Sometimes when imaging we purposely leave space between spots to save time or maybe there is a gap in your image from an instrument glitch. In either case, the cell space image will contain regions of null data, and often we would like to replace those missing parts to make a better looking image.

When acquiring images, it is fairly common that more than just the target is ablated and analyzed. For example, maybe you want to be sure that you get the material boundaries or perhaps you are not exactly sure where the boundaries are, so you setup your sequence to cover a broader area.