The motivation for the present study was the need to develop methods of urgent intraoperative biopsy during surgery for removal of intracranial tumors. Based on the experience of previous joint work of GPI RAS and N.N. Burdenko National Medical Research Center of Neurosurgery to introduce fluorescence spectroscopy methods into clinical practice, an approach combining  various optical-spectral techniques, such as autofluorescence spectroscopy, fluorescence of 5-ALA induced protoporphyrin IX, diffuse reflection of broadband light, which can be used to determine hemoglobin concentration in tissues and their optical density, Raman spectroscopy, which is a spectroscopic method that allows detection of various molecules in tissues by vibrations of individual characteristic molecular bonds. Such a variety of optical and spectral characteristics makes it difficult for the surgeon to analyze them directly during surgery, as it is usually realized in the case of fluorescence methods – tumor tissue can be distinguished from normal with a certain degree of certainty by fluorescence intensity exceeding  a threshold value. In case the number of parameters exceeds a couple of dozens, it is necessary to use machine learning algorithms  to build a intraoperative decision support system for the surgeon. This paper presents research in this direction. Our earlier statistical analysis of the optical-spectral features allowed identifying  statistically significant spectral ranges for analysis of diagnostically  important tissue components. Studies of dimensionality reduction techniques of the optical-spectral feature vector and methods of clustering of the studied samples also allowed us to approach the implementation  of the automatic classification method. Importantly, the classification task can be used in two applications  – to differentiate between different tumors and to differentiate between different parts of the same (center, perifocal zone, normal) tumor. This paper presents the results of our research in the first direction. We investigated the combination of several methods and showed the possibility of differentiating glial and meningeal tumors based on the proposed optical-spectral analysis method.

Colposcopy allows the examiner to localize potential lesions, assess the severity of the lesion, and obtain a colposcopic guided biopsy. This method has limited sensitivity and specificity, raising serious concerns about the possibility of missing cervical dysplasia. Fluorescent methods for diagnosing precancerous diseases of the cervix and early forms of cancer have an extremely high sensitivity, reaching 90%. The presented results of the study allow us to fully declare the high information content of fluorescent colposcopy in identifying dysplastic lesions on the cervix.

The purpose of the work is to follow the dynamics of changes in fluorescent signals in the near-surface layers of tissue of injured areas of the back of laboratory animals, which will allow, by indirect evidence, to evaluate the information content of fluorescence diagnosis for subsequent possible diagnostic monitoring of photodynamic therapy of the spinal cord. The model animals were Wistar rats. Two types of contusions were modeled: pneumo-contusion and contusion by a falling load. Methylene blue and indocyanine green were used as photosensitizers. Fluorescence measurements were carried out by imaging and spectrometric methods. A stroboscopic fluorescence imager with an excitation wavelength of 630 nm was used to acquire fluorescence images. The LESA-01-BIOSPEC  spectrometer with a He-Ne laser excitation allowed to obtain spectra. It was shown that both methods make it possible to estimate the fluorescence value of methylene blue and indocyanine green in the tissues under study. Moreover, the photographic method also allows to obtain the spatial distribution of fluorescence. The general trend found in the data is a more intense and uniform fluorescence of the dorsal region of rats with methylene blue and a less intense, but more contrasting distribution of indocyanine green. The presented methods are non-invasive, which makes them attractive for diagnostic use. However, due to the shallow depth of signal reception, the condition of the spine can be determined only indirectly, by the condition of the near-surface layers of tissue that accumulate the photosensitizer.

A significant  therapeutic effect of photodynamic  therapy (PDT) is shown in a patient with extensive vulvar cancer after ineffective surgical and chemoradiotherapy. During the year, three courses of local PDT with a photosensitizer based on chlorin e6 were carried out. The photosensitizer was administered intravenously three hours before irradiation at a dose of 1.2 mg/kg. For laser irradiation (662 nm) of the vulvar tumor, a light guide for external irradiation was used: the power density was 0.2 W/cm², the light dose was from 100 to 250 J/cm². As a result of treatment, tumor regression and stable remission are observed. The patient remains under observation.

Literature review reflects the current status and development status of intraoperative photodynamic therapy in neurooncology and discusses the results of the most important studies on photodynamic  therapy (PDT). We searched the Pubmed, EMBASE, Cochrane Library and eLibrary data-bases for publications  published  between January 2000 and December 2022. Found 204 publications  in foreign sources and 59 publications  in domestic editions, dealing with the issues of photodynamic  therapy in neurooncology. An analysis of the literature has shown that intraoperative PDT in neurooncology is an important tool that contributes to increasing the radicality of the operation and local control. The basic rationale for the effectiveness of PDT lies in the study of the pathways leading to the complete devitalization of a malignant tumor, the study of the mechanisms of the local and systemic immune response. In addition, subcellular targets in PDT are determined by the properties of photosensitizers (PS). Second generation PSs have already been introduced into clinical practice. The effectiveness of PDT using photoditazine, 5-aminolevulinic acid has been demonstrated. The mechanisms of action and targets of these PS have been established. In Russia, a number of studies have repeatedly shown and proved the clinical effectiveness of PDT in groups of neurooncological patients with glial tumors and secondary metastatic tumors, but so far, the method has not been included in the clinical guidelines for the provision of high-tech neurosurgical care. There is certainly a need for further development of PTD techniques in neurooncology, especially in patients at high risk of recurrence and aggressive CNS tumors.