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.
We applied reflection-mode terahertz (THz) pulsed spectroscopy to study ex vivo the optical properties of human brain tumors with the different World Health Organization grades, as well as of perifocal regions comprised of intact (healthy) and edematous tissues. We applied gelatin-embedding in order to fix freshly-excised tissues, thus, preserving them from hydration/dehydration and sustaining their THz response unaltered for a couple of hours after resection. We observed a contrast between the THz optical properties of intact tissues and tumors, including gliomas and meningiomas of the brain, in turn, the response of edematous tissues is close to that of a tumor. The observed contrast between intact tissues and tumors has an endogenous character and originates reportedly from increased water content in a tumor due to edema, abnormal vascularity and, in some cases, necrotic debris. The observed results justify a prospect of THz technology in the intraoperative label-free diagnosis of human brain tumors.
Intraoperative diagnosis of brain tumors remains a challenging problem of modern neurosurgery. A complete resection of tumor is the most important factor, determining an efficiency of its treatment, while an incomplete resection, caused by inaccurate detection of tumor margins, increases a probability of the tumor recurrence. The existing methods of the intraoperative neurodiagnosis of tumors are plagued with limited sensitivity and specificity; they remain laborious, time-consuming and/or rather expensive. Therefore, the development of novel methods for the intraoperative diagnosis of gliomas relying on modern instruments of medical imaging is a topical problem of medicine, physics, and engineering. In our research, we studied the ability of dual-modality imaging that combines such methods as optical coherence tomography (OCT) and terahertz (THz) pulsed spectroscopy, for intraoperative diagnosis of brain tumors with a strong emphasize on a human brain gliomas. We performed experimental studies of the frequency-dependent THz dielectric properties and OCT imaging of healthy (intact) and pathological brain tissues ex vivo in order to analyze the prospect for differentiation between tissue classes. The observed results highlight a potential of the considered instruments in the label-free intraoperative neurodiagnostics.
We applied terahertz (THz)-pulsed spectroscopy to study ex vivo the refractive index and absorption coefficient of human brain gliomas featuring different grades, as well as perifocal regions containing both intact and edematous tissues. Glioma samples from 26 patients were considered and analyzed according to further histological examination. In order to fix tissues for the THz measurements, we applied gelatin embedding, which allows for sustaining their THz response unaltered, as compared to that of the freshly excised tissues. We observed a statistical difference between the THz optical constants of intact tissues and gliomas of grades I to IV, while the response of edema was similar to that of tumor. The results of this paper justify a potential of THz technology in the intraoperative label-free diagnosis of human brain gliomas for ensuring the gross-total resection.
A 5-ALA-induced fluorescence-based imaging device for guidance during surgery of malignant and non-malignant preliminary photosensitized tumors is presented. The setup fits existing clinical optical rigid and flexible endoscopes and operation microscopes. It consists of three light sources including white light, red light fluorescence excitation and blue light fluorescence excitation sources. The light from any combination of the latter sources is delivered to tissue using specially designed fiber optic light guide. Two cameras are used to acquire fluorescence and back reflected white light images: a gray-level camera for fluorescence in the far red range and a color camera for white light images. A dichroic mirror is implemented to spectrally split the light coming from tissue. Images from both cameras are processed into a computer with specially developed software where it can be displayed in different modes including overlaying or been used for image mosaicing which allows for increasing the intrinsic reduced field of view of endoscopes by providing highly resolved extended cartography. Experiments were carried out on phantoms and on patients in clinical conditions during surgery of brain and other tissues. Blue light excitation was more sensitive for thin tumors but red light excitation was more beneficial for solid tumors and for navigation in presence of slight bleeding.
We have performed the in vitro terahertz (THz) spectroscopy of human brain tumors. In order to fix tissues for the THz measurements, we have applied the gelatin embedding. It allows for preserving tissues from hydration/dehydration and sustaining their THz response similar to that of the freshly-excised tissues for a long time after resection. We have assembled an experimental setup for the reflection-mode measurements of human brain tissues based on the THz pulsed spectrometer. We have used this setup to study in vitro the refractive index and the amplitude absorption coefficient of 2 samples of malignant glioma (grade IV), 1 sample of meningioma (grade I), and samples of intact tissues. We have observed significant differences between the THz responses of normal and pathological tissues of the brain. The results of this paper highlight the potential of the THz technology in the intraoperative neurodiagnosis of tumors relying on the endogenous labels of tumorous tissues.
We have proposed a wavelet-domain de-noising technique for imaging of human brain malignant glioma by optical coherence tomography (OCT). It implies OCT image decomposition using the direct fast wavelet transform, thresholding of the obtained wavelet spectrum and further inverse fast wavelet transform for image reconstruction. By selecting both wavelet basis and thresholding procedure, we have found an optimal wavelet filter, which application improves differentiation of the considered brain tissue classes – i.e. malignant glioma and normal/intact tissue. Namely, it allows reducing the scattering noise in the OCT images and retaining signal decrement for each tissue class. Therefore, the observed results reveals the wavelet-domain de-noising as a prospective tool for improved characterization of biological tissue using the OCT.
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.
We present the nanoparticle-enabled experimentally trained wavelet-domain denoising method for optical coherence tomography (OCT). It employs an experimental training algorithm based on imaging of a test-object, made of the colloidal suspension of the monodisperse nanoparticles and contains the microscale inclusions. The geometry and the scattering properties of the test-object are known a priori allowing us to set the criteria for the training algorithm. Using a wide set of the wavelet kernels and the wavelet-domain filtration approaches, the appropriate filter is constructed based on the test-object imaging. We apply the proposed approach and chose an efficient wavelet denoising procedure by considering the combinations of the decomposition basis from five wavelet families with eight types of the filtration threshold. We demonstrate applicability of the wavelet-filtering for the in vitro OCT image of human brain meningioma. The observed results prove high efficiency of the proposed OCT image denoising technique.
The method of intraoperative analysis of tumor markers such as structural changes, concentrations of 5- ALA induced protoporphyrin IX and hemoglobin in the area of tissue resection was developed. A device for performing this method is a neurosurgical aspiration cannulae coupled with the fiber optic probe. The configuration of fibers at the end of cannulae was developed according to the results of numerical modeling of light distribution in biological tissues. The optimal distance between the illuminating and receiving fiber was found for biologically relevant interval of optical properties. On this particular distance the detected diffuse reflectance depends on scattering coefficient almost linearly. Array of optical phantoms containing hemoglobin, protoporphyrin IX and fat emulsion (as scattering media) in various concentrations was prepared to verify the method. The recovery of hemoglobin and protoporphyrin IX concentrations in the scattering media with an error less than 10% has been demonstrated. The fat emulsion concentration estimation accuracy was less than 12%. The first clinical test was carried out during glioblastoma multiforme resection in Burdenko Neurosurgery Institute and confirmed that sensitivity of this method is enough to detect investigated tumor markers in vivo. This method will allow intraoperative analysis of the structural and metabolical tumor markers directly in the zone of destruction of tumor tissue, thereby increasing the degree of radical removal and preservation of healthy tissue.
Brain glial tumors have peculiar features of the perifocal region extension, characterized by its indistinct area, which
complicates determination of the borders for tissue resection. In the present study filter-reduced back-scattered laser light
signals, compared to the data from mathematical modeling, were used for description of the brain white matter. The
simulations of the scattered light distributions were performed in a Monte Carlo program using scattering and absorption
parameters of the different grades of the brain glial tumors. The parameters were obtained by the Mie calculations for
three main types of scatterers: myelinated axon fibers, cell nuclei and mitochondria. It was revealed that diffuse-reflected
light, measured at the perifocal areas of the glial brain tumors, shows a significant difference relative to the signal,
measured at the normal tissue, which signifies the possibility to provide diagnostically useful information on the tissue
state, and to determine the borders of the tumor, thus to reduce the recurrence appearance. Differences in the values of
ratios of diffuse reflectance from active growth parts of tumors and normal white matter can be useful for determination
of the degree of tumor progress during the spectroscopic analysis.
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