Computed tomography (CT) is one of the most widely used clinical imaging
modalities. In order to increase the sensitivity of CT, small iodinated compounds
are used as injectable contrast agents. However, the iodinated contrast
agents are excreted through the kidney and have short circulation times.
This rapid renal clearance not only restricts in vivo applications that require
long circulation times but also sometimes induces serious adverse effects
related to the excretion pathway. In addition, the X-ray attenuation of iodine is
not effi cient for clinical CT that uses high-energy X-ray. Due to these limitations,
nano-sized iodinated CT contrast agents have been developed that can
increase the circulation time and decrease the adverse effects. In addition to
iodine, nanoparticles based on heavy atoms such as gold, lanthanides, and
tantalum are used as more effi cient CT contrast agents. In this review, we
summarize the recent progresses made in nano-sized CT contrast agents.