Photodynamic diagnosis using 5-aminolevulinic acid (5-ALA) is now widely used for neurosurgical resection of brain tumors.

Distinguishing a tumor from healthy tissue is based on greater 5-ALA-derived protoporphyrin IX accumulation in glioma cells than in non-cancerous cells, resulting in much greater red fluorescence (peak at 635 nm) when excited at 405 nm.

However, it is still difficult to precisely distinguish the tumor margin and infiltrating regions from non-tumor tissue because the fluorescent boundary is usually vague.

In our previous study, we noticed that bright spots in confocal microscopy images may be able to distinguish tumors from normal tissue.

Brain tumor tissues resected from 5-ALA-treated patients was sectioned to evaluate bright spots captured by a 544.5-619.5 nm wavelength band-pass filter that eliminated the fluorescence induced by 5-ALA under a confocal microscope.

Boarder regions and adjacent normal tissues were observed.

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