Nanoparticles consisting of a HER2 affibody radiolabelled with a unique near-infrared dye (NIR-830), used as a PET imaging probe conjugated to magnetic iron oxide nanoparticles, have been tested in HER2-positive SKOV3 and HER2-negative OVCAR3 tumour xenograft models. The gene discussed is ERBB2; the disease is neoplasm.