Cell therapy offers promising opportunities to approach several diseases for which no effective therapies are currently available. However, the prognosis of treatment efficacy commonly only relies on the progression of the disease symptoms. There is a need of tools to evaluate and predict the safety and success of cell-based treatments in earlier stages. The lack of methods providing real-time tracking of transplanted cells and knowledge on their early biodistribution and viability is one of the major weaknesses of the available cell-based treatments.