Novel medical image processing techniques for the detection of abnormalities of functional and structural connectivity in the brain

The interconnectivity of more than 100 billion neurons produces the thoughts, perceptions and behaviors of the adult human brain. At the macroscopic scale, magnetic resonance imaging (MRI) is used to investigate functional and structural connections in the healthy and diseased human brain in-vivo. Within this thesis, novel MRI processing techniques with very high reproducibility are developed and used to investigate subtleties regarding the brain connectivity of patients with schizophrenia.;Schizophrenia is hypothesized to be a manifestation of altered brain connectivity but the results from imaging studies are not always consistent. We investigated sources of variance and artifacts in the image processing techniques that are commonly used and found areas that are prone to type I errors with whole brain significance probability mapping of diffusion tensor imaging (DTI) data. To better investigate brain connectivity in schizophrenia we designed an image processing system and developed a highly reproducible white matter tractography technique that was able to reveal subtleties about the disease.;We developed a template based DTI tractography technique to investigate the relationship between duration of illness and white matter abnormalities in a very large sample. We found a correlation between the duration of illness and a white matter integrity index in the genu and splenium of the corpus callosum but not in the pyramidal tracts. The findings suggest that there are white matter tract-specific degenerative mechanisms that progress throughout the illness.;In a smaller sample of patients, we investigated the relationship between structural and functional connectivity in schizophrenia. The relationship between white matter integrity and functional connectivity in schizophrenia was investigated using a combined DTI and functional MRI approach. A correlation was found between connectivity measures in the left but not right hemisphere. The results agree with previous reports of left lateralized abnormalities in schizophrenia and lend strong support to the hypothesis that white matter abnormalities are related to altered function in patients with schizophrenia.;The medical image processing platform that was designed for this thesis facilitated the development of advanced brain connectivity algorithms. The highly reproducible techniques revealed subtleties about the disease progression and function/structure relationships in schizophrenia.