3-DIMENSIONAL IMAGE-RECONSTRUCTION BY DIGITAL TOMO-SYNTHESIS USING INVERSE FILTERING

Conventional X-ray tomo-synthesis with film can provide a sagittal sli ce image with a single scan. This technique has the advantage of enabl ing reconstruction of a sagittal slice which is difficult to obtain fr om the X-ray CT system. However, only an image on the focal plane is o btained by a single scan. Furthermore, the image is degraded by superi mpositions of the structures outside of the focal plane. In this paper a new three-dimensional image reconstruction method is proposed. This method utilizes a three-dimensional convolution process with an inver se filter function which is derived analytically by the point spread f unction of the projection and backprojection geometry. A digital tomo- synthesis system has also been constructed for the purpose of evaluati ng the proposed method. This system was used in phantom experiments an d clinical evaluations, and it was confirmed that the proposed method was able to reconstruct a better three-dimensional image with less art ifacts from outside of the focused slice.