A functional and morphometric approach to magnetic resonance imaging of the brain at low magnetic field strength
The signal produced in functional MRI (fMRI) is most often based on the Blood Oxygenation Level Dependent (BOLD) technique, which relies upon a localised change in the magnetic susceptibility difference between the blood and surrounding tissue following functional activation. This activation signal is dependent on the field strength of the MR scanner, and hence the purpose of this project was to investigate the feasibility of performing fMRI at a field strength of 0.95 T. The scanner used in the project did not have the gradient hardware necessary to perform echo-planar imaging (EPI), and therefore whole brain activation studies. Thus, the experiments were performed using a range of different signal- and multi-slice pulse sequences, as well as a number of different activation tasks, including motor, visual and somatosensory paradigms. The datasets were analysed using the Statistical Parametric Mapping package, from which they were found to display activation sites largely within the cortical areas most associated with the task performed or stimulation applied to each subject. Thus, it could be concluded that fMRI was indeed feasible at low magnetic field strength, at least for the paradigms used in the project. As a secondary aim of the project, the same analysis package was used to perform some voxel-based morphometry (VBM) of both the normal and pathological brain.