method for reconstructing objects from analysis to corner limitanto in computed tomography.

摘要

The accuracy of limited-angle x-ray computerized tomography scannings is improved by incorporating additional a priori information on the object. In industrial nondestructive testing and other situations the object A contains a medium which is the dominant component whose density is known; flaws 11 inside the medium are to be imaged. The contribution of the medium is eliminated and an image is reconstructed which is the difference between the original object and a hypothetical object made up entirely of the medium which has the same boundary as the original object. Calculated projections of the hypothetical object at various scan angles are subtracted from measured projections to yield difference projections di. The latter are backprojected to derive image strips to which the flaws are confined and these are overlapped to construct a region enclosing the flaws. Using the difference projections and flaw- enclosing regions, the shape and density of the flaws are reconstructed by limited-angle reconstruction algorithms. IMAGE