Diagram illustrates the experimental design of immune cell imaging in vivo. A, VX2 liver tumor chunks were injected into the hind leg of a donor rabbit. B, Tumor chunks were harvested and injected into the left liver of the recipient rabbit and allowed to grow for 14 days. C, Three rabbits received intra-arterial (IA) injections of gadolinium 160 (160Gd)–labeled anti–human leukocyte antigen–DR isotope antibodies and, D, three were intravenously (IV) injected with superparamagnetic iron oxide nanoparticles (SPION). E, 160Gd-conjugated antibodies target antigen-presenting immune cells (APC) in the peritumoral rim and SPIONs are phagocytosed by peritumoral macrophages. F, MRI was performed and imaging findings were confirmed with radiologic-pathologic correlation.