A method for reducing streaking artifacts in 4D-CT reconstruction by generating additional projections is proposed. This method uses optical flow to track anatomy motion across the complete set of projections and then uses this information to compute interpolated projections while compensating for breathing motion. Original and interpolated projections, all belonging to one respiratory phase, are used to reconstruct a 4D-CT volume. Experimental results showed that the proposed method reduces artifacts and blurring in reconstructed 4D-CT volumes and improves the image quality.