Magnetic resonance current density image reconstruction in the spatial frequency domain

The purpose of this study is to improve noise immunity of electrical current density image reconstruction in magnetic resonance current density imaging (MRCDI) and magnetic resonance electrical impedance tomography (MREIT). In the MRCDI and MREIT techniques, electrical current densities have been calculated by taking curls to the extra magnetic fields generated by externally applied electrical currents. The extra magnetic fields are calculated from the phase information in magnetic resonance images. Both the phase calculations and curl operations are very sensitive to the noise. Since the curl operation in the space domain appears as a high pass filter in the spatial frequency domain and the current density images have very little high frequency components, we can adopt various kinds of spatial filtering techniques during the curl operation to improve the signal-to-noise ratio of the current density images. We have compared current density estimation results between the proposed and conventional methods for several kinds of current distribution patterns. For the current distributions with little high spatial frequency components, the proposed current density reconstruction method has been found to be superior to the conventional method.