FLUOROSPECTRAL STUDY OF THE RAT-BRAIN AND GLIOMA INVIVO

An animal model of cerebral glioma was utilized by implanting C6 gliom a cells into the brains of adult Wistar rats. Once tumors developed to 7-12 mm in diameter, we conducted continuous fluorimetry monitoring o f glioma up to 24 hours using a fibre-optic system connected to an int ensified multichannel photodetector after an intravenous injection of hematoporphyrin derivative (HPD) into the rats. The intensity of the f luorescence in normal brain reached a plateau 6 hours after intravenou s injection of HPD while that in glioma reached a plateau 80 minutes a fter injection. These fluorescence intensities of glioma, brain adjace nt to tumor (BAT), and surrounding normal brain were measured in vivo 24 hours after intravenous administration of 5 mg/kg of HPD. The ratio of fluorescence intensities between glioma and brain was 6.1 while th e ratio between BAT and brain was 3.9. There were no obvious differenc es in shapes between the spectra of the natural fluorescence (autofluo rescence) of rat glioma and brain but the intensity of autofluorescenc e was much weaker in glioma. There are many problems in spectroscopic studies of biological tissues in vivo. It cannot be overemphasized tha t very strict criteria must be applied in order to get accurate data. Fluorescence from HPD administration may be used to discriminate tumor tissue from surrounding normal brain tissue during operation if the m easuring conditions could be kept constant. It is important to underst and the photospectral properties of glioma and brain tissue in order t o get the most benefits in clinical application of light-induced fluor escence or photoradiation therapy.