GABA-glutamate interaction as neurochemical basis of cerebral resting-state dysfunction in depression and schizophrenia: A 7 tesla multimodal imaging project
Final Report Abstract
To our knowledge this is the only project that was measuring GABA and Glu in vmPFC with 7T in people with depression and schizophrenia. Such a project came with challenges to build specific coil as well as to optimize measuring protocols. An 8-channel transmit receive RF coil was designed, built and characterized. To improved spectral quality voxel size was adjusted from 20 × 20 × 20 mm³, to 20 × 20 × 12 mm³ to enable an improved B0 homogeneity, and consequently an improved spectral quality with fewer artifacts. Decreased voxel size, that derived from adjustment above was addressed by increasing the number of averages acquired in each volunteer. MRS postprocessing and analysis was additionally complicated because due to complexity of this particular reagion there is currently no literature values for relaxation behaviour of metabolite signals in this region acquired at 7T available. To allow the best possible analysis, MRS results were visually inspected and frequency alignment and a weighted coil combination were performed. In the end resulting spectra were analysed in LCModel and the obtained quantification results were corrected for T2 relaxation of the water and analysed metabolite. During the study, taking into consideration also time of corona, it became clear that inclusion criteria for people with schizophrenia needed to change. Our first criteria was to include only unmedicated patients with both schizophrenia and depression. Later in the study we decided to include people with schizophrenia that were medicated because we would not be able to reach significant number of participants. We found out that unmedicated patients with schizophrenia found very challenging to spend almost two hours in 7 Tesla MRI. In general recruitment and fulfillment of the study were fairly challenging in the time of corona lockdowns and strict hygienic measures. All together in this study 117 participants were recruited. Age range was between 18 and 55 years, 74 were women end 43 men. Division between groups was 46 participants with depression 21 with schizophrenia and 50 healthy controls. Not all results acquired from 117 participants were fully usable. There was a tendency of lower GABA in participants with schizophrenia, but this tendency didn’t reach statistical significance. The analysis of the resting state data is still in progress. The Analysis is focusing on the correction of image distortions which occur typically in 7T MRI scanners. Results are expected in spring 2023.
Publications
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“Assessment of measurement precision in single-voxel spectroscopy at 7 T: Toward minimal detectable changes of metabolite concentrations in the human brain in vivo”, Magn Reson Med 87(3): 1119-1135 (2022)
Layla Tabea Riemann, Christoph Stephan Aigner, Stephen L.R. Ellison, Rüdiger Brühl, Ralf Mekle, Sebastian Schmitter, Oliver Speck, Georg Rose, Bernd Ittermann, Ariane Fillmer
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“Fourier-based decomposition for simultaneous 2-voxel MRS acquisition with 2SPECIAL”, Magn Reson Med
Layla Tabea Riemann, Christoph Stefan Aigner, Ralf Mekle, Oliver Speck, Georg Rose, Bernd Ittermann, Sebastian Schmitter, Ariane Fillmer
