This system allows simultaneous acquisition of MRI and PET images of an animal or sample. The technology combines the exquisite structural and functional characterisation of tissue provided by MRI with the extreme sensitivity of PET imaging of metabolism and tracking of uniquely labeled cell types or cell receptors. The MRI system is comprised of a 7 Tesla, 30 cm bore superconducting magnet, with operating software identical to the Siemens clinical MRI platform.