LASER-INDUCED FLUORESCENCE - EXPERIMENTAL INTRAOPERATIVE DELINEATION OF TUMOR RESECTION MARGINS

The ability of laser-induced fluorescence spectroscopy to delineate tu mor margins intraoperatively was studied using a rat intracerebral gli oma model. A fluorescent dye, chloro-aluminum phthalocyanine tetrasulf onate (ClAlPcS4), was injected intravenously 24 hours before tumor res ection. The animals underwent tumor resection under the operating micr oscope, guided by laser-induced fluorescence measurement in one group (Group 1) and visual assessment in the other (Group 2). The Group 1 ra ts had a significantly reduced volume of residual tumor following rese ction (0.5 +/- 0.2 cu mm vs. 13.7 +/- 4.0 cu mm, mean +/- standard err or of the mean, p < 0.02). Three of the nine animals in Group 1 were t umor-free at 2 weeks following resection, compared with none of the 10 rats in Group 2 (p < 0.05). Interference from brain autofluorescence was minimized using spectrally resolved detection and the ClAlPcS4 dye , which has a 680-nm fluorescence peak significantly higher than the 4 70-nm autofluorescence peak of normal brain. Contrast ratios of up to 40:1 were found for glioma:normal brain fluorescence signals. Spatiall y-resolved spectra were acquired in approximately 5 seconds using a fi beroptic probe. This study demonstrates the ability of an intraoperati ve laser-induced fluorescence system to detect tumor margins that coul d not be identified with the operating microscope.