Fig. 3.

Using the process described in Fig. 2, images of phase change (in degrees) relative to the baseline time period were generated for several time bins and slice positions. Each column of images corresponds to a different time bin, with the time corresponding to the bin center shown at the top of each column (e.g., the center of the first time bin is 7.5 s after current onset). Each row of images corresponds to a different slice position, indicated by the dashed green line on the schematic diagram to the left of each row. Ionic current flows “up” the left capillary tube (in the positive z-direction), through the body of the phantom and “down” the right capillary tube (in the negative z-direction), as shown by the red arrows in the schematic diagrams. The black contour in the images indicates the boundary of the phantom. Note that the spatial pattern of phase changes develops over the course of tens of seconds, as is particularly evident in the images from the central slice (fourth row of images).