Methods and apparatuses for generating a blur model of a detector, and methods and apparatus for generating a medical image are provided. A method of generating a blur model of a detector may involve: changing locations of linear gamma ray sources along at least one line and obtaining signals emitted from the linear gamma ray sources; obtaining a point spread function (PSF) with respect to at least one voxel included in the at least one line; and generating a blur model of the detector from the PSF.