拡散強調MR信号強度の撮像パラメータならびに制限サイズ依存性に関する検討

抄録

Neuronal cells in the human brain has minute and intricate structures in which a lot of water molecules diffuse restrictedly. In recent years, DWI has been focusd on as a method which can detect restricted diffusion of water molecules and visualize the structures containing water molecules. This approach is mainly used for diagnosis of pathology such as acute stroke. In addition, lately it has been suggested that this approach can be applied to fMRI with the fact that neuronal cells in the brain change their volumes during their activation. In the present study, with the Monte-Calro method we simulated the motions of water molecules in the restricted structures whose sizes were similar to those of neurons to find appropriate imaging parametrs for DW-fMRI. Simulation results demonstrated that imaging parameters and the size of restricted areas may change signal intensities. Furthermore, it was found that the difference of signal intensities due to the change in the size of restricted areas largely depends on the q-value which is one of imaging parameters. These results indicate that the present simulation can estimate the imaging parameters which emphasize the difference of signal intensities in DWI between before and after the sizes of cells change. In addition, we should choose appropriate q-value more carefully than b-value for the measurements of brain activations with DWI.