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.
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.
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