ABSTRACT
Noninvasive imaging has evolved into an important tool for diagnosing, understanding, and monitoring disease. Molecular imaging has distinguished itself as an interdisciplinary field that enables in vivo visualization, characterization, and quantification of biologic processes at the cellular and subcellular level with high sensitivity, specificity, spatial, and temporal resolution. To date, many of the molecular imaging approaches have focused on extracellular targets, exploiting receptors, ion channels, transporters, antigens and enzymes at the cell surface or extracellular environment. They are often regarded as the ideal molecular imaging structure as these targets are relatively easy to access in vivo. Targeted imaging probes that interact with intracellular components or events are becoming increasingly important. The intracellular compartment presents many different processes that can potentially be targeted, some more challenging than others. In addition to target selection and probe design, one must also take into account the choice of imaging modality.
