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Examples of color depth encoded en face microvascular images obtained for different filter thresholds F min , demonstrating the gradual appearance of finer vessels with different rates of speckle variability. Presumably, for the highest F min > 160 Hz , the contributions of faster flows are dominant (first arterioles and then venules), whereas for F min ∼ 40 – 60 Hz , the slower regions of flow and possibly the Brownian scatterer motion in finer microvessels ( ∼ capillaries) contribute to the angiographic image. The signal from the motionless background tissue begins to degrade the image quality at F min = 30 Hz . FOV = 2 mm × 2 mm for all panels. A video record showing significant bulk motions of the tissue while obtaining these images is given in Media 1. Another example of a vascular image (maximum intensity projection) superposed with the corresponding photographic image is given in Media 2.
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We propose a novel OCT-based method for visualizing microvasculature in three-dimension using reference-free processing of individual complex valued B-scans with highly overlapped A-scans. In the lateral direction of such a B-scan, the amplitude and phase of speckles corresponding to vessel regions exhibit faster variability and, thus, can be detec...
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We describe a modification of a recently proposed unconventional OCT approach to 3D microvasculature imaging based on high-pass filtering of B-scans in the lateral direction. The B-scans are acquired in M-mode-like regime with highly overlapped A-scans. The goal of the described modification is to suppress non-fluid artifacts in the resultant micro...
In this paper, we proposed a contrast-enhanced homemade spectral domain optical coherence tomography (SD-OCT) method for monitoring of brain microcirculation. We used the polyethylene glycol (PEG)-ylated gold nanorods (GNRs) as a contrast-enhanced agent, obtained clearly 2D and 3D OCT images of blood vessels and dynamic changes of probes in mouse b...
Citations
... The OCA makes it possible to visualize the perfused blood vessels with transverse spatial resolution of~15 µm and depth resolution of~10 µm from a depth of up to~1.5 mm. The studies were carried out on the spectral multimodal OCT system (BioMedTech, Nizhny Novgorod, Russia) with a central wavelength of 1310 nm, radiation power of 20 mW, the size of the resulting OCT image is 2.4 × 2.4 mm and the scanning speed is 20,000 A-scans/s [53]. OCA images were presented in the form of maximum signal intensity projection-en face image of the vascular network from the entire visualization depth. ...
This work was aimed at the complex analysis of the metabolic and oxygen statuses of tumors in vivo after photodynamic therapy (PDT). Studies were conducted on mouse tumor model using two types of photosensitizers—chlorin e6-based drug Photoditazine predominantly targeted to the vasculature and genetically encoded photosensitizer KillerRed targeted to the chromatin. Metabolism of tumor cells was assessed by the fluorescence lifetime of the metabolic redox-cofactor NAD(P)H, using fluorescence lifetime imaging. Oxygen content was assessed using phosphorescence lifetime macro-imaging with an oxygen-sensitive probe. For visualization of the perfused microvasculature, an optical coherence tomography-based angiography was used. It was found that PDT induces different alterations in cellular metabolism, depending on the degree of oxygen depletion. Moderate decrease in oxygen in the case of KillerRed was accompanied by an increase in the fraction of free NAD(P)H, an indicator of glycolytic switch, early after the treatment. Severe hypoxia after PDT with Photoditazine resulted from a vascular shutdown yielded in a persistent increase in protein-bound (mitochondrial) fraction of NAD(P)H. These findings improve our understanding of physiological mechanisms of PDT in cellular and vascular modes and can be useful to develop new approaches to monitoring its efficacy.
... DOI: 10.61011/OS.2024.01.57556. [14][15][16][17][18][19][20][21][22][23][24] Введение Заболеваемость злокачественными новообразованиями кожи ежегодно растет. Рост заболеваемости, вероятно, связан с воздействием ультрафиолетового излучения, увеличения активности на свежем воздухе, изменения стиля одежды, увеличения продолжительности жизни, истощения озонового слоя, генетики и т. д. ...
... Оптическая когерентная томография, основанная на низкокогерентной интерферометрии в ближнем ИК диапазоне длин волн (700−1300 nm), обеспечивает визуализацию кожи с высоким (близким к гистологическому) пространственным разрешением, составляющим несколько микрометров, и глубиной проникновения 1−3 mm. Метод обеспечивает структурную визуализацию биотканей, дает возможность визуализации микрокровотока без использования контрастных агентов, за счет чего востребован в ряде медицинских применений [14]. Однако метод не позволяет различать отдельные клетки [15][16][17]. ...
Конфокальная сканирующая микроспектроскопия комбинационного рассеяния света и флуоресценции
является структурно чувствительным оптическим методом, позволяющим проводить неинвазивный анализ
биомаркеров в тканях кожи. Отчетливые спектральные различия были замечены в спектрах комбинационного
рассеяния света базальноклеточной карциномы и плоскоклеточной карциномы по сравнению со здоровой
кожей и папилломой. Наш анализ спектров комбинационного рассеяния света и флуоресценции при длине
волны возбуждения 532 nm позволил предложить два спектральных критерия: отношения интенсивностей для
полос 2880 и 1445 cm−1
и полос 2930 и 1445 cm−1
. Это основано на различиях колебаний липидов клеточных
мембран, используемых в качестве биомаркеров. Эти критерии позволили дифференцировать здоровую
кожу от базальноклеточной карциномы, плоскоклеточной карциномы и папилломы с чувствительностью
и специфичностью более 90%, продемонстрировав высокую клиническую значимость в дифференциальной
диагностике новообразований кожи.
... In methods based on comparison of complexvalued OCT signals (i.e., the signals with amplitude and phase) the signal variability is dominated by axial motions rather than lateral ones (similarly to the domination of axial Doppler effect over the transversal Doppler effect). Axial motions with essentially subwavelength amplitudes mostly affect the signal phase and can be efficiently compensated using estimation of depth-averaged phases of compared in-depth A-scans [23]. However, motions with significantly stronger (supra-wavelength) axial displacements cause significant phase variations of the order of several periods and, moreover, are accompanied by appreciable variations in the signal amplitude. ...
... Rather, the compensation procedure should take into account the spatial inhomogeneity of the displacements. Paper [20] demonstrated a variant of such compensation which was based on signal-phase correction (similarly to the translational case [23], but with additional accounting for depth-dependence). Compensation in such a form, nevertheless, retains to an appreciable degree the deformation-induced masking decorrelation of the scans in areas of "solid" tissue, especially in regions of supra pixel displacements, when the signal phase and amplitude both contribute to the scan decorrelation. ...
... The first option is to physically immobilize the examined tissue, e.g., using a dorsal chamber with a transparent window which is often used in experiments with animals [21,23]. Such immobilization helps to deal with large-amplitude translational tissue motions relatively to the OCT probe. ...
... The spatial resolution of traditional contrast-based computed tomography [7] and magnetic resonance imaging [8] methods are inadequate for visualizing the capillary network in vivo . Alternatively, various intravital optical microscopy approaches [9][10][11] can be used for high-resolution angiography with the caveat of having poor penetration depth and small field of view, which limits most studies to superficial observations on a submillimeter scale. Doppler ultrasound imaging has an appropriate penetration depth but suffers from insufficient contrast and spatial resolution [12] , making it incapable of clearly discerning small vessels having a slow blood flow [13] . ...
Tumor microvascular responses may provide a sensitive readout indicative of radiation therapy efficacy, its time course and dose dependencies. However, direct high-resolution observation and longitudinal monitoring of large-scale microvascular remodeling in deep tissues remained challenging with the conventional microscopy approaches.
We report on a non-invasive longitudinal study of morphological and functional neovascular responses by means of scanning optoacoustic (ОА) microangiography. In vivo imaging of CT26 tumor response to a single irradiation at varying dose (6, 12, and 18 Gy) has been performed over ten days following treatment. Tumor oxygenation levels were further estimated using diffuse optical spectroscopy (DOS) with a contact fiber probe.
OA revealed the formation of extended vascular structures on the whole tumor scale during its proliferation, whereas only short fragmented vascular regions were identified following irradiation. On the first day post treatment, a decrease in the density of small (capillary-sized) and medium-sized vessels was revealed, accompanied by an increase in their fragmentation. Larger vessels exhibited an increase in their density accompanied by a decline in the number of vascular segments. Short-lasting response has been observed after 6 and 12 Gy irradiations, whereas 18 Gy treatment resulted in prolonged responses, up to the tenth day after irradiation. DOS measurements further revealed a delayed increase of tumor oxygenation levels for 18 Gy irradiations, commencing on the sixth day post treatment. The ameliorated oxygenation is attributed to diminished oxygen consumption by inhibited tumor cells but not to the elevation of oxygen supply.
This work is the first to demonstrate the differential (size-dependent) nature of vascular responses to radiation treatments at varying doses in vivo. The OA approach thus facilitates the study of radiation-induced vascular changes in an unperturbed in vivo environment while enabling deep tissue high-resolution observations at the whole tumor scale.
... Proposed fixation scheme allows us to obtain a volumetric dataset that is completely free of motion-related artifacts and requires almost no post-processing procedures to correct them. For high precision measurements of small capillaries (<10 µm) described clamping approach could be empowered with a modern software motion estimation, correction and vessels enchantments algorithms [32][33][34] to further increase the SNR of the imaging setup. ...
Optical coherence tomography (OCT) has become widespread in clinical applications in which precise three-dimensional functional imaging of living organs is required. Nevertheless, the kidney is inaccessible for the high resolution OCT imaging due to a high light attenuation coefficient of skin and soft tissues that significantly limits the penetration depth of the probing laser beam. Here, we introduce a surgical protocol and fixation scheme that enables functional visualization of kidney’s peritubular capillaries via OCT microangiography. The model of reversible/irreversible glomerulus embolization using drug microcarriers confirms the ability of OCT to detect circulatory disorders. This approach can be used for choosing optimal carriers, their dosages and diagnosis of other blood flow pathologies.
... Realization of such scatterer-motion-based modalities requires application of advanced signalprocessing methods to extract signals related to J of Biomedical Photonics & Eng 7(1) 31 Mar 2021 © J-BPE 010304-2 informative motions of scatterers and, in contrast, to filter out various kinds of distortions related to masking motions. For example, in OCT-angiography it is necessary to separate bulk motions of the "solid" tissue (due to breathing, heart-beat pulses, etc.) from the detected motion of scattering particles in the blood flow, which is not a trivial issue in living tissues [17]. For real biological tissues, performing experimental studies in highly controllable and reproducible conditions often is rather difficult or even impossible. ...
... In the following section we demonstrate how the abovepresented model Eqs. (1) -(4) are applied for simulation of angiographic processing using the high-pass filtering principles suggested in Ref. [6,17] and correlation processing discussed in Ref. [45]. ...
... This idea can be realized in somewhat different forms. One variant is acquiring dense B-scans with significantly overlapped A-scans (say, the inter-A-scan step is ~50 times smaller than the illuminating-beam diameter) as proposed in Ref. [17]. Then 3D volumetric data can be composed from a series of such dense B-scans. ...
A computationally efficient and fairly realistic model of OCT-scan formation in spectral-domain optical coherence tomography is described. The model is based on the approximation of discrete scatterers and ballistic character of scattering, these approximations being widely used in literature. An important feature of the model is its ability to easily account for arbitrary scatterer motions and computationally efficiently generate large sequences of OCT scans for gradually varying configurations of scatterers. This makes the proposed simulation platform very convenient for studies related to the development of angiographic processing of OCT scans for visualization of microcirculation of blood, as well as for studies of decorrelation of speckle patterns in OCT scans due to random (Brownian type) motions of scatterers. Examples demonstrating utilization of the proposed model for generation OCT scans imitating perfused vessels in biological tissues, as well as evolution of speckles in OCT scans due to random translational and rotational motions of localized (but not-point-like) scatterers are given. To the best of our knowledge, such numerical simulations of large series of OCT scans in the presence of various types of motion of scatterers have not been demonstrated before.
... OCT-1300E device (IAP RAS, BioMedTech Ltd., Russia) operating at the central wavelength of 1300 nm and providing 3D OCT imaging with axial spatial resolution of 15 µm combined with OCT-angiography was employed to monitor structural and functional changes after the light exposure with or without PS. OCT-angiography concept implemented in the device is based on the analysis of decorrelation of OCT image speckle pattern induced by blood flow within the tissue vasculature [60,61]. The device is equipped with the contact probe which pressure to the tissue was controlled by a custom-designed holder to avoid effects of tissue compression on OCT images [62]. ...
... These vessels have typical wavy shape and relatively large density. Since OCT-A approach is based on the speckle correlation measurement [60], it maps only vessels with active blood flow, while disappearance of vessels in OCT-A images indicates interruption in microcirculatory activity and can serve as a positive prognostic factor of the tumor response to the treatment [49,50]. Figure 9 demonstrates that total disappearance of the vessels is observed only in PDT_r250-i group (bottom line), while for both control group and topical administration protocol PDT_r250-t the microcirculatory activity is preserved. ...
The goal of this study is a comparative analysis of the efficiency of the PDT protocols for CT26 tumor model treatment in Balb/c mice employing red and blue light with both topical and intravenous administration of chlorin-based photosensitizers (PSs). The considered protocols include the doses of 250 J/cm² delivered at 660 nm, 200 J/cm² delivered at 405 nm, and 250 J/cm² delivered at both wavelengths with equal energy density contribution. Dual-wavelength fluorescence imaging was employed to estimate both photobleaching efficiency, typical photobleaching rates and the procedure impact depth, while optical coherence tomography with angiography modality (OCT-A) was employed to monitor the tumor vasculature response for up to 7 days after the procedure with subsequent histology inspection. Red light or dual-wavelength PDT regimes with intravenous PS injection were demonstrated to provide the most pronounced tumor response among all the considered cases. On the contrary, blue light regimes were demonstrated to be most efficient among topical application and irradiation only regimes. Tumor size dynamics for different groups is in good agreement with the tumor response predictions based on OCT-A taken in 24h after exposure and the results of histology analysis performed in 7 days after the exposure.
... However, it seems that the only morphology analysis is not enough to differentiate between invasive and in situ stages of melanoma. OCA, an imaging modality on the basis of optical coherence tomography (OCT), provides the possibility of real-time visualization and quantification of the blood vessels network with an imaging depth of up to 1 mm in the skin and a resolution of 3-15 µm 20 . OCA employs the analysis of the speckle variation frequency of the full complex OCT signal (amplitude and phase) of a series of pixelated OCT images taken of a same area of tissue 21,22 . ...
There is a wide range of equivocal melanocytic lesions that can be clinically and dermoscopically indistinguishable from early melanoma. In the present work, we assessed the possibilities of combined using of multiphoton microscopy (MPM) and optical coherence angiography (OCA) for differential diagnosis of the equivocal melanocytic lesions. Clinical and dermoscopic examinations of 60 melanocytic lesions revealed 10 benign lesions and 32 melanomas, while 18 lesions remained difficult to diagnose. Histopathological analysis of these lesions revealed 4 intradermal, 3 compound and 3 junctional nevi in the “benign” group, 7 superficial spreading, 14 lentigo maligna and 11 nodular melanomas in the “melanoma” group and 2 lentigo simplex, 4 dysplastic nevi, 6 melanomas in situ, 4 invasive lentigo melanomas and 2 invasive superficial spreading melanomas in the “equivocal” group. On the basis of MPM, a multiphoton microscopy score (MPMS) has been developed for quantitative assessment of melanoma features at the cellular level, that showed lower score for benign lesions compare with malignant ones. OCA revealed that the invasive melanoma has a higher vessel density and thicker blood vessels than melanoma in situ and benign lesions. Discriminant functions analysis of MPM and OCA data allowed to differentiate correctly between all equivocal melanocytic lesions. Therefore, we demonstrate, for the first time, that a combined use of MPM and OCA has the potential to improve early diagnosis of melanoma.
... In terms of further clinical translation, in vivo methods of assessing these effects are of particular interest. The studies described here used two emerging optical techniques -optical coherence angiography to visualize perfused blood vessels network [11], [12] and fiber-based phosphorescence lifetime spectroscopy with an oxygen-sensitive phosphorescent dye [13] to measure tissue oxygen level. Using mouse model of colorectal cancer, we monitored in vivo tumor oxygenation and blood perfusion upon treatment with conventional doses of irinotecan. ...
The effects of chemotherapy on the tumor microenvironment remain poorly investigated, although these are crucial for the drug delivery and anti-tumor activity and can modify physiological behavior of cancer cells. are promising optical methods to characterize both tumor vasculature and its oxygenation, respectively. In this study, we used these methods to explore the influence of irinotecan, a widely used chemotherapeutic agent, on tumor angiogenesis and oxygen content in a mouse model of colorectal cancer
$in vivo$
. For the first time, it was shown that irinotecan at conventional dosing reduces tumor oxygenation and blood perfusion via antiangiogenic mechanism of action. Immunohistochemistry for hypoxia and for the endothelial cell marker CD31 verified the
$in vivo$
findings. These data show the prospects of the optical techniques to monitor tumor microenvironment in the course of chemotherapy, which can help to optimize and individualize the treatment.
... The device had a spatial resolution of 15 μm laterally and about 10 μm (in air) in depth 72 in structural images. It is also able to perform real-time angiographic imaging 67,73 and cross-polarization imaging 4,59 . oce imaging. ...
We present a non-invasive (albeit contact) method based on Optical Coherence Elastography (OCE) enabling the in vivo segmentation of morphological tissue constituents, in particular, monitoring of morphological alterations during both tumor development and its response to therapies. The method uses compressional OCE to reconstruct tissue stiffness map as the first step. Then the OCE-image is divided into regions, for which the Young’s modulus (stiffness) falls in specific ranges corresponding to the morphological constituents to be discriminated. These stiffness ranges (characteristic "stiffness spectra") are initially determined by careful comparison of the "gold-standard" histological data and the OCE-based stiffness map for the corresponding tissue regions. After such pre-calibration, the results of morphological segmentation of OCE-images demonstrate a striking similarity with the histological results in terms of percentage of the segmented zones. To validate the sensitivity of the OCE-method and demonstrate its high correlation with conventional histological segmentation we present results obtained in vivo on a murine model of breast cancer in comparative experimental study of the efficacy of two antitumor chemotherapeutic drugs with different mechanisms of action. The new technique allowed in vivo monitoring and quantitative segmentation of (1) viable, (2) dystrophic, (3) necrotic tumor cells and (4) edema zones very similar to morphological segmentation of histological images. Numerous applications in other experimental/clinical areas requiring rapid, nearly real-time, quantitative assessment of tissue structure can be foreseen.
