Advancements in technology have led to the ability to tag virtually any cell with magnetic particles so long as the surface protein is known. In theory, these tagged cells may then be identified, imaged, or manipulated by magnetic force. In vitro separation using a magnetized stent and magnetically tagged cells was demonstrated by . The motivation for this work was to investigate the feasibility of a magnetized inferior vena cava (IVC) filter for in vivo separation of metastatic cancer cells from the bloodstream. In use, the device would consist of a standard IVC filter plated with nickel, making it paramagnetic yet still biocompatible. The IVC filter is placed inside the vena cava, as is routinely done for other applications. Permanent magnets, which the patient would wear as an external vest, generate a field and the presence of the magnetized filter within this field can attract magnetic particles to the filter. In particular, our goal was to develop a numerical model that could be used to assess the feasibility and performance of such a device over a range of design space.