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. Author manuscript; available in PMC: 2023 Apr 1.
Published in final edited form as: Med Image Anal. 2022 Jan 29;77:102372. doi: 10.1016/j.media.2022.102372

Fig. 3.

Fig. 3.

Illustration of geometry transformation with backward projection (blue) and forward projection (purple). The back projector puts the pixel intensities in the source-view image back to the corresponding voxels in the 3D volume according to the cone-beam geometry of the physical model. When the X-ray source rotates to the target view angles, the forward projection operator integrates along the projection line and projects onto the detector plane.