Abstract: The disclosure relates to methods for labeling cells ex vivo with agents that can be detected by MRI or PET techniques, or other techniques that permit non-invasive imaging of living organisms. The labeled cells can be re-administered to the patient and the movements of the labeled cells can be tracked in vivo by MRI, PET or other techniques. In part, the disclosed methods involve labeling a series of cell samples ex vivo determining the association of label with the cells, such that an appropriate dosage of labeled cells can be determined for each patient.