An ultra-dense electrode-based brain imaging system with high spatial and temporal resolution. A Sparsity and Smoothness enhanced Method Of Optimized electrical TomograpHy (s-SMOOTH) based reconstruction technique to improve the spatial resolution and localization accuracy of reconstructed brain images is described. Also described is a graph Fractional-Order Total Variation (gFOTV) based reconstruction technique to improve the spatial resolution and localization accuracy of reconstructed brain images.