Radionuclide probes for molecular imaging of pancreatic beta-cells

Islet transplantation is a promising treatment option for patients with type 1 diabetes (T1D); however, the fate of the graft over time remains difficult to follow, due to the lack of available tools capable of monitoring graft rejection and inflammation prior to islet graft loss. Due to the challenges imposed by the location of the pancreas and the sparsely dispersed beta-cell population within the pancreas, currently, the clinical verification of beta-cell abnormalities can only be obtained indirectly via metabolic studies, which typically is not possible until after a significant deterioration in islet function has already occurred. The development of non-invasive imaging methods for the assessment of the pancreatic beta-cells, however, offers the potential for the early detection of beta-cell dysfunction prior to the clinical onset of T1D and type 2 diabetes (T2D). Ideal islet imaging agents would have an acceptable residence time in the human body, be capable of providing high-resolution images with minimal uptake in surrounding tissues (e.g., the liver), would not be toxic to islets, and would not require pre-treatment of islets prior to transplantation. A variety of currently available imaging techniques, including magnetic resonance imaging (MRI), bioluminescence imaging (BLI), and nuclear imaging have been tested for the study of beta-cell diseases. In this article, we summarize the recent advances made in nuclear imaging techniques for non-invasive imaging of pancreatic beta-cells. The use of radioactive probes for islet imaging is also discussed.