Table 1.

Characteristics of an ideal cell label for stem cell tracking in clinical studies.13

1. Biocompatible, safe, and nontoxic

2. No genetic modification or perturbation to the stem cell

3. Single-cell detection at any anatomic location

4. Quantification of cell number

5. Minimal or no dilution with cell division

6. Minimal or no transfer of contrast agent to non-stem cells

7. Noninvasive imaging in the living subject over months to years

8. No requirement for injectable contrast agent