Complex sentence: Several systems have been proposed which combine MRI capability with optical lanthanides probes in dual assays, the optical probe may for instance serve to localize the MRI contrast agent or help visualize the delivery of nucleic acids into cultured cells.
Split into simpler sentences: Several systems have been proposed which combine MRI capability with lanthanides probes in dual assays. This has helped to visualize the delivery of nucleic acids into cultured cells.