Structure of Total Reconstructed Sets from Given Two Projection Data

We discuss the structure of the total reconstructed sets from given two projections of a plane figure. In case uniqueness does not hold, we have many solutions which are related among them via exchange of switching pair. We let this structure correspond a graph, named switching graph. Through this consideration we might overview the origin of complexity of non-uniqueness of the reconstruction, and the way to obtain good reconstruction. We present some such results toward this direction.