Nanoparticle contrast agents for CT : their potential and the challenges that lie ahead

The number of reports of nanoparticle CT contrast agents has been growing swiftly over the past 5 years. These nanoparticles can be applied to produce long-lived CT contrast in the blood vessels and to perform targeted imaging, and can be used in conjunction with a new CT technique – multicolor CT. Such innovations offer the promise of new applications and diagnoses that can be performed with CT in fields such as image-guided surgery and evaluation of risk in atherosclerosis and cancer. However, there are a number of obstacles to be overcome in the field, such as the lack of standardized evaluation of new CT contrast agents, the cost of the agents and the need to prove biocompatibility. Over the past 15 years, nanoparticles have become widely applied as contrast agents for MRI [1–3]. In comparison, there have been relatively few nanoparticle contrast-agent formulations reported for CT. Nevertheless, over the past 5 years, the number of publications on nanoparticle contrast agents for CT has been growing exponentially. There have been exciting recent reports of contrast agents that are long-circulating, that are targeted for molecular CT imaging and that allow multicolor CT imaging. There is great potential that these new formulations could allow major advances in preclinical and, eventually, clinical CT imaging. In this article, we will highlight some of the advances made and the challenges facing the field.