Emission CT Image Reconstruction Using the Augmented Lagrangian Method with a Modified Form of Nonnegativity Constraints

: The augmented Lagrangian method was applied to emission CT image reconstruction to attain the satisfactory elimination of negative pixels using a modified form of the original nonnegativity constraints. A penalty function was included in the augmented Lagrangian method to suppress image noise due to statistical noise in the projection data. A slight change in the original constraint form achieved almost complete nonnegativity without loss in the closeness of reconstruction to the original image.