During surgery to remove a brain tumor it is important to discriminate normal tissue from cancerous tissue. Here we report a method to identify tumor tissue using a confocal microscope with laser illumination. The confocal microscope has several useful qualities for this work:it has high resolution and can also reject light that is not from the focal plane. The microscope was set up with an illumination laser of wavelength 405nm and a red fluorescence filter at wavelength 610-680nm in front of the CCD camera. This arrangement attenuated the direct light of the laser to increase the contrast in the fluorescence image. The field of view of the microscope was about 100μm square with a×40 objective. Before surgery, the patient drank a solution containing 5-ALA which induces formation of fluorescent porphyrins in tumors of type glioblastoma. Tissue samples taken during surgery were put onto the microscope stage. CCD images were obtained and it was found that tumor tissue emitted more red light and could be visually distinguished from normal tissue in the images. To quantify the difference, the intensity of all red pixels was added to form a total intensity in several images. The CCD red response to tumor tissue was found to be more than 2 times the response to normal tissue. We conclude that the confocal microscope method can distinguish tumor tissue at distance scale 100μm.
