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Technical characteristics of laser Doppler flowmetry (LDF), Laser Speckle Contrast Imaging (LSCI) and Tissue Viability Imaging (TiVi).
Source publication
Microvascular changes in the skin due to pharmacological and physiological provocations can be used as a marker for vascular function. While laser Doppler flowmetry (LDF) has been used extensively for measurement of skin microvascular responses, Laser Speckle Contrast Imaging (LSCI) and Tissue Viability Imaging (TiVi) are novel imaging techniques....
Similar publications
Objective
To investigate the potential role of alpha1-adrenoceptor (α1-AR) in the pathogenesis of hepatorenal syndrome.
Methods
Hepatorenal syndrome was induced in male rats by intraperitoneal injection of D-galactosamine and orally treatment with α1-AR antagonist tamsulosin. Hyperresponsiveness of the renal artery contraction was evaluated by the...
Citations
... Laser speckle contrast imaging (LSCI) was used to determine MC skin (Abdulhameed et al., 2020), Moor Instruments, Millwey, UK), measuring to a maximum depth of approximately 1 mm in the skin (Limited, 2012). This macroscopic, noncontact device with a high spatial and temporal resolution has been shown to be sensitive for assessing MC skin (Iredahl et al., 2015). The calibration procedure was performed according to the manufacturer's recommendations the day before the measurements. ...
Introduction
Methyl salicylate, the main compound of wintergreen oil, is widely used in topical applications. However, its vascular and thermosensory effects are not fully understood. The primary aim was to investigate the effects of topical methyl salicylate on skin temperature (Tskin), skin microcirculation (MCskin) and muscle oxygen saturation (SmO2) compared to a placebo gel. The secondary aim was to assess thermosensory responses (thermal sensation, thermal comfort) and to explore to which extent these sensations correspond to the physiological responses over time.
Methods
21 healthy women (22.2 ± 2.9 years) participated in this single-blind, randomized controlled trial. Custom-made natural wintergreen oil (12.9%), containing methyl salicylate (>99%) and a placebo gel, 1 g each, were applied simultaneously to two paravertebral skin areas (5 cm × 10 cm, Th4-Th7). Tskin (infrared thermal imaging), MCskin (laser speckle contrast imaging) and SmO2 (deep tissue oxygenation monitoring) and thermosensation (Likert scales) were assessed at baseline (BL) and at 5-min intervals during a 45 min post-application period (T0-T45).
Results
Both gels caused an initial decrease in Tskin, with Tskin(min) at T5 for both methyl salicylate (BL-T5: Δ-3.36°C) and placebo (BL-T5: Δ-3.90°C), followed by a gradual increase (p < .001). Methyl salicylate gel resulted in significantly higher Tskin than placebo between T5 and T40 (p < .05). For methyl salicylate, MCskin increased, with MCskin(max) at T5 (BL-T5: Δ88.7%). For placebo, MCskin decreased (BL-T5: Δ-17.5%), with significantly lower values compared to methyl salicylate between T0 and T45 (p < .05). Both gels had minimal effects on SmO2, with no significant differences between methyl salicylate and placebo (p > .05). Thermal sensation responses to topical methyl salicylate ranged from “cool” to “hot”, with more intense sensations reported at T5.
Discussion
The findings indicate that topical methyl salicylate induces short-term cutaneous vasodilation, but it may not enhance skeletal muscle blood flow. This study highlights the complex sensory responses to its application, which may be based on the short-term modulation of thermosensitive transient receptor potential channels.
... The skin condition known as post-occlusive reactive hyperemia (PORH) can be utilized to investigate the role of sensory nerves and hyperpolarizing processes. Significantly, the reproducibility of microvascular assessment in the skin has been further enhanced by the recent development of image-based blood flow measurement techniques [60]. ...
The purpose of this paper is to review the specialized literature to highlight the effects produced by energy drinks in terms of skin health. To carry out this review, we consulted previous articles with descriptive cross-sectional designs, case series, and individual case reports published between 2000 and 2023. Therefore, while caffeine acute consumption among adults can have beneficial effects, in children, it can cause health problems like overnight breaks, headaches, and dulled cognition since their organs are still developing and their endocrine system is not yet stable. Despite the antioxidant and neuroprotective effects of caffeine from energy drinks, their excessive consumption among adolescents can cause disorders like high systolic blood pressure, agitation, nausea, anxiety, osteoporosis, heart palpitations, poor sleep quality, and stomach ulcers. Among athletes, taurine supplementation has been proven to improve exercise capacity in cold weather conditions. Also, vigilance, attention, and reaction time were all improved by caffeine consumption. Caffeine administration in low doses caused a risk of cardiovascular disease. It was effective in treating migraines in children, but raised systolic blood pressure, and contributed to skin healing in adolescents. On the other side, taurine prevents obesity among children, causes positive effects on oxidative stress and inflammation in adolescents, helps shield the skin from damaging oxidative stress among students, and impacts exercise capacity in athletes. Significant increases in serum levels of uric acid, creatinine, BUN, ALT, and ALP caused by chronic intake of EDs indicated different degrees of injury to the kidneys and liver. Furthermore, the effects on the cardiovascular system could be worse if taurine and caffeine are combined. Caffeine alone does not significantly decrease sleep as much as a taurine/high caffeine ratio. On the other hand, a low ratio does.
... LSCI is a real-time non-invasive, non-contact method for quantifying perfusion and so could be used to quantify facial flushing (Ambrus et al., 2016). LSCI is already used for perfusion assessment in several medical specialties (Heeman et al., 2019;Iredahl et al., 2015;Miller et al., 2022;Boas and Dunn, 2010) and has previously been used to quantify facial flushing in patients developing MTS (Ring et al., 2018;Zaar et al., 2014). One study found a significant difference in facial skin perfusion between patients developing severe MTS and patients developing moderate/no MTS using LSCI (Ring et al., 2018). ...
Brief abstract
Today, the diagnosis and grading of mesenteric traction syndrome relies on a subjective assessment of facial flushing. However, this method has several limitations. In this study, Laser Speckle Contrast Imaging and a predefined cut-off value are assessed and validated for the objective identification of severe mesenteric traction syndrome.
Background
Severe mesenteric traction syndrome (MTS) is associated with increased postoperative morbidity. The diagnosis is based on an assessment of the developed facial flushing. Today this is performed subjectively, as no objective method exists. One possible objective method is Laser Speckle Contrast Imaging (LSCI), which has been used to show significantly higher facial skin blood flow in patients developing severe MTS. Using these data, a cut-off value has been identified. This study aimed to validate our predefined LSCI cut-off value for identifying severe MTS.
Methods
A prospective cohort study was performed on patients planned for open esophagectomy or pancreatic surgery from March 2021 to April 2022. All patients underwent continuous measurement of forehead skin blood flow using LSCI during the first hour of surgery. Using the predefined cut-off value, the severity of MTS was graded. In addition, blood samples for prostacyclin (PGI2) analysis and hemodynamics were collected at predefined time points to validate the cut-off value.
Main results
Sixty patients were included in the study. Using our predefined LSCI cut-off value, 21 (35 %) patients were identified as developing severe MTS. These patients were found to have higher concentrations of 6-Keto-PGFaα (p = 0.002), lower SVR (p < 0.001), lower MAP (p = 0.004), and higher CO (p < 0.001) 15 min into surgery, as compared with patients not developing severe MTS.
Conclusion
This study validated our LSCI cut-off value for the objective identification of severe MTS patients as this group developed increased concentrations of PGI2 and more pronounced hemodynamic alterations compared with patients not developing severe MTS.
... To gain optimal insight into the complex control mechanisms of skin microcirculation in normal and diseased states, various optical imaging techniques, coupled with different pharmacological or physical stimuli to challenge microvascular reactivity, are usually used (Mizeva et al., 2018). Laser Doppler flowmetry (LDF) 2 , which provides non-invasive, semi-quantitative, and real-time microcirculatory signal tracking (Mahé et al., 2012;Iredahl et al., 2015;Rodrigues et al., 2019), is still considered the gold standard (Lenasi, 2011). ...
Laser Doppler flowmetry (LDF) has long been considered a gold standard for non-invasive assessment of skin microvascular function. Due to the laser Doppler (LD) microcirculatory signal’s complex biological and physiological context, using spectral analysis is advisable to extract as many of the signal’s properties as feasible. Spectral analysis can be performed using either a classical Fourier transform (FT) technique, which has the disadvantage of not being able to localize a signal in time, or wavelet analysis (WA), which provides both the time and frequency localization of the inspected signal. So far, WA of LD microcirculatory signals has revealed five characteristic frequency intervals, ranging from 0.005 to 2 Hz, each of which being related to a specific physiological influence modulating skin microcirculatory response, providing for a more thorough analysis of the signals measured in healthy and diseased individuals. Even though WA is a valuable tool for analyzing and evaluating LDF-measured microcirculatory signals, limitations remain, resulting in a lack of analytical standardization. As a more accurate assessment of human skin microcirculation may better enhance the prognosis of diseases marked by microvascular dysfunction, searching for improvements to the WA method is crucial from the clinical point of view. Accordingly, we have summarized and discussed WA application and its limitations when evaluating LD microcirculatory signals, and presented insight into possible future improvements. We adopted a novel strategy when presenting the findings of recent studies using WA by focusing on frequency intervals to contrast the findings of the various studies undertaken thus far and highlight their disparities.
... In this context, it is impossible to ignore the modern methods of endothelial and micro-circulation assessment, such as LDF, which have a recognized clinical value [11]. The LDF method has some limitations resulting from the sensitivity of the results to various external measurement conditions, individual and local variability of blood flow in microcirculation; therefore, measurements should be standardized through the use of so-called provocation tests, most often causing local tissue hyperaemia [12]. ...
... In theopinion of the authors, the need to assess the endothelial status and micro-circulation in patients with hypertension seems unquestionable. It is worth remembering here about the multitude of factors influencing the PORH measurement result, both dependent on the homeostasis of the organism, such as metabolic factors [7] and medications taken [19], as well as external factors or individual characteristics [12]. Further research should focus on the study and evaluation of factors influencing the microcirculation status and function of the endothelium, and how to prevent and monitor disturbances in its function. ...
Objective:
The aim of the study was to assess the reactivity of the cutaneous microcirculation in patients with arterial hypertension (AH), taking into account the intake of anti-hypertensive drugs, using laser doppler flowometry (LDF) and the post-occlusive reactive hyperaemia (PORH) test.
Material and methods:
The analysis included 44 patients with well-controlled AH, and 22 subjectively healthy volunteers aged 23 - 74 years, matched with the study group. During the study period, 22 patients in the study group were taking ACEI drugs, also in combination with other drug groups in terms of gender and age. 19 patients were taking other groups of drugs, including: ARB, beta-blockers, alpha-blockers, CCB, diuretics, also in combination, while 3 patients were not taking medication for AH; they were recommended non-pharmacological treatment. Blood biochemical tests, ambulatory blood pressure monitoring (ABPM) and PORH test using LDF were performed.
Results:
The study showed that the PORH flow parameters were not differ statistically significantly between the study and control groups (p> 0.05). Statistically significant differences were shown in the PORH maximum level (ML) on the skin forearm between the study group not taking ACEI drugs and the control group. No statistically significant differences were shown between the study group taking ACEI and the control group.
Conclusions:
The pathogenesis of AH is multifactorial and depends, inter alia, on disturbances at the level of microcirculation. Proper treatment, especially with the use of ACEI, can improve the microcirculation in AH patients.
... Because decreased NO activity and increased endothelial expression of the VCAM-1 gene are functionally interrelated (38), we expected that VCAM-1 would be related to decreased Ach-induced vasodilation. In terms of SNP-induced vasodilation, any factors involved in mineral metabolism were not associated with SNP-induced vasodilation, which is consistent with previous studies (14,15,39). ...
IntroductionEndothelial dysfunction commonly occurs in chronic kidney disease (CKD) patients and increases the risk for cardiovascular disease. Among CKD patients, biomarkers involved in the pathogenesis of CKD-mineral bone disorder (CKD-MBD), such as phosphorus, parathyroid hormone, and fibroblast growth factor 23, are associated with endothelial dysfunction. We investigated whether these biomarkers induce endothelial dysfunction in CKD patients with normal phosphorus levels.Methods
This cross-sectional study examined CKD patients with normal phosphorus levels; patients with an estimated glomerular filtration rate (eGFR) <15 or who were under dialysis were excluded. Iontophoresis with laser doppler flowmetry (ILDF) and peripheral arterial tonometry were performed to assess endothelial function in 85 patients. Pearson's correlation coefficient, multiple regression, and mediation analyses were performed to examine the association between CKD-MBD biomarkers and endothelial dysfunction.ResultsEndothelial dysfunction was observed in all subjects with a low response to ILDF and 27% of subjects according to peripheral arterial tonometry. Acetylcholine (Ach)-induced ILDF was significantly associated with eGFR (r = 0.22, P = 0.04), intact parathyroid hormone (iPTH; r = −0.46, P < 0.01), and VCAM-1 (r = −0.36, P < 0.01). The reactive hyperemia index (RHI) was significantly related to phosphorus levels (r = 0.32, P < 0.01) and iPTH (r = −0.39, P = 0.02). After adjusting for eGFR, iPTH and VCAM-1 remained independent factors for predicting endothelial dysfunction measured using Ach-induced ILDF. In addition, iPTH and phosphorus levels were independent predictors for endothelial dysfunction measured using RHI in the eGFR-adjusted model. Mediation analyses showed that the individual indirect effects of iPTH were significantly affected ILDF and RHI.Conclusion
Serum levels of phosphorus and iPTH are associated with endothelial dysfunction, even in CKD patients with normal phosphorus levels.
... Laser speckle contrast imaging (LSCI) is a commercially available technique for noninvasive monitoring of blood perfusion in skin with high spatial and temporal resolution. 8 LSCI has been used in measurements of perfusion in human periocular flaps and reconstructive surgery with convincing results 9,10 and has also been used to study hypoperfusion in porcine eyelid flaps resulting from vasoconstrictive agents. 5 Optical spectroscopy is the most common technique used to monitor sO 2 noninvasively. ...
Purpose:
Epinephrine is used in local anesthetics to induce vasoconstriction and thus reduce bleeding and prolong the anesthetic effect. Finding the optimal delay between the administration of the anesthetic and skin incision to ensure vasoconstriction and minimize bleeding is important and has recently become the subject of debate. This is the first study to assess blood perfusion and oxygen saturation (sO2) simultaneously in response to a local anesthetic containing epinephrine in human oculoplastic surgery.
Methods:
A local anesthetic consisting of lidocaine and epinephrine (20 mg/ml + 12.5 μg/ml) was injected in the eyelids of 9 subjects undergoing blepharoplasty. The perfusion and sO2 of the eyelids were monitored using laser speckle contrast imaging and hyperspectral imaging, respectively.
Results:
Laser speckle contrast imaging monitoring showed a decrease in perfusion over time centrally at the site of injection. Half-maximum effect was reached after 34 seconds, and full effect after 115 seconds, determined by exponential fitting. The drop in perfusion decreased gradually further away from the injection site and hypoperfusion was less prominent 4 mm from the injection site, with a spatially dependent half-maximum effect of 231 seconds. Hyperspectral imaging showed only a slight decrease in sO2 of 11 % at the injection site.
Conclusions:
The optimal time delay for skin incision in oculoplastic surgery is approximately 2 minutes after the injection of lidocaine with epinephrine. Longer delay does not lead to a further decrease in perfusion. As sO2 was only slightly reduced after injection, the results indicate that the use of epinephrine is safe in the periocular region.
... The LSCI signal origin at~0.5 mm [37] is not as deep as PPG (1.5-2 mm) but is still subcutaneous and can therefore be sensitive to melanin concentration [37]. While both rPPG and LSCI have limitations associated with increased concentration of melanin, and rPPG has also been shown to be impaired in the presence of cosmetic makeup, SRVI has the potential to overcome these issues. ...
... The LSCI signal origin at~0.5 mm [37] is not as deep as PPG (1.5-2 mm) but is still subcutaneous and can therefore be sensitive to melanin concentration [37]. While both rPPG and LSCI have limitations associated with increased concentration of melanin, and rPPG has also been shown to be impaired in the presence of cosmetic makeup, SRVI has the potential to overcome these issues. ...
Specular reflection from tissue is typically considered as undesirable, and managed through device design. However, we believe that specular reflection is an untapped light-tissue interaction, which can be used for imaging subcutaneous blood flow. To illustrate the concept of subcutaneous blood flow visualization using specular reflection from the skin, we have developed a ray tracing for the neck and identified conditions under which useful data can be collected. Based on our model, we have developed a prototype Specular Reflection Vascular Imaging (SRVI) device and demonstrated its feasibility by imaging major neck vessels in a case study. The system consists of a video camera that captures a video from a target area illuminated by a rectangular LED source. We extracted the SRVI signal from 5 × 5 pixels areas (local SRVI signal). The correlations of local SRVIs to the SRVI extracted from all pixels in the target area do not appear to be randomly distributed, but rather form cohesive sub-regions with distinct boundaries. The obtained waveforms were compared with the ECG signal. Based on the time delays with respect to the ECG signal, as well as the waveforms themselves, the sub-regions can be attributed to the jugular vein and carotid artery. The proposed method, SRVI, has the potential to contribute to extraction of the diagnostic information that the jugular venous pulse can provide.
... LSCI may have greater reproducibility in larger areas of skin, but this has only been examined with respect to the cutaneous vasodilation response. Compared to LDF, LSCI exhibits greater reproducibility of the dilation response that occurs during post-occlusive reactive hyperemia (Iredahl et al., 2015;Roustit et al., 2010b;Shirazi et al., 2021;Tew et al., 2011), local heating (Iredahl et al., 2015;Roustit et al., 2010b), and localized drug infusion (Cracowski et al., 2011;Iredahl et al., 2015) administered on the forearm. While LSCI has been shown to accurately measure cutaneous blood flow in the thigh during systemic cooling (Hohenauer et al., 2019), there is no data comparing the reproducibility or reliability of the VC response with other more established methods of vascular measurement such as LDF. ...
... LSCI may have greater reproducibility in larger areas of skin, but this has only been examined with respect to the cutaneous vasodilation response. Compared to LDF, LSCI exhibits greater reproducibility of the dilation response that occurs during post-occlusive reactive hyperemia (Iredahl et al., 2015;Roustit et al., 2010b;Shirazi et al., 2021;Tew et al., 2011), local heating (Iredahl et al., 2015;Roustit et al., 2010b), and localized drug infusion (Cracowski et al., 2011;Iredahl et al., 2015) administered on the forearm. While LSCI has been shown to accurately measure cutaneous blood flow in the thigh during systemic cooling (Hohenauer et al., 2019), there is no data comparing the reproducibility or reliability of the VC response with other more established methods of vascular measurement such as LDF. ...
... LSCI may have greater reproducibility in larger areas of skin, but this has only been examined with respect to the cutaneous vasodilation response. Compared to LDF, LSCI exhibits greater reproducibility of the dilation response that occurs during post-occlusive reactive hyperemia (Iredahl et al., 2015;Roustit et al., 2010b;Shirazi et al., 2021;Tew et al., 2011), local heating (Iredahl et al., 2015;Roustit et al., 2010b), and localized drug infusion (Cracowski et al., 2011;Iredahl et al., 2015) administered on the forearm. While LSCI has been shown to accurately measure cutaneous blood flow in the thigh during systemic cooling (Hohenauer et al., 2019), there is no data comparing the reproducibility or reliability of the VC response with other more established methods of vascular measurement such as LDF. ...
Objective
Reproducibility of the reflex cutaneous vasoconstriction response is currently unknown. Our aim was to determine the test-retest reproducibility of laser speckle contrast imaging (LSCI) and varying sampling depths of laser Doppler flowmetry (LDF) in response to whole-body cooling.
Methods
Over two studies, nine and fourteen healthy, young adults underwent a 40-min cooling bout over two separate experiments. Participants were cooled from 34.0 °C to 30.5 °C and held at a 30.5 °C plateau for 10-min prior to rewarming. Throughout the cooling bout, changes in blood flow were measured as LSCI flux and LDF flux for Study 1 and LDF flux by three different LDF sampling depths in Study 2. Test-retest reproducibility and reliability were evaluated by the coefficient of variation (CV) and intraclass correlation coefficients (ICC), respectively. Vasoconstriction was presented as cutaneous vascular conductance (CVC = flux / mean arterial pressure) and expressed as a percent change from baseline (%ΔCVCBASELINE).
Results
For Study 1, test-retest reproducibility displayed good reproducibility for LSCI (CV: <9.0%) and good-to-moderate for LDF (CV: <17.0%) throughout the cooling bout and at plateau (LSCI CV: 1.0%; LDF CV: 1.9%). For Study 2, all Doppler depths displayed good reproducibility during the cooling bout (CV: <9.0%) and at plateau (CV: 0.9–2.0%). Only LSCI demonstrated reliability across both studies (ICC: 0.58–0.88). A reduced vasoconstriction response was measured with the shallowest penetration in the skin (LSCI: 26 ± 0.9%ΔCVCBASELINE) compared to the Doppler with the deepest penetration (35 ± 0.6%ΔCVCBASELINE, p < 0.001).
Conclusions
Although Dopplers better discriminate the reflex cutaneous vasoconstriction response, LSCI exhibits greater test-retest reproducibility and reliability, and thus may be more suitable for longitudinal assessments.
... Transdermal in vivo microdosing of vasoactive drugs by iontophoresis offers an interesting alternative. Used in conjunction with non-invasive imaging methods, such as laser Doppler owmetry (LDF), local pharmacodynamic effects in e.g., the skin can be successfully assessed [3][4][5]. All Doppler based optical measurement techniques are, however, susceptible to movement artifacts and the signal obtained is dependent on both the velocity and the concentration of red blood cells (RBC) within the measurement volume. ...
... ). ED50 values for the dose response curves for the pulses and concentrations were compared using an extra-sums-of-squares F test to nd any difference between data sets.Dose response curves and statistical analysis were plotted and performed in GraphPad Prism version 8.4.3 for Windows, GraphPadSoftware, San Diego, California USA, www.graphpad.com.A p-value of ≤0.05 was considered as signi cant in all calculations. ...
Objective: Transdermal iontophoresis offers an in vivo alternative to the strain-gauge model for measurement of vascular function but is limited due to lack of technical solutions for outcome assessment. The aims of this study were to, after measurement by polarized reflectance spectroscopy (PRS), use pharmacodynamic dose-response analysis on responses to different concentrations of acetylcholine (ACh); and to examine the effect of three consecutively administered iontophoretic current pulses.
Methods: The vascular responses in 15 healthy volunteers to iontophorised ACh (5 concentrations, range 0.0001% to 1%, three consecutive pulses of 0.02 mA for 10 minutes each) were recorded using PRS. Data were fitted to a four-parameter logistic dose response model and compared regarding ED50 values.
Results: Vascular responses were quantifiable by PRS. Similar pharmacodynamic dose response curves (ED50 values) could be generated irrespectively of the ACh concentration. Linearly increasing maximum vasodilatory responses were registered with increasing concentration of ACh. A limited linear dose effect of the concentration of ACh was seen between pulses.
Conclusions: Polarized reflectance spectroscopy is well suited for measuring vascular responses to iontophoretically administrated ACh. The results of this study support further development of iontophoresis as a method to study vascular function and pharmacological responses in vivo.
