Hafnium-Based Contrast Agents for X‑ray Computed Tomography

Heavy-metal-based
contrast agents (CAs) offer enhanced X-ray absorption for X-ray computed
tomography (CT) compared to the currently used iodinated CAs. We report
the discovery of new lanthanide and hafnium azainositol complexes
and their optimization with respect to high water solubility and stability.
Our efforts culminated in the synthesis of BAY-576, an uncharged hafnium
complex with 3:2 stoichiometry and broken complex symmetry. The superior
properties of this asymmetrically substituted hafnium CA were demonstrated
by a CT angiography study in rabbits that revealed excellent signal
contrast enhancement.