Simulation studies on appropriate imaging parameters for DW-fMRI using 3D and 2-compartment models

A new method of functional magnetic resonance imaging by using diffusion weighted imaging(DWI) has been recently reported as DW-fMRI. It can measure brain functions more directly based on the property that neuronal cells swell when the brain is activated than conventional BOLD (blood oxygenation level dependent)-fMRI. To find out appropriate settings of DWI for DW-fMRI, we investigated influence of imaging parameters on DW-fMRI, particularly b- and q- values. We calculated the differences between the normalized signal intensities of DWI before and after cell swelling with Monte-Carlo simulation using a 3D cubic model which has 2 compartments. Simulation results showed that a b-value of more than 2000 s/mm² and a small q-value should be selected for DW-fMRI measurement and that the q-value must be selected more carefully than the b-value as MPG parameters.