Cell tracking using multimodal imaging.

In vivo imaging plays a key role in cell tracking, particularly for the optimization of cellular therapeutics. A recent trend is to use more than one imaging modality (multimodality imaging) for this purpose. There are several advantages to multimodal cell tracking, particularly the corroboration of data obtained using a new imaging agent or technique with an established one, and the ability to glean complementary information from a single experiment. In this review, we examine the different types of labels and imaging strategies used in the literature for multimodal cell tracking, and discuss the pros and cons of these approaches, with a focus on MRI. Despite many efforts and novel technologies, we still have to face situations where current imaging methods are simply not sensitive enough and new labeling strategies are hampered by the lack of approved reagents. Finally, we examine new in vitro and preclinical developments, which have the potential to tackle unresolved challenges in in vivo multimodal imaging.