Cone beam CT (CBCT) technique provides true three-dimensional (3D) images of a breast; however, metal clips and
needles used for surgical planning can cause artifacts, which may extend to many adjacent slices, in the reconstructed
images obtained by the Feldkamp-Davis-Kress (FDK) filtered backprojection method,. In this paper, a sinogram
based method to remove the metal clips in the projection image data is described and discussed for improving the
quality of reconstructed breast images. First, the original projection data was reconstructed using the FDK algorithm
to obtain a volumetric image with metal clips and artifacts. Second, the volumetric image was segmented by using
the threshold method to obtain a 3D map of metal objects. Third, a forward projection algorithm is applied to the
metal object map to obtain projection map of metal objects. Finally, the original projection images and projection
map of metal objects are reorganized into sinograms for correction in the angular space on a pixel-by-pixel basis.
Cone beam CT images of a mastectomy breast specimen are used to demonstrate the feasibility of using this
technique for removal of metal object artifacts. Preliminary results have demonstrated that metal objects artifacts in
3D images were reduced and the image quality were improved.