Instrumentation and probes for molecular and cellular imaging.

Molecular and cellular imaging is a branch of biomedical sciences that combines the use of imaging instrumentation and biotechnology to characterize molecular and cellular processes in living organisms in normal and pathologic conditions. The two merging areas of research behind molecular and cellular imaging are detection technology, i.e. scanners and imaging devices, and development of tracers, contrast agents and reporter probes that make imaging with scanners and devices possible. Several in vivo imaging instruments currently used in human studies, such as computer tomography, ultrasound, magnetic resonance, positron emission tomography and single photon emission computed tomography, have been rescaled for small animal studies, while other methods initially used for in vitro evaluation, such as bioluminescence and fluorescence, have been refined for in vivo imaging. Conventional imaging relies on the use of non specific contrast agents and classical probes; however, newly developed targeted contrast agents and activable ''smart'' imaging probes for so-called ''targeted imaging'' have demonstrated high specificity and high signal to noise ratio in small animal studies. This review focuses on basic recent findings in the technical aspects of molecular and cellular imaging modalities (equipment, targeted probe and contrast agents and applied combinations of instrumentation and probe) with particular attention to the choice of the future: the multimodal imaging approach.