Angiogenesis is integral to the development and progression of atherosclerotic disease and solid tumor growth. New microvessels form in atherosclerotic plaque and the presence of new vessels has been associated with carotid plaque instability. Likewise, solid tumor growth depends upon angiogenesis to provide tumor cells with oxygen and nutrients. Recently, Lanza et al. have demonstrated molecular imaging of angiogenesis both in human melanoma xenografts in nude mice and atherosclerotic rabbits by magnetic resonance imaging (MRI) with clinical magnet strengths using ανβ3-targeted nanoparticles developed in their lab. ανβ3-integrin is a selective molecular epitope expressed by angiogenic endothelium and the MRI contrast agent consists of a lipid-encapsulated, liquid perfluorocarbon nanoparticle directly coupled to a selective ανβ3 ligand. The nanoparticle also contains the paramagnetic contrast agent gadolinium linked to the nanoparticle as Gd-DTPA-bis-oleate. In this work we report on the use of neutron activation analysis to confirm the Gd content of the nanoparticle formulations and determine the biodistribution of Gd post injection.