Experimental and clinical study of detection of glioma at surgery using fluorescent imaging by a surgical microscope after fluorescein administration.

Total resection is the optimal treatment for malignant gliomas. However, an unexpected residual tumor mass is sometimes found on magnetic resonance imaging performed after an operation because of a macroscopically unclear margin of the tumor at surgery. This study was designed to evaluate the effectiveness of fluorescent imaging by a surgical microscope after fluorescein administration for the detection of gliomas at surgery. For this study, we produced two filters for the excitation and emission of fluorescein that can be easily fitted to and removed from a surgical microscope manually during the operation. For the experimental study, Wistar rat brains bearing C6 glioma were removed at appropriate intervals after intravenous administration of 10-20 mg kg-1 body weight of sodium fluorescein, and their surface and coronal section through the tumor were observed using a surgical microscope with the filters. In clinical cases, 1000 mg of sodium fluorescein was intravenously administered to five patients with glioma before tumor resection. In the experimental study, the C6 glioma itself and the edematous brain adjacent to the tumor (within 2-3 mm of the gross surface of the tumor) were well stained a brilliant yellowish green for a few hours. The normal brain was not stained. In clinical cases, the tumors were stained a brilliant yellowish green under fluorescent observation at surgery. The patients had no side effects. At all times the fluorescent observation could be quickly changed to ordinary observation by removing the filters from the surgical microscope. The tumor was also stained a faint yellow under ordinary nonfluorescent observation. Although this contributed to detection of the tumor, the fluorescent staining demarcated the tumor more clearly than nonfluorescent staining. These results suggest that this imaging technique by a surgical microscope with special filters at surgery may be practical and useful for detection of gliomas and warrants further clinical evaluations.