A method of acquiring a tomography image includes acquiring a plurality of raw data by detecting an X-ray irradiated to an object from an X-ray generator a plurality of times, wherein an X-ray detector performs the detecting； setting at least a part of the object as a region of interest； and reconstructing the tomography image including the region of interest, based on the plurality of raw data, wherein the reconstructing of the tomography image includes: selecting filter kernels based on distances between positions of the X-ray generator that irradiated the X-ray to the region of interest and positions of voxels included in the region of interest； generating filter images by applying the selected filter kernels to the raw data corresponding to the positions of the X-ray generator that irradiated the X-ray； and reconstructing the tomography image from the filter images by back-projecting the filter images.
