolescents with a history of childhood sexual abuse related PTSD (CSA-related PTSD), anxiety and/or... Show moreThis thesis describes a cross-sectional behavioral and neuroimaging study in a sample of n=85 adolescents with a history of childhood sexual abuse related PTSD (CSA-related PTSD), anxiety and/or depressive disorders or no psychiatric symptoms. We assessed attachment representation as well as psychopathological symptoms, attentional bias and emotional face processing among diagnostic groups. We also correlated unresolved-disorganized attachment representation (Ud) and psychopathology using a general psychopathology factor (GPF) to grey matter (volume), white matter (tracts) and resting state functional connectivity (RSFC) of the brain in the entire sample. We found that clinical groups did not significantly differ in psychopathology. The unresolved-disorganized cannot classify category (Ud/CC) was overrepresented in the CSA-related PTSD group. Coherence of mind also differentiated the clinical groups, but Ud did not. The CSA-related PTSD group had a negative attention bias for neutral and fearful faces, the anxiety/depressive disorders group only for fearful faces. No differences were found for emotional face processing among diagnostic groups. We found a differential relationship of Ud and a GPF to grey matter volume, white matter integrity of white matter tracts and RSFC for Ud. Ud was associated with lateralization of the brain to the left with regard to amygdala RSFC and hippocampal volume. Show less
Purpose: To compare the recently introduced inhomogeneous magnetization transfer ihMT) technique with more established MRI techniques including myelin water imaging (MWI) and diffusion tensor... Show morePurpose: To compare the recently introduced inhomogeneous magnetization transfer ihMT) technique with more established MRI techniques including myelin water imaging (MWI) and diffusion tensor imaging (DTI), and to evaluate the microstructural attributes correlating with this new contrast method in the human brain white matter.Methods: Eight adult healthy volunteers underwent T-1-weighted, ihMT, MWI, and DTI imaging on a 3T human scanner. The ihMT ratio (ihMTR), myelin water fraction (MWF), fractional anisotropy (FA), radial diffusivity (RD), axial diffusivity (AD), and mean diffusivity (MD) values were calculated from different white matter tracts. The angle (theta) between the directions of the principal eigenvector, as measured by DTI, and the main magnetic field was calculated for all voxels from various fiber tracts. The ihMTR was correlated with MWF and DTI metrics.Results: A strong correlation was found between ihMTR and MWF (rho = 0.77, P < 0.0001). This was followed by moderate to weak correlations between ihMTR and DTI metrics: RD (rho = 20.30, P < 0.0001), FA (rho = 0.20, P < 0.0001), MD (rho = 20.19, P < 0.0001), AD (rho = 0.02, P < 0.0001). A strong correlation was found between ihMTR and u (rho = 20.541, P < 0.0001).Conclusion: The strong correlation with myelin water imaging and its low coefficient of variation suggest that ihMT has the potential to become a new structural imaging marker of myelin. The substantial orientational dependence of ihMT should be taken into account when evaluating and quantitatively interpreting ihMT results. Show less
PurposeTo develop a method of suppressing the multi-resonance fat signal in diffusion-weighted imaging of skeletal muscle. This is particularly important when imaging patients with muscular... Show morePurposeTo develop a method of suppressing the multi-resonance fat signal in diffusion-weighted imaging of skeletal muscle. This is particularly important when imaging patients with muscular dystrophies, a group of diseases which cause gradual replacement of muscle tissue by fat.Theory and MethodsThe signal from the olefinic fat peak at 5.3 ppm can significantly confound diffusion-tensor imaging measurements. Dixon olefinic fat suppression (DOFS), a magnitude-based chemical-shift-based method of suppressing the olefinic peak, is proposed. It is verified in vivo by performing diffusion tensor imaging (DTI)-based quantification in the lower leg of seven healthy volunteers, and compared to two previously described fat-suppression techniques in regions with and without fat contamination.ResultsIn the region without fat contamination, DOFS produces similar results to existing techniques, whereas in muscle contaminated by subcutaneous fat signal moved due to the chemical shift artefact, it consistently showed significantly higher (P=0.018) mean diffusivity (MD). Because fat presence lowers MD, this suggests improved fat suppression.ConclusionDOFS offers superior fat suppression and enhances quantitative measurements in the muscle in the presence of fat. DOFS is an alternative to spectral olefinic fat suppression. Magn Reson Med 79:152-159, 2018. (c) 2017 International Society for Magnetic Resonance in Medicine. Show less
Koini, M.; Rombouts, S.A.R.B.; Veer, I.M.; Buchem, M.A. van; Huijbregts, S.C.J. 2017
This thesis aims at providing insights in the neural mechanisms and brain structures underlying individual differences in second language acquisition. It reports on a series of experiments... Show moreThis thesis aims at providing insights in the neural mechanisms and brain structures underlying individual differences in second language acquisition. It reports on a series of experiments investigating neural correlates of novel grammar learning and of the analytical component of language aptitude, using a variety of neuroimaging methods: functional magnetic resonance imaging, diffusion tensor imaging and electroencephalography. This thesis aims at providing insights in the neural mechanisms and brain structures underlying individual differences in second language acquisition. It reports on a series of experiments investigating neural correlates of novel grammar learning and of the analytical component of language aptitude, using a variety of neuroimaging methods: functional magnetic resonance imaging, diffusion tensor imaging and electroencephalography. Show less
Schouten, T.M.; Koini, M.; Vos, F. de; Seiler, S.; Rooij, M. de; Lechner, A.; ... ; Rombouts, S.A.R.B. 2017
Diffusion-weighted magnetic resonance spectroscopy (DW-MRS) can play a key role in understanding neurobiological mechanisms of diseases that affect the human brain. The specific changes that occur... Show moreDiffusion-weighted magnetic resonance spectroscopy (DW-MRS) can play a key role in understanding neurobiological mechanisms of diseases that affect the human brain. The specific changes that occur within neurons can be reflected as changes in the diffusivity of tNAA, whereas the changes in glial cells can cause pronounced changes in the diffusivities of tCr and tCho. This information combined with that obtained from diffusion tensor imaging (DTI) and other MRI tools can help elucidate various disease processes in the future. The main purposes of this thesis are (i) to investigate neuroanatomy in vivo with DW-MRS, (ii) to develop methodology to enable future clinical applications of the technique in human brain in vivo, and (iii) to characterize the microstructural deficit in neuropsychiatric systemic lupus erythematous (NPSLE) with DW-MRS and other microstructural tools such as DTI and magnetization transfer imaging. The studies presented in this thesis show the robustness and clinical relevance of microstructural information obtained via DW-MRS. The contributions of this thesis such as the optimized acquisition protocols for single volume DW-MRS, the robust DW-CSI and DW-MRS post-processing pipelines that comprise information from DTI, will all facilitate the applications of DW-MRS both for basic neuroscience research and clinical research studies. Show less
The aims of this thesis were to gain insight into specific disease processes in Huntington__s Disease (HD) and to identify biomarkers. To achieve these aims, cognitive functioning, structural brain... Show moreThe aims of this thesis were to gain insight into specific disease processes in Huntington__s Disease (HD) and to identify biomarkers. To achieve these aims, cognitive functioning, structural brain characteristics and intrinstic functional brain connectivity of premanifest and early HD subjects were examined. Cortical, subcortical and the intermediate white matter brain tissue shows evidence of structural and functional decline. We found evidence that disease processes, such as altered metabolism, excessive iron accumulation and cell loss, play a role in the changes. We conclude that changes occur throughout the brain from the earliest disease phase onwards. Hence, both premanifest and manifest HD should not be regarded as a disorder of the basal ganglia, but as a disease affecting the whole brain. Candidate biomarkers that have the potential to objectively reflect the early changes and the progressive nature of the disease are measures of subcortical atrophy, integrity of white matter pathways and of intrinsic functional brain connectivity. Iron, creatine, and N-acetylaspartate concentrations in the caudate nucleus and putamen may prove to be useful as markers of disease state for objectifying transitional disease processes from premanifest to manifest HD. Visuospatial working memory could be applied as a state marker for stage two HD. Show less
The aim of this thesis was to find potential MRI biomarkers for Huntington__s disease (HD). Therefore, after an overview of the current literature on MRI biomarkers, followed by examinations of... Show moreThe aim of this thesis was to find potential MRI biomarkers for Huntington__s disease (HD). Therefore, after an overview of the current literature on MRI biomarkers, followed by examinations of volumetric MRI, magnetization transfer imaging (MTI), diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS) were applied in patients in different disease stages of HD. The main conclusions demonstrate that choosing the optimal biomarker for evaluating therapeutic effects is dependent on the disease stage and therapeutic compound. To evaluate the premanifest stages of the disease volumetric MRI and DTI are most suitable. When the transition period is the desired timeframe for evaluation, also MRS can be very useful, especially if the compound in question has a direct potential influence on certain pathogenic pathways which in turn have an impact on specific metabolites. Future research should focus on combining multiple imaging techniques; __multimodal imaging__. A composite MRI biomarker has the potential to distinguish between disease groups more accurately than a single biomarker and in this way improve the evaluation of therapeutic compounds. Show less
Ayling, E.; Aghajani, M.; Fouche, J.P.; Wee, N. van der 2012
Diffusion tensor imaging (DTI) can be used to examine the structural integrity of regional white matter and to map white matter tracts. DTI studies have been performed in several psychiatric... Show moreDiffusion tensor imaging (DTI) can be used to examine the structural integrity of regional white matter and to map white matter tracts. DTI studies have been performed in several psychiatric disorders, especially in those for which a developmental or a neuropsychiatric component was postulated. Thus far, the use of DTI has been very limited in panic disorder, social anxiety disorder, and generalized anxiety disorder, and somewhat more extensive in post-traumatic stress disorder and obsessive-compulsive disorder. In most anxiety disorders, the results of DTI studies are in line with other structural and functional MRI findings and can be interpreted within the frameworks of existing models for the neurocircuitry of the various disorders. DTI findings could further enrich neurobiological models for anxiety disorders, although replication is often warranted, and studies in pediatric populations are lagging behind remarkably. Show less
Brain function has long been the realm of philosophy, psychology and psychiatry and since the mid 1800s, of histopathology. Through the advent of magnetic imaging in the end of the last century, an... Show moreBrain function has long been the realm of philosophy, psychology and psychiatry and since the mid 1800s, of histopathology. Through the advent of magnetic imaging in the end of the last century, an in vivo visualization of the human brain became available. This thesis describes the development of two unique techniques, imaging of diffusion of water protons and manganese enhanced imaging, that both allow for the depiction of white matter tracts. The reported studies show, that these techniques can be used for a three-dimensional depiction of fiber bundles and that quantitative measures reflecting fiber integrity and neuronal function can be extracted from such data. In clinical applications, the potential use of the developed methods is illustrated in human gliomas, as measure for fiber infiltration, and in spinal cord injury, to monitor potential neuroprotective and __regenerative medication. Show less
