Monitoring of rat brain ischemia degree with visible light diffuse reflectance spectra and its significance

Objective To observe role of the visible light diffuse reflectance spectra in monitoring the severity of brain ischemia in normal,ischemic and necrotic rat brain tissues so as to offer research basis for intraoperative real-time monitoring of brain reperfusion.Methods Thirty-six SD rats were randomly divided into noumal group and ischemia 1 hour,3 hours,6 hours,12 hours and 24 hours groups,with 6 rats per group.Models of middle cerebral artery occlusion were established using thread technique in ischemic groups.Visible light diffuse reflectance spectroscopy was detected by a spectrometer and mean diffuse reflectance spectroscopy ratio (R630/R545) was measured.Results Spectral reflectance of infarcted brain tissue was enhanced with the prolonged ischemic time while the trough of the spectra at 542 nm and 577 nm was shallowed.Moreover,small trough was appeared at 630 nm at 12 h and 24 h after ischemia.Diffuse reflectance spectroscopy ratio (R630/R545) showed statistical difference among all groups (P ＜ 0.05) with the exception between ischemic 12 hours and 24 hours groups.Conclusion Visible diffuse reflectance spectroscopy can timely monitor and discriminate the normal,ischemic and necrotic brain tissues and even the severity of brain ischemia and hence lay a research basis for intraoperative real-time monitoring of brain reperfusion. Key words: Infarction, middle cerebral artery;  Brain ischemia;  Rats;  Diffuse reflectance spectra