The present invention relates to compositions and methods useful in connection with magnetic resonance imaging. In various embodiments, the invention employs the PASADENA polarization technique to prepare contrast agents that target complementary molecules in the body and/or that are processed through predetermined, natural metabolic pathways. The invention includes methods of using the contrast agents and kits including the same. In one embodiment, a diagnostic and prognostic method relating to Alzheimer's disease is described. Further embodiments relate to medical devices including the contrast agents.