The present invention is directed to synthetic nanoparticles useful as imaging agents for use in MRI, CT, Gamma-scintigraphy, or optical imaging techniques. The synthetic nanoparticles comprise at least one apolipoprotein that is not an apoB lipoprotein, at least one amphipathic lipid, and at least one metallic or non-metallic contrast agent linked through a chelator to a component of the nanoparticle, wherein the one metallic or non-metallic contrast agent is present in an amount of between 5% to about 50% (w/w) of the nanoparticle, and the nanoparticle has a diameter of from about 5 nm to about 50 nm. Compositions and kits comprising the synthetic nanoparticles and methods of making and using the same are also provided.