Adaptability, sensitivity, resolution and non-invasiveness are the attributes that have contributed to the longstanding use of light as an investigational tool and form the basis of optical imaging (OI). OI, which encompasses numerous techniques and methods, is rapid (<5 min), inexpensive, noninvasive, nontoxic (no radiation) and has molecular (single-cell) sensitivity, which is equal to that of conventional nuclear imaging and several orders of magnitude greater than MRI. This article provides a comprehensive overview of emerging applications of OI-based techniques for in vivo monitoring of new stem cell-based therapies. Different fluorochromes for cell labeling, labeling methods and OI-based cell-tracking techniques will be reviewed with respect to their technical principles, current applications and aims for clinical translation. Advantages and limitations of these new OI-based cell-tracking techniques will be discussed. Non-invasive mapping of cells labeled with fluorochromes or OI marker genes has the potential to evolve further within the clinical realm.
