We undertook this study to address the persistent need for noninvasive assessment of β-cell mass in type 1 diabetes. We aimed to determine whether 18F-exendin positron emission tomography/computed tomography can reliably visualize residual β-cell mass and distinguish stages of disease. We found that pancreatic tracer uptake was consistently reduced in type 1 diabetes, differentiated insulin-dependent patients from control participants, and aligned with markers of β-cell function and glycemic sta