Abstract: Compositions and methods are disclosed for evaluating a subject's vasculature integrity, for differentiating between a malignant lesion and a benign lesion, for evaluating the accessibility of a tumor to nano-sized therapeutics, for treating tumors, and for live or real time monitoring of a nano-probe's biodistribution.

Abstract: Example compositions of liposomes with hydrophilic polymers on their surface, and containing relatively high concentrations of contrast-enhancing agents for computed tomography are provided. Example pharmaceutical compositions of such liposomes, when administered to a subject, provide for increased contrast of extended duration, as measured by computed tomography, in the bloodstream and other tissues of the subject. Also provided are example methods for making the liposomes containing high concentrations of contrast-enhancing agents, and example methods for using the compositions.