Superparamagnetic iron oxide nanoparticles (SPIONs) have a history of clinical use as contrast agents in T2 weighted MRI, though relatively low T2 relaxivity has caused them to fall out of favor as new faster MRI techniques have gained prominence.
Chlorin e6-Coated Superparamagnetic Iron Oxide Nanoparticle (SPION) Nanoclusters as a Theranostic Agent for Dual-Mode Imaging and Photodynamic Therapy