Sodium Fluorescein in Brain Tumor Surgery: Assessing Relative Fluorescence Intensity at Tumor Margins

PURPOSE: The use of intraoperative 5-aminolevulinic acid fluorescence has been shown to increase the extent of resection in high-grade glioma surgery. Sodium fluorescein is an alternate fluorescence agent with advantages of low cost, low adverse effect profile, and ability to visualize anatomical detail under the fluorescence filter. Sodium fluorescein-based fluorescence is not specific to tumor cells, and the significance of residual fluorescence at tumor margins has been questioned. In this article, the authors sought to correlate fluorescence intensity at tumor margins with the presence of residual contrast-enhancing tumor on magnetic resonance imaging (MRI). METHODS: Eleven patients with a total of 12 lesions were enrolled in the study. Sodium fluorescein was administered at a dose of 5 mg/kg on induction of anesthesia. Relative intensity of fluorescence was extrapolated from intraoperative photographs through isolation of the green channel from the red/green/blue image, then graphically representing of pixel intensity through application of a thermal map. The correlation between areas of avid fluorescence at tumor cavity margins and the presence of residual contrast-enhancing tumor on postoperative MRI was evaluated. RESULTS: All tumors demonstrated fluorescence. The presence of avid fluorescence at tumor cavity margins had a sensitivity of 66.7% and specificity of 75% for the presence of residual contrast-enhancing tumor on postoperative MRI. There were no adverse effects of fluorescein administration. CONCLUSION: Quantification of relative fluorescence intensity allows easy identification of areas that are high risk for residual contrast-enhancing tumor. Graphical representation of green pixel intensity requires validation through histopathological analysis but has the potential for real-time clinical application.