Fluorescent imaging in a glioma model in vivo.

Background and Objective Nile blue dyes have been shown to have affinity for tumor tissue as compared to surrounding normal tissue and to be relatively non-toxic. We have employed EtNBA, a lipophilic, fluorescent benzophenoxazine dye, in a murine model to image subcutaneous and intracranial U-87 glioma implants. Study Design/Materials and Methods The imaging system used to detect fluorescence consists of a SIT video camera fitted with a zoom microscope-magnifying lens. The tumor was illuminated with a 632.8-nm diffuse beam from a helium–neon laser. The video image was processed using a Sony image processor 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 tumor which peaked 1–3 hours post-injection with variable selectivity (typically 4:1) for tumor to normal surrounding tissues permitting the clear demarcation of the tumor. Conclusions The present in vivo study demonstrates that EtNBA is a safe and effective photodiagnostic agent, able to demarcate U87-MG solid tumors in mice on a real-time basis at a concentration of 2.5–5.0 mg/kg 1–3 hours after administration. Lasers Surg. Med. 29:11–17, 2001. © 2001 Wiley-Liss, Inc.