The vulva is a specific topographic region of the skin with complex morphology and a variety of functions. The combination of the urinary, reproductive and gastrointestinal systems in the same area makes the vulva susceptible to a wide range of diseases that require a multidisciplinary approach. As a result of these anatomical and physiological features, vulvar diseases are difficult to diagnose and insufficiently recognized. Multimodal optical coherence tomography (MM OCT) is an optical tool that allows real-time assessment of the structure of vulvar tissues with a resolution of 10-15 μm, and also provides label-free visualization of blood and lymphatic vessels. The advantages of the MM OCT method are its non-invasiveness, the possibility of examining a large tissue area, as well as obtaining data from various parts of the organ under study. In this paper, we use cross-polarization OCT, angiography, and lymphangiography with parallel histological examination to describe the structure of normal hairless vulvar skin. Two variants of the structure of vulvar skin were identified: skin with epidermal ridges, skin without epidermal ridges. For the first time, a change in the architecture of the microvasculature in response to a change in the structure of the epidermis has been described. Knowledge and understanding of the normal processes of change in the skin of the vulva are the main study of any pathology that occurs in this organ.
Lichen sclerosus (LS) is the most common vulvar dermatosis, which is characterized by damage to the connective tissue of the dermis. The affected area in lichen sclerosus is characterized by a sequential change in the main components of the connective tissue - collagen and elastin fibers. The affected area is polymorphic and remains poorly defined from a histological point of view. Among histopathologists, there are no unequivocal opinions on changes in the connective tissue of the dermis in LS. However, an assessment of the degree of dermis damage is important for the timely diagnosis of the condition and adequate treatment. Nonlinear microscopy includes second-harmonic generation (SHG) and twophoton autofluorescence (TPEF). SHG allows to selectively examine the signal from heterotypic collagen fibers of the dermis that contain type 1 collagen. TPEF allows to identify elastic fibers of the connective tissue matrix. It has been demonstrated that nonlinear microscopy allows visualizing the changes in the microstructure of collagen and elastin fibers. Three histological patterns were revealed as a result of the analysis of the nonlinear optical microscopy of the classical VLS. These histological patterns cannot be distinguished using histological stains and indicate a polymorphism of connective tissue changes. Nonlinear microscopy makes it possible to assess the changes in tissue structure, which is important for the histological interpretation of changes in the dermis and to clarify histological classification system in the future.
Lichen sclerosus is recurrence chronic autoimmune disease of skin and mucosa. Multimodal OCT is a promising tool for non-invasive, label-free and real-time investigation of vulvar tissue structure and vascularization for diagnosis and therapy control.
The study is devoted to in vivo assessment of the vulvar tissue affected by lichen sclerosus and determining the severity of the disease by the state of connective tissue, blood flow and lymph flow using multimodal optical coherence tomography. This research will open up the possibility of developing and applying an effective noninvasive high-resolution method for visualization the state and depth of connective tissue lesions by scattering and polarization properties of the vulvar tissue, the blood flow and lymph flow based on the method of spectral multimodal OCT to assess the severity of lichen sclerosus. The in vivo OCT monitoring both the early dynamics of the response of all components of the vulvar tissue to low-level laser therapy (LLLT), and the degree of structure reparation after the treatment was carried out. Different response to LLLT was revealed: 3 of 10 patients had complete resolution of symptoms, 4 patients noted improvement in symptoms and 3 patients had no change in symptoms within 6 months of treatment and it was visualized by OCT.
Dystrophic diseases of the vulva represent a large group of dermatoses. The clinical picture of these lesions is often nonspecific, and non-invasive diagnosis is ineffective. The in vivo diagnosis of dystrophic diseases is difficult due to the lack of informative imaging methods for examining the vulvar mucosa. The new method of multimodal optical coherence tomography (OCT) is a non-invasive approach for biological tissues visualization with high spatial resolution, which does not require contrasting agents. Here we report the application of multimodal OCT to in vivo study the vulvar mucosa structure and its lymphatic and blood microcirculation. Multimodal OCT showed that normally the mucous membrane of the vulva has a good blood supply and a well-developed lymphatic vessels network. The difference in the diameter of the vessels in depth is clearly traced. In the subepithelial zone, only blood capillary loops are visualized. Lymphatic capillaries are visualized starting from submucosa.
KEYWORDS: Optical coherence tomography, Lymphatic system, Blood, Blood vessels, In vivo imaging, Angiography, Connective tissue, Visualization, Biopsy, Medical research
The purpose of the study was in vivo assessment of the vulvar blood and lymphatic vessels characteristics in norm and lichen sclerosus by multimodal optical coherence tomography (OCT). The study was performed using a multimodal OCT setup developed at the Institute of Applied Physics RAS (Russia). OCT angiography and OCT lymphangiography are based on the analysis of speckle structure. Visualization of blood and lymph vessels does not require the use of exogenous contrast agents. A histological study of vulvar biopsy samples from two points was carried out for 10 patients without vulvar pathology and 12 patients with lichen sclerosus. 3D OCT data was obtained from six vulvar points in each patient. OCT images were verified by histological examination. It was shown that normally the vulvar mucosa has good blood supply and a well-developed network of lymphatic vessels. In the case of lichen sclerosus, the density of blood vessels in the area of hyalinosis significantly reduced and amounted to 2.5 ± 0.79% versus 3.9 ± 0.23% in norm (p = 0.0003). OCT lymphangiographic images also show a significant decrease in the number of lymphatic vessels, their density was 1.7 ± 0.75% versus 3.7 ± 0.54% in norm (p = 0.02). A direct relationship between the state of the blood and lymph vessels from the condition of the connective tissue of the vulva was shown. The number of blood and lymph vessels is sharply reduced in the area of hyalinosis and sclerosis of collagen fibers.
Lichen Sclerosus is a chronic recurrent inflammatory dermatosis of unknown etiology, which affects both the skin and also the mucous membrane and is usually localized at the genital area. OCT angiography is a promising tool for microcirculation mapping in 3D with ~micrometer resolution. During the study, we developed and implemented a robust real time OCT angiography realization for routine clinical practice. This allows clinicians to combine structural OCT imaging with angiograms during routine clinical practice. Normal vulvar mucosa and dystrophic vulvar mucosa were analyzed by multimodal OCT. In the structural OCT scans of connective tissue, lymphatic vessels were visualized as contrast, low-signal regions. The angiographic images of the normal mucosa show dense, uniform network, mostly consisting of relatively thin vessels. Lymphatic vessel network presented by rare, very thick vessels. Further realization of OCT lymphangiography in real-time in parallel with OCT blood-vessel angiography can improve diagnostic capabilities of the multifunctional OCT in real clinical practice.
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