Researchers at Stanford University have developed a way to image chimeric antigen receptor (CAR) T cells in patients by adding a positron emission tomography (PET) reporter gene to glioma-targeting cells. The same team had previously shown that in a single patient, such CAR T cells could be visualized after an autologous transplant, but due to constraints of the study protocol, it was not possible to take a baseline reading. In the current phase I study, the researchers treated seven patients with reporter gene-containing CAR T cells and showed that they could track the infused cells, though the study was not powered to relate cell uptake into tumors to clinical outcome.