GLP-1 receptor imaging by PET For specific non-invasive imaging of beta cells, we have developed a highly beta cell-specific radiolabeled exendin-based GLP-1 analog which, after radiolabeling, can non-invasively be detected in the human body. GLP-1 is an incretin hormone that specifically binds to beta cells and is responsible for post-prandial insulin-secretion. Its specificity for beta cells has been shown and a linear correlation of the beta cell mass and the signal obtained with this tracer has been established.