Multimodal CT/optical agents

A method for performing one or more imaging modalities on a subject in need thereof, the method comprising administering an effective amount of a composition comprising an iodinated contrast agent and indocyanine green co-encapsulated inside a pegylated liposomal carrier, wherein the molar ratio of the iodinated contrast agent to indocyanine green is about 1,000:1 to about 10,000:1, wherein the liposomal carrier comprises a) one or more lipids, b) cholesterol, and c) one or more PEGylated lipids, and wherein the indocyanine green in the pegylated liposomal carrier retains at least 50% of its original fluorescence for at least 72 hours to the subject, and performing the one or more imaging modalities on the subject.