In vivo analysis of mechanism for neuronal regeneration in damaged brain by using multi-nuclear, multi-modality MRI methods

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We have developed multi-modality magnetic resonance imaging(MRI) techniques for analysis of neuronal regeneration in damaged brain. Those are ; (1)Fiber tracking imaging method by using diffusion tensor images obtained from ultra-fast diffusion weighted imaging ; (2)Neuronal activation imaging method by using manganese-enhanced MRI(MEMRI). This method depends on the theory that Mn ion can enter into neuronal cell in conjunction with Ca ion during the neuronal activation ; (3)Two dimensional MR spectroscopy(2D-MRS) by which various brain metabolites can be analyzed precisely in damaged brain ; (4)Perfusion imaging using arterial spin tagging method, (4)Non-invasive perfusion imaging of the brain by using water signal in the vessel as a tracer(Arterial spin tagging method). MRI devices used were experimental MRI machines (4.7T Bruker Biospec and TOT Varian INOVA300SWB) and a whole body MRI machine for human(1.5T GE Signa Horizon, 1.5T Siemens Symphony and 3.0T GE Signa Horizon).In fiber … More tracking imaging method, three dimensional distribution of fiber orientation was clearly demonstrated by the images based on diffusion tensor direction. Disconnection of fiber was demonstrated in cases of cerebral infarction. In MEMRI method, neuronal fibers were clearly demonstrated in rat olfactory grove, optic nerve and optic radiation. Also the six cortical layers were clearly demonstrated by this method. This method is useful to detect the neuronal orientation and brain structure directly based on the nerve cell activation. In 2D-MRS, 2D-JPRESS and 2D-COSY were developed on 1.5T and 3.0T clinical MRI devices. Brain metabolites which could not be detected by conventional MRS method were obtained by those 2D-MRS method, such as glutamine/glutamate, glutathione, threonine and GABA. 2D-MRS is useful to examine the viability of damaged brain from the metabolic point of view. The perfusion imaging using arterial spin tagging method was useful to detect the cerebral blood flow change non-invasively, and the combination with diffusion weighted imaging is useful to know the viability of penumbra region in cerebral infarction.In conclusion, the multi-modality MR methods are unique and useful to examine the regeneration of damaged brain tissue and nerve cell function non-invasively. Since there are still more techniques in MRI methods to evaluate the brain function and metabolism, further research should be continued. Less