The numerous foreign objects (e.g. dental implants, surgical clips and wires, orthopedic screws and plates, prosthetic devices, etc.) that can be present in the subject lead to susceptibility artifacts in the MR images that propagate as signal voids in the corresponding attenuation maps. 

We developed a method to estimate the location, shape, and linear attenuation coefficient of the implant using a joint reconstruction of the activity and attenuation algorithm. The implant PET-based attenuation map completion (IPAC) method performs a join reconstruction of radioactivity and attenuation from the emission data (Fuin et al 2017).