3-Tesla magnetic resonance imaging of the equine brain in healthy horses - Potentials and limitations

摘要

For evaluating neurological diseases, magnetic resonance imaging (MRI) has been widely recommended as the method of choice in human medicine. It has been proposed as a valuable tool in clinical diagnostics and research projects in veterinary medicine as well. The aim of this study was to elaborate optimal settings appropriate for an examination of the equine brain in a 3-Tesla tomograph within an adequate examination time and with related optimal image quality. A key issue was the evaluation of those neuro-anatomical structures (formations of Grey and White Matter included) which were always clearly recognisable and, as such, were useful orientation landmarks. Furthermore, the average sizes of selected structures were measured in the magnetic resonance images in transversal views. MRI of 11 healthy horses was performed in general anaesthesia. After the examination the horses were euthanised, their heads were fixated by perfusion, the brain was removed and cut either in transversal, dorsal or sagittal slices (approximately 4 mm thick). Photographic images of these slices corresponded to the magnetic resonance images in the equivalent planes. In the anatomical slices, all visible neurological structures (gyri, nuclei, and formations of White Matter) were identified. In the corresponding magnetic resonance images, these structures were evaluated with regard to the image quality (intensity, delineation). Those best visible were proposed as landmarks for orientation. The evaluation of the image quality was performed using a score system. In general, the anatomical slices displayed more details compared to the magnetic resonance images. In the latter, large nuclei like, e.g. Nucleus caudatus could always be identified with certainty, whereas small nuclei like those of the thalamic region or of the area of the Medulla oblongata could not be identified. The relation between operational effort and benefit was discussed considering the parameters 'acquisition time' (and related duration of general anaesthesia) and 'image quality' (which depended on the selection of sectional planes and matrix sizes, as displayed in the proposed protocols).