Optical coherence tomography (OCT) has been recently suggested as a promising method to obtain in vivo and real-time high-resolution images of tissue structure in brain tumor surgery. This review focuses on the basics of OCT imaging, types of OCT images and currently suggested OCT scanner devices and the results of their application in neurosurgery. OCT can assist in achieving intraoperative precision identification of tumor infiltration within surrounding brain parenchyma by using qualitative or quantitative OCT image analysis of scanned tissue. OCT is able to identify tumorous tissue and blood vessels detection during stereotactic biopsy procedures. The combination of OCT with traditional imaging such as MRI, ultrasound and 5-ALA fluorescence has the potential to increase the safety and accuracy of the resection. OCT can improve the extent of resection by offering the direct visualization of tumor with cellular resolution when using microscopic OCT contact probes. The theranostic implementation of OCT as a part of intelligent optical diagnosis and automated lesion localization and ablation could achieve high precision, automation and intelligence in brain tumor surgery. We present this review for the increase of knowledge and formation of critical opinion in the field of OCT implementation in brain tumor surgery.

The possibility to assess molecular-biological and morphological features of particular breast cancer types can improve the precision of resection margin detection and enable accurate determining of the tumor aggressiveness, which is important for treatment selection. To enable reliable differentiation of breast-cancer subtypes and evaluation of resection margin, without performing conventional histological procedures, here we apply cross-polarization optical coherence tomography (CP-OCT) and compare it with a novel variant of compressional optical coherence elastography (C-OCE) in terms of the diagnostic accuracy (Ac) with histological verification. The study used 70 excised breast cancer specimens with different morphological structure and molecular status (Luminal A, Luminal B, Her2/Neo+, non-luminal and triple-negative cancer). Our first aim was to formulate convenient criteria of visual assessment of CP-OCT and C-OCE images intended (i) to differentiate tumorous and non-tumorous tissues and (ii) to enable more precise differentiation among different malignant states. We identified such criteria based on the presence of heterogeneities and characteristics of signal attenuation in CP-OCT images, as well as the presence of inclusions/mosaic structures combined with visually feasible assessment of several stiffness grades in C-OCE images. Secondly, we performed a blinded reader study of the Ac of C-OCE versus CP-OCT, for delineation of tumorous versus non-tumorous tissues followed by identification of breast cancer subtypes. For tumor detection, C-OCE showed higher specificity than CP-OCT (97.5% versus 93.3%) and higher Ac (96.0 versus 92.4%). For the first time, the Ac of C-OCE and CP-OCT were evaluated for differentiation between non-invasive and invasive breast cancer (90.4% and 82.5%, respectively). Furthermore, for invasive cancers, the difference between invasive but low-aggressive and highly-aggressive subtypes can be detected. For differentiation between non-tumorous tissue and low-aggressive breast-cancer subtypes, Ac was 95.7% for C-OCE and 88.1% for CP-OCT. For differentiation between non-tumorous tissue and highly-aggressive breast cancers, Ac was found to be 98.3% for C-OCE and 97.2% for CP-OCT. In all cases C-OCE showed better diagnostic parameters independently of the tumor type. These findings confirm the high potential of OCT-based examinations for rapid and accurate diagnostics during breast conservation surgery.

New modalities of optical coherence tomography (OCT) are based not only on the analysis of light beam scattering by biological tissues, but also, to a greater extent, on the assessment of spatio-temporal changes in the speckle structure (both the amplitude and the speckle phase). The aim of the study was to develop a method for eliminating parasitic vibrations in the scanning system, which interfere with the new OCT modalities such as angiography, relaxography, and slow process monitoring. Materials and Methods. The task of stabilizing the beam scan trajectory was successfully solved by actively filtering the controlling voltage. Results. The effect of the proposed approach application is demonstrated both on a phantom sample and examples of implementation of several modalities applied to real tissues, including: exudate visualization in vivo; OCT-angiography for visualization of microcirculation of the brain; OCT-relaxography on the example of mapping the time of mechanical relaxation of cartilage tissue; increasing the lateral resolution of OCT by compensating for defocusing. Conclusion. Vibrations of the scanning system cause artifact speckle variations that mask the informative variations of the speckles due to the relative change of the position of the scatterers inside the biological tissue caused by Brownian motion, flow, and deformation. Without proper stabilization of the scanning pattern, it is impossible to implement these modalities with quality suitable for practical use.

Optical coherence tomography (OCT) is a promising tool for intraoperative tissue morphology determination. Several studies suggest that attenuation coefficient derived from the OCT images, can differentiate between tissues of different morphology, such as normal and pathological structures of the brain, skin and other tissues. In the present study, the depth‐resolved method for attenuation coefficient calculation was adopted for the real‐world situation of the depth‐dependent OCT sensitivity and additive imaging noise with non‐zero mean. It was shown that in the case of sharp focusing (~10 μm spot full width at half maximum (FWHM) or smaller at 1.3 μm central wavelength) only the proposed method for depth‐dependent sensitivity compensation does not introduce misleading artifacts into the calculated attenuation coefficient distribution. At the same time, the scanning beam focus spot with FWHM greater than 10 μm at 1.3 μm central wavelength allows one to use multiple approaches to the attenuation coefficient calculation without introducing noticeable bias. This feature may hinder the need for robust corrections for the depth‐resolved attenuation coefficient estimations from the community.This article is protected by copyright. All rights reserved.

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