[Optical imaging of fluorescence in the near infrared. From passive to enzymatically activated contrast medium]

The molecular imaging of specific targets using optical methods is currently possible in vivo, in part due to the advances in imaging modalities (epifluorescence, fluorescent endoscopy, fluorescence mediated tomography, intravital fluorescence microscopy), and in part due to the development of better contrast media. These are composed of a suitable fluorochrome, usually with emission in the near infrared due to tissue penetration, as well as by molecular specific contrast media from ligands. The latest generation of contrast media is not fluorescent in its unactivated state. Fluorescence first occurs after contact with certain (e.g. disease specific) enzymes by which a minimally unspecific fluorescent background as well as molecular specificity is made possible.