A method for correcting a positron emission tomography (PET) image includes obtaining a magnetic resonance (MR) image dataset, classifying at least one object in the MR image as a bone, generating MR-derived PET attenuation correction factors based on the object classified as the bone, and attenuation correcting a plurality of positron emission tomography (PET) emission data using the MR-derived PET attenuation correction factors. A medical imaging system and a non-transitory computer readable medium are also described herein.