SignificanceThe study of the effect of aging on the optical properties of biological tissues, in particular polarization, is important in the development of new diagnostic approaches.AimThis work aims to provide a comprehensive analysis of the factors and mechanisms that contribute to the alteration of skin polarization properties caused by aging, using polarization-sensitive hyperspectral imaging measurements and Monte Carlo simulation.ApproachOur investigation involved both experimental studies of in vivo human skin of volunteers of different ages and computational modeling that accounted for changes in the absorption and scattering properties of the skin model. Specifically, we analyzed alterations in the degree of linear polarization (DOLP) to better understand the impact of aging on skin polarization properties.ResultsA statistically significant increase in the DOLP was found for the elderly group. At the same time, there was no correlation between changes in polarization and the calculated blood volume fraction parameter for different ages. According to the simulation results, it was also found that a change in the scattering properties of biological tissues has a more significant effect on the change in polarizing light compared to the change in absorption.ConclusionsThe results of the work prove that the sensitivity of polarization imaging to age- or pathological-related skin changes may be primarily due to changes in scattering, which in turn is associated with changes in the collagen fibers of the dermis. The proposed technique shows promise for in vivo non-invasive real-time assessment of age-associated skin changes and can also be extended to monitor changes associated with the development of age-related pathologies.
The paper is aimed at comparing blood microcirculation parameters of conditionally healthy volunteers and patients undergoing rehabilitation after COVID-19 to identify possible blood flow dysregulation that may result from the disease. A system of wearable laser Doppler monitors was used to conduct the study. The study demonstrated an increase in overall oscillatory blood flow activity in the group of patients compared to the control group, with especially pronounced differences in the neurogenic, respiratory and cardiac ranges. It had been shown that optical non-invasive technologies have the potential for further application in the research related to COVID-19.
The possibility of using the laser Doppler flowmetry (LDF) method for the diagnosis of masked hypertension is considered. Significant trends in changes in parameters between groups of volunteers were identified. This indicates the possibility of using the LDF method to make decisions about the further follow-up of patients for the presence of a hidden increase in BP.
Advances in the development of ultra-compact semiconductor lasers have opened up new possibilities for the development of wearable devices implementing biophotonic technologies, such as laser Doppler flowmetry (LDF) and fluorescence spectroscopy (FS). This work is aimed to evaluate the correlation between diagnostic parameters simultaneously registered by a newly developed wearable device and a standard bedside fiber-based technique. Experimental studies with healthy volunteers using the occlusion test showed a high correlation between the parameters recorded by the two devices.
In this talk we demonstrate what kind of relative alterations can be expected in average perfusion and blood flow oscillations during postural changes being measured in skin of wrists by wearable laser Doppler flowmetry (LDF) sensors.
This study is devoted to the trials of wearable diagnostic system that implements the laser Doppler flowmetry technique to analyse the blood microcirculation. We do preliminary test with involvement of limited group of healthy volunteers of different age and in patients with type 2 diabetes. During the series of measurements, the microcirculation parameters was measured for 10 minutes in the palmar surfaces of the big toes and in the inner sides of the upper thirds of the shins. A statistically significant differences was found in bypass index, nutritive and shunt blood ow in shins between older group of volunteers and patients' group as well as in shunt blood flow in fingers between younger and older groups of volunteers.
Early diagnostics of microcirculation complications is an important area for biomedical photonics application. The blood perfusion measurements are capable of identification of particular markers for diagnostics of many pathological conditions of blood microcirculation in the skin. In this work, we apply the laser Doppler flowmetry method with the ability to record and process the power spectra of registered photocurrent. This approach provides the estimation of signal amplitude distribution along with the frequencies of Doppler-broadened laser radiation and blood perfusion distribution. In this work, we investigate the blood ow in the skin by the time- frequency analysis of the recorded laser Doppler spectra. The conducted studies allowed us to propose new diagnostic criteria for the diagnosis of diabetes mellitus type 2 complications. The diagnostic parameters have been tested together with binary classifiers based on the linear discriminant analysis and demonstrated to be able to successfully distinguish the groups of volunteers of different age and patients with microvascular complications.
The problem of diabetes mellitus (DM) has attracted scientists of different specialities, as its prevalence is increasing worldwide and assumes the character of a pandemic. The use of optical non-invasive diagnostic methods is a promising direction for the early determination of the presence and severity of diabetic complications. This work is aimed at assessing changes in the uorescence intensity and the blood microcirculation level, evaluated in the skin of patients with DM with the use of local cold and heating tests. An experimental studies were carried out involving patients with type 2 DM and healthy controls. Significant differences were found in the changes in the level of microcirculation and oxidative metabolism under the in uence of local temperature effects (local heating and cooling) among patients and control group. The results can be used in further development of an optical non-invasive diagnosis of diabetes complications.
The article is aimed at conducting pilot studies of microcirculation changes in patients with diabetes mellitus during the course of intravenous infusions of alpha lipoic acid. The study was conducted with patients with diabetes during the passage of a standard course of treatment. The change in parameters was compared before the start of the infusion course, during and after the course. A system of wearable laser Doppler monitors was used to conduct the study. The study showed that although the microcirculation index does not undergo significant changes during the treatment process, spectral analysis of the recorded signal has potential applicability. Further studies with a larger sample group are required for a qualitative analysis of the observed effects.
The growing interest in the development of new wearable electronic devices for mobile healthcare provides great opportunities for the development of methods for assessing blood perfusion in this direction. Laser Doppler flowmetry (LDF) is one of the promising methods. A fine analysis of capillary blood ow structure and rhythm in the time and frequency domains, coupled with a new possibility of round-the-clock monitoring can provide valuable diagnostic information about the state of microvascular blood ow. In this study, wearable implementation of laser Doppler flowmetry was utilised for microcirculatory function assessment in patients with diabetes and healthy controls of two distinct age groups. Four wearable laser Doppler flowmetry monitors were used for the analysis of blood microcirculation. Thirty-seven healthy volunteers and 18 patients with type 2 diabetes mellitus participated in the study. The results of the studies have shown that the average perfusion differs between healthy volunteers of distinct age groups and between healthy volunteers of the younger age group and patients with diabetes mellitus. It was noted that the average level of perfusion measured on the wrist in the two groups of healthy volunteers has no statistically significant differences found in similar measurements on the fingertips. The wearable implementation of LDF can become a truly new diagnostic interface to monitor cardiovascular parameters, which could be of interest for diagnostics of conditions associated with microvascular disorders.
Laser Doppler flowmetry (LDF) was used for detection of age-related changes in the blood microcirculation. The LDF signal was simultaneously recorded from the 3rd fingers' pads of both hands. Amplitudes of the blood flow oscillations and wavelet coherence of the signals were used for the data analysis. A statistical difference in the synchronisation of myogenic oscillations was found between the two studied age groups. Myogenic oscillations of blood perfusion in the younger group had a higher wavelet coherence parameter than in the older group. Observed site-specific and age-related differences in blood perfusion can be used in the future in the design of experimental studies of the blood microcirculation system in patients with different pathologies.
Laser Doppler flowmetry (LDF) was utilized to assess age-related changes in the blood microcirculation at the skin sites with different morphology and regulation. The LDF signals obtained from the glabrous skin of the middle finger pad and nonglabrous skin on the dorsal wrist surface were analyzed. Statistically higher baseline perfusion was observed in the zone with glabrous skin in the older group of volunteers compared to younger participants. Observed site-specific and age-related differences in perfusion can be used in the future experimental design for the studies of the blood microcirculation system in patients with different pathologies.
A novel non-invasive, wearable VCSEL-based system for multipoint in − vivo measurements of blood perfusion was introduced. The system operates on the basis of the laser Doppler flowmetry (LDF) method and allows for microcirculation studies. The sensors developed were used to analyse the skin blood flow synchronization in homologous regions of the contralateral limbs, both in the basal state and during various functional tests. A high synchronisation of blood flow rhythms in the contralateral limbs of healthy volunteers was shown in the studies presented.
Local hemodynamic parameters were studied by means of laser Doppler flowmetry in 15 patients with psoriasis in the stationary stage, who have plaques on the inner surface of the forearm.
LDF signals recorded at the site of psoriatic lesions of the tissue as well as in the intact tissue at a distance of 1-2 cm from the affected area were analysed. LDF signals were postprocessed by continuous wavelet transform using the Morlet wavelet.
Laser Doppler flowmetry (LDF) was utilized for blood ow measurements. Wavelet analysis was used to identify spectral characteristics of the LDF signal in patients with rheumatic diseases and diabetes mellitus. Baseline measurements were applied for both pathological groups. Blood flow oscillations analyses were performed by means of the wavelet transform.
Higher baseline perfusion was observed in both pathological groups in comparison to controls. Differences in the spectral properties between the groups studied were revealed. The results obtained demonstrated that spectral properties of the LDF signal collected in basal conditions may be the signature of microvasculature functional state.
Laser Doppler flowmetry (LDF) is widely used to study blood microcirculation in the skin. However, during tradition signal processing based on the integral estimations of the power spectrum of detector photocurrent, the significant part of the information about the skin blood ow is lost. In this study, we propose to analyse the distribution of the blood perfusion over the Doppler shift frequencies, which correlate with the RBC velocity. This approach provides localisation of the blood ow oscillations in different subranges of the Doppler shift. The method applied together with the wavelet analysis has been tested in healthy volunteers and patients with psoriasis on the unaffected surface of the skin. It was revealed, that the significant difference in the amplitude of myogenic oscillations is allocated in the region of the low frequency Doppler shift (1-200 Hz). This frequency region can be associated with the signal from slow components of the skin microcirculation, that can point out on a different state of the lymphatic system of the skin in psoriasis.
KEYWORDS: Blood, Luminescence, Skin, Diffuse reflectance spectroscopy, Tissue optics, Diagnostics, Monte Carlo methods, Absorption, In vivo imaging, Neural networks
To minimise the influence of blood content on the fluorescence measurements in vivo, a fibre optical probe combining fluorescence and diffuse reflectance measurements was developed. For the inverse solution of the blood content recovery, a set of neural networks trained by the Monte Carlo generated learning set was used. An approach of fluorescence measurements triggered by simultaneous real-time measurements of blood content in living tissue during moderate changes in contact pressure of the optic probe is proposed. The method allows one to decrease the necessary pressure on the probe as well as increase the repeatability of the measurements. The developed approach was verified in a series of experiments on volunteers with fluorescence excitation at 365 nm and 450 nm. The proposed technology is of particular interest in the development of new fluorescence-based optical biopsy systems.
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.
Laser Doppler flowmetry (LDF) is widely used for diagnosing blood microcirculation diseases. It is well known that the Doppler shift of laser radiation scattered by moving red blood cells (RBC) can be assessed through analyzing photocurrent produced by a photodetector. LDF signal contains information about regulating blood flow rhythms: myogenic, cardiac, nervous and endothelial. The method of videocapillaroscopy (VCS) allows local capillary blood flow velocity evaluation and, using video data processing algorithms, is able to assess RBC velocity changes into capillary. We present the results of simultaneous investigations of changes in tissue perfusion of the distal phalanx of human finger by the LDF as well as changes in capillary blood flow velocity in the nail bed evaluated by the VCS method during arterial occlusion test. The experimental results confirmed the correspondence between blood perfusion and blood flow velocity.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.