Spectral image filtration by means of acousto-optical tunable filters (AOTFs) has multiple applications. For its implementation, a few different optical schemes are in use. They differ in image quality, number of coupling components, dimensions and alignment complexity. To choose the optical system of AOTF-based spectral imager properly, many factors have to be considered. Though various schemes of acousto-optic (AO) filtration have been tested and discussed, their comparative analysis has not been reported up to now. In this study, we assembled the four most popular schemes (confocal, collimating, tandem and double-path) using the same AO cells and experimentally compared their main features. Depending on the application, each scheme may be the basis of compact cost-effective spectral imaging devices.

The lack of oxygen (O2) causes changes in the cell functioning. Modeling hypoxic conditions in vitro is challenging given that different cell types exhibit different sensitivities to tissue O2 levels. We present an effective in vivo platform for assessing various tissue and organ parameters in Danio rerio larvae under acute hypoxic conditions. Our system allows simultaneous positioning of multiple individuals within a chamber where O2 level in the water can be precisely and promptly regulated, all while conducting microscopy. We applied this approach in combination with a genetically encoded pH-biosensor SypHer3s and a highly H2O2-sensitive Hyper7 biosensor. Hypoxia causes H2O2 production in areas of brain, heart and skeletal muscles, exclusively in the mitochondrial matrix; it is noteworthy that H2O2 does not penetrate into the cytosol and is neutralized in the matrix upon reoxygenation. Hypoxia causes pronounced tissue acidosis, expressed by a decrease in pH by 0.4-0.6 units everywhere. Using imaging photoplethysmography, we measured in D.rerio fry real-time heart rate decrease under conditions of hypoxia and subsequent reoxygenation. Our observations in this experimental system lead to the hypothesis that mitochondria are the only source of H2O2 in cells of D.rerio under hypoxia.

The capillary system immediately responds to many pathologies and environmental conditions. Accurate monitoring of its functioning often enables early detection of various diseases related to disorders in skin microcirculation. To expand the scope of capillaroscopy application, it is reasonable to visualize and assess blood microcirculation exactly in the areas of inflamed skin. Body vibrations, breathing, non-flat skin surface and other factors hamper the application of conventional capillaroscopes outside the nailfold area. In this paper, we propose an exoscope-based optical system for high-quality non-invasive computational imaging of capillary network in various areas of the body. Accurate image matching and tracking temporal intensity variations allow detecting the presence of blood pulsations, precise mapping of capillaries and photoplethysmogram acquisition. We have demonstrated the efficiency of the proposed approach experimentally by in vivo mapping and analysis of microvessels in wrist, forearm, upper-arm, breast and hip areas. We believe that the developed system will increase the diagnostic value of video capillaroscopy in clinical practice.

We address the optical design procedure of prism-based stereoscopic imaging systems. Conventional approach includes two sequential stages: selection of the hardware and development of the proper digital image processing algorithms. At each of these stages, specific techniques are applied, which are almost unrelated to each other. The main requirements to the imaging system include only the key parameters and the image quality. Therefore, the insufficient measurement accuracy may be revealed only after the prototype is assembled and tested. In this case, even applying complex time-consuming image processing and calibration procedures does not ensure the necessary precision. A radical solution of this issue is to include the measurement error estimation into the optical design stage. In this research, we discuss a simplified implementation of this approach and demonstrate the capabilities of optical design software for this purpose. We demonstrate the effectiveness of this approach by the analysis and optimization of a prism-based stereoscopic imager with respect to required 3D measurement accuracy. The results are meaningful for the development of 3D imaging techniques for machine vision, endoscopic and measurement systems.

The zebrafish (Danio rerio) is an increasingly popular animal model biological system. In cardiovascular research, it has been used to model specific cardiac phenomena as well as to identify novel therapies for human cardiovascular disease. While the zebrafish cardiovascular system functioning is well examined at larval stages, the mechanisms by which vessel activity is initiated remain a subject of intense investigation. In this research, we report on an in vivo stain-free blood vessel imaging technique at pre-larval stages of zebrafish embryonic development. We have developed the algorithm for the enhancement, alignment and spatiotemporal analysis of bright-field microscopy images of zebrafish embryos. It enables the detection, mapping and quantitative characterization of cardiac activity across the whole specimen. To validate the proposed approach, we have analyzed multiple data cubes, calculated vessel images and evaluated blood flow velocity and heart rate dynamics in the absence of any anesthesia. This non-invasive technique may shed light on the mechanism of vessel activity initiation and stabilization as well as the cardiovascular system’s susceptibility to environmental stressors at early developmental stages.