Advanced magnetic resonance imaging techniques in diagnostic neuroradiology

Advanced magnetic resonance imaging (MRI) techniques in neuroimaging allow the assessment of a wide range of different parameters, including structural analyses of grey matter, white matter and iron deposition as well as functional analyses of neuronal activations. These techniques have substantially extended our knowledge of brain physiology in healthy volunteers and brain pathophysiology in a wide range of diseases. The number of publications implementing these techniques has continuously increased in the last years, paralleled by substantial improvements of MRI hardware, MR sequences, data post-processing and statistical analyses. Despite all these progress, the transfer of these advanced neuroimaging techniques into daylily clinical neuroradiology has been minimal. There are two main causes. First, theses technique become more complex, hence they are simply not applicable in clinical routine. Second, most analyses lead to group level differences, which are difficult to transfer to the diagnosis of individual patients. In agreement with the current neuroradiological approach, the thesis is divided into a structural and a functional part. In the first part of this thesis, three structural studies will be discussed that are tailored to the early diagnosis of individual patients with neuropsychiatric conditions such as first episode psychosis and progressive mild cognitive impairment. In the second part, modified and newly developed functional magnetic resonance (fMRI) techniques tailored for clinical applications will be discussed. BOLD ceiling fMRI allows the assessment of continuous neuronal activations such as continuous tinnitus, which cannot be assessed directly with “standard” fMRI. CO2BOLD allows the non-invasive assessment of the cerebral perfusion reserve at the level of the brain parenchyma, which allowed detecting patients at risk for the development of new peri-interventinal ischemic lesions in patients with high-grade stenosis of the internal carotid artery. Notably, this technique can be used to assess the cerebral autoregulation in dementia. This method can thus be combined with the developed morphometric methods described in the first part, to obtain an even more precise individual assessment of structural and functional brain parameters at the individual level in clinical neuroradiology