Computed Tomographic (CT) Reconstruction From Limited Projection Angles

Kenneth M. Hanson

doi:10.1117/12.933824

29 December 1982 Computed Tomographic (CT) Reconstruction From Limited Projection Angles

Kenneth M. Hanson

Proceedings Volume 0347, Application of Optical Instrumentation in Medicine X; (1982) https://doi.org/10.1117/12.933824
Event: Application of Optical Instrumentation in Medicine X, 1982, New Orleans, United States

Abstract

When the available CT projection data are incomplete, there exists a null space in the space of possible reconstructions about which the data provide no information. Deterministic CT reconstructions are impotent in regard to this null space. Furthermore, it is shown that consistency conditions based on projection moments do not provide the missing projections. When the projection data consist of a set of parallel projections that do not encompass a complete 180° rotation, the null space corresponds to a missing sector in the Fourier transform of the original 2-D function. The long-range streak artifacts created by the missing sector can be reduced by attenuating the Fourier transform of the reconstruction smoothly to zero at the sector boundary. It is shown that the Fourier transform of a reconstruction obtained under a maximum entropy constraint is nearly zero in the missing sector. Hence, maximum entropy does not overcome the basic lack of information. It is suggested that some portion of the null space might be filled in by use of a priori knowledge of the type of image expected.

Citation Download Citation

Kenneth M. Hanson "Computed Tomographic (CT) Reconstruction From Limited Projection Angles", Proc. SPIE 0347, Application of Optical Instrumentation in Medicine X, (29 December 1982); https://doi.org/10.1117/12.933824

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