Andrey V. Dunaev

Individual variability analysis of fluorescence parameters measured in skin with different levels of nutritive blood flow

Fluorescence spectroscopy has recently become more common in clinical medicine. However, there are still many unresolved issues related to the methodology and implementation of instruments with this technology. In this study, we aimed to assess individual variability of fluorescence parameters of endogenous markers (NADH, FAD, etc.) measured by fluorescent spectroscopy (FS) in situ and to analyse the factors that lead to a significant scatter of results. Most studied fluorophores have an acceptable scatter of values (mostly up to 30%) for diagnostic purposes. Here we provide evidence that the level of blood volume in tissue impacts FS data with a significant inverse correlation. The distribution function of the fluorescence intensity and the fluorescent contrast coefficient values are a function of the normal distribution for most of the studied fluorophores and the redox ratio. The effects of various physiological (different content of skin melanin) and technical (characteristics of optical filters) factors on the measurement results were additionally studied. The data on the variability of the measurement results in FS should be considered when interpreting the diagnostic parameters, as well as when developing new algorithms for data processing and FS devices.

Substantiation of medical and technical requirements for noninvasive spectrophotometric diagnostic devices

Abstract. A scientific approach to the formulation of medical and technical requirements (MTRs) for noninvasive spectrophotometric diagnostic devices using optical technologies such as laser Doppler flowmetry and absorption spectroscopy is proposed. The theoretical modeling framework, metrological certification, and testing of these devices are still in the early stages of development. The theoretical estimation of the received signal levels for wavelengths between 514 and 940 nm is highly dependent on the blood volume level in the subject tissue. The proposed approach allows, in particular, the calculation of technical and metrological performance constraints of the instruments, such as the ranges of the sensitivity and power-related signal-to-noise ratios for different spectral channels and different biomedical (biochemical and physiological) parameters. Substantiation of specialized MTRs for the noninvasive spectrophotometric diagnostic devices can enable them to develop to the level of standardized measurement techniques.

Laser reflectance oximetry and Doppler flowmetry in assessment of complex physiological parameters of cutaneous blood microcirculation

The integration of multiple optical techniques within a single diagnostic device is used to address the difficulties in standardising measurement of cutaneous blood micro-dynamics caused by high variability. We demonstrate the benefits of simultaneous assessment of blood relative volume (Vb), microcirculation index (Im) and tissue oxygen saturation (StO2), during long-term examination of healthy volunteers. Consequently, five rhythmic components: endothelial, neurogenic, myogenic, breath and heart pulses were established showing high variability up to 30 – 50% as well as in initial parameters around 16%. All rhythmic components were synchronous with some latency between Im and StO2 in the myogenic component supports the hypothesis of strong correlation between peripheral hemodynamics and oxygen utilisation in tissues.

Combined use of laser Doppler flowmetry and skin thermometry for functional diagnostics of intradermal finger vessels

We introduce a noninvasive diagnostic approach for functional monitoring of blood microflows in capillaries and thermoregulatory vessels within the skin. The measuring system is based on the combined use of laser Doppler flowmetry and skin contact thermometry. The obtained results suggest that monitoring of blood microcirculation during the occlusion, performed in conjunction with the skin temperature measurements in the thermally stabilized medium, has a great potential for quantitative assessment of angiospatic dysfunctions of the peripheral blood vessels. The indices of blood flow reserve and temperature response were measured and used as the primarily parameters of the functional diagnostics of the peripheral vessels of skin. Utilizing these parameters, a simple phenomenological model has been suggested to identify patients with angiospastic violations in the vascular system.

Computational model of bladder tissue based on its measured optical properties

Abstract. Urinary bladder diseases are a common problem throughout the world and often difficult to accurately diagnose. Furthermore, they pose a heavy financial burden on health services. Urinary bladder tissue from male pigs was spectrophotometrically measured and the resulting data used to calculate the absorption, transmission, and reflectance parameters, along with the derived coefficients of scattering and absorption. These were employed to create a “generic” computational bladder model based on optical properties, simulating the propagation of photons through the tissue at different wavelengths. Using the Monte-Carlo method and fluorescence spectra of UV and blue excited wavelength, diagnostically important biomarkers were modeled. Additionally, the multifunctional noninvasive diagnostics system “LAKK-M” was used to gather fluorescence data to further provide essential comparisons. The ultimate goal of the study was to successfully simulate the effects of varying excited radiation wavelengths on bladder tissue to determine the effectiveness of photonics diagnostic devices. With increased accuracy, this model could be used to reliably aid in differentiating healthy and pathological tissues within the bladder and potentially other hollow organs.

Analysis of skin blood microflow oscillations in patients with rheumatic diseases

Laser Doppler flowmetry (LDF) has been applied for the assessment of variation in blood microflows in patients with rheumatic diseases and healthy volunteers. Oscillations of peripheral blood microcirculation observed by LDF have been analyzed utilizing a wavelet transform. A higher amplitude of blood microflow oscillations has been observed in a high frequency band (over 0.1 Hz) in patients with rheumatic diseases. Oscillations in the high frequency band decreased in healthy volunteers in response to the cold pressor test, whereas lower frequency pulsations prevailed in patients with rheumatic diseases. A higher perfusion rate at normal conditions was observed in patients, and a weaker response to cold stimulation was observed in healthy volunteers. Analysis of blood microflow oscillations has a high potential for evaluation of mechanisms of blood flow regulation and diagnosis of vascular abnormalities associated with rheumatic diseases.

Multimodal optical measurement for study of lower limb tissue viability in patients with diabetes mellitus.

According to the International Diabetes Federation, the challenge of early stage diagnosis and treatment effectiveness monitoring in diabetes is currently one of the highest priorities in modern healthcare. The potential of combined measurements of skin fluorescence and blood perfusion by the laser Doppler flowmetry method in diagnostics of low limb diabetes complications was evaluated. Using Monte Carlo probabilistic modeling, the diagnostic volume and depth of the diagnosis were evaluated. The experimental study involved 76 patients with type 2 diabetes mellitus. These patients were divided into two groups depending on the degree of complications. The control group consisted of 48 healthy volunteers. The local thermal stimulation was selected as a stimulus on the blood microcirculation system. The experimental studies have shown that diabetic patients have elevated values of normalized fluorescence amplitudes, as well as a lower perfusion response to local heating. In the group of people with diabetes with trophic ulcers, these parameters also significantly differ from the control and diabetes only groups. Thus, the intensity of skin fluorescence and level of tissue blood perfusion can act as markers for various degrees of complications from the beginning of diabetes to the formation of trophic ulcers.

The development of attenuation compensation models of fluorescence spectroscopy signals

This study examines the effect of blood absorption on the endogenous fluorescence signal intensity of biological tissues. Experimental studies were conducted to identify these effects. To register the fluorescence intensity, the fluorescence spectroscopy method was employed. The intensity of the blood flow was measured by laser Doppler flowmetry. We proposed one possible implementation of the Monte Carlo method for the theoretical analysis of the effect of blood on the fluorescence signals. The simulation is constructed as a four-layer skin optical model based on the known optical parameters of the skin with different levels of blood supply. With the help of the simulation, we demonstrate how the level of blood supply can affect the appearance of the fluorescence spectra. In addition, to describe the properties of biological tissue, which may affect the fluorescence spectra, we turned to the method of diffuse reflectance spectroscopy (DRS). Using the spectral data provided by the DRS, the tissue attenuation effect can be extracted and used to correct the fluorescence spectra.

Study of the functional state of peripheral vessels in fingers of rheumatological patients by means of laser Doppler flowmetry and cutaneous thermometry measurements

Vasospastic disorders are a common class of rheumatic disease. These include syndromes such as vegetative dystonia, Raynauds syndrome, vibration disease and rheumatoid arthritis among others. The aim of this work is to develop an original method of diagnosing the functional state of peripheral vessels of the fingers, based on the simultaneous recording of LDF- and thermograms during the occlusion test, for determining vascular disorders of rheumatological patients. A diagnostic method was developed for assessing the functional state of the peripheral vessels of fingers, based on carrying out occlusion test in a thermally stabilized environment, with simultaneous recording of signals of laser Doppler flowmetry and skin thermometry. To verify the diagnostic value of the proposed method, a series of experiments were carried out on 41 rheumatological patients: 5 male and 36 females (average age 56.0±12.2 years). The most common diagnoses in the patient group were rheumatoid arthritis, arthrosis, gout and systemic lupus erythematosus. The laser analyser of blood microcirculation “LAKK-02” (SPE “LAZMA” Ltd, Russia) and a custom developed multi-channel thermometry device for low inertia thermometry were used for experimental measurements. The measurements of cutaneous temperature and the index of microcirculation were performed on the distal phalanx of the third finger of the right hand. Occlusion tests were performed with water baths at 25 and 42 °C and a tonometer cuff with a pressure of 200-220 mmHg for 3 min on the upper arm. The results of experimental studies are presented and interpreted. These data indicate a violation of the blood supply regulation in the form of a pronounced tendency towards microvascular vasoconstriction in the fingers. Thus, the response displaying a tendency toward angiospasm among patients in the rheumatological diseases profile group was observed mainly in the most severe cases (49 % of this group). The prospects of the developed diagnostic method of microcirculatory disorders in rheumatic diseases are evaluated. Thus, cutaneous blood microcirculation and temperature measurements performed together can help in diagnosis of the functional state of peripheral vessels both in a healthy state and when expressing pathology.

Changes in autofluorescence based organoid model of muscle invasive urinary bladder cancer.

Muscle invasive urinary bladder cancer is one of the most lethal cancers and its detection at the time of transurethral resection remains limited and diagnostic methods are urgently needed. We have developed a muscle invasive transitional cell carcinoma (TCC) model of the bladder using porcine bladder scaffold and the human bladder cancer cell line 5637. The progression of implanted cancer cells to muscle invasion can be monitored by measuring changes in the spectrum of endogenous fluorophores such as reduced nicotinamide dinucleotide (NADH) and flavins. We believe this could act as a useful tool for the study of fluorescence dynamics of developing muscle invasive bladder cancer in patients. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.