MRIを用いた脳機能・代謝評価の検討と問題点

Several methods have been introduced in order to evaluate brain function using MRI. One is the blood oxygen level dependent (BOLD) method, which detects oxygen saturation level in a capillary region, and other is the method of flow volume measurement. Each method can detect activated regions in the brain depending on a kind of tasks and give us functional geometric information of activated brain. However, the activated pixels are not detected depending on electric activity of neurons, but the hemodynamic changes using MRI. Then there may be some cases with discrepancy between true activation of neurons and depicted activation areas by MRI. It will be important to consider difference of mechanism to depict activation when the result of functional MRI is interpreted. To evaluate metabolism in the brain, MR spectroscopy (MRS) is useful for both scientific research and clinical diagnosis. But the sensitivity of MRS is relatively lower than radioisotope methods, and our attention should be paid to maintenance of instrument condition and accuracy of the MRS measurement. MRI has huge possibility to detect function and metabolism in the brain noninvasivelly, but it will be important to understand background mechanism of used technique and avoid misinterpretation.