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Operating principle of the imaging system, showing the polarization gating method. Both 1 and 2 are polarization filters and are arranged so that their pass-directions are perpendicular, thus creating a cross-polarized (CR) image. By this method, the surface reflections are suppressed and only the light emanating from the dermis is received by the detection array. LP and RP represent linear and randomly polarized light, respectively.
Source publication
Background/aims:
Many clinical conditions that affect the microcirculation of the skin are still diagnosed and followed up by observational methods alone in spite of the fact that non-invasive, more user-independent and objective methods are available today. Limited portability, high cost, lack of robustness and non-specificity of findings are amo...
Contexts in source publication
Context 1
... schematic for the polarization light spectroscopy imaging system is shown in Fig. 1. White linearly polarized light emitted from a wide-angle source is incident on the skin. In the superficial layers of the skin, approximately 4% and 3% of the incident light is directly reflected (Fresnel reflection) as surface glare and reflectance from the initial skin layers respectively, retaining the original polarization state ...
Context 2
... three skin sites were expected to demonstrate erythema (vasodilatation) and blanching (vasoconstriction) respectively. The photo and image displayed in Fig 8 was recoded 10 minutes following application of methyl nicotinate and removal of the occlusion cover over the site exposed to clobestal propionate. The average TiVi index value for the methyl nicotinate site was calculated to be 30% above normal skin control levels. ...
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Citations
... Vascular responses were quantified using polarized reflectance spectroscopy by tissue viability imaging (TiVi700 2.0 Tissue Viability Imager, WheelsBridge AB, Linköping, Sweden). The technique has previously been described in detail 8,18 . In short, the system comprises a high-performance digital camera equipped with perpendicular oriented polarization filters in front of the light source and the camera lens. ...
... The technology takes advantage of the wavelength dependence in RBC absorption. By first separating the red, green, and blue color matrixes and then applying an algorithm in which the value of each picture element in the green color matrix is subtracted from corresponding value of the red color matrix, an output matrix linearly proportional to the local RBC concentration can be generated 8 www.nature.com/scientificreports/ resolution and positioned at approximately 25 cm above the active drug delivery electrodes. ...
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. 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 min each) were recorded using PRS. Data were fitted to a four-parameter logistic dose response model and compared. Vascular responses were quantifiable by PRS. Similar pharmacodynamic dose response curves 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. 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.
... Tissue Viability Imaging (TiVi, WheelsBridge AB, Linköping, Sweden) was used to estimate erythema (rubor). The measurement principle has previously been described in detail [28]. Briefly, based on the wavelength-dependent absorption properties of red blood cells (RBCs) and imaging-processing algorithms, a TiVi-value (in arbitrary units, AU) that is linearly proportional to the local RBC concentration in the skin is calculated for each pixel. ...
The high-density microneedle array patch (HD-MAP) is a promising alternative vaccine delivery system device with broad application in disease, including SARS-CoV-2. Skin reactivity to HD-MAP applications has been extensively studied in young individuals, but not in the >65 years population, a risk group often requiring higher dose vaccines to produce protective immune responses. The primary aims of the present study were to characterise local inflammatory responses and barrier recovery to HD-MAPs in elderly skin. In twelve volunteers aged 69–84 years, HD-MAPs were applied to the forearm and deltoid regions. Measurements of transepidermal water loss (TEWL), dielectric permittivity and erythema were performed before and after HD-MAP application at t = 10 min, 30 min, 48 h, and 7 days. At all sites, TEWL (barrier damage), dielectric permittivity (superficial water);, and erythema measurements rapidly increased after HD-MAP application. After 7 days, the mean measures had recovered toward pre-application values. The fact that the degree and chronology of skin reactivity and recovery after HD-MAP was similar in elderly skin to that previously reported in younger adults suggests that the reactivity basis for physical immune enhancement observed in younger adults will also be achievable in the older population.
... The perfusion estimations provided by LDF are based in a small vascular volume, likely at a depth of around 1 mm, since contact with the skin allows the light to penetrate deeper and to access larger vessels and higher volumes of blood [38,39]. In turn, the PSp is a non-contact system using a white light with a wavelength of 633 nm and measures in a sub-epidermal area at an estimated depth of 0.5 mm, where light is scattered and absorbed primarily by the haemoglobin molecule in the red blood cells [37,40]. It is clear that PSp reads more superficial areas with smaller vessels and blood volumes. ...
Physiological perfusion asymmetries in the lower limb are known, although poorly understood, as are asymmetries reported in plantar pressure and stance. This preliminary study aims to explore potential relationships between perfusion and pressure variables in humans. A convenience sample of eight healthy individuals (25.25 ± 5.37 years old) of both sexes, was selected. Chosen variables were perfusion, plantar pressure, and stance. Perfusion was measured in both feet by laser Doppler flowmetry (LDF) and polarized light spectroscopy (PSp), and plantar pressure and stance obtained by a pressure plate. These were measured in baseline (Phase I) in a repeated squatting (Phase II), and in recovery (Phase III). A 95% confidence interval was adopted. Intraindividual significant perfusion asymmetries between both feet were detected by LDF in Phase I. These disappeared in Phase II and returned in Phase III. PSp did not detect any asymmetries. Plantar pressure was also asymmetric and differently distributed along both feet with no statistical significance except in the hindfoot. Significant correlations were found between BMI and mean Plantar Pressure in Phase I and Phase III, and an inverse correlation between LDF perfusion and Plantar Pressure in Phase I. These results seem to suggest an interesting direction for exploration and study of these asymmetries in the absence of disease.
... 2 Quantification of erythema is relatively easily achieved by non-invasive spectrophotometric techniques such as polarization spectroscopy or by use of an internal calibrator in the perfusate, but there is as yet no robust method for quantification of water in living tissue in real time. 1,3,4 Our group is developing the use of spatial frequency domain spectroscopy (SFDS) to provide real-time data on tissue water content. ...
Significance:
Tissue simulating phantoms are an important part of validating biomedical optical techniques. Tissue pathology in inflammation and oedema involves changes in both water and hemoglobin fractions.
Aim:
We present a method to create solid gelatin-based phantoms mimicking inflammation and oedema with adjustable water and hemoglobin fractions.
Approach:
One store-bought gelatin and one research grade gelatin were evaluated. Different water fractions were obtained by varying the water-to-gelatin ratio. Ferrous stabilized human hemoglobin or whole human blood was added as absorbers, and the stability and characteristics of each were compared. Intralipid® was used as the scatterer. All phantoms were characterized using spatial frequency domain spectroscopy.
Results:
The estimated water fraction varied linearly with expected values (R2 = 0.96 for the store-bought gelatin and R2 = 0.99 for the research grade gelatin). Phantoms including ferrous stabilized hemoglobin stayed stable up to one day but had methemoglobin present at day 0. The phantoms with whole blood remained stable up to 3 days using the store-bought gelatin.
Conclusions:
A range of physiological relevant water fractions was obtained for both gelatin types, with the stability of the phantoms including hemoglobin differing between the gelatin type and hemoglobin preparation. These low-cost phantoms can incorporate other water-based chromophores and be fabricated as thin sheets to form multilayered structures.
... The technique has previously been described in detail. 16 Image analysis and calculation of TiVi-values were made using Wheels- ...
Background
The high‐density microarray patch (HD‐MAP) promises to be a robust vaccination platform with clear advantages for future global societal demands for health care management. The method of action has its base not only in efficient delivery of vaccine but also in the reliable induction of a local innate physical inflammatory response to adjuvant the vaccination process. The application process needs to induce levels of reactivity, which are acceptable to the vaccine, and from which the skin promptly recovers.
Materials and methods
1 × 1 cm HD‐MAP patches containing 5000, 250‐μm long microprojections were applied to the skin in 12 healthy volunteers. The return of skin barrier function was assessed by transepidermal water loss (TEWL) and reaction to topical histamine challenge.
Results
Skin barrier recovery by 48 h was confirmed for all HD‐MAP sites by recovered resistance to the effects of topical histamine application.
Conclusions
Our previous observation, that the barrier disruption indicator TEWL returns to normal by 48 h, is supported by this paper's demonstration of return of skin resistance to topical histamine challenge in twelve healthy subjects.
... Another optical, non-invasive technique for assessing microvascular reactivity is re ectance spectroscopy [6]. The obtained signal correlates to changes in red blood cell concentration and thus indirectly re ects blood vessel diameter [7]. Thus, this better compares to the in vitro strain gauge vascular model. ...
... Vascular responses were quanti ed using polarized re ectance spectroscopy by tissue viability imaging (TiVi700 2.0 Tissue Viability Imager, WheelsBridge AB, Linköping, Sweden). The technique has previously been described in detail [7]. Image analysis and calculation of TiVivalues were made using WheelsBridge AB Software, version 1.2.20, ...
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.
... 13,14 The tissue viability (TiVi) imaging system was suggested as a low-cost alternative to estimate human microcirculation. 15 TiVi quantifies red blood cell concentration in microcirculation, while laser Doppler or laser speckle contrast imaging (LSCI) are noninvasive investigations of microcirculatory blood flow. TiVi technology is based on polarization spectroscopy measurements of light absorption by red blood cells within the red and green wavelength regions. ...
... TiVi technology is based on polarization spectroscopy measurements of light absorption by red blood cells within the red and green wavelength regions. 15,16 The system's advantages include that it can be handheld and shows lower inter-subject variability than laser Doppler flowmetry, although it seems to discriminate vasoconstriction responses better than vasodilation responses. 16,17 As for anodal stimulation using LSCI-detected CIV, this study confirms that ASA is probably the only drug associated with CIV impairment in cathodal-induced and TiVidetected CIV, since we consider that antidiabetic drug are not responsible by themselves for the CIV impairment, but only indicate the existence of underlying diabetes mellitus (and of the neurovascular dysfunction associated with this disease). ...
Background
Galvanic current-induced vasodilation (CIV) is impaired in patients under low-dose aspirin (ASA; ≤ 500 mg/day), but potential covariates and the impact of the time since the last ASA intake are unknown.
Objectives
We used tissue viability imaging (TiVi) in patients at risk of cardiovascular disease and examined its association with self-reported treatments.
Patients/Methods
We recorded the age, gender, height, weight, smoking status, and use of 14 different drug categories in 822 patients either with known peripheral artery disease or at risk thereof. The difference between TiVi arbitrary units (TAUs) where stimulation was applied and an adjacent skin area was recorded, as well as the time since the last ASA intake. Step-by-step regression analysis was used to determine the factors that affect CIV amplitude.
Results and Conclusions
CIV was 28.2 ± 22.9 vs. 14.6 ± 18.0 TAUs (p < 0.001) in patients treated with ASA (n = 287) and not treated with ASA (n = 535), respectively. The main determinants of CIV amplitude, by order of importance, were: aspirin intake, diabetes mellitus, age, and male sex. In ASA-treated patients, the main determinants were diabetes mellitus, time since the last ASA intake, male gender, and age. Non-invasive determination of the physiological effects of low-dose ASA is feasible in routine clinical practice. It could be a clinical approach to provide objective evidence of ASA intake, and potentially could be used to test adherence to treatment in ASA-treated patients.
... Trong nghiên cứu này, chúng tôi sử dụng thiết bị soi CTC sử dụng nguồn sáng phân cực. Kỹ thuật phân cực chéo giúp loại bỏ hiện tượng chóa do phản xạ từ nước, dịch nhầy trên bề mặt, ngoài ra, ánh sáng phân cực còn giúp tăng độ tương phản của hình ảnh các mô và cấu trúc của mạch máu sâu bên trong 12,13 . Hình ảnh được thu lại có độ phân giải full hd (1920 x 1080 pixels). ...
Cervical cancer is one of the two most common gynecological cancers in the world, including breast cancer. Signs of cervical disease are usually the presence of atypical epithelium, superficial bleeding or abnormal vascular proliferation. Most of these signs are directly related to cervical intraepithelial neoplasia (CIN) and cervical cancer. Currently, to detect epithelial lesions as well as to observe the shape of blood vessels, the main diagnostic methods used are colposcopy and visual examination. This method has low sensitivity and specificity because subjective factors still exist and the method does not clearly distinguish the shape of proliferating blood vessels. Therefore, in order to improve the efficiency of disease diagnosis, many studies applying image processing techniques to support auto-diagnosis have become topics of interest. However, studies that support automatic identify abnormal blood vessel shape and density are very limited. In this study, colposcopy images were recorded by digital colposcopes. These images are taken under polarized light to help reduce reflections from the surface and support for better image processing steps. Then, Sauvola threshold method is used to separate blood vessels on the surface of the cervix. It is combined with three different image preprocessing methods to enhance the contrast between the blood and the background. Finally, the sensitivity and specificity of these methods were calculated and evaluated. The results of the study set the stage for cervical blood vessel identification studies as well as cervical cancer assessment.
... The lower limbs and in particular, their extremities, are fundamental for the biomechanical and vascular stability that under normal conditions harmoniously support, all the body load in quasi-static or dynamic conditions, that is, associated or not to movement (1,2). Structural and functional variations that alter the dynamic function of the foot may predispose it to injury (3,4,5). The implications of the orthostatic variation of body positioning in the microcirculation of the lower limb and foot are known (6,7,8,9), but the influence of movement, especially of the lower limb, on the most peripheral vascular dynamics has been little explored (6,10). ...
... O membro inferior e em especial as suas porções mais distais, são fundamentais para a estabilidade biomecânica e vascular que sustenta harmoniosamente, em condições normais, toda a carga corporal em condições quasi-estáticas ou dinâmicas, associadas ou não ao movimento (1,2). Variações estruturais e funcionais que alterem a função dinâmica do pé, podem predispor a lesão (3,4,5). São conhecidas as consequências que a variação ortostática do posicionamento corporal envolvem na microcirculação do membro inferior e do pé (6,7,8,9) mas, a influência do movimento, em especial do membro inferior sobre a dinâmica vascular periférica tem sido pouco explorada (6,10). ...
... As this is an opticalbased technology, the interaction of light with tissues depends on the wavelength of the laser used and its sensitivity to detect related phenomena (21). The recent introduction of TiVi to quantify the concentration of red blood cells in more superficial areas of the skin seems to offer another assessment potential for measuring during movement (5,22,23). Hence, our exploratory study was designed to identify the dynamics of microcirculatory perfusion alteration as a function of posture. Since the first description of perfusion reduction in the leg from dorsal decubitus to the sitting position nearly 50 years ago (24), more recent studies have allowed a deeper knowledge of the impact of posture changes on the distribution of blood in the lower limb (6,7,8,9). ...
Body posture and movement seem to be responsible for multiple variations of microcirculation in the foot, although difficulties associated with measurement during movement have limited their characterization. This pilot study sought to explore a new non-invasive instrument based on polarized light spectroscopy – the TiVi system, under orthostatic and dynamic conditions. Five healthy participants (duly informed, 26.0 ± 6.5 years of age) of both genders were selected. The protocol involved sequential posture changes (orthostatic variation) and dynamic movements (squatting and unipodal flexion). Perfusion variations were evaluated in both feet by laser-Doppler flowmetry (LDF) and polarized spectroscopy (TiVi). Both systems revealed the same type of modification of these flow-related variables. The most pronounced changes were obtained with exercise, especially with squatting, which caused a marked increase in foot perfusion. Less dramatic but in the same direction, the increased perfusion with unipodal flexion was also observed in the contralateral limb. This study confirmed the interest in using the TiVi system in these domains, as well as the appropriateness of this experimental design to look deeper into the impact of lower limb movement on the functional dynamics of the foot.
Keywords: foot microcirculation, LDF, TiVi, orthostatic, symmetrical squatting, unipodal flexion.
... The laser Doppler technique has later been refined to overcome one of its shortcomings, that is, that it measures in a single Tissue Viability imaging is a technique based on a commercial digital camera that overcomes many of the aforementioned limitations of the common techniques for blood flow measurement. 13 It is a hand-held system that is easy to use and enables quick measurements. However, the calculation of red blood cell concentration from the images still requires the images to be transferred to a computer for further analysis. ...
... The inter-subject variability of SkinSight was, however, significantly lower than of TiVi, both during baseline, during post-occlusive hyperemia, and after 5 min of venous occlusion. Skin color is considered the largest source of variability between subjects with polarized light spectroscopy imaging.13 The two techniques used in this study utilize different algorithms to correct for melanin in the skin, but both are based on the fact that melanin absorbs light more or less equally for the red and green channels. ...
Background
Existing techniques for assessment of microcirculation are limited by their large size and high costs and are often not so easy to use. Advances in mobile technology have enabled great improvements in smartphone sensor technology. In this study, we used SkinSight, an app for iPhone and iPad, to measure changes in skin microcirculation during physiological provocations. The system estimates changes in the concentration of hemoglobin in the skin by analyzing the reflected light emitted from the built‐in light‐emitting diode and detected by the camera of the smartphone.
Methods
A relative hemoglobin (Hb) index was measured during a 5‐min arterial occlusion, post‐occlusive reactive hyperemia, and a 5‐min venous occlusion in 10 healthy subjects, on two separate days. The index was calculated in an area of the skin from the color information in the images acquired by the phone camera. Polarized light spectroscopy imaging was used to measure changes in red blood cell concentration for comparison.
Results
During arterial occlusion, relative Hb index was unchanged compared to baseline (P = .40). After release of the cuff, a sudden 60%‐75% increase in Hb index was observed (P < .001) followed by a gradual return to baseline. During venous occlusion, Hb index increased by 80% (P < .001) followed by a gradual decrease to baseline after reperfusion. Day‐to‐day reproducibility of the relative Hb index was excellent (ICC: 0.92, r = 0.94), although relative Hb index was consistently higher during the second day, possibly as a result of changed lighting conditions or calibration issues.
Conclusion
Microvascular responses to physiological provocations in the skin can be accurately and reproducibly measured using a smartphone application. Although the system offers a handheld, easy to use and flexible technique for skin microvascular assessment, the effects of lighting on the measured values and need for calibration need to be further investigated.
