1. A method comprising: obtaining a projection image of a projection object; pre-processing, by a processor, the projection image acquired by an imaging device to generate a processed projection image, the imaging device including a radiation source and a detector; reconstructing, by the processor, the processed projection image to generate a reconstructed image including an artifact; and removing, by the processor, the artifact in the reconstructed image, the pre-processing the projection image including segmenting the projection image to generate a segmented projection image, the segmented projection image including a region of interest, and the segmenting the projection image including determining an average gray value of one or more pixels of the projection image; for each pixel of the one or more pixels of the projection image, assigning mark A or mark B to the pixel based on a relationship between a gray value of the pixel and the average gray value; and determining a boundary of the region of interest based on the assigned mark of each pixel of the one or more pixels of the projection image, the reconstructing the processed projection image to generate the reconstructed image including filtering the processed projection image to generate a filtered projection image including a highlighted artifact and an X-ray attenuation artifact; correcting the highlighted artifact and the X-ray attenuation artifact in the filtered projection image to generate a first image; and performing back projection to generate the reconstructed image based on the first image.