Laser-induced fluorescent visualization and photodynamic therapy in surgical treatment of glial brain tumors

High-grade gliomas have a diffuse and infiltrative nature of the growth of tumor cells, due to which the achievement of radical resection is difficult. Surgical resection completeness of brain tumors is an important factor in prolonging the life of patients. An accurate definition of tumor boundaries and residual fluorescent regions is impossible due to imperfections of the equipment used for fluorescent imaging. 5-aminolevulinic acid (5-ALA) is a precursor of protoporphyrin IX (PpIX) in humans and is clinically used to detect and treat tumors. Currently, fluorescence-guided surgery with PpIX used a surgical microscope with an excitation wavelength in the blue spectrum range. Because of its low ability to penetrate into biological tissue, blue light is ineffective for providing high-quality fluorescent navigation. Also, when performing an operation using radiation in the blue spectrum range, the photosensitizer's surface layer (PS) often bleaches out, which leads to frequent errors. The use of red light emission makes it possible to slow down the PS bleaches out due to the absorption properties of PpIX, but this task is technically more complicated and requires highly sensitive cameras and specialized optical filters. The new two-channel video system for fluorescent navigation has a radiation source in the red range of the spectrum, the penetration depth of which is greater than the blue light, which makes it possible to increase the depth of probing into biological tissues. The study's clinical part involved 5 patients with high grade glioma and 1 patient with low grade glioma: grade III oligodendrogliomas (2), grade IV glioblastomas (3), and grade II diffusion astrocytoma (1). (c) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

High-grade gliomas are difficult to completely resect due to their diffuse nature, and current fluorescent imaging equipment has limitations. 5-aminolevulinic acid is used clinically for tumor detection and treatment, but the technical challenges of using red light for fluorescence-guided surgery are significant.