Optical imaging of cells treated with MGd at concentration of 100 μg/mL at various incubation durations. A, Optical image shows that signal intensity (SI) of MGd-emitting fluorescence increases as MGd incubation time increases. B, Graph shows time to fluorescence signal intensity curve in which signal intensity increases from 0 to 24 hours and then plateaus for following 24 hours. C, Confocal microscopy confirms early uptake of MGd by cells after MGd incubation for 15 minutes, D, while no intracellular red fluorescence was seen in nontreated control cells (magnification, ×20).