Fluorescent imaging in a glioma model in vivo

Background and Objective: Nile blue dyes have been shown to have affinity f or tumor tissue as compared to surrounding normal tissue and to be relative ly non-toxic. We have employed EtNBA, a lipophilic, fluorescent benzophenox azine dye, in a murine model to image subcutaneous and intracranial U-87 gl ioma implants. Study Design/Materials and Methods: The imaging system used to detect fluor escence consists of a SIT video camera fitted with a zoom microscope-magnif ying lens. The tumor Suss illuminated with a 632.8-nm diffuse beam from a h elium-neon laser. The video image was processed using a Sony image processo r to give real-time pseudocolor and enhanced black and white images. Results: Following subcutaneous injection of the dye at doses of 2.5-5.0 mg /kg bw, we observed a gradual increase of the fluorescent signal from the t umor which peaked 1-3 hours post-injection with variable selectivity (typic ally 4:1) for tumor to normal surrounding tissues permitting the clear dema rcation of the tumor. Conclusions: The present in vivo study demonstrates that EtNBA is a safe an d effective photodiagnostic agent, able to demarcate U87-MG solid tumors in mice on a realtime basis at a concentration of 2.5-5.0 mg/kg 1-3 hours aft er administration. (C) 2001 Wiley-Liss, Inc.