A non-invasive imaging of targeted molecules in living organisms. The purpose is to identify a specific [altered] biological process with the aid of a molecular probe that is subject to alteration by the process and the alteration is detectable by light or near-infrared emission or by radioisotopes. An example is shown by the Fig. M100.

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Another example is that the dopamine receptor gene (D2R) in an adenovirus vector is injected into the tail of a mouse, and two days later the positron-labeled D2R ligand, (¹⁸F) FESP (the dopamine analog 3-(-2-(¹⁸F) fluoroethylpiperone, is injected into the mouse’s bloodstream. MicroPET tomography then reveals the concentration of the molecular target by direct labeling. There are a wide variety of techniques for imaging other molecules. Direct-binding probes reveal the quantity of the target whereas indirect probes shed information on the activity status of the target. For the detection, one of the tomography or magnetic resonance imaging techniques or optical devices for luciferase activity are used.  tomography,  nuclear magnetic resonance spectroscopy,  luciferase,  GUS; Herschman H R 2003 Science 302:605.