Ultrahigh-field 9.4T MRI for Evaluating Neonatal Piglet Brain

Understanding normal brain development can provide references for assessment of brain injury associated with various diseases. For brain development studies, pig models have increasingly been used because of the similarities in anatomical and physiological characteristics shared by brains of pig and that of humans. Magnetic resonance imaging (MRI) is a noninvasive imaging method in the diagnosis of neurological diseases in preclinical research and clinical settings. Although MRI has been used to evaluate the pig brain, there is a lack of study to illuminate the neonatal piglet brain anatomy with high-resolution MRI performed with an ultra-high magnetic field. The aim of this thesis was two folds. Firstly, we investigated the anatomy of neonatal brain of 12-day-old piglet and generated a database based on ex vivo MR images. These images were acquired with a three-dimensional fast spin-echo T2-weighted sequence at a resolution of 0.2344 × 0.2539 × 0.2539 mm. Fifteen brain structures were segmented manually and a 3D piglet brain model was reconstructed. We found that the cerebral cortex, the cerebellum, and the brain stem contributed to 87.1% of the whole brain, while the hippocampus contributed to 2.13% on average. Secondly, we compared the volumes measured from five brain structures—cerebellum, midbrain, thalamus, olfactory bulb and hippocampus—along with the whole brain between in vivo and ex vivo MR images. Two different image resolutions were applied for in vivo MRI. We found no differences in volume between in vivo and ex vivo images for structures located in the back such as the cerebellum and midbrain. However, while structures in the middle such as the thalamus and hippocampus showed no difference in volume between high-resolution ex vivo images and one low-resolution images, significant volume difference were found between ex vivo images and the other low-resolution images. The volume measurements of olfactory bulb and whole brain showed difference regardless the resolutions of in vivo images. Our results can provide references for in vivo assessment of brain growth in metabolism, nutrition research for pediatric brain development and studies using more advanced image analyzing techniques, for example, voxel-based morphometry. In addition, our results from in vivo and ex vivo MR images comparison can provide guidance for proper handling brain samples for other studies. Further studies to build a neonatal piglet brain atlas and the piglet brain database according to stages of brain development will benefit brain development and neurological studies using piglet as a translational animal model.