One recent application of magnetic nanoparticles is to deploy an endovascular magnetic device to selectively remove magnetically-linked chemotherapy during an intra-arterial treatment procedure. In order to measure the device’s efficacy, 89Zr-iron oxide nanoparticles could be imaged using PET-MR. We measured quantitative susceptibility values (Δχ), R2*, and 89Zr-PET uptake of increasing concentrations of 89Zr-IONP in vitro, and in liver in vivo by acquiring a multi-echo UTE GRE sequence and time-of-flight PET. Phantom evaluations demonstrated linear correlation between Δχ, R2*, and 89Zr-IONP uptake. In vivo, substantial increase was observed after 89Zr-IONP infusion. This approach shows promise tracking the biodistribution of radiolabelled magnetic nanoparticles.