Stimulated Raman Histology and 5-ALA Fluorescence

In the treatment of diffuse infiltrating gliomas (DIG) maximal safe surgical removal is crucial for patient prognosis. Nevertheless, based on infiltrative growth and insufficient visualization of the tumor border, residual tumor tissue is common. A new laser technique, named Stimulated Raman Histology (SRH) was recently developed to provide digital, high-resolution images of unprocessed tissue samples directly in the operating room. Furthermore, SRH images are comparable to conventional histopathological images. Additionally, in the last decades fluorescence-guided surgery with 5-aminolevulinic acid (5-ALA) was used to increase the rate of complete tumor removal. Recently, based on the combination of both techniques, 5-ALA and SRH, we were able to label for the first-time glioma cells on a microscopical level. So far, the combination of 5-ALA and SRH has not been studied in a large patients series of suspected DIG. Based on our preliminary data the following aims are declared: (1) The use of the combination of SRH and 5-ALA will be studied for feasibility during surgery in a large group of suspected DIG. (2) Visible as well as non-visible fluorescence in tumor tissue can be detected by SRH. (3) Different histopathological characteristics are detected comparing fluorescing and non-fluorescing tumor tissue based on visible fluorescence and SRH. (4) The distribution of fluorescence inside and outside of glioma cells will be studies based on SRH images. This study will be performed at the Dept. of Neurosurgery, NYU, were the use of SRH and 5-ALA is frequently used. In this study, patients diagnosed with suspected DIG and scheduled for fluorescence- guided tumor removal will be included. A modified microscope will be used to detect visible fluorescence during tumor removal. Next, routinely collected tissue samples from fluorescing and/or non-fluorescing tumor regions and tumor margins will be analyzed immediately in the operating room using SRH. All collected samples will be examined by neuropathology in order to compare histopathological characteristics with fluorescence patterns based on visible fluorescence and SRH images. For the first-time, the combination of both techniques, 5-ALA and SRH, will be analyzed in a large group of suspected DIG. In this study we intend to overcome the limitations of conventional fluorescence technology by using SRH directly in the operating room to visualize fluorescing glioma cells on a microscopical level. In this sense, by analyzing fluorescence behavior inside and outside of glioma cells, we expect to expand our understanding of 5-ALA in these tumors.