The new approach to intraoperative navigation during glial brain tumors removal is presented. A combined method is proposed for simultaneous spectroscopic and video fluorescence analysis of the state of tissues in the destruction zone using the applied part performed in the form of a neurosurgical aspirator cannula. In the walls of the applied part there are tubular channels into which lighting and receiving optical fibers are integrated. At the end of the cannula, the channels for optical fibers are arranged so as to perform spectroscopic analysis in contact with the surface of the biological tissue, as well as video fluorescence analysis at the working distance to the surface of the tissue. The joint use of fiber-optic systems for recording the video stream and spectral dependences allows real-time assessment of the degree of pathological tissue changes in the field of view of the video system, which are also located in the aspiration zone, with the simultaneous quantification of diagnostically significant spectroscopic criteria. System testing was carried out on samples of human intracranial tumors obtained during neurosurgical operations. During the removal of a tumor from different sites (tumor center, perifocal area), the degree of in vivo fluorescence signal from the tumor site was determined intraoperatively using a Zeiss Opmi Pentero intraoperative microscope in Blue 400 mode. From the selected area of the tumor, biopsy material was taken (presumably homogeneous in its properties) with subsequent measurement of spectra and combined images using the developed device. A high correlation was shown between the level of the fluorescence signal recorded spectroscopically and the brightness of the fluorescence image in the endoscopic channel of the device. The level of the fluorescent signal showed a high correlation with the degree of malignancy of tissues according to the results of pathomorphological examination.
The limited penetration of laser radiation into biological tissue prevents the widespread distribution of photodiagnostics (PD) and photodynamic therapy (PDT) methods to clinical practice. We have investigated several approaches for PD and PDT of deep-seated tumors: 1. Stereotactic biopsy cannula with a laser spectroscopic control. Special fiber ports for long-term installation in the tumor removal area were developed in order to cause tumor cells to migrate not into the depth of brain but along the fibers with occasional laser irradiation for PD and PDT. The fibers are coated with a special compound containing photosensitizer (PS) and nutrients for cancer cells. 2. Neurosurgical aspirator with the function of video-fluorescence and spectroscopic analysis system. More than 500 patients with various types of brain tumors were operated on using fluorescent navigation based on 5-aminolevulinic acid (5-ALA) induced protoporphyrin IX (Pp IX) fluorescence under laser excitation in red spectral range. 3. Diagnostics and navigation of tumors when fluorescence is excited in the red and near infrared ranges. We used indocyanine green (ICG) as near infrared dye to observe blood and lymph vasculature of laboratory animals. This method could be useful while examining tumor bed and adjacent area. 4. Joint action of radiopharmaceuticals and PS based on Cherenkov radiation. Cell death by PDT mechanism via Pp IX excitation by Cherenkov radiation in mitochondria during 18F-fludeoxyglucose decay. This idea achieved good results on rats with C6 glioma. The results of using this approach with chlorin e6 PS in comparable doses are negative. 5. Action through photodynamic inactivation of tumor-associated macrophages and microglia. Idea of minimally invasive method for determining macrophage (microglia) phenotype and their polarization in tumors and their immediate vicinity in situ. This would allow evaluating the effectiveness of the treatment, including PDT. The most promising results were obtained with Pp IX and aluminum phthalocyanine nanoparticles. Studies have been conducted on experimental animals with grafted tumors and, in part, on cancer patients in the clinic.
The complexity of the biological tissue spectroscopic analysis due to the overlap of biological molecules’ absorption spectra, multiple scattering effect, as well as measurement geometry in vivo has caused the relevance of this work. In the neurooncology the problem of tumor boundaries delineation is especially acute and requires the development of new methods of intraoperative diagnosis. Methods of optical spectroscopy allow detecting various diagnostically significant parameters non-invasively. 5-ALA induced protoporphyrin IX is frequently used as fluorescent tumor marker in neurooncology. At the same time analysis of the concentration and the oxygenation level of haemoglobin and significant changes of light scattering in tumor tissues have a high diagnostic value. This paper presents an original method for the simultaneous registration of backward diffuse reflectance and fluorescence spectra, which allows defining all the parameters listed above simultaneously. The clinical studies involving 47 patients with intracranial glial tumors of II-IV Grades were carried out in N.N. Burdenko National Medical Research Center of Neurosurgery. To register the spectral dependences the spectroscopic system LESA- 01-BIOSPEC was used with specially developed w-shaped diagnostic fiber optic probe. The original algorithm of combined spectroscopic signal processing was developed. We have created a software and hardware, which allowed (as compared with the methods currently used in neurosurgical practice) to increase the sensitivity of intraoperative demarcation of intracranial tumors from 78% to 96%, specificity of 60% to 82%. The result of analysis of different techniques of automatic classification shows that in our case the most appropriate is the k Nearest Neighbors algorithm with cubic metrics.
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