Fluorescent labeled probes targeting tumor-associated proteins are applied to detect tumors in vivo as well as to evaluate novel concepts of tumor therapies. Dyes in the near-infrared range, coupled to monoclonal antibodies targeting ion channels expressed in tumor cells are injected intravenously to nude mice prior to scans with the time domain optical imager Optix MX2. (Right) A fluorescence intensity map of an immunodeficient tumor bearing nude mouse is shown after in vivo application of a fluorescently labeled antibody targeting a voltage-gated potassium channel demonstrating high accumulation of the probe within the tumor.