In in-vitro experiment, you may use marker, like antibody tagged with fluorescence to see the movement with time interval. You may also use the cells tagged with Cr. 51 and infuse into tissue of interest. The tissue then can be exposed to the negative X-ray film. After certain time interval, the X-ray film can be developed. Wherever the area burned with radioactivity would be where the location of cells is. that way the migration of cells could be measure.