Body QSM relies on accurate magnetic field-mapping. A well-established water–fat voxel signal model with shared $$$R_2^*$$$ has successfully been used for body QSM based on multi-echo data at conventional echo times. However, when UTE echoes are recorded to obtain field-map information in previously unavailable MR signal voids, such as trabecular bone, the above water–fat model is no longer accurate. Therefore a joint 2-signal-model fitting using graph-cuts is proposed and applied. Further, this work demonstrates the importance of UTE echoes to obtain correct susceptibility values of cortical bone and more importantly, for bone marrow.