Stem cells hold great potential for treating a variety of human diseases, but more information is needed on how they will function once administered to patients for regenerative medicine purposes. Our studies are focused on addressing new ways to optimize the use of positron emission tomography (PET), an imaging technology used in the human clinical setting, to monitor stem and progenitor cells post-transplantation. In our studies we have accomplished our stated milestones and optimized PET imaging techniques by addressing the sensitivity of the scanner and ways to improve the detection of small quantities of transplanted cells. We have also carefully identified methods for safely placing imaging labels on the cells without altering the proliferative and growth potential of the cells under investigation. We are now poised to use our model systems to test how these improvements enhance our established imaging protocols.