Three-dimensional axonal fiber tracking and ischemic study in brain using diffusion magnetic resonance imaging techniques

The overall goal of this thesis project is to perform preliminary studies for the application of a recently developed diffusion magnetic resonance imaging (MRI) technique to the study of axonal fiber structures and brain ischemic processes. One major part is to develop and apply high-resolution 3D diffusion tensor MRI (DT-MRI) techniques to map axonal fiber projections in brain, which will enable us to visualize the 3D organization of brain white matter fiber structures. The second part is to study in detail the acute ischemic process for a mouse stroke model using our newly developed rapid 3D isotropic diffusion-weighted imaging (DWI) sequence. This technique is further applied to a comparative stroke study between wild-type and PARP-deficient transgenic mice using a transient middle cerebral artery occlusion (MCAO) model.; Study of neuronal connectivity is of central importance in the interpretation of normal and abnormal brain functions. In vivo three-dimensional (3D) reconstruction of axonal projections was achieved using a rapid 3D high-resolution DTI technique combined with a fiber reconstruction algorithm. As a first example, neuronal pathways in the rat brain were probed. In addition, the diffusion tensor imaging technique was further applied to fixed sheep brain at different developmental stages for a preliminary study of white matter fiber development during brain maturation.; Another important application of diffusion MRI is to depict brain ischemia during early stroke onset, while conventional T₁- or T₂-weighted MRI shows normal brain appearance. In this project, we applied a newly developed rapid 3D DWI sequence for the study of experimental stroke in a mouse model of reversible MCAO. Lesion volumes were successfully delineated using our 3D whole brain imaging with high spatial (0.34 x 0.5 x 1.0 mm 3 before zerofilling) and temporal (7 minutes) resolution.; This 3D diffusion MRI technique was further applied to a comparative stroke study between PARP transgenic and wild-type control mice using the same reversible MCAO model. The temporal courses of acute and chronic stroke evolution were characterized for both the control and PARP−/− mutant mice, and the difference of stroke progression between these two groups was determined. Using diffusion MRI, we found that PARP mutant mice with MCAO had significantly smaller lesion volumes than the control group during the 1-hour occlusion period and at 6 and 21 hours after reperfusion. (Abstract shortened by UMI.)...