Application of cerebral blood flow and metabolism imaging with multi-nuclear, multi-modality MRI techniques to cerebral

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We have developed multi-nuclear and multi-modality magnetic resonance microscopic imaging (MRI) techniques for analysis of brain functions and various cerebral disorders, both experimentally and clinically. These methods are ; (1) Fast Chemical Shift Imaging (CSI) method for detecting various metabolite in the brain, (2) Diffusion-weighted imaging using ultrafast MRI (EPI-DWI), (3) Perfusion Imaging using arterial spin tagging method and (4) Functional MRI using ultrafast MRI.In magnetic resonance spectroscopy (MRS), various metabolites in the brain were detected and their distribution was visualized by the CSI method. Energy metabolism and phospholipid metabolism can be examined by ^<31>P-MRS.The increase of phosphomonoesters in brain tumors and infant brain indicates the changes of phospholipid metabolism. Decreased phosphocreatine and increased lactate in cerebral infarction indicate the impairment of aerobic metabolism. Amino acids, choline, creatine and lactate can be detected by … More ^1H-MRS.The decrease of N-acetyl aspartate (NAA) in brain tumors, degenerative diseases and cerebral infarction indicates the loss of neurons. Increased lactate was observed in hypoxic cell fractions in malignant tumors and infarction. In the EPI-DWI, cerebral infarction is detected at an ultra-acute stage such as 30 minutes after the onset. The EPI-DWI would be used as a first choice for detecting cerebral vascular diseases. The perfusion imaging using arterial spin tagging method (FAIR) is useful to detect the realative changes in cerebral blood flow, but it still requires more sensitivity for a clinical application using 1.5 T system. At moment, the perfusion imagin using contrast material is practical to know the cerebral hemodynamics using MRI.The combination of EPI-DWI and Perfusion Imaging can possibly indicate the reversibility of damaged brain tissue. In functional MRI (fMRI), an increase of signal intensity was observed in the primary cortical area corresponding to each activation task such as finger movements, photic stimulation and hearing words. The fMRI was also obtained by complex tasks such as imagination. Fast fMRI can be used to detect the time deference of activation in primary and secondary motor cortex. Although there are still some problems in fMRI, it is useful for evaluating brain function non-invasively with highly temporal and spatial resolution. The multi-modality MR methods are unique and useful methods to examine the brain metabolism and function non-invasively and to examine pathophysiology of various cerebral disorders. In this sense, further research should be continued. Less