The problem of determining the structure of an object from knowledge of its projections along straight lines arises in a variety of optical contexts. The general solution to this problem is given by the inverse Radon transform of the projections. A superposition principle is developed to show the relation between this general inversion and the more familiar inverse Abel transform that is associated with radially symmetric objects.
C. M. Vest, "Formation of images from projections: Radon and Abel transforms," J. Opt. Soc. Am. 64, 1215-1218 (1974)