The MPI (magnetic particle imaging) scanner is needed for realizing the full potential of the centers: MPI enables straightforward quantitation of iron oxide nanoparticles. This allows one to do dose-response studies, e.g. a) How many stem or immune cells are at the target site, and how does this affect therapeutic outcome? b) For gene and drug delivery in theranostic applications, how many particles need to accumulate at the target site to induce the desired (anti-tumor) response? c) What is the minimal particle dose that is locally required to induce effective hyperthermia?