In conclusion, in our opinion, Alavi and Werner’s discussion of PET imaging does not reflect the impressive technical developments in recent years, particularly following the introduction of integrated PET/computerised tomography (CT) systems. These improvements include widespread use of integrated PET/CT, as well as the introduction of PET/magnetic resonance (MR) (enabling precise motion correction for improved quantification), time-of-flight imaging and, most recently, digital PET systems [
6,
7,
15,
16]. The current development of innovative technology to further improve the performance of clinical PET scanners, namely innovative detector technology and optimised system geometries, is expected to improve image quality in the near future, with spatial resolutions as low as 1–2 mm [
6]. In addition, we expect that novel beta cell-specific ligands (for example, those binding to beta cell-specific proteins or highly specific protein splice variants) will provide us with a choice of novel radiotracers [
17,
18]. In our view, and based on ongoing work by us and others, in vivo imaging of human pancreatic beta cells is close to become a clinical reality, which is also reflected by the number of ongoing clinical studies using PET for imaging of beta cells that can be found on
www.clinicaltrials.gov (for example, NCT03182296, NCT02542059, NCT03182231). Rather than abandon this promising approach, we should redouble our efforts to reach the point, hopefully in the near future, where beta cell mass quantification may be included among the clinical tests used to evaluate and follow-up individuals with diabetes [
3].