A method of generating a tomographic image includes radiating X-rays onto an object and acquiring X-ray data by detecting the X-rays passed through the object； generating a first tomographic image by reconstructing the X-ray data； identifying, in the first tomographic image, a first region corresponding to a metal particle included in the object； generating a second tomographic image by changing a pixel value of the first region to a predetermined value； acquiring first projection data by performing forward projection on the second tomographic image； generating second projection data by performing interpolation on first signal intensity values corresponding to the first region, based on the first projection data； generating reconstruction data by subtracting the first projection data from the second projection data； generating a third tomographic image based on the reconstruction data； and generating a fourth tomographic image based on the third tomographic image and the first tomographic image.
