The current study is aimed at investigating the influence of radiotherapy on the optical properties of white matter in patients with brain gliomas using cross-polarization OCT. It was performed on ex vivo samples of peritumoral white matter collected from patients with primary surgery and patients who underwent a course of radiotherapy before surgery. The enhancement of scattering properties in case of use of radiotherapy was detected and the optical coefficients that most accurately reflect the relationship between the optical and morphological properties of white matter in both groups of patients were determined.
KEYWORDS: Optical coherence tomography, States of matter, Optical fibers, Data analysis, Brain, Tumors, Statistical analysis, Data processing, Tissue optics, Signal attenuation
Log-and-linear fit and depth-resolved approaches for OCT data processing were applied for white matter state evaluation. Both approaches are suitable for this purpose, however, the choice of necessary method depends on features of used OCT device.
The aim of this study was to evaluate the application of attenuation coefficients calculated from the cross-polarization optical coherence tomography (CP OCT) data for differentiation of breast cancer from non-tumorous breast tissues. For this purpose, surgically obtained breast specimens from 45 patients were examined using CP OCT in order to construct color-coded en-face OCT maps based on calculation of three optical coefficients (the commonly used rate of attenuation in the co- polarization channel; and, additionally, the attenuation in the cross- polarization channel; and the interchannel attenuation difference). It was shown that the use of these optical coefficients significantly increased the amount of obtained information from the OCT data in comparison with unprocessed images, enabling objective quantification for differentiating non-tumorous and tumorous tissue (adipose tissue, normal stroma, tumor stroma and agglomerates of tumor cells). The attenuation in the cross- polarization channel and the interchannel attenuation difference provided greater contrast for the visualization of the different breast cancer structures compared to the attenuation coefficient in the co- polarization channel. The findings of this study suggest that assessment of CP OCT images of breast cancer based on optical coefficients calculation may in perspective enable real-time feedback about accurate resection margin in patient with breast cancer to the surgeon.
The aim of our work was to investigate energy metabolism of patient’s tumor ex vivo using fluorescence lifetime imaging (FLIM). Tumor metabolism was examined by detecting the fluorescence lifetime of metabolic cofactor NAD(P)H. In glioma tumor samples was shown a different energy metabolism with white matter. Colorectal tumors displayed marked intertumor heterogeneity and shift towards oxidative energy metabolism. Thereby, the possibility of assessing the energy metabolism in postoperative tumor samples of patients was shown.
Cross-polarization (CP) OCT is a so-called functional extension of OCT that seems to have benefits in visualization of myelin. During surgery it may be quite useful receiving information concerning myelination rate in white matter surrounding tumor mass. It this study it was shown that the quantification of peritumoral white matter using pseudocolor en-face OCT maps based on three optical coefficients (the rate of attenuation in the co- and cross-channel, and the interchannel attenuation difference) correlated well with histological data. Therefore, accurate quantitative CP OCT assessment of peritumoral white matter condition supports the developing the intraoperative implementation of this method.
Optical coherence tomography (OCT) is a promising method for clarifying the boundaries of the infiltrative brain tumors within surrounding white matter. Since gliomas often tend to grow close to eloquent brain areas, the question of the proximity of the tumor to white matter tracts sharply arise during tumor resection to prevent their damage. Crosspolarization (CP) OCT is a so-called functional extension of OCT that seems to have benefits in visualization of myelin. It looks perspective not just to detect white matter, but also receive information about its condition – the myelination rate and presence of ordered fibers. The aim of this study was to visualize white matter organization of eloquent brain areas with CP OCT using post-processing methods. The ex vivo CP OCT images were collected from autopsy subjects of the human brain. The brain specimens contained white matter of different organization and localization: brainstem, corpus callosum, frontal and parietal tracts, subcortical white matter. Two optical coefficients (attenuation and inter-channel attenuation difference) were calculated for each A-scan and two types of color-coded maps based on them were built. No significant differences based on CP OCT attenuation and inter-channel attenuation difference coefficients were demonstrated between white matter from different brain areas. However, in vivo studies can show conversely results. The detection of white matter microstructure during surgery looks promising therefore additional CP OCT performance build-up can be considered.
An introduction of innovative minimally invasive methods like multimodal optical coherence tomography (OCT) with polarization-sensitivity and angiography modes for intrasurgical guidance appears to be a critical challenge for the modern neurooncology. This study aimed to develop a new instrument for targeted stereotactic brain biopsy based on cross-polarization (CP) OCT realized in standard biopsy needle to increase the safety of ongoing neurosurgical procedures. Experimental studies in vivo on the healthy rat’s brain allow detecting blood vessels in the process of moving the biopsy needle along the brain surface and detect tissue type (cerebral cortex or white matter) when the needle went inside the brain. The images was assessed by visual criteria. However, CP OCT signal quantification methods will increase the sensitivity/specificity for the tissue type differentiation and blood vessels detection. The potential of CP OCT as an effective instrument for OCT-guided stereotactic biopsy of brain tumors was demonstrated.
The methods used for digital processing of optical coherence tomography (OCT) and crosspolarization (CP) OCT images are focused on improving the contrast ratio of native structural OCT images. Such advances are particularly important for the intraoperative detection of glioma margins where the visual assessment of OCT images can be difficult and lead to errors. The aim of the study was to investigate the application of optical coefficients obtained from CP OCT data for the differentiation of glial tumorous tissue from a normal brain. Pseudocolor en-face OCT maps based on two optical coefficients (the commonly used rate of attenuation in the cochannel, and in addition, the interchannel attenuation difference) were constructed for normal rat brain coronal cross sections and for brains with a 101.8 rat glioblastoma model. It was shown that the use of optical coefficients significantly increased the available information from the OCT data in comparison with unprocessed images. As a result, this allowed contrasting of the white matter from the gray matter and tumorous tissue ex vivo, and for this purpose, the interchannel attenuation difference worked better. The interchannel attenuation difference values of white matter were at least seven and two times higher than corresponding values of the cortex and tumorous tissue, whereas the same parameter for cochannel attenuation coefficient values of white matter are about 4 and 1.4. However, quantitative analysis shows that both coefficients are suitable for the purpose of glioblastoma detection from normal brain tissue regardless of whether a necrotic component was present (in all compared groups p < 0.001).
OCT is a perspective method for glial tumor margins detection during surgical operation. The challenging clinical problem of improving the functional outcomes of the surgeries on the central nervous system could be solved with the aid of cross-polarization (CP) OCT, which visualizes light backscattered from the sample in two orthogonal polarizations and gives sensitivity to the myelinated fibers. This study aimed to evaluate CP OCT feasibility to distinguish different types of brain tissue during glioma surgery to assess tumor margins and the proximity to the conductive pathways of the brain. Postoperative human specimens (tumorous tissue and peritumoral tissue, n = 40) for ex vivo СP OCT study were taken with considering the location of eloquent brain areas and tracts. Regions of sampling were also recorded at the neuronavigation station. It was shown, that the quantitative characteristics of the OCT signal of the tumor and peritumoral area have quite good correspondence with the tumor location according to the preoperative MRI, and better correlated with histological data. The same results were demonstrated for comparison of the OCT signal of the peritumoral areas and the normal white matter with the MRI-tractography and histological data. In conclusion, the CP OCT method has a high potential for intraoperative application to clarify the presence of infiltration areas and proximity to eloquent brain areas and tracts. The study was supported by RFBR projects No. 18-29-01049_mk and No. 16-32-60178 mol_а_dk.
Optical coherence tomography (OCT) is a promising method of glial tumors borders diagnostics. Nowadays it is possible to use hand-held and microscope mounted OCT devices during tumor removal. But still there are no clearly visual assessment criteria of OCT images, on the basis of which good differentiation between glioma tissue and white matter can be performed. This paper presents such criteria for crosspolarization OCT (CP OCT), which can detect both the scattering and polarization properties of tissues.
In the case of infiltrative brain tumors the surgeon faces difficulties in determining their boundaries to achieve total resection. The aim of the investigation was to evaluate the performance of multimodal OCT (MM OCT) for differential diagnostics of normal brain tissue and glioma using an experimental model of glioblastoma. The spectral domain OCT device that was used for the study provides simultaneously two modes: cross-polarization and microangiographic OCT. The comparative analysis of the both OCT modalities images from tumorous and normal brain tissue areas concurrently with histologic correlation shows certain difference between when accordingly to morphological and microvascular tissue features.
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