Purpose:To image β‐cells noninvasively using radio‐manganese PET and to develop efficient small cyclotron production of 51Mn (t1/2=46m, β+=97%) and 52Mn (t1/2=5.6d, β+=29%).Methods:51Mn and 52Mn were produced by 16 MeV proton irradiation (GE PETtrace) of electrodeposited 54Fe on silver and Cr metal pressed into a silver disc, respectively. 51Mn was radiochemically isolated from target material by anion exchange chromatography and 52Mn was isolated by ethanolic anion exchange trap‐and‐release. A final injectable product of 51Mn2+ or 52Mn2+ was obtained in 0.01M pH 6.0 NaOAc. To assess pancreatic uptake, fasted ICR mice were administered and intravenous bolus or infusion of 52Mn2+. Additionally, to demonstrate the correlation between β‐cell function and 52Mn2+ pancreatic uptake, prior to tracer administration groups of ICR mice were administered glibenclamide (5mg/kg) and diazoxide (20 mg/kg) as an insulin release stimulator and blocker, respectively. To validate PET ROI quantification, ex vivo biodistribtution studies were conducted on each subject after the final imaging time‐point.Results:Dynamic PET data using a left atrium ROI revealed that 52Mn2+ cleared from the blood with a 10 second half‐life. Significant uptake was seen in the pancreas (approximately 20% ID/g, SUVmean= 5.5), liver, kidneys, intestine, heart, and thyroid. Pancreatic uptake was found to be highly sensitive to volatile anesthesia administration (p=0.0002), insulin release stimulation by glibenclamide (p=0.017), and by insulin release inhibition by diazoxide (p=0.046). Excellent agreement was found between in vivo PET ROI quantification and ex vivo biodistribution measurements.Conclusion:This work demonstrates the feasibility of using radiomanganese‐PET for measuring functional β‐cell mass in vivo. The decay characteristics and dosimetric properties of 51Mn are well suited for clinical PET, which will allow for rapid translation and application.