Correcting positron emission tomography image attenuation

A PET/MRI device, comprising:

• a processor, and
• a non-transitory machine-readable storage medium storing machine executable instructions which are executable by the processor to:
• segment an MRI image of a subject to obtain respective MRI sub-images corresponding to attenuation units of the subject;
• for each MRI sub-image, obtain a pseudo CT sub-images corresponding to the MRI sub-images based on an MRI-CT atlas, wherein;
• the pseudo CT sub-image is obtained by selecting a plurality of CT template sub-images present in the MRI-CT atlas that corresponds to a plurality of MRI template sub-images in the MRI-CT atlas matched to the MRI sub-image, and
• the plurality of MRI template sub-images is matched to the MRI sub-image by a matching relationship comprising shape factors and intensity weight factors;
• splice the respective pseudo CT sub-images to obtain a pseudo CT image;
• and
• perform attenuation correction for a PET image of the subject according to the pseudo CT image, wherein the PET image and the MRI image are obtained through a same scan process for the subject.