Abstract: Disclosed herein are collagen-targeted imaging agents for positron emission tomography and related imaging methods using the collagen-targeted imaging agents. The collagen-targeted imaging agent is a cyclic polypeptide comprising a cyclic main body, wherein the cyclic main body comprises at least one S—S bond; at least two branches, wherein each of the at least two branches comprises at least three amino acids; and a linker, wherein the linker is capable of linking an imaging reporter.