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Accuracy of laser speckle contrast imaging in the assessment of pediatric scald wounds
Abstract
Background:
Changes in microvascular perfusion in scalds in children during the first four days, measured with laser speckle contrast imaging (LSCI), are related to the time to healing and need for surgical intervention. The aim of this study was to determine the accuracy (sensitivity and specificity) of LSCI on different days after injury in the prediction of healing outcome and if the accuracy can be improved by combining an early and a late measurement. Also, the accuracy of LSCI was compared with that of clinical assessment.
Methods:
Perfusion was measured between 0-24h and between 72-96h using LSCI in 45 children with scalds. On the same occasions, burn surgeons assessed the burns as healing <14days or healing >14days/surgery. Receiver operating characteristic (ROC) curves were constructed for the early and late measurement and for the double measurement (DM) using two different methods.
Results:
Sensitivity and specificity were 92.3% (95% CI: 64.0-99.8%) and 78.3% (95% CI: 69.9-85.3%) between 0-24h, 100% (95% CI: 84.6-100%) and 90.4% (95% CI: 83.8-94.9%) between 72-96h, and was 100% (95% CI: 59.0-100%) and 100% (95% CI: 95.1-100%) when combining the two measurements into a modified perfusion trend. Clinical assessment had an accuracy of 67%, Cohen's κ=0.23.
Conclusion:
The perfusion in scalds between 72-96h after injury, as measured using LSCI, is highly predictive of healing outcome in scalds when measured. The predictive value can be further improved by incorporating an early perfusion measurement within 24h after injury.
... Previous studies have shown that perfusion measured with laser Doppler imaging (LDI) and laser speckle contrast imaging (LSCI) on days 3-4 after injury can assist in the assessment of depth of the burn, and early identify areasthat could benefit from excision and autograft [11,12]. Whether the perfusion measured on days 3-4 is related to different outcome measures has not to our knowledge been studied previously for assessments of LSCI. ...
... Methods that can better verify the burn depth in these types of injuries have therefore been sought for several decades. Recent publications have discussed the role of LSCI in assessment of the depth of burns [17,18], and recommend its use in children with scalds [12]. Its role, however, needs validation to prove its association with outcome measures in burn care. ...
... Previous studies have investigated the association of low perfusion values measured with LSCI/LDI and the decision to operate [12,19], and they used the perfusion patterns of the skin between 72-96h after injury to predict depth of burn and outcome of healing. In short, decreased perfusion indicated increased depth. ...
Background:
Scalds are the most common type of burn injury in children, and the initial evaluation of burn depth is a problem. Early identification of deep dermal areas that need excision and grafting would save unnecessary visits and stays in hospital. Laser speckle contrast imaging (LSCI) shows promise for the evaluation of this type of burn. The aim of this study was to find out whether perfusion measured with LSCI has an influence on the decision for operation, duration of healing and care period, and costs, in children with scalds.
Methods:
We studied a group of children with scalds whose wounds were evaluated with LSCI on day 3-4 after injury during the period 2012-2015. Regression (adjustment for percentage total body surface area burned (TBSA%), age, and sex) was used to analyse the significance of associations between degree of perfusion and clinical outcome.
Results:
We studied 33 children with a mean TBSA% of 6.0 (95% CI 4.4-7.7)%. Lower perfusion values were associated with operation (area under the receiver-operating characteristic curve 0.86, 95% CI 0.73-1.00). The perfusion cut-off with 100% specificity for not undergoing an operation was ≥191 PU units (66.7% sensitivity and 72.7% accurately classified). Multivariable analyses showed that perfusion was independently associated with duration of healing and care period.
Conclusion:
Lower perfusion values, as measured with LSCI, are associated with longer healing time and longer care period. By earlier identification of burns that will be operated, perfusion measurements may further decrease the duration of care of burns in children with scalds.
... In clinical practice, repeated wound care and application of specialized burn dressings are often used during the first two weeks [1,2,5,7]. Several imaging modalities have been evaluated for their utility in burn wound assessment [4,6,[8][9][10][11]. Laser Doppler imaging is the most cited, but it lacks the ability to provide structural information of the burn wound [2,4,6]. ...
... The total body surface area (BSA) affected ranged from 2 to 35 %. The median length of hospital stay was 7 days (2-45 days), with a median of three surgical procedures/bandage changes under sedation or anesthesia (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). Wound healing was observed at a median of 12 days. ...
Objectives
Deep thermal injuries are among the most serious injuries in childhood, often resulting in scarring and functional impairment. However, accurate assessment of burn depth by clinical judgment is challenging. Optical coherence tomography (OCT) provides structural images of the skin and can detect blood flow within the papillary plexus. In this study, we determined the depth of the capillary network in healthy and thermally injured skin and compared it with clinical assessment.
Methods
In 25 children between 7 months and 15 years of age (mean age 3.5 years (SD±4.14)) with thermal injuries of the ventral thoracic wall, we determined the depth of the capillary network using OCT. Measurements were performed on healthy skin and at the center of the thermal injury (16 grade IIa, 9 grade IIb). Comparisons were made between healthy skin and thermal injury.
Results
The capillary network of the papillary plexus in healthy skin was detected at 0.33 mm (SD±0.06) from the surface. In grade IIb injuries, the depth of the capillary network was 0.36 mm (SD±0.06) and in grade IIa injuries 0.23 mm (SD±0.04) (Mann–Whitney U test: p<0.001). The overall prediction accuracy is 84 %.
Conclusions
OCT can reliably detect and differentiate the depth of the capillary network in both healthy and burned skin. In clinical IIa wounds, the capillary network appears more superficial due to the loss of the epidermis, but it is still present in the upper layer, indicating a good prognosis for spontaneous healing. In clinical grade IIb wounds, the papillary plexus was visualized deeper, which is a sign of impaired blood flow.
... The difference in perfusion is at its highest between post burn day 3À5, suggesting measurements should be done on post burn day 3À5 to predict healing outcome. Mirdell et al. [15] To evaluate accuracy in the prediction of healing outcome in burn wounds, compared to actual healing outcome (<21 days or >21 days/surgery) and clinical assessment (<14 days or >14 days/ surgery). Surgery was delayed until post burn day 14. ...
... Fundamental work was done in the first two studies [13,14] by determining perfusion differences, measurable with LSCI, which were associated with longer healing durations. Building on this work, a study by Mirdell et al. [15] reports a sensitivity of 100% and specificity of 90.4% in predicting a delayed healing time of >21 days/surgery in paediatric scalds on day 3À4 after burn, when compared to actual healing outcomes. A different, more recent study measured a cut-off value of <191 perfusion units for the decision to undergo surgery (sensitivity 66.7%, specificity 100%) [16]. ...
Objective
To assess validity of Laser Speckle Contrast Imaging (LSCI) for the measurement of burn wound healing potential (HP) in a burn centre patient population, based on Laser Doppler Imaging (LDI) as reference standard.
Method
A single-centre prospective observational cohort study was performed between September–December 2019. A total of 50 burns in 14 patients were included. Imaging and data collection were standardized. Correlation between LSCI and LDI flux values was tested. ROC curves were developed to test the discriminative ability of LSCI between LDI HP categories.
Results
Number of adults and children were equal. Mean total body surface area burnt was 5.5%. Main burn causes were scalds (64%) and flame burns (36%). LSCI set-up and imaging duration was 3 min and 10 s, respectively. LSCI was able to discriminate between wounds with early versus delayed HP (<14 versus ≥14 days) with sensitivity 71% and specificity 95% (p < 0.001). For HP ≤21 versus >21 days, similar sensitivity (74%) and specificity (95%) were found (p < 0.001). Correlations between LSCI and LDI flux values were moderate (<14 days) to absent (>21 days).
Conclusion
LSCI shows good validity for the prediction of burn wound HP. It is a highly feasible, patient and physician friendly tool.
... LDI remains the prominent tool and widely accepted for burns examination today with additional advantage of scanning wide area of up to 50 cm by 50 cm, unfortunately the cost of the equipment is high with an estimated cost of £50,000 [7][8][9], it is cumbersome, it requires high expertise to operate, it is slow where a scan takes up to 1 or 2 min. Laser speckle contrast imaging (LSCI) is a recent objective technique for measuring microcirculation non-invasively that shorten the scanning time to about 200-1000 ms compared to LDI [8,10], and less sensitive to patient movement artifacts. Despite its performance and advantages over LDI, its usage has limited application on burn evaluation and achieve accuracy of approximately 95% from day 3 after injury [10][11][12]. ...
... Laser speckle contrast imaging (LSCI) is a recent objective technique for measuring microcirculation non-invasively that shorten the scanning time to about 200-1000 ms compared to LDI [8,10], and less sensitive to patient movement artifacts. Despite its performance and advantages over LDI, its usage has limited application on burn evaluation and achieve accuracy of approximately 95% from day 3 after injury [10][11][12]. ...
Purpose
Burns depth evaluation is a lifesaving task and very challenging that requires objective techniques to accomplish. While the visual assessment is the most commonly used by surgeons, its accuracy reliability ranges between 60 and 80% and subjective that lacks any standard guideline. Currently, the only standard adjunct to clinical evaluation of burn depth is Laser Doppler Imaging (LDI) which measures microcirculation within the dermal tissue, providing the burns potential healing time which correspond to the depth of the injury achieving up to 100% accuracy. However, the use of LDI is limited due to many factors including high affordability and diagnostic costs, its accuracy is affected by movement which makes it difficult to assess paediatric patients, high level of human expertise is required to operate the device, and 100% accuracy possible after 72 h. These shortfalls necessitate the need for objective and affordable technique.
Method
In this study, we leverage the use of deep transfer learning technique using two pretrained models ResNet50 and VGG16 for the extraction of image patterns (ResFeat50 and VggFeat16) from a a burn dataset of 2080 RGB images which composed of healthy skin, first degree, second degree and third-degree burns evenly distributed. We then use One-versus-One Support Vector Machines (SVM) for multi-class prediction and was trained using 10-folds cross validation to achieve optimum trade-off between bias and variance.
Results
The proposed approach yields maximum prediction accuracy of 95.43% using ResFeat50 and 85.67% using VggFeat16 . The average recall, precision and F1-score are 95.50%, 95.50%, 95.50% and 85.75%, 86.25%, 85.75% for both ResFeat50 and VggFeat16 respectively.
Conclusion
The proposed pipeline achieved a state-of-the-art prediction accuracy and interestingly indicates that decision can be made in less than a minute whether the injury requires surgical intervention such as skin grafting or not.
... LSCI as a technique is a lot more recent and has so far only been used in a few studies with human patients [56][57][58][59][60][61]. During the last 5 years, LSCI has however received increasing attention and is now being used more and more within different areas. ...
... To summarize, current perfusion research is promising and has provided us with several methods for determining surgical need in burn wounds; but actual wound depth cannot be determined until at least 2 days have passed after injury [33,56]. It would therefore be of great interest to find reliable methods that work within the first 48 hours after injury. ...
... Laser speckle contrast imaging (LSCI) is a newer imaging system, which also measures perfusion. [5][6][7] These devices, which are expensive and mainly available in burn centers, require several days to identify burn depth with reliable accuracy. ...
... It was reported that burn sensitivity and specificity were 92.3 and 78.3%, respectively, between 0 and 24 hours, 100 and 90.4%, respectively, between 72 and 96 hours after injury, and 100% for both when combining the two measurements into a modified perfusion model. 7 This means that the method used in 7 can detect different types of burn depth only after 72 to 96 hours with the perfusion measured between 0 and 24 hours after injury. If this condition for measurement is not applicable, the combination cannot be done, and as a consequence, the classification cannot be obtained. ...
We present in this paper the application of deep convolutional neural networks, which are a state-of-the-art artificial intelligence (AI) approach in machine learning, for automated time-independent prediction of burn depth. Colour images of four types of burn depth injured in first few days, including normal skin and background, acquired by a TiVi camera were trained and tested with four pre-trained deep convolutional neural networks: VGG-16, GoogleNet, ResNet-50, and ResNet-101. In the end, the best 10-fold cross-validation results obtained from ResNet- 101 with an average, minimum, and maximum accuracy are 81.66%, 72.06% and 88.06%, respectively; and the average accuracy, sensitivity and specificity for the four different types of burn depth are 90.54%, 74.35% and 94.25%, respectively. The accuracy was compared to the clinical diagnosis obtained after the wound had healed. Hence, application of AI is very promising for prediction of burn depth and therefore can be a useful tool to help in guiding clinical decision and initial treatment of burn wounds.
... Nevertheless, in recent years advanced speckle imaging has gained popularity for superficial blood flow evaluation in animals [29][30][31][32] and in humans. [33][34][35][36] This is in concordance with its favorable clinical position compared with other methods and its potential to influence clinical practice in the future, as elaborated further in this review. ...
... 68 Studies on humans in the clinical setting that compared different burn depths evaluated by LSCI found significant perfusion differences according to the burn severity, 69 showed significant perfusion differences between superficial and deep dermal burns 51 and provided similar accuracy to LDI in burn depth estimation, an accuracy that improves even further when repeating the measurements within the first 24 hours. 36 Given that LDI is well established for burn depth assessment but infrequently employed, these 3 preliminary observational studies show that LSCI, with its short image acquisition times, possesses the diagnostic abilities and practicality to be further considered for the routine early determination of the particular course of treatment of burn injuries. ...
: Microcirculatory integrity and proper function are the cornerstones to tissue nourishment and viability. In the clinical environment extended immobility, injuries, and inflammatory reactions demand local microcirculatory adaption to provide adequate supply. Assessment of endothelial adjustment capability and microcirculatory perfusion status, as direct or surrogate markers of disease, are therefore of uttermost interest to the treating physician. Given the simple, noninvasive, nonradiating nature of laser-based techniques for bedside or intraoperative microcirculatory perfusion assessment, this article's objective is to present a comprehensive overview of available techniques, their technological aspects, and current application. Advantages of individual methods are pointed out and compared with each other. The areas of medical utilization relevant to orthopedics and trauma surgery are exemplified and their available evidence elaborated. A particular focus is put on laser speckle contrast imaging, with its current and future influence on medical practice.
... The exploratory analysis performed herein opens new fields for research in microcirculation. First, although LSCI is an experimental device, its use in clinical practice is safe and reliable (Mirdell et al. 2018;Ruaro et al. 2017, Ruaro et al. 2015. Compared to laser Doppler and videomicroscopy, LSCI offers better two-dimensional spatial resolution and lower spatial variability, and allows the use of a wide variety of microcirculatory reactivity tests Cracowski 2013, Roustit andCracowski 2012). ...
Background
Up to 42% of patients develop acute kidney injury (AKI) after cardiac surgery. The aim of this study was to describe the relationship between preoperative microcirculatory function and postoperative AKI after cardiac surgery using cardiopulmonary bypass (CPB).
Methods
The prospective observational cohort MONS enrolled 60 patients scheduled for valvular (n = 30, 50%) or coronary (n = 30, 50%) surgery using CPB. Preoperative microcirculation was assessed during preoperative consultation from January 2019 to April 2019 at the University Hospital of Angers, France, using endothelium-dependent and endothelium-independent reactivity tests on the forearm (iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP), respectively). Skin blood flow was measured by laser speckle contrast imaging. The primary endpoint was the occurrence of AKI according to the KDIGO classification during the hospital stay.
Results
Forty-three (71.7%) patients developed AKI during the in-hospital follow-up, and 15 (25%) were classified as KDIGO stage 1, 20 (33%) KDIGO stage 2, and 8 (13%) KDIGO stage 3. Regarding preoperative microcirculation, a higher peak amplitude of vasodilation in response to iontophoresis of ACh was found in patients with postoperative occurrence of AKI (35 [20–49] vs 23 [9–44] LSPU, p = 0.04). Iontophoresis of SNP was not significantly different according to AKI occurrence (34 [22–49] vs 36 [20–50] LSPU, p = 0.95). In a multivariable model, the preoperative peak amplitude at iontophoresis of ACh was independently associated with postoperative AKI (OR 1.045 [1.001–1.092], p = 0.045).
Conclusions
The preoperative peak amplitude of endothelium-dependent vasodilation is independently associated with the postoperative occurrence of AKI.
Trial registration
Clinical-Trials.gov, NCT03631797. Registered 15 August 2018, https://clinicaltrials.gov/ct2/show/NCT03631797
... 19 In 2019, Mirdell et al. used LSI to assess wounds at various times post-injury in 45 paediatric burn patients and predict healing outcomes, with results showing sensitivities and specificities of 92.3% and 78.3% within 0-24 h, and 100% and 90.4% within 72-96 h, respectively. 20 Notably, the team also demonstrated that medical personnel with different clinical experience in burns had no difference in assessing burn depth using LSI, suggesting that introducing LSI measurement could improve the accuracy of early assessment of burn depth. 21 Additionally, Zheng et al. confirmed through research on 14 adult and paediatric burn patients that LSI can accurately predict wound healing time, making it an effective tool for assessing burn wounds. ...
Currently, the clinical diagnosis of burn depth primarily relies on physicians' judgements based on patients' symptoms and physical signs, particularly the morphological characteristics of the wound. This method highly depends on individual doctors' clinical experience, proving challenging for less experienced or primary care physicians, with results often varying from one practitioner to another. Therefore, scholars have been exploring an objective and quantitative auxiliary examination technique to enhance the accuracy and consistency of burn depth diagnosis. Non‐invasive medical imaging technology, with its significant advantages in examining tissue surface morphology, blood flow in deep and changes in structure and composition, has become a hot topic in burn diagnostic technology research in recent years. This paper reviews various non‐invasive medical imaging technologies that have shown potential in burn depth diagnosis. These technologies are summarized and synthesized in terms of imaging principles, current research status, advantages and limitations, aiming to provide a reference for clinical application or research for burn specialists.
... Many applications of the LASCA involved measurements on skin in relation to diseases and burns. [7][8][9][10] The application of polarizing optics can reduce the surface scattering 11 and even make possible the imaging of skin microvascularization. 12 However, in addition to the dynamic light scattering of the moving red blood cells (RBC), there is an intense volume scattering from the stationary components, which causes the asymptotic contrast value for long exposure time [Kð∞Þ] to be much larger than zero. Since static scattering adversely affects the accuracy of data evaluation based on Eq. (1), several methods have been proposed to address this issue, which have significantly reduced the discrepancy between the results obtained on tissue phantoms consisting of microsphere emulsions covered with various scattering layers. ...
Significance
Application of multiexposure speckle contrast imaging (MESI) methods for perfusion measurements can correct for the contribution of static scattering of the skin, at the expense of reduced temporal resolution as compared to classical single-exposure methods. Persistence of tissue scattering properties during the measurements could allow for an initial calibration and enhancement of the temporal resolution of the measurements.
Aim
We aim to study the influence of the perfusion on the light scattering of the forearm skin and to use the obtained data for the enhancement of the temporal resolution.
Approach
A wide range of skin perfusion states was induced while monitoring the changes in the dynamic range of the exposure-dependent contrast. Different measurement and evaluation methods were tested based on an initial MESI calibration followed by image recording with reduced number of exposure time values.
Results
The changes in the skin perfusion can alter not only the contribution of the static scattering to the speckle images but also the short-exposure time contrast limit.
Conclusions
The perfusion-dependent scattering of the skin can invalidate the precalibrations (e.g., β calibration) characterizing the combination of the given tissue and the measurement system.
... LSCIs have been widely used in various clinical applications, such as diagnosis of keloids classification, [5][6][7][8][9] burn evaluation, [10][11][12][13] observation of microcirculation following treatment, [14][15][16][17] robot-assisted surgery, 18 intraoperative cerebral blood flow monitoring, [19][20][21] surgery monitoring, [22][23][24][25] reperfusion evaluation after tissue transplantation, 26,27 prediction of tissue necrosis risk, [28][29][30] and reperfusion evaluation after oral wound healing. 31,32 To ensure accurate measurement in the region of interest, the imaging region of interest (IROI) must be matched with the LSCI displayed on the monitor screen, which may be time-consuming due to potential spatial mismatching between the IROI and the monitor screen. ...
Significance:
Laser speckle contrast images (LSCIs) have been utilized to monitor blood flow perfusion. However, they have conventionally been observed on monitor screens, resulting in potential spatial mismatching between the imaging region of interest (IROI) and monitor screen.
Aim:
This study proposes a projection mapping (PM) system for LSCIs (PMS_LSCI) that projects LSCIs to directly observe the blood flow perfusion in the IROI.
Approach:
The PMS_LSCI consists of a camera, imaging optics, a laser projector, and graphic user interface software. The spatial matching in the regions of interest was performed by adjusting the software screen of the LSCI in the IROI and evaluated by conducting in-vitro and in-vivo studies. An additional in-vivo study was performed to investigate the feasibility of real-time PM of the LSCI.
Results:
The spatial mismatching in the regions of interest was ranged from 2.74% to 6.47% depending on the surface curvature. The PMS_LSCI could enable real-time PM of LSCI at four different blood flow states depending on blood pressure.
Conclusions:
The PMS_LSCI projects the LSCI in the IROI by interacting with a projector instead of the monitor screen. The PMS_LSCI presented clinical feasibility in the in-vitro and in-vivo studies.
... Moreover, LSCI was implemented for monitoring of skin burn healing process [116]. A number of articles describes the LSCI use for children scald wound healing monitoring [117]- [119]. In particular, it was shown that LSCI allows one to estimate the scald wound depth [120]. ...
Laser speckle contrast imaging is a modern technique uniquely suited for the full-field, noninvasive measurement of the motion of particles within randomly inhomogeneous highly scattering and absorbing media, including biological tissues. This technique is based on illuminating the medium with a coherent laser light, detecting the arising speckle pattern and further statistical analysis of the speckle pattern fluctuations caused by the motion of the scattering particles in the observed medium. Despite the active use of laser speckle contrast imaging for biomedical applications, this technique suffers from several issues complicating the understanding of obtained speckle contrast data. The present work is aimed at the investigation of limitations, improving, and discovering new potentials of currently existing methods of laser speckle contrast imaging. In particular, the influence of effects of non-ergodicity on the results of speckle contrast analysis was investigated using the phantom and animal models. It was shown that the presence of a thin static layer above the dynamic layer does not introduce significant errors in speckle contrast calculation. The simple approach for the adjustment of speckle contrast values in different types of brain vasculature during transcranial visualisation was introduced. For the first time, the protocol for the monitoring of skin acute vascular permeability reaction in response to simultaneous application of tree different chemical substances has been described. Moreover, in a new approach, the optical setup combining a hyperspectral camera and multi-wavelength light source was implemented for the depth-resolved blood flow and perfusion assessment. The proposed technique was applied for skin perfusion monitoring. Finally, the unprecedented use of laser speckle contrast imaging was
introduced for handwriting pressure and kinematics evaluation.
... They recommended that all modern specialist burn centers should rely on speckle-based techniques for a more accurate assessment of wound depth and healing time. The use of LSCI for burns is far less common, although the same accuracy as LDPI has been demonstrated (compare [42] and [43]). Recently, it was also demonstrated that analysing the perfusion pulsatility in the burn wound greatly increased the predictive value for the healing potential [44]. ...
The microcirculation, the blood flow in the smallest blood vessels in the body, has a vital function as this is where oxygen and nutrients diffuses from the blood to to the surrounding cells. An important quantity is the tissue perfusion, a measure of the microcirculation’s capacity to provide oxygen and nutrients to the cells. Laser speckle contrast imaging (LSCI) is a non-invasive optical technique that captures images of the microcirculatory perfusion by analysing the local contrast in the laser speckle pattern that forms when tissue is illuminated by a laser. LSCI has seen extensive use in clinical research due to the easy and cheap measurement setup, and high spatial and temporal resolution. Despite this, clinical acceptance and routine use remains low. Some of the drawbacks of the technique is a limitation to relative measurements in arbitrary units, as well as high susceptibility to measurement noise and confounding properties of the tissue. This makes comparisons difficult, especially between patients. An extension of LSCI called multi-exposure laser speckle contrast imaging (MELSCI) was proposed to deal with some of these issues, although the more complicated data acquisition and models prevented real-time use. MELSCI has in-stead been used exclusively as an offline technique where data is post-processed, and the clinical use has been non-existent. Furthermore, existing models for LSCI and MELSCI are designed for tissues where individual vessels are visible, such as the surface of the brain or on the retina. For measurements in the diffuse regime, such as on skin tissue, these models are no longer physiologically accurate, resulting in incorrect perfusion estimates.
This thesis presents a MELSCI-based perfusion imaging instrument that is simultaneously fast and physiologically accurate for measurements of skin. There are three main parts to this work; development of a real-time MELSCI system, development of perfusion models for skin, and demonstration of the system in a clinical feasibility study.
A real-time MELSCI instrument was developed based on a high-speed CMOS camera tightly integrated with algorithms in a field programmable gate array (FPGA). The algorithm was based on synthetic multi-exposure, where a set of 64 individual 1-ms images were digitally added to create multi-exposure images at 1, 2, 4, 8, 16, 32, and 64 ms. The resulting multi-exposure data was demonstrated to have high quality and less susceptibility to measurement noise than previous models. The instrument enabled continuous acquisition and analysis of MELSCI data in real-time at 15.6 frames per second, sufficiently fast to capture the temporal dynamics of the skin perfusion.
To enable real-time estimation of accurate and physiologically relevant perfusion from the MELSCI data, two artificial neural networks were trained on synthetic data from a mathematical model of skin. The first estimated perfusion as computed by conventional laser Doppler flowmetry (LDF), demonstrating a high correlation between the two methods. The second estimated true perfusion in absolute units %RBC × mm/s separated into three distinct speed components, 0-1 mm/s, 1-10 mm/s and >10 mm/s. The ANNs removed the need for iterative optimization algorithms, resulting in more than 1000x speed-up over previous methods, and enabled real-time use in an imaging setting.
The instrument was demonstrated in controlled experiments on healthy volunteers, using standardized occlusion-release provocations, and in a clinical feasibility study where the foot perfusion was monitored during endovascular interventions in patients with chronic limb-threatening ischemia. The instrument enabled continuous imaging of perfusion, with sufficiently high framerate to capture the pulsatile dynamics, or lack thereof, at each point in time. The necessity for both high spatial and temporal resolution to properly asses the microcirculation was demonstrated.
The advancements to MELSCI proposed in this thesis has the potential to improve the clinical viability of the technique, increase interpretability of the results, and might lead to improved treatments based on a better understanding of the complex processes in the microcirculation.
... Laser speckle contrast imaging (LSCI) has been broadly applied to visualize blood flow imaging in living tissues, such as the retina [1][2][3][4], skin [5][6][7][8][9], and brain [10][11][12][13][14][15][16] since it was first introduced in the 1980s [1]. It can monitor the dynamic blood flow response and relative changes in values. ...
Laser speckle imaging has been an indispensable tool for visualizing blood flow in biomedical applications. We proposed a novel design of the laser speckle imaging system, which combines confocal illumination and detection with various speckle analysis methods. The system can be operated by three imaging modes. One is surface illumination laser speckle contrast imaging (SI-LSCI) and the other two are line scan temporal speckle contrast imaging (LS-TSCI) and line scan spatial speckle contrast imaging (LS-SSCI). The experimental results of flow phantoms have validated the mixture model, which combines the Lorentzian and Gaussian models to describe the simultaneous existence of both Brownian motions and ordered flow. Our experimental results of in vivo chick embryos demonstrate that LS-SSCI maintains high temporal resolution and is less affected by motion artifacts. LS-SSCI can provide better image quality for in vivo imaging blood chick embryos than LS-TSCI. Furthermore, the experiential results present that LS-SSCI can detect and quantify the blood flow change during vascular clipping, and shows great potential in diagnosing vascular diseases, such as angiosclerosis, angiostenosis, or angiemphraxis.
... For all these reasons, an objective, fast, automatic, and possibly cheap way to evaluate burn wounds is highly needed. Normally, burn centres evaluate burn wounds using laser doppler imaging (LDI) [51] or laser speckle contrast imaging (LSCI) [57,65,66]. Both methods return accurate measurements for the diagnosis, but they require some time and quite expensive equipment, which not many hospitals are equipped with. ...
... Laser speckle contrast imaging (LSCI) is a noninvasive technique that has proven especially useful in clinical perfusion monitoring of free flaps, burns, and medium to large flap transfer in reconstructive surgery. [9][10][11] In the present study, the authors used LSCI for intraoperative and postoperative perfusion monitoring in glabellar flap reconstruction in 7 patients following tumor excision in the medial canthal area. Improved knowledge of the perfusion and reperfusion of the flap may help reduce the risk of complications such as partial flap necrosis and poor cosmetic outcome. ...
Background:
The glabellar flap is a common technique for surgical repair after tumor excision in the medial canthal area. However, the outcome may be affected by partial flap necrosis. Little is known about the impact of surgery on blood perfusion and the postoperative course of reperfusion due to the absence of reliable and noninvasive perfusion monitoring techniques. The aim of this study was to use a modern imaging technique to assess blood perfusion in glabellar flaps.
Methods:
Glabellar flaps were used to repair medial canthal defects following tumor excision in 7 patients. Blood perfusion was monitored using laser speckle contrast imaging: during surgery, immediately postoperatively (0 weeks), and at follow-up, 1, 3, and 6 weeks after surgery.
Results:
Perfusion decreased gradually along the length of the flap, and reached a minimum 15 mm from the flap base. Perfusion in the proximal 20 mm of the flap was completely restored after 1 week, while the distal part of the flap was gradually reperfused over 6 weeks. Both the functional and esthetic surgical outcomes were excellent.
Conclusions:
The rapid reperfusion of the glabellar flap may be explained by its connection to the vascular network via the flap pedicle. In flaps longer than 20 mm, the distal part can be considered a free skin transplant, and a combination of a glabellar flap and a free skin graft could then be considered.
... Laser speckle contrast imaging (LSCI) is first introduced in the 1980s, is a powerful tool for imaging blood flow in tissue [6]. LSCI has been widely used to image blood flow in the brain [7][8][9][10][11][12][13], skin [14][15][16][17][18], retina [19][20][21] and other organs. Recent developments on the theoretical models, instrumentation, and biomedical applications of LSCI have been reviewed [22][23][24][25][26]. Liu et al. [27] proposed an alternative model that allows measuring blood flow changes with higher accuracy based on these observations and guided by the experimental results. ...
... LASCA became popular as it is contact-free, cheap, fast, and able to accomplish real-time large area investigations [2]. Most applications of LASCA involve measurements on the skin in order to study, e.g., arterial diseases [3], burn injuries [4,5], or scald wounds [6]. In the evaluation of the dynamic light scattering data obtained from the moving red blood cells, the additional intense scattering from the stationary components has a detrimental effect on the measurement accuracy, resulting in even orders of magnitude shift in the calculated data depending on the actual structure of the skin. ...
Static scattering is detrimental to the accuracy of laser speckle contrast analysis (LASCA) measurements on skin when, instead of percentile change monitoring, absolute perfusion values are needed, e.g., for tissue injury examination. Perfusion values were calculated using two evaluation models, while changing the dynamic/static scattering ratio of monitored skin and tissue phantoms. Results were strongly affected by the significant increase of static contribution. Measurements on a modified tissue phantom showed that the changes in the measured perfusion values were mostly caused by the mixed scattering, which was omitted by the tested models. Dynamic ratio values obtained by multi-exposure LASCA could be used for perfusion data correction.
... A number of other techniques, however, such as laser speckle contrast imaging (LSCI) and laser doppler flowmetry (LDF) have been commercialized and subsequently used to assess burn-damaged skin. Such techniques utilize blood flow as the primary source of information, and in doing so, have revealed abnormal blood perfusion patterns in burn-damaged skin [7][8][9]. Whilst LSCI and LDF have provided invaluable, noninvasive, real-time evalua-tions, their limited resolutions make it difficult to visualize individual vasculature and thusly quantify depth information. Moreover, neither of these modalities can provide structural information alongside perfusion, let alone provide all-important insights into structural alterations at a cellular level. ...
Background and Objectives
There remains a need to objectively monitor burn wound healing within a clinical setting, and optical coherence tomography (OCT) is proving itself one of the ideal modalities for just such a use. The aim of this study is to utilize the noninvasive and multipurpose capabilities of OCT, along with its cellular‐level resolution, to demonstrate the application of optical attenuation coefficient (OAC), as derived from OCT data, to facilitate the automatic digital segmentation of the epidermis from scan images and to work as an objective indicator for burn wound healing assessment.
Study Design/Materials and Methods
A simple, yet efficient, method was used to estimate OAC from OCT images taken over multiple time points following acute burn injury. This method enhanced dermal–epidermal junction (DEJ) contrast, which facilitated the automatic segmentation of the epidermis for subsequent thickness measurements. In addition, we also measured and compared the average OAC of the dermis within said burns for correlative purposes.
Results
Compared with unaltered OCT maps, enhanced DEJ contrast was shown in OAC maps, both from single A‐lines and completed B‐frames. En face epidermal thickness and dermal OAC maps both demonstrated significant changes between imaging sessions following burn injury, such as a loss of epidermal texture and decreased OAC. Quantitative analysis also showed that OAC of acute burned skin decreased below that of healthy skin following injury.
Conclusions
Our study has demonstrated that the OAC estimated from OCT data can be used to enhance imaging contrast to facilitate the automatic segmentation of the epidermal layer, as well as help elucidate our understanding of the pathological changes that occur in human skin when exposed to acute burn injury, which could serve as an objective indicator of skin injury and healing.
... In this study, we therefore used LSCI to measure changes in microcirculation in the skin after CTO-PCI. This technique is already clinically used for the assessment of skin burns, where changes in skin perfusion during the first week after the injury accurately predict the healing time of the wound (17) . ...
Skin injuries may occur when radiation doses to the skin exceed 2 Gy. This study aimed to measure changes in skin microcirculation in patients undergoing chronic total occlusion percutaneous coronary interventions (CTO-PCI). In 14 patients, peak skin dose (PSD) was estimated with radiographic films and skin microcirculation was assessed with laser speckle contrast imaging (LSCI), before, 1 day after the intervention, and 4-6 weeks later. The mean PSD was 1.8 ± 0.9 Gy. Peak skin microcirculation increased by 12% from 45 ± 6 PU before to 50 ± 9 PU 1 day after the intervention (p = 0.01), and returned to 46 ± 8 PU after 4-6 weeks (p = 0.15). There was no significant correlation between PSD and the change in perfusion, neither 1 day (r = -0.13, p = 0.69) nor 4-6 weeks after the intervention (r = 0.33, p = 0.35). These results suggest that there are no radiation-induced microvascular changes in the skin after CTO-PCI at skin doses below 2 Gy.
... These results are concordant with the potential value of using iontophoresis of ACh to identify of a preoperative microcirculatory frailty state in patients with some chronic diseases. In clinical practice, LSCI is recognized as an excellent tool to estimate burn depth and its value in predicting the healing capacity of a burn wound is well established [28]. LSCI is also useful for classification and follow-up of systemic sclerosis [29,30]. ...
Background
Cardiac surgery is known to induce acute endothelial dysfunction, which may be central to the pathophysiology of postoperative complications. Preoperative endothelial dysfunction could also be implicated in the pathophysiology of postoperative complications after cardiac surgery. However, the relationship between preoperative endothelial function and postoperative outcomes remains unknown. The primary objective was to describe the relationship between a preoperative microcirculatory dysfunction identified by iontophoresis of acetylcholine (ACh), and postoperative organ injury in patients scheduled for cardiac surgery using cardiopulmonary bypass (CPB).
Methods
Sixty patients undergoing elective cardiac surgery using CPB were included in the analysis of a prospective, observational, single-center cohort study conducted from January to April 2019. Preoperative microcirculation was assessed with reactivity tests on the forearm (iontophoresis of ACh and nitroprusside). Skin blood flow was measured by laser speckle contrast imaging. Postoperative organ injury, the primary outcome, was defined as a Sequential Organ Failure Assessment score (SOFA) 48 h after surgery greater than 3.
Results
Organ injury at 48 h occurred in 29 cases (48.3%). Patients with postoperative organ injury (SOFA score > 3 at 48 h) had a longer time to reach the peak of preoperative iontophoresis of acetylcholine (133 s [104–156] vs 98 s [76–139] than patients without, P = 0.016), whereas endothelium-independent vasodilation to nitroprusside was similar in both groups. Beyond the proposed threshold of 105 s for time to reach the peak of preoperative endothelium-dependent vasodilation, three times more patients presented organ dysfunction at 48 h (76% vs 24% below or equal 105 s). In multivariable model, the time to reach the peak during iontophoresis of acetylcholine was an independent predictor of postoperative organ injury (odds ratio = 4.81, 95% confidence interval [1.16–19.94]; P = 0.030).
Conclusions
Patients who postoperatively developed organ injury (SOFA score > 3 at 48 h) had preoperatively a longer time to reach the peak of endothelium-dependent vasodilation.
Trial registration Clinical-Trials.gov, NCT03631797. Registered 15 August 2018, https://clinicaltrials.gov/ct2/show/NCT03631797
... *p < 0.05, **p < 0.01, ***p < 0.001. [9,12,13,43,44]. Here we show that, in the absence of VTE, EV TF activity negatively correlated with lag time, which is consistent with the role of TF in the initiation phase of TG. ...
Background
Pancreatic ductal adenocarcinoma (PDAC) is associated with a hypercoagulable state and high mortality. Increases in the plasma levels of tumor marker carbohydrate antigen (CA) 19-9 are used in diagnosis and follow-up but have also been reported to precede venous thromboembolism (VTE).
Aims
We examined the association between CA 19-9 and thrombin generation (TG) in plasma from PDAC patients, as well as their association with coagulation biomarkers prior to pancreatic surgery. In addition, we determined the effect of commercial sources of CA 19-9 on TG.
Methods
We collected plasma from 58 treatment-naïve PDAC patients without any signs of VTE. We measured levels of CA 19-9, FVIII, fibrinogen, D-dimer, antithrombin and extracellular vesicle (EV) tissue factor (TF) activity and TG using a Calibrated Automated Thrombogram (CAT). The effect of different commercial sources of CA 19-9 on TG in Standard Human Plasma (SHP) was also studied.
Results
Patient plasma samples were divided into 4 preoperative groups based on the level of CA 19-9: none<2, low=3-200, high=201-1000, and very high>1000 U/mL. CA 19-9 levels were associated with several of the TG parameters, including endogenous thrombin potential, peak, and time to peak. CA 19-9 did not associate with any of the coagulation biomarkers. Spiking of SHP with CA 19-9 increased TG but this was decreased by an anti-TF antibody.
Conclusions
CA 19-9 was associated with TG in patients prior to any pancreatic cancer treatments or signs of VTE. Some commercial sources of CA 19-9 enhanced TG in SHP seemingly due to contaminating TF.
... Laser speckle contrast imaging (LSCI) is a wild-field and noninvasive method for the observation of dynamic motion in biological tissue with spatial and temporal resolutions [1,2]. LSCI is able to quantify blood flow in various biological applications such as cerebral blood flow [3,4], skin [5,6], diabetes [7,8], and burn wounds [9,10]. The cause of speckle variance is due to the intensity variation induced by the moving particles in biological tissue and coherent light [11,12]. ...
Laser speckle contrast imaging (LSCI) can be used to observe dynamic changes in the tissue microcirculation in vivo according to the dynamic interaction between red blood cells and coherent light. In this study, a dual-wavelength LSCI system based on a microscope was developed for in vivo observation of the microvascular pattern and measurement of the blood flow change in the animal model. Additionally, based on the dual-wavelength setup, including 635 and 855 nm wavelengths, the oxygenation of biological tissue was evaluated. Finally, the developed LSCI microscope was implemented for the studies of tissue microcirculation. The results indicate that the developed LSCI microscope could be a potential tool for in vivo observation of the tissue microcirculation and quantitative evaluation of hemodynamics in animal experiments.
... The technique relies on the scattering of coherent laser light by moving particles in the illuminated tissue, forming a speckle pattern that contains information on the concentration and speed of the moving particles, i.e., blood cells. 5 Laser speckle contrast imaging has been used in studies of microvascular blood perfusion in plastic reconstructive procedures, 6-8 burns, 9 and wound healing 10 to gain deeper knowledge on blood perfusion and the healing process. It has also been used to detect systemic microvascular dysfunction in several vascular pathologies, 11 including Alzheimer's disease, schizophrenia, hypertension, renal disease, diabetes, peripheral vascular disease, atherosclerotic coronary artery disease, heart failure, and systemic sclerosis. ...
Background:
H-plasty reconstructive surgery is commonly used to close defects after tumor excision in the periorbital region. Revascularization of the bipedicle skin flaps is essential for healing. However, it has not previously been possible to study this revascularization in humans due to the lack of noninvasive perfusion monitoring techniques. The aim was to monitor perfusion in H-plasty flaps during surgery and during postoperative follow-up, using laser speckle contrast imaging.
Method:
H-plasty, i.e., bipedicle random advancement skin flaps, was used for reconstruction of the eyelids after tumor removal in 7 patients. The median length and width of the skin flaps were 13 mm (range, 8-20 mm) and 10 mm (range, 5-11 mm), respectively. Blood perfusion was measured using laser speckle contrast imaging during surgery and at follow up 1, 3, and 6 weeks postoperatively, to monitor revascularization.
Results:
Immediately postoperatively, the perfusion in the distal end of the flaps had fallen to 54% (95% CI, 38%-67%). The perfusion then quickly increased during the healing process, being 104% (86%-124%) after 1 week, 115% (94%-129%) after 3 weeks, and 112% (96%-137%) after 6 weeks. There was no clinically observable ischemia or tissue necrosis.
Conclusions:
Revascularization of the H-plasty procedure flaps occurs quickly, within a week postoperatively, presumably due to the existing vascular network of the flap pedicle, and was not dependent on significant angiogenesis. This perfusion study confirms the general opinion that H-plasty is a good reconstructive technique, especially in the periorbital region with its rich vascular supply.
... LSCI has become a valuable and powerful tool to investigate the fast change in microcirculation blood flow because of safety, wide measurement range, good reliability, high stability, and strong practicability. [34][35][36][37] Patient populations, such as those with peripheral vascular disease, those receiving vasodilator drugs prior to surgery, or those with infected toenails might have altered the BFI values 11 and thus require separate determination. ...
Background: Laser speckle contrast imaging (LSCI) is a powerful optical imaging technique for real-time and dynamic measurement of regional blood flow. The objective of this prospective observational study was to investigate blood flow changes after blockade of lumbar plexus or its three major branches respectively, with LSCI technique. Methods: This study included 47 adult patients scheduled for elective lower limb surgery. For the selective blockade of lumbar plexus, femoral nerve, obturator nerve, and lateral femoral cutaneous nerve, blood flow images and pinprick sensory scores of the blocked lower limb were recorded 5 min pre block and every 5 min for 30 min post block. Blood flow index (BFI) values of toes were calculated by LSCI software. Results: In this study, we have 21 cases of successful lumbar plexus blocks, 2 cases of failed lumbar plexus block, 8 cases of successful femoral nerve blocks, 8 cases of successful obturator nerve blocks, and 8 cases of successful lateral femoral cutaneous nerve blocks. The BFI values of all five toes were significantly increased as early as 5 min after successful lumbar plexus block, whereas no significant difference was found in BFI values after failed lumbar plexus block. BFI changes after successful selective blockade of femoral nerve, obturator nerve, or lateral femoral cutaneous nerve were negligible. BFI value of the big toe at 5 min after the successful lumbar plexus block was increased by 2.57 fold compared with the baseline value, which represented the highest increase among five tested toes. BFI value of the big toe at 10 min after lumbar plexus block showed great power to predict block outcome with a sensitivity of 100% and a specificity of 100%. The optimal cut-off value given by ROC analysis was 22.11 PU. Conclusions: Increased blood flow index measured by laser speckle contrast imaging is a reliable indicator of successful lumbar plexus block, but cannot indicate successful selective blocks of three major branches of the lumbar plexus. BFI value of the big toe at 10 min after lumbar plexus block could well predict block outcome with the cut-off value of 22.11 PU.
... Previous studies using LSCI in children examined skin blood flow related to wound healing and scaling injuries (Lindahl et al., 2013;Mirdell et al., 2018;Mirdell et al., 2016). No work has used LSCI in healthy children, nor has it been compared with the more commonly used laser-Doppler technique. ...
Objective:
We compare microvascular reactivity assessed by laser-Doppler fluxmetry (LDF) and laser speckle contrast imaging (LSCI) of boys and men during rest, post-occlusive reactive hyperaemia (PORH), and cycling exercise.
Methods:
19 boys (9 ± 1 y) and 18 men (22 ± 2 y) participated. LDF and LSCI measures were taken of the forearm during rest, PORH, and exercise.
Results:
For all 3 assessments, the LSCI presented with higher flux values than the LDF for both boys and men (p < 0.001). Bland-Altman analyses indicated that there was a positive linear bias between LSCI and LDF measurements in both boys and men. Regression analyses showed that the responses for the two methods were variable, depending on the particular assessment. For instance, at rest in boys there was no relationship between LDF and LSCI (r2 = 0.002), while in men there was a strong relationship (r2 = 0.86).
Conclusions:
LSCI presented with higher values than LDF during rest, PORH, and exercise; the disparity between the two measures was larger as blood flow increased. The assessments were generally consistent, both methods appear to provide usable data for the assessment of microvascular reactivity in both boys and men. There are biases to each method and the data are not interchangeable between LDF and LSCI.
... Depth of burn and TBSA% were assessed clinically by different burn surgeons, which risks it not being done in a standardised way. Future studies should involve the consistent use of objective assessments, such as laser speckle contrast imaging (LSCI), which is already in use for research at our centre [51][52][53], or software programs such as BurnCase 3D, which enables more objective calculations of TBSA from digital images [54] to improve diagnostic precision and comparability of groups. We have previously used wound tracing as a part of the assessments of the time to complete healing [10], and the use of the Visitrak 1 system has often been suggested by other authors. ...
Aim:
Our aim was to compare two different regimens for the treatment of children with partial-thickness scalds. These were treated with either a porcine xenograft (EZderm®, Mölnlycke Health Care, Gothenburg, Sweden) or a silver-foam dressing (Mepilex® Ag, Mölnlycke Health Care, Gothenburg, Sweden).
Methods:
We organised a prospective randomised clinical trial that included 58 children admitted between May 2015 and May 2018 with partial-thickness scalds to The Burn Centre in Linkoping, Sweden. The primary outcome was time to healing. Secondary outcomes were pain, need for operation, wound infection, duration of hospital stay, changes of dressings, and time taken.
Results:
The patients treated with silver-foam dressing had a significantly shorter healing time. The median time to 97% healing for this group was 9 (7-23) days compared to 15 (9-29) days in the porcine xenograft group (p = 0.004). The median time to complete healing for the silver-foam group was 15 (9-29) days and for the porcine xenograft group 20.5 (11-42) days (p = 0.010). Pain, wound infection, duration of hospital stay, and the proportion of operations were similar between the groups. Number of dressing changes and time for dressing changes were lower in the silver-foam dressing group (p = 0.03 for both variables).
Conclusions:
We compared two different treatments for children with partial-thickness scalds, and the data indicate that wound healing was faster, fewer dressing changes were needed, and dressing times were shorter in the silver-foam group.
... For instance for skin one can expect n = 0.5 or mixed dynamics everywhere (see Supplemental Fig.11), meaning that current applications of LSCI for imaging the skin are underestimating flow changes. It should be expected that clinical applications such as diagnosis of skin burns 47 will be strongly affected, as well applications imaging the kidney 33, 48 and liver 49 . For imaging large retinal vessels, single scattering and ordered motion (i.e. ...
Utilizing a high-speed camera and recording back-scattered laser light at more than 20,000 frames per second, we introduce the first wide-field dynamic laser speckle imaging (DLSI) in which we are able to quantify the laser speckle intensity temporal auto-correlation function g 2 (τ) for every pixel individually to obtain a quantitative image of the dynamics of the light scattering particles in the sample. The ability to directly and quantitatively measure the intensity auto-correlation function allows us to solve the problem of how to quantitatively interpret data measured by laser speckle contrast imaging (LSCI), multi-exposure laser speckle imaging (MESI) and laser Doppler flowmetry (LDF). The intensity auto-correlation function is related to the field temporal auto-correlation function g 1 (τ), which has been quantitatively related to the dynamics of the light scattering particles including flowing red blood cells. The form of g 1 (τ) depends on the amount of light scattering (i.e. single or multiple scattering) and the type of particle motion (i.e. ordered or unordered). Although these forms of the field correlation functions have been established for over 30 years, there is no agreement nor experimental support on what scattering and motion regimes are relevant for the varied biomedical applications. We thus apply DLSI to image cerebral blood flow in mouse through a cranial window and show that the generally accepted form of g 1 (τ), is applicable only to visible surface vessels of a specific size (20-200 micrometers). We demonstrate that for flow in smaller vessels and in parenchymal regions that the proper g 1 (τ) form corresponds with multiple scattering light and unordered motion which was never considered to be relevant for these techniques. We show that the wrong assumption for the field auto-correlation model results in a severe underestimation of flow changes when measuring blood flow changes during ischemic stroke. Finally, we describe how DLSI can be integrated with other laser speckle methods to guide model selection, or how it can be used by itself as a quantitative blood flow imaging technique.
... For instance for skin one can expect n = 0.5 or mixed dynamics everywhere (see Supplemental Fig.11), meaning that current applications of LSCI for imaging the skin are underestimating flow changes. It should be expected that clinical applications such as diagnosis of skin burns 47 will be strongly affected, as well applications imaging the kidney 33, 48 and liver 49 . For imaging large retinal vessels, single scattering and ordered motion (i.e. ...
... Further development saw the use of LSCI to progress from retinal imaging to skin imaging in the 1990s 97 . Since then, LSCI has been used for a multitude of preclinical-and clinical-based studies; for example, as a microvascular function research tool in patients with coronary artery disease 115 and a plausible mechanism for predicting healing times of pediatric scald wounds 106 . ...
Despite our understanding that the microvasculature plays a multifaceted role in the development and progression of various conditions, we know little about the extent of this involvement. A need exists for non-invasive, clinically meaningful imaging modalities capable of elucidating microvascular information to aid in our understanding of disease, and to aid in the diagnosis/monitoring of disease for more patient-specific care. In this review article, a number of imaging techniques are summarized that have been utilized to investigate the microvasculature of skin, along with their advantages, disadvantages and future perspectives in preclinical and clinical settings. These techniques include dermoscopy, capillaroscopy, Doppler sonography, laser Doppler flowmetry (LDF) and perfusion imaging, laser speckle contrast imaging (LSCI), optical coherence tomography (OCT), including its Doppler and dynamic variant and the more recently developed OCT angiography (OCTA), photoacoustic imaging, and spatial frequency domain imaging (SFDI). Attention is largely, but not exclusively, placed on optical imaging modalities that use intrinsic optical signals to contrast the microvasculature. We conclude that whilst each imaging modality has been successful in filling a particular niche, there is no one, all-encompassing modality without inherent flaws. Therefore, the future of cutaneous microvascular imaging may lie in utilizing a multi-modal approach that will counter the disadvantages of individual systems to synergistically augment our imaging capabilities.
A novel system and method for 3D laser speckle imaging of coagulation depth in partial thickness burn wounds using a line laser to provide depth-varying imaging is presented.
Partial thickness burn wounds extend partially through the dermis, leaving many pain receptors intact and making the injuries very painful. Due to the painfulness, quick assessment of the burn depth is important to not delay surgery of the wound if needed. Laser speckle imaging (LSI) of skin blood flow can be helpful in finding severe coagulation zones with impaired blood flow. However, LSI measurements are typically too superficial to properly reach the full depth of adult dermis and cannot resolve the flow in depth. Diffuse correlation spectroscopy (DCS) uses varying source-detector separations to allow differentiation of flow depths but requires time-consuming 2D scanning to form an image of the burn area. We here present a prototype for a hybrid DCS and LSI technique called speckle contrast Diffuse Correlation Spectroscopy (scDCS) with the novel approach of using a laser line as a source and using the speckle contrast of averaged images to obtain an estimate of static scattering in the tissue. This will allow for fast non-contact 1D scanning to perform 3D tomographic imaging, making quantitative estimates of the depth and area of the coagulation zone from burn wounds. Simulations and experimental results from a volumetric flow phantom and a gelatin wedge phantom show promise to determine coagulation depth. The aim is to develop a method that in the future could provide more quantitative estimates of coagulation depth in partial thickness burn wounds to better estimate when surgery is needed.
Partial thickness burn wounds extend partially through the dermis, leaving many pain receptors intact and making the injuries very painful. Due to the painfulness, quick assessment of the burn depth is important to not delay surgery of the wound if needed. Laser speckle imaging (LSI) of skin blood flow can be helpful in finding severe coagulation zones with impaired blood flow. However, LSI measurements are typically too superficial to properly reach the full depth of adult dermis and cannot resolve the flow in depth. Diffuse correlation spectroscopy (DCS) uses varying source-detector separations to allow differentiation of flow depths but requires time-consuming 2D scanning to form an image of the burn area. We here present a prototype for a hybrid DCS and LSI technique called speckle contrast Diffuse Correlation Spectroscopy (scDCS) with the novel approach of using a laser line as a source and using the speckle contrast of averaged images to obtain an estimate of static scattering in the tissue. This will allow for fast non-contact 1D scanning to perform 3D tomographic imaging, making quantitative estimates of the depth and area of the coagulation zone from burn wounds. Simulations and experimental results from a volumetric flow phantom and a gelatin wedge phantom show promise to determine coagulation depth. The aim is to develop a method that in the future could provide more quantitative estimates of coagulation depth in partial thickness burn wounds to better estimate when surgery is needed.
Dynamic light scattering (DLS) is a well known experimental approach uniquely suited for the characterization of small particles undergoing Brownian motion in randomly inhomogeneous turbid scattering medium, including water suspension, polymers in solutions, cells cultures, and so on. DLS is based on the illuminating of turbid medium with a coherent laser light and further analyzes the intensity fluctuations caused by the motion of the scattering particles. The DLS-based spin-off derivative techniques, such laser Doppler flowmetry (LDF), diffusing wave spectroscopy (DWS), laser speckle contrast imaging (LSCI), and Doppler optical coherence tomography (DOCT), are exploited widely for non-invasive imaging of blood flow in brain, skin, muscles, and other biological tissues. The recent advancements in the DLS-based imaging technologies in frame of their application for brain blood flow monitoring, skin perfusion measurements, and non-invasive blood micro-circulation characterization are overviewed. The fundamentals, breakthrough potential, and practical findings revealed by DLS-based blood flow imaging studies, including the limitations and challenges of the approach such as movement artifacts, non-ergodicity, and overcoming high scattering properties of studied medium, are also discussed. It is concluded that continued research and further technological advancements in DLS-based imaging will pave the way for new exciting developments and insights into blood flow diagnostic imaging.
Objective:
Cold sensitivity of the fingers is common in several conditions. It has been linked to digital vasospasm, microvascular dysfunction, and neural mechanisms. This study aimed to investigate the normal digital microvascular response to a cold stress test in healthy individuals using Laser Speckle Contrast Imaging (LSCI).
Methods:
Twenty-six healthy individuals, mean age 31 (SD 9) years were included. Skin perfusion of digits II-V was measured using Laser Speckle Contrast Imaging before and after a standardized cold stress test. Changes in skin perfusion from baseline were analyzed between hands, digits, and sexes.
Results:
Skin perfusion was significantly (p < 0.0001) affected by cold provocation in both the cold exposed and the contralateral hands in all participants of the study. This effect was significantly different between the radial (digit II and III) and the ulnar (digit V) side of the hands (p < 0.001). There was a trend towards a larger decrease in perfusion in men (ns), and a faster recovery to baseline values in women (ns). A larger inter subject variability was seen in perfusion values in women.
Conclusions:
The normal microvascular response to cold provocation may involve both centrally and regionally mediated processes. When exposing one hand to a cold stress test, the contralateral hand responds with simultaneous but smaller decreases in perfusion.
Purpose:
The aim of this study was to monitor how the blood perfusion in human upper eyelids is affected during full-thickness blepharotomy.
Methods:
Seven eyelids in 5 patients with upper eyelid retraction due to Graves' disease underwent full-thickness blepharotomy. Perfusion was measured using laser speckle contrast imaging in the eyelid margin and in the conjunctival pedicle.
Results:
Immediately following the procedure, a nonsignificant reduction in perfusion was observed in the skin of the pretarsal eyelid margin, being 66% of the initial value ( p = n.s.). However, a statistically significant decrease in perfusion, to 53% of the initial value ( p < 0.01), was seen in the central pedicle of the conjunctiva. There were no surgical complications such as infection, signs of ischemia, or bleeding.
Conclusions:
In this study, eyelid perfusion was mapped during full-thickness blepharotomy for the first time using laser speckle contrast imaging. The results showed that perfusion is sufficiently preserved during surgery, probably due to the rich vascular supply in the periocular region, which may explain the low risk of postoperative complications such as ischemia and infection.
Burn wound progression (BWP) leads to vertical and horizontal injury extension. The “burn comb model” is commonly used, in which a full-thickness burn with intercalated unburned interspaces is induced.
We aimed to establish an injury progressing to the intermediate dermis, allowing repeated wound evaluation. Furthermore, we present a new dorsal frame that enables topical drug application.
8 burn field and 6 interspaces were induced on each of 17 rats’ dorsa with a 10-second burn comb application. A developed 8-panel aluminum frame was sutured onto 12 animals and combined with an Elizabethan collar. Over 14 days, macroscopic & histologic wound assessment and Laser-Speckle-Contrast-Imaging (LSCI) were performed besides evaluation of frame durability. The 10-second group was compared to 9 animals injured with a full-thickness 60-second model.
Frame durability was sufficient up to day 4 with 8 of 12 frames (67%) still mounted. The 60-second burn led to an increased extent of interspace necrosis (p=0.002). The extent of necrosis increased between days 1 and 2 (p=0.001), following the 10-second burn (24%±SEM 8% to 40%±SEM 6%) and the 60-second burn (57%±SEM 6% to 76%±SEM 4%). Interspace LSCI perfusion was higher than burn field perfusion. It earlier reached baseline levels in the 10-second group (on day 1: 142%±SEM 9% vs. 60%±SEM 5%; p<0.001). Within day 1, the 10-second burn showed histological progression to the intermediate dermis, both in interspaces and burn fields.
This burn comb model with its newly developed fixed dorsal frame allows investigation of topical agents to treat BWP in partial-thickness burns.
Purpose:
Knowledge of how blood perfusion is affected during and after reconstructive surgery is of great importance to predict the survival of grafts and flaps. When commonly used reconstructive procedures were developed a century ago, they were based on empirical observations of clinical outcome.
Methods:
This is a comprehensive literature review that summarizes the current state of knowledge regarding microvascular perfusion monitoring during oculoplastic procedures.
Results:
Over the years, a number of techniques for perfusion monitoring have been developed as an attempt to be more objective than clinical examination using traditional methods such as observations of skin temperature, turgor, color, smell, and capillary refill time. There are limited publications regarding microvascular perfusion monitoring during reconstructive procedures in the periocular area. Modern laser-based techniques have been attractive due to their noninvasive nature.
Conclusions:
Today, modern, noninvasive techniques are available to monitor perfusion during and after surgery. This has increased our knowledge on the perfusion in common oculoplastic surgery procedures. A detailed understanding of how blood perfusion is affected will hopefully allow the improvement of surgical techniques for better clinical outcome.
Surgical treatment of Hirschsprung's disease commonly involves resection of the aganglionic segment of the colon and endorectal pull-through. Postoperative complications include anastomotic leakage and/or stricture, both believed to be caused by inadequate perfusion of the mobilized bowel or high tension in the anastomosis, but this has never been investigated.
In this case, laser speckle contrast imaging (LSCI) was used for the first time to monitor colonic perfusion during endorectal pull-through. A 6-week-old child with a 24-cm aganglionosis underwent laparoscopic-assisted endorecto pull-through with mobilization of the left colonic flexure to be able to reach the anus. LSCI perfusion monitoring showed that perfusion was 41% in the tip of the colon without tension, and was reduced 17% by a stretching force of 2 N.
In conclusion, perfusion of the colonic end can be monitored by LSCI during surgery for Hirschsprung's disease. This provides new opportunities to evaluate the effects of such surgical interventions in the future.
A critical need exists for early, accurate diagnosis of burn wound severity to help identify the course of treatment and outcome of the wound. Laser speckle imaging (LSI) is a promising blood perfusion imaging approach, but it does not account for changes in tissue optical properties that can occur with burn wounds, which are highly dynamic environments. Here, we studied optical property dynamics following burn injury and debridement and the associated impact on interpretation of LSI measurements of skin perfusion. We used spatial frequency domain imaging (SFDI) measurements of tissue optical properties to study the impact of burn-induced changes in these properties on LSI measurements. An established preclinical porcine model of burn injury was used (n = 8). SFDI and LSI data were collected from burn wounds of varying severity. SFDI measurements demonstrate that optical properties change in response to burn injury in a porcine model. We then apply theoretical modeling to demonstrate that the measured range of optical property changes can affect the interpretation of LSI measurements of blood flow, but this effect is minimal for most of the measured data. Collectively, our results indicate that, even with a dynamic burn wound environment, blood-flow measurements with LSI can serve as an appropriate strategy for accurate assessment of burn severity.
This paper illustrates the efficacy of an artificial intelligence (AI) (a convolutional neural network, based on the U-Net), for the burn-depth assessment using semantic segmentation of polarized high-performance light camera images of burn wounds. The proposed method is evaluated for paediatric scald injuries to differentiate four burn wound depths: superficial partial-thickness (healing in 0–7 days), superficial to intermediate partial-thickness (healing in 8–13 days), intermediate to deep partial-thickness (healing in 14–20 days), deep partial-thickness (healing after 21 days) and full-thickness burns, based on observed healing time.
In total 100 burn images were acquired. Seventeen images contained all 4 burn depths and were used to train the network. Leave-one-out cross-validation reports were generated and an accuracy and dice coefficient average of almost 97% was then obtained. After that, the remaining 83 burn-wound images were evaluated using the different network during the cross-validation, achieving an accuracy and dice coefficient, both on average 92%.
This technique offers an interesting new automated alternative for clinical decision support to assess and localize burn-depths in 2D digital images. Further training and improvement of the underlying algorithm by e.g., more images, seems feasible and thus promising for the future.
Early clinical assessment of burn depth and associated healing potential (HP) remains extremely challenging, even for experienced surgeons. Inaccurate diagnosis often leads to prolonged healing times and unnecessary surgical procedures, resulting in incremental costs and unfavorable outcomes. Laser Doppler imaging (LDI) is currently the most objective and accurate diagnostic tool to measure blood flow and its associated HP, the main predictor for a patient’s long term functional and aesthetic outcome. A systematic review was performed on non-invasive, laser-based methods for burn depth assessment using skin microcirculation measurements to determine time to healing: Laser Doppler flowmetry (LDF), LDI and laser speckle contrast imaging (LSCI).
Important drawbacks of single point LDF measurements are: direct contact with numerous small points on the wound bed and the need to carry out serial measurements over several days. LDI is a fast, ‘non-contact’, single measurement tool allowing to scan large burned areas with a 96% accuracy. LDI reduces the number of surgeries, improves the functional and aesthetic outcome and is cost-effective. There is only limited evidence for the use of LSCI in burn depth assessment.
LSCI still needs technical improvements and scientific validation, before it can be approved for reliable burn assessment. LDI has proven to be invaluable in determining the optimal treatment of a burn patient. For unclear reasons, LDI is still not routinely used in burn centers worldwide. Additional research is required to identify potential ‘barriers’ for universal implementation of this evidence-based burn depth assessment tool.
Objectives
Measurement of perfusion is an established method to evaluate the depth of burns. However, high accuracy is only achievable >48 h after injury. The aim of the study was to investigate if measurement of blood flow pulsatility, combined with perfusion measurement, can improve early assessment of burn depth using laser speckle contrast imaging (LSCI).
Methods
Perfusion and pulsatility were measured with LSCI in 187 regions of interest in 32 patients, between 0 and 5 days after injury. The reproducibility of pulsatility was tested for recording durations between 1 and 12 s. The most reproducible duration was chosen, and receiver operator characteristics were created to find suitable pulsatility cut-offs to predict surgical need.
Results
A measurement duration of 8 s resulted in a good reproducibility of the pulsatility (%CV: 15.9%). Longer measurement durations resulted in a small improvement of the accuracy of the assessment.
A pulsatility of <1.45 (Perfusion Units)² on day 0–2 after injury predicted surgical need with a sensitivity of 100% (95% CI: 83.2–100%), specificity of 100% (95% CI: 95.2–100%), a positive predictive value of 100%, and a negative predictive value of 100%. Pulsatility was not significantly different when comparing measurements done day 0–2 to day 3–5. Perfusion was however significantly higher day 3–5 compared to day 0–2 for wounds healing within 3 weeks.
Conclusion
Measurement of pulsatility improves the accuracy of the assessment of burns with LSCI and makes it possible to predict the need for surgery during day 0–2 after injury with a high accuracy.
Background: Laser speckle contrast imaging (LSCI) is a powerful optical imaging technique for real-time and dynamic measurement of regional blood flow. The objective of this prospective observational study was to investigate blood flow after changes blockade of lumbar plexus or its three major branches respectively, with LSCI technique.
Methods: This study included 47 adult patients scheduled for elective lower limb surgery. For the selective blockade of lumbar plexus, femoral nerve, obturator nerve, and lateral femoral cutaneous nerve, blood flow images and pinprick sensory scores of the blocked lower limb were recorded 5 min pre block and every 5 min for 30 min post block. Blood flow index (BFI) values of toes were calculated by LSCI software.
Results: In this study, we have 21 cases of successful lumbar plexus blocks, 2 cases of failed lumbar plexus block, 8 cases of successful femoral nerve blocks, 8 cases of successful obturator nerve blocks, and 8 cases of successful lateral femoral cutaneous nerve blocks. The BFI values of all five toes were significantly increased as early as 5 min after successful lumbar plexus block, whereas no significant difference was found in BFI values after failed lumbar plexus block. BFI changes after successful selective blockade of femoral nerve, obturator nerve, or lateral femoral cutaneous nerve were negligible. BFI value of the big toe at 5 min after the successful lumbar plexus block was increased by 2.57 fold compared with the baseline value, which represented the highest increase among five tested toes. BFI value of the big toe at 10 min after lumbar plexus block showed great power to predict block outcome with a sensitivity of 100% and a specificity of 100%. The optimal cut-off value given by ROC analysis was 22.11 PU.
Conclusions: Increased blood flow index measured by laser speckle contrast imaging is a reliable indicator of successful lumbar plexus block, but cannot indicate successful selective blocks of three major branches of the lumbar plexus. BFI value of the big toe at 10 min after lumbar plexus block could well predict block outcome with the cut-off value of 22.11 PU.
Trial registration: NCT03169517 (Date of registration: May 25, 2017).
When a biological tissue is illuminated with coherent light, an interference pattern will be formed at the detector, the so-called speckle pattern. Laser speckle contrast imaging (LSCI) is a technique based on the dynamic change in this backscattered light as a result of interaction with red blood cells. It can be used to visualize perfusion in various tissues and, even though this technique has been extensively described in the literature, the actual clinical implementation lags behind. We provide an overview of LSCI as a tool to image tissue perfusion. We present a brief introduction to the theory, review clinical studies from various medical fields, and discuss current limitations impeding clinical acceptance.
.
Objectives:
Laser speckle contrast imaging (LSCI) is an emerging technique for the assessment of burns in humans and interobserver differences have not been studied. The aim of this study was to compare assessments of perfusion images by different professional groups regarding (i) perfusion values and (ii) burn depth assessment.
Methods:
Twelve observers without LSCI experience were included. The observers were evenly recruited from three professional groups: plastic surgeons with experience in assessing burns, nurses with experience in treating burns, and junior doctors with limited experience of burns. Ten cases were included. Each case consisted of one digital photo of the burn with a pre-marked region of interest (ROI) and two unmarked perfusion images of the same area. The first and the second perfusion image was from 24h and 72-96h after injury, respectively. The perfusion values from both perfusion images were used to generate a LSCI recommendation based on the perfusion trend (the derivative between the two perfusion values). As a last step, each observer was asked to estimate the burn depth using their clinical experience and all available information. Intraclass correlation (ICC) was calculated between the different professional groups and among all observers.
Results:
Perfusion values and perfusion trends between all observers had an ICC of 0.96 (95% CI 0.91-0.99). Burn depth assessment by all observers yielded an ICC of 0.53 (95% CI: 0.31-0.80) and an accuracy of 0.53 (weighted kappa). LSCI recommendations generated by all observers had an ICC of 0.95 (95% CI: 0.90-0.99).
Conclusion:
Observers can reliably identify the same ROI, which results in observer-independent perfusion measurements, irrespective of burn experience. Extensive burn experience did not further improve burn depth assessment. The LSCI recommendation was more accurate in all professional groups. Introducing LSCI measurements would be likely improve early assessment of burns.
General purpose:
The purpose of this learning activity is to provide an overview about burns and current burn care.
Target audience:
This continuing education activity is intended for physicians, physician assistants, nurse practitioners, and nurses with an interest in skin and wound care.
Learning objectives/outcomes:
After completing this continuing education activity, you should be better able to:1. List factors affecting the types, size, and depth of burns.2. Propose first aid and treatment for various burns.
Abstract:
Burns are a very specific type of injury and, particularly in the case of large and/or deep lesions, require highly specialized care. This article gives a basic overview of burns and burn care and is not intended to discuss overall burn care in detail.
Background
Laser Speckle Contrast Imaging (LSCI) is a non-invasive and fast technique for measuring microvascular blood flow that recently has found clinical use for burn assessment and evaluation of flaps. Tissue motion caused by for example breathing or patient movements may however affect the measurements in these clinical applications, as may distance between the camera and the skin and tissue curvature. Therefore, the aims of this study were to investigate the effect of frame rate, number of frames/image, movement of the tissue, measuring distance and tissue curvature on the measured perfusion.
Methods
Methyl nicotinate-induced vasodilation in the forearm skin was measured using LSCI during controlled motion at different speeds, using different combinations of frame rate and number of frames/image, and at varying camera angles and distances. Experiments were made on healthy volunteers and on a cloth soaked in a colloidal suspension of polystyrene microspheres.
Results
Measured perfusion increased with tissue motion speed. The relation was independent of the absolute perfusion in the skin and of frame rate and number of frames/image. The measured perfusion decreased with increasing angles (16% at 60°, p = 0.01). Measured perfusion did not vary significantly between measurement distances from 15 to 40 cm (p = 0.77, %CV 0.9%).
Conclusion
Tissue motion increases and measurement angles beyond 45° decrease the measured perfusion in LSCI. These findings have to be taken into account when LSCI is used to assess moving or curved tissue surfaces, which is common in clinical applications.
Significance: Burn assessments, including extent and severity, are some of the most critical diagnoses in burn care, and many recently developed imaging techniques may have the potential to improve the accuracy of these evaluations. Recent Advances: Optical devices, telemedicine, and high-frequency ultrasound are among the highlights in recent burn imaging advancements. We present another promising technology, multispectral imaging (MSI), which also has the potential to impact current medical practice in burn care, among a variety of other specialties. Critical Issues: At this time, it is still a matter of debate as to why there is no consensus on the use of technology to assist burn assessments in the United States. Fortunately, the availability of techniques does not appear to be a limitation. However, the selection of appropriate imaging technology to augment the provision of burn care can be difficult for clinicians to navigate. There are many technologies available, but a comprehensive review summarizing the tissue characteristics measured by each technology in light of aiding clinicians in selecting the proper device is missing. This would be especially valuable for the nonburn specialists who encounter burn injuries. Future Directions: The questions of when burn assessment devices are useful to the burn team, how the various imaging devices work, and where the various burn imaging technologies fit into the spectrum of burn care will continue to be addressed. Technologies that can image a large surface area quickly, such as thermography or laser speckle imaging, may be suitable for initial burn assessment and triage. In the setting of presurgical planning, ultrasound or optical microscopy techniques, including optical coherence tomography, may prove useful. MSI, which actually has origins in burn care, may ultimately meet a high number of requirements for burn assessment in routine clinical use.
We aimed to assess the effects of age, sex, body mass index (BMI), and anatomical site on skin thickness in children and adults with diabetes.
We studied 103 otherwise healthy children and adolescents with type 1 diabetes aged 5-19 years, and 140 adults with type 1 and type 2 diabetes aged 20-85 years. The thicknesses of both the dermis and subcutis were assessed using ultrasound with a linear array transducer, on abdominal and thigh skin.
There was an age-related thickening of both dermis (p<0.0001) and subcutis (p = 0.013) in children and adolescents. Girls displayed a substantial pubertal increase in subcutis of the thigh (+54%; p = 0.048) and abdomen (+68%; p = 0.009). Adults showed an age-related decrease in dermal (p = 0.021) and subcutis (p = 0.009) thicknesses. Pubertal girls had a thicker subcutis than pubertal boys in both thigh (16.7 vs 7.5 mm; p<0.0001) and abdomen (16.7 vs 8.8 mm; p<0.0001). Men had greater thigh dermal thickness than women (1.89 vs 1.65 mm; p = 0.003), while the subcutis was thicker in women in thigh (21.3 vs 17.9 mm; p = 0.012) and abdomen (17.7 vs 9.8 mm; p<0.0001). In boys, men, and women, both dermis and subcutis were thicker on the abdomen compared to thigh; in girls this was only so for dermal thickness. In both children and adults, the skin (dermis and subcutis) became steadily thicker with increasing BMI (p<0.0001).
Skin thickness is affected by age, pubertal status, gender, BMI, and anatomical site. Such differences may be important when considering appropriate sites for dermal/subcutaneous injections and other transdermal delivery systems.
The kappa statistic is frequently used to test interrater reliability. The importance of rater reliability lies in the fact that it represents the extent to which the data collected in the study are correct representations of the variables measured. Measurement of the extent to which data collectors (raters) assign the same score to the same variable is called interrater reliability. While there have been a variety of methods to measure interrater reliability, traditionally it was measured as percent agreement, calculated as the number of agreement scores divided by the total number of scores. In 1960, Jacob Cohen critiqued use of percent agreement due to its inability to account for chance agreement. He introduced the Cohen's kappa, developed to account for the possibility that raters actually guess on at least some variables due to uncertainty. Like most correlation statistics, the kappa can range from -1 to +1. While the kappa is one of the most commonly used statistics to test interrater reliability, it has limitations. Judgments about what level of kappa should be acceptable for health research are questioned. Cohen's suggested interpretation may be too lenient for health related studies because it implies that a score as low as 0.41 might be acceptable. Kappa and percent agreement are compared, and levels for both kappa and percent agreement that should be demanded in healthcare studies are suggested.
Laser-Doppler imaging (LDI) of cutaneous blood flow is beginning to be used by burn surgeons to predict the healing time of burn wounds; predicted healing time is used to determine wound treatment as either dressings or surgery. In this paper, we do a statistical analysis of the performance of the technique.
We used data from a study carried out by five burn centers: LDI was done once between days 2 to 5 post burn, and healing was assessed at both 14 days and 21 days post burn. Random-effects ordinal logistic regression and other models such as the continuation ratio model were used to model healing-time as a function of the LDI data, and of demographic and wound history variables. Statistical methods were also used to study the false-color palette, which enables the laser-Doppler imager to be used by clinicians as a decision-support tool.
Overall performance is that diagnoses are over 90% correct. Related questions addressed were what was the best blood flow summary statistic and whether, given the blood flow measurements, demographic and observational variables had any additional predictive power (age, sex, race, % total body surface area burned (%TBSA), site and cause of burn, day of LDI scan, burn center). It was found that mean laser-Doppler flux over a wound area was the best statistic, and that, given the same mean flux, women recover slightly more slowly than men. Further, the likely degradation in predictive performance on moving to a patient group with larger %TBSA than those in the data sample was studied, and shown to be small.
Modeling healing time is a complex statistical problem, with random effects due to multiple burn areas per individual, and censoring caused by patients missing hospital visits and undergoing surgery. This analysis applies state-of-the art statistical methods such as the bootstrap and permutation tests to a medical problem of topical interest. New medical findings are that age and %TBSA are not important predictors of healing time when the LDI results are known, whereas gender does influence recovery time, even when blood flow is controlled for.The conclusion regarding the palette is that an optimum three-color palette can be chosen 'automatically', but the optimum choice of a 5-color palette cannot be made solely by optimizing the percentage of correct diagnoses.
Skin anatomy and physiology undergo modifications throughout the whole lifespan. In children the skin appears with structural characteristics, as evaluated by histology, which differ from those of adults, especially in the first years of life.
The aim of our study was to evaluate skin thickness and echogenicity at different sites in children by 20-MHz ultrasound.
Eight skin sites of 42 children and 30 young adults were studied with a 20-MHz B scanner. Skin thickness and mean echogenicity were evaluated. The echographic images were processed and segmented by a dedicated program: the 0-30 amplitude interval, which marks the hypoechogenic parts of the tissue, and the 201-255 range, highlighting the hyperreflecting areas, have been selected.
Whereas skin thickness shows a gradual increase from birth to adulthood, maturation of the skin leads to variations in the intensity of its echogenicity, depending on the different skin areas. Whereas on the face and the trunk it appears lower in adults with respect to children, a gradual increase can be observed on the limbs with growing age. The distribution of skin reflectivity also greatly varies in different phases of life.
Laser Doppler velocimetry uses the frequency shift produced by the Doppler effect to measure velocity. It can be used to monitor blood flow or other tissue movement in the body. Laser speckle is a random interference effect that gives a grainy appearance to objects illuminated by laser light. If the object consists of individual moving scatterers (such as blood cells), the speckle pattern fluctuates. These fluctuations provide information about the velocity distribution of the scatterers. It can be shown that the speckle and Doppler approaches are different ways of looking at the same phenomenon. Both these techniques measure at a single point. If a map of the velocity distribution is required, some form of scanning must be introduced. This has been done for both time-varying speckle and laser Doppler. However, with the speckle technique it is also possible to devise a full-field technique that gives an instantaneous map of velocities in real time. This review article presents the theory and practice of these techniques using a tutorial approach and compares the relative merits of the scanning and full-field approaches to velocity map imaging. The article concludes with a review of reported applications of these techniques to blood perfusion mapping and imaging.
Burn wound depth is a significant determinant of patient treatment and morbidity. While superficial partial-thickness burns generally heal by re-epithelialization with minimal scarring, deeper wounds can form hypertrophic or contracted scars, often requiring surgical excision and grafting to prevent a suboptimal result. In addition, without timely intervention, more superficial burn wounds can convert to deeper wounds. As such, the rapid and accurate assessment of burn wound depth is a priority in treating burn-injured patients. The object of this article is to review current research on modalities useful in the assessment of burn wound depth with emphasis on the relative costs and benefits of each technique.
PubMed and Cochrane computerized databases were used for data retrieval, using the search terms "burns," "burn wounds," "burn depth," "burn depth measurement," and "burn depth progression." In addition, bibliographic references from prior reviews of burn depth were reviewed. All peer-reviewed, English-language articles relevant to the topic of burn depth measurement were reviewed, including those focusing on animal and human populations. Where appropriate, conclusions drawn from review articles and expert analyses were included.
Although bedside evaluation remains the most common modality of diagnosing the depth of burn wounds, recent technological advances have broadened the scope of depth assessment modalities available to clinicians. Other depth assessment techniques include biopsy and histology, and perfusion measurements techniques such as thermography, vital dyes, indocyanine green video angiography, and laser Doppler techniques.
Of the depth assessment modalities currently used in clinical practice, LDI and ICG video angiography offer the best data-supported estimates of accuracy. Until the future of new modalities unfolds, a combination of clinical evaluation and another modality--thermography, biopsy, or, ideally, ICG video angiography or LDI--is advised to best assess the depth of acute burn wounds.
Background and objective:
Accurate assessment of burn depth is important for determination of treatment modality. Laser Doppler imaging (LDI) is known to be an objective and effective measurement tool in burn depth assessment. Our study evaluated the diagnostic accuracy of LDI across enrolled studies and subgroups.
Methods:
A systematic literature review and meta-analysis were performed using MEDLINE, EMBASE, and Cochrane databases. Data from LDI cases were extracted from all primary studies and categorized into four cell values (true positives, false positives, true negatives, and false negatives). Subgroup analyses were performed according to perfusion units of LDI, clinical criteria of superficial and deep burns during the treatment period, and publication date of enrolled studies.
Results:
The search strategy identified 321 publications. After screening, 10 articles were selected for review. The pooled sensitivity and specificity of LDI in all enrolled studies and subgroups were found to be similarly high. However, the sensitivity of LDI in our meta-analysis was not as high as that identified in previous studies.
Conclusion:
Although LDI in burn depth assessment was identified as an accurate measurement tool in this meta-analysis, careful clinical assessment should be performed along with LDI in patients with deep burns.
Background:
Microvascular perfusion changes in scalds in children during the first weeks after injury is related to the outcome of healing, and measurements of perfusion, based on laser Doppler imaging, have been used successfully to predict the need for excision and grafting. However, the day-to-day changes in perfusion during the first weeks after injury have not to our knowledge been studied in detail. The aim of this study, based on a conservative treatment model where excision and grafting decisions were delayed to day 14 after injury, was to measure changes in perfusion in scalds using laser speckle contrast imaging (LSCI) during the first three weeks after injury.
Methods:
We measured perfusion with LSCI in 34 patients at regular intervals between 6h after injury until complete reepithelialization or surgery. Duration of healing was defined as the time to complete reepithelialization.
Results:
Less perfusion, between 6 and 96h after injury, was associated with longer duration of healing with the strongest association occurring between 72 and 96h. Burns that healed within 14 days had relatively high initial perfusion, followed by a peak and subsequent slow decrease. Both the maximum perfusion and the time-to-peak were dependent on the severity of the burn. Burns that needed excision and grafting had less initial perfusion and a gradual reduction over time.
Conclusion:
The perfusion in scalds in children shows characteristic patterns during the first weeks after injury depending on the duration of wound healing, the greatest difference between wounds of different severity being on the 4th day. Perfusion should therefore preferably be measured on the fourth day if it is to be used in the assessment of burn depth.
Burn wound conversion describes the process by which superficial partial thickness burns convert into deeper burns necessitating surgical intervention. Fully understanding and thus controlling this phenomenon continues to defy burn surgeons. However, potentially guiding burn wound progression so as to obviate the need for surgery while still bringing about healing with limited scarring is the major unmet challenge. Comprehending the pathophysiologic background contributing to deeper progression of these burns is an essential prerequisite to planning any intervention. In this study, a review of articles examining burn wound progression over the last five years was conducted to analyze trends in recent burn progression research, determine changes in understanding of the pathogenesis of burn conversion, and subsequently examine the direction for future research in developing therapies. The majority of recent research focuses on applying therapies from other disease processes to common underlying pathogenic mechanisms in burn conversion. While ischemia, inflammation, and free oxygen radicals continue to demonstrate a critical role in secondary necrosis, novel mechanisms such as autophagy have also been shown to contribute affect significantly burn progression significantly. Further research will have to determine whether multiple mechanisms should be targeted when developing clinical therapies.
Background:
Currently, the only evidence-based adjunct to clinical evaluation of burn depth is laser Doppler imaging (LDI), although preliminary studies of alternative imaging modalities with instant image acquisition are promising. This is a study to investigate the accuracy of infrared thermography (IRT) and spectrophotometric intracutaneous analysis (SIA) for burn depth assessment, and compare this to the current gold standard: LDI. We include a comparison of the three modalities in terms of cost, reliability and usability.
Methods:
We recruited 20 patients with burns presenting to the Chelsea and Westminster Adult Burns Service. Between 48h and 5 days afterburn we recorded imaging using moorLDI2-BI-VR (LDI), FLIR E60 (IRT) and Scanoskin™ (SIA). Subsequent clinical management and outcome was as normal, and not affected by the extra images taken.
Results:
24 burn regions were grouped according to burn wound healing: group A healed within 14 days, group B within 14-21 days, and group C took more than 21 days or underwent grafting. Both LDI and IRT accurately determined healing potential in groups A and C, but failed to distinguish between groups B and C (p>0.05). Scanoskin™ interpretation of SIA was 100% consistent with clinical outcome.
Conclusion:
FLIR E60 and Scanoskin™ both present advantages to moorLDI2-BI-VR in terms of cost, ease-of-use and acceptability to patients. IRT is unlikely to challenge LDI as the gold standard as it is subject to the systematic bias of evaporative cooling. At present, the LDI colour-coded palette is the easiest method for image interpretation, whereas Scanoskin™ monochrome colour-palettes are more difficult to interpret. However the additional analyses of pigment available using SIA may help more accurately indicate the depth of burn compared with perfusion alone. We suggest development of Scanoskin™ software to include a simplified colour-palette similar to LDI and additional work to further investigate the potential of SIA as an alternative to the current gold standard.
Introduction:
Laser speckle contrast imaging (LSCI) allows an easy non-contact monitoring of the cutaneous blood flow (CBF), but is highly sensitive to movement artifacts (ARTm). Subtraction of a signal recorded on an adhesive opaque surface (AOS) close to the area of interest was reported as a mean of reducing noise from the raw skin LSCI (LSCIsk) signal, provided an individual calibration was performed. Assuming that AOS=a·CBF+b·ARTm, an ideal patch should completely block the light reflection due to CBF and thus be insensitive to skin blood flow changes ("a"~0), while keeping a reflection signal amplitude similar to the one from the skin in case of artifact ("b"~1). This ideal AOS has not been determined and may discriminate flow from movements during LSCI recordings.
Materials and methods:
We tested different AOSs to determine their "a" and "b" parameters in 35 and 34 healthy volunteers, respectively. The AOS surface providing results as close as possible to an ideal AOS, was used for a point-by-point de-noising of post occlusive reactive hyperemia (PORH) on two different days in 15 new subjects. Correlation of raw, smoothed (average smoothing over 1s intervals) and denoised signals was tested through a cross-correlation analysis of the two POHR tests.
Results:
The optimal "a" and "b" values were obtained with a homemade bilayer adhesive patch (a=0.06±0.05 and b=1.03±0.17) whereas other tested AOS had "a" values ranging from 0.05 to 0.23 and "b" values ranging from 2.69 to 3.82. Using the bilayer adhesive patch the cross-correlation between the two tests of POHR increased from 0.330±0.128 for raw, to 0.461±0.168 for smoothed and 0.649±0.128 for denoised signals respectively (p<0.05 from raw coefficients).
Conclusion:
The home-made bilayer adhesive seems the optimal AOS for the removal of ARTm from the LSCIsk signal while respecting CBF signal. This specific AOS allows for an efficient de-noising of LSCI measurements without the need for individual calibration.
Hypertrophic scarring is extremely common and is the source of most morbidity related to burns. The biology of hypertrophic healing is complex and poorly understood. Multiple host and injury factors contribute, but protracted healing of partial thickness injury is a common theme. Hypertrophic scarring and heterotopic ossification may share some basic causes involving marrow-derived cells. Several traditional clinical interventions exist to modify hypertrophic scar. All have limited efficacy. Laser interventions for scar modification show promise, but as yet do not provide a definitive solution. Their efficacy is only seen when used as part of a multimodality scar management program.
Introduction:
Laser Doppler imaging (LDI) provides early accurate determination of wound healing potential. LDI can scan large areas of up to 2500 cm2 within 2 min. This duration may require additional sedation in a mobile, uncooperative child. In five burn centres a faster Laser Doppler Line Scanner (LDLS) was assessed. This new imager scans 300 cm2 in 4s with potential benefit for patients and operators. The aim of this study was to assess the accuracy and convenience of the LDLS and to compare this with an established LDI imager.
Methods:
Outpatients and admitted patients were included. LDI and LDLS images were obtained between 2 and 5 days post burn (PB). Photographs and records of wound and healing were obtained on day of scan and at 14 and 21 days PB. This provided data on three categories of burn wounds: healing within 14 days, 14-21 days and not healed within 21 days.
Results:
The analysis included 596 burn areas from 204 burns patients. An accuracy of 94.2% was found with use of the LDLS compared with 94.4% for the original LDI imager.
Conclusions:
The high accuracy of the new line-scan imager was comparable to that of the traditional LDI. Its size and mobility enabled easier ward and outpatient use. The higher scan speed was particularly beneficial for scans in paediatric patients.
Background:
The use of objective methods for assessment of burns is limited. Laser Speckle Contrast Imaging (LSCI) is a non-invasive technique for instant measurement of tissue perfusion, making it potentially valuable for early prediction of burn wound outcome.
Aim:
To evaluate the influence of technical factors on perfusion and to measure perfusion in burns 0-14 days post-burn and compare this with the outcome of the burn wound at 14 days after burn.
Method:
The effect of room light, camera distance and camera angle was studied using a suspension of polystyrene particles. LSCI measurements were performed on 45 scald burns and 32 uninjured areas 0-14 days after burn.
Result:
Technical factors had no clinically relevant effect on measured perfusion. Burns that healed within 14 days had a higher perfusion during the first week post-burn than burns that healed after 14 days or underwent surgery. The difference in perfusion was largest 4-7 days after burn.
Conclusion:
LSCI allows for robust, instant measurement of burns and can easily be applied in a clinical setting. Differences in perfusion during the first week post-burn are related to the outcome after 14 days.
Hypertrophic scarring (HTS) is a fibroproliferative disorder that commonly develops after severe burn injuries. Overexpression of transforming growth factor-β (TGF-β) by an increased number of fibrocytes has been associated with increased extracellular matrix molecule expression leading to HTS. The most widely accepted adjuvant to clinical assessment of burn depth is laser Doppler imaging (LDI) and may predict injury to the dermis that corresponds to cellular and molecular changes associated with HTS. A prospective, blinded, control trial was performed comparing LDI and clinical assessment for the decision to operate. Immunohistochemistry and real-time reverse transcription polymerase chain reaction was performed to determine whether there is a correlation between histological assessment of burn depth and LDI, and the presence of fibrocytes was detected using confocal microscopy. The positive predictive value for a burn requiring a graft was calculated to be >90%. Immunohistochemistry on biopsy samples revealed an increased expression of TGF-β, connective tissue growth factor, heat shock protein 47, and collagen type I in deep burn wounds compared to superficial burns. Using the fibrocyte-specific markers procollagen type I and leukocyte-specific phosphoprotein-1, there was an increased number of fibrocytes in deep burn areas compared to superficial burn. In deep burn injuries, increased infiltration of fibrocytes occurs leading to an overexpression of TGF-β1 and connective tissue growth factor. More importantly, LDI was >90% accurate at predicting the need for excision and grafting. The accuracy of the decision to debride deep dermal burns to avoid HTS using both clinical parameters and LDI was supported by histological and biochemical measurements.
Speckle pattern forms when a rough object is illuminated with coherent light (laser) and the backscattered radiation is imaged on a screen. The pattern changes over time due to movement in the object. Such time-integrate speckle pattern can be statistically analyzed to reveal the flow profile. For higher velocity the speckle contrast gets reduced. This theory can be utilized for tissue perfusion in capillaries of human skin tissue and cerebral blood flow mapping in rodents. Early, the technique was suffered from low resolution and computational intricacies for real-time monitoring purpose. However, modern engineering has made it feasible for real-time monitoring in microcirculation imaging with improved resolution. This review illustrates several modifications over classical technique done by many researchers. Recent advances in speckle contrast methods gain major interest, leading towards practical implementation of this technique. The review also brings out the scopes of laser speckle-based analysis in various medical applications.
Deep burn assessment made by clinical evaluation has an accuracy varying between 60% and 80% and will determine if a burn injury will need tangential excision and skin grafting or if it will be able to heal spontaneously. Laser Doppler Imaging (LDI) techniques allow an improved burn depth assessment but their use is limited by the time-consuming image acquisition which may take up to 6 min per image.
To evaluate the effectiveness and reliability of a newly developed full-field LDI technology, 15 consecutive patients presenting with intermediate depth burns were assessed both clinically and by FluxExplorer LDI technology. Comparison between the two methods of assessment was carried out.
Image acquisition was done within 6 s. FluxEXPLORER LDI technology achieved a significantly improved accuracy of burn depth assessment compared to the clinical judgement performed by board certified plastic and reconstructive surgeons (P < 0.05, 93% of correctly assessed burns injuries vs. 80% for clinical assessment).
Technological improvements of LDI technology leading to a decreased image acquisition time and reliable burn depth assessment allow the routine use of such devices in the acute setting of burn care without interfering with the patient's treatment. Rapid and reliable LDI technology may assist clinicians in burn depth assessment and may limit the morbidity of burn patients through a minimization of the area of surgical debridement. Future technological improvements allowing the miniaturization of the device will further ease its clinical application.
Recent research has suggested that differences between intelligent tutor lessons predict a large amount of the variance in the prevalence of gaming the system [4]. Within this paper, we investigate whether such differences also predict how much students choose to go off-task, and if so, which differences predict how much off-task behavior will occur. We utilize an enumeration of the differences between intelligent tutor lessons, the Cognitive Tutor Lesson Variation Space 1.1 (CTLVS1.1), to identify 79 differences between tutor lessons, within 20 lessons from an intelligent tutoring system for Algebra. We utilize a machine-learned detector of off-task behavior to predict 58 students' off-task behavior within that tutor, in each lesson. Surprisingly, the best model predicting off-task behavior from lesson features contains only one feature: lessons that involve equation-solving. We discuss possible explanations for this finding, and further studies that could shed light on this relationship.
Burns commonly occur in children and their first aid remains inadequate despite burn prevention programmes. While scald injuries predominate, contact and flame burns remain common. Although typically less severe injuries overall than those in adults, hypertrophic scarring complicating both the burn wound and even donor sites occur more frequently in children. The heterogeneous nature of burn wounds, coupled with the difficulties associated with the early clinical assessment of burn depth, has stimulated the application of novel technologies to predict burn wound outcome. This review explores current best practice in the management of paediatric burns, with a focus on prevention, optimal first aid, resuscitation, burn wound prediction and wound management strategies.
Clinical examination alone is not always sufficient to determine which burn wounds will heal spontaneously and which will require surgical intervention for optimal outcome. We present a review of optical modalities currently in clinical use and under development to assist burn surgeons in assessing burn wound severity, including conventional histology/light microscopy, laser Doppler imaging, indocyanine green videoangiography, near-infrared spectroscopy and spectral imaging, in vivo capillary microscopy, orthogonal polarization spectral imaging, reflectance-mode confocal microscopy, laser speckle imaging, spatial frequency domain imaging, photoacoustic microscopy, and polarization-sensitive optical coherence tomography.
First introduced in the 1980s, laser speckle contrast imaging is a powerful tool for full-field imaging of blood flow. Recently laser speckle contrast imaging has gained increased attention, in part due to its rapid adoption for blood flow studies in the brain. We review the underlying physics of speckle contrast imaging and discuss recent developments to improve the quantitative accuracy of blood flow measures. We also review applications of laser speckle contrast imaging in neuroscience, dermatology and ophthalmology.
Laser Doppler perfusion imaging (LDPI) has been proven to be a useful tool in predicting the burn wound outcome in an early stage. A major disadvantage of scanning beam LDPI devices is their slow scanning speed, leading to patient discomfort and imaging artifacts. We have developed the Twente Optical Perfusion Camera (TOPCam), a whole field laser Doppler perfusion imager based on a CMOS imaging array, which is two orders of magnitude faster than scanning beam LDPI systems. In this paper the first clinical results of the TOPCam in the setting of a burn centre are presented. The paper shows perfusion images of burns of various degrees. While our system encounters problems caused by blisters, tissue necrosis, surface reflection and curvature in a manner similar to scanning beam imagers, it poses a clear advantage in terms of procedure time. Image quality in terms of dynamic range and resolution appears to be sufficient for burn diagnosis. Hence, we made important steps in overcoming the limitations of LDPI in burn diagnosis imposed by the measurement speed.
Laser Doppler imaging (LDI) is a noninvasive technique used to assess burn depth. However, there have been no studies regarding the use of LDI in predicting burn healing time.
The aims of this study are to evaluate the relationship between healing time and the amount of perfusion seen on LDI and to determine a cut-off value for LDI that predicts if a burn will heal within 14 days.
Consecutive patients younger than 15 years old with partial-thickness burns were recruited from May to November 2006 for this prospective observational study. The mean number of perfusion units (PU) as determined by LDI (Periscan PIM 3 system) was obtained within 2-3 days following injury. Healing time was estimated clinically by two physicians and marked by the observation of reepithelization. The mean PU was compared between the early (healed with 14 days) and late healing groups (healed later than 14 days). The usefulness of the mean PU in predicting healing time within 14 days was estimated by receiver operating characteristic curve analysis.
A total of 103 patients with 181 partial-thickness burn wounds were enrolled in this study. The mean PU from LDI was higher in the early healing group compared to the late healing group (380.2+/-157.8 vs. 185.8+/-115.8, p<0.001). When using 250 PUs as a cut-off value to predict early healing, the sensitivity and specificity were 80.6% and 76.9%, respectively. The area under the ROC curve was 0.844 (p<0.001, 95% CI=0.780-0.908).
This study suggests the mean PU as determined by LDI can be used as a valuable tool in predicting the healing time of burn wounds.
Accurate diagnosis of burn depth is essential in selecting the most appropriate treatment. Early assessment of burn depth by clinical means only has been shown to be inaccurate, resulting in unnecessary operations or delay of grafting procedures. Laser Doppler imaging (LDI) was reported as an objective technique to determine the depth of a burn wound, but the accuracy on very early days post burn has never been investigated yet.
In 40 patients with intermediate depth burns, we prospectively evaluated and compared the accuracy of the LDI measurements with the clinical assessments on days 0, 1, 3, 5, 8. Clinical evaluation of the depth of the burn was performed by two observers blinded to the LDI images. Accuracies were assessed by comparison with outcome: healing times longer than 21 days were considered to be equivalent to a biopsy finding of a deep dermal wound. Obviously superficial and full thickness wounds were excluded. LDI flux level was used for LDI prediction of outcome: less than 220PU to predict non-healing at day 21.
The accuracies of burn depth assessments on the day of burn and post burn days 0, 1, 3, 5 and 8 using LDI were 54%, 79.5%, 95%, 97% and 100% compared with clinical assessment accuracies of 40.6%, 61.5%, 52.5%, 71.4% and 100%, respectively. LDI accuracy was significantly higher than clinical accuracy on day 3 (p<0.001) and day 5 (p=0.005). Burn depth conversion was also considered. This is the first study to quantify the advantage of LDI scanning over clinical assessments during these important early after burn days.
The ability of laser Doppler imaging (LDI) to evaluate burn depth in children was investigated. Fifty-seven patients were prospectively studied over a 10-month period. Each patient was clinically assessed, photographed and independently scanned between 36 and 72 h of the burn. Patients were reviewed until wound healing had occurred within 12 days or skin grafting had been performed. The median age was 1 year and 10 months (range 5 months to 15 years and 8 months). The median body surface area burnt was 7.0% (range 0.5-30%). In 30 patients, the burn did not heal within 12 days, 17 of which were grafted. Clinical examination correctly determined 66% of deep partial or full thickness burns between 36 and 72 h of injury compared to 90% using LDI. The LDI was also more specific; correctly diagnosing 96% of superficial partial thickness burns as opposed to 71% on clinical examination. Moderate degrees of movement did not appear to limit the accuracy of the scan.
The effects of estrogen on the female reproductive system are well known. In contrast, comparatively recent research has demonstrated that estrogen also exerts specific effects on the cardiovascular system--particularly the vasculature. This review summarizes some of the current ideas of how estrogen regulates and modulates vascular function, and focuses primarily on potential mechanisms of estrogen-induced vasodilation. Although many studies indicate estrogen exerts beneficial effects on the circulatory system, the overall conclusions from clinical studies remain somewhat equivocal. In contrast, it is clear that estrogen reduces atherosclerosis by reducing low-density lipoproteins (LDL) and inflammatory processes in the vasculature, and may also act as an antioxidant; however, these effects account for only a portion of the total cardiovascular benefit of estrogen. Estrogen is also a vasodilator and hypotensive agent, and can induce vascular relaxation by stimulating release of endothelium-derived vasodilatory substances (e.g., nitric oxide [NO]) or by acting directly on the vascular smooth muscle (VSM). Recent evidence indicates that calcium and potassium channels in VSM cells play an important role in mediating estrogen-induced relaxation of many vascular beds, but elucidating the signal transduction mechanisms coupling estrogen receptor (ER alpha and/or ER beta) activation to generation of second messengers and effector mechanisms remains an area of intense study. Not surprisingly, it is becoming apparent that the molecular basis of estrogen's influence on vascular function is multifactorial. A better understanding of these signaling mechanisms should lead to the development of powerful therapeutic agents which can maximize the many beneficial effects of estrogen action, while helping minimize the harmful (and sometimes lethal) side effects.
Dehydroepiandrosterone (DHEA) and its sulfate conjugate (DHEA-S) are the most abundantly produced human adrenal steroids to be reduced with age. DHEA may be related to the process of skin aging through the regulation and degradation of extracelluar matrix protein. In this study, we demonstrate that DHEA can increase procollagen synthesis and inhibit collagen degradation by decreasing matrix metalloproteinases (MMP)-1 synthesis and increasing tisuue inhibitor of matrix metalloprotease (TIMP-1) production in cultured dermal fibroblasts. DHEA was found to inhibit ultraviolet (UV)-induced MMP-1 production and the UV-induced decrease of procollagen synthesis, probably due to the inhibition of UV-induced AP-1 activity. DHEA (5%) in ethanol:olive oil (1:2) was topically applied to buttock skin of volunteers 12 times over 4 weeks, and was found to significantly increase the expression of procollagen alpha1(I) mRNA and protein in both aged and young skin. On the other hand, topical DHEA significantly decreased the basal expression of MMP-1 mRNA and protein, but increased the expression of TIMP-1 protein in aged skin. We also found that DHEA induced the expressions of transforming growth factor-beta1 and connective tissue growth factor mRNA in cultured fibroblasts and aged skin, which may play a role in the DHEA-induced changes of procollagen and MMP-1 expression. Our results suggest the possibility of using DHEA as an anti-skin aging agent.
This study sought to assess the validity of independent, blinded reporting of Laser Doppler Imaging (LDI) prediction of burn wound outcome in children. Two experienced paediatric burn consultants were invited to report on LDI scans performed routinely within 3 days of burn. They were provided with the LDI flux image, a low-resolution colour digital photograph of the burnt area and a basic history. Report predictions were correlated with outcome. Reports were compiled on 50 scans performed on 31 patients at a mean of 54h post burn. Of the 100 reports generated, mean correlation with outcome was 97%. If the LDI predicted a deep burn, it was always correct. Non-correlations were due to a number of factors including inadequate scanning of the affected area, excessive movement and residual wound debris. Accurate prediction of burn wound outcome could be made via the standard information generated by LDI and appeared more reliable than clinical prediction. The correlation improved with increasing experience with LDI.
The relationship between burn depth, healing time and the development of hypertrophic scarring (HTS) is well recognised by burn surgeons but is seldom mentioned in the published literature. We studied 337 children with scalds whose scars were monitored for up to 5 years. Overall HTS rates were found to be: under 10 days to healing=0%, 10-14 days=8%, 15-21 days=20%, 22-25 days=40%, 26-30 days=68% and over 30 days=92%. In the conservatively treated group the HTS rates are: under 10 days=0%, 10-14 days=2%, 15-21 days=20%, 22-25 days=28%, 26-30 days=75% and over 30 days=94%. If skin grafting is undertaken there is a much higher incidence of HTS in the 10-14 days group: 10-14 days=33%, 15-21 days=19%, 22-25 days=54%, 26-30 days=64% and over 30 days=88%. We conclude that there is a low risk of HTS formation in scalds healed before 21 days, and that surgery should be reserved for scalds likely to take more than 21 days to heal.
Testosterone supplementation can help reduce many of the symptoms associated with androgen deficiency in the aging male by its effects on various parts of the body. Bone mineral density can decrease in the hypogonadal man and this may contribute to the increased fracture rate in the elderly. Testosterone therapy can improve bone mineral density and bone architecture by increasing bone formation and decreasing bone resorption - the possible benefits on fracture rate are unknown. Testosterone also improves body composition by reducing body fat mass and increasing lean body mass, and by increasing epidermal thickness, but its effects on muscle strength are still debated. In patients with diabetes and androgen deficiency, testosterone supplementation appears to reduce blood glucose and this could have important implications for cardiovascular risk reduction in patients with diabetes or the metabolic syndrome. The wide-ranging benefits of testosterone therapy in young and old men are clear and it appears that the route of administration (intramuscular, oral, or transdermal) does not alter this fact, but future work could illustrate even more profound effects of testosterone (e.g., in reducing cardiovascular risk) that could result in its recommended use in a wider range of patients.
Burn wound progression is a poorly understood process by which certain superficial partial-thickness burns spontaneously advance into deep partial-thickness or full-thickness wounds. Progression of an injury into deeper tissue is an important phenomenon in the treatment of thermal injury due to the fact that burn wound depth may be a significant determinant of morbidity and treatment. This article reviews current knowledge of the pathogenesis, molecular and cellular mechanisms, local and systemic factors, and treatment modalities related to wound conversion.
All peer-reviewed, original, and review articles published in English-language literature relevant to the topic of burn wound conversion on animals and human subjects were selected for this review.
After assessing data relevance, independent extraction by a sole reviewer was performed. Data were tabulated according to the following categories: pathogenesis, mechanisms, local and systemic factors, and treatment.
Burn wound progression is complex and caused by additive effects of inadequate tissue perfusion, free radical damage, and systemic alterations in the cytokine milieu of burn patients, leading to protein denaturation and necrosis. Even though insufficient evidence exists for causal inferences, infection, tissue desiccation, edema, circumferential eschar, impaired wound perfusion, metabolic derangements, advanced age, and poor general health play important roles. Although consensus-building research is ongoing, current mainstays of treatment include adequate fluid resuscitation, nutritional support, and local wound care, with an emphasis on topical antimicrobial agents and biosynthetic dressings. Identifying early indicators by elucidating possible interacting or synergistic mechanisms and by developing preventative strategies will enhance prevention and treatment.
There is a need, both in clinical and research settings, for an affordable, objective method of assessing burn depth. This study compares burn depth assessment by videomicroscopy with laser Doppler imaging (LDI) in patients with dermal burns. The videomicroscope is inexpensive compared to LDI, and can visualise the dermal capillary structure, therefore potentially allowing objective assessment of dermal burn injuries.
Patients admitted <72 h post-injury were included in the trial. Blinded LDI and videomicroscopy assessments were carried out. The patients were then followed up to one of three end-points: primary healing without surgery; early surgery; delayed healing and subsequent split skin grafting. The incidence of infection was also noted.
Twenty-seven burn wounds were examined. In superficial partial thickness injuries, the videomicroscope reliably demonstrated an intact or nearly intact dermal vascular structure, progressing through to large amounts of capillary destruction and haemoglobin deposition in deep partial thickness injuries and complete destruction in full thickness injuries. The videomicroscope findings correlated strongly with both those of the LDI (p<0.001) and with clinical outcome (p<0.001).
The videomicroscope is capable of accurately and objectively assessing burn depth. The results correlated well with both the clinical outcome and the laser Doppler findings. In addition, videomicroscopy is significantly cheaper than LDI and avoids several of the disadvantages of LDI.
The depth of a burn wound and/or its healing potential are the most important determinants of the therapeutic management and of the residual morbidity or scarring. Traditionally, burn surgeons divide burns into superficial which heal by rapid re-epithelialization with minimal scarring and deep burns requiring surgical therapy. Clinical assessment remains the most frequent technique to measure the depth of a burn wound although this has been shown to be accurate in only 60-75% of the cases, even when carried out by an experienced burn surgeon. In this article we review all current modalities useful to provide an objective assessment of the burn wound depth, from simple clinical evaluation to biopsy and histology and to various perfusion measurement techniques such as thermography, vital dyes, video angiography, video microscopy, and laser Doppler techniques. The different needs according to the different diagnostic situations are considered. It is concluded that for the initial emergency assessment, the use of telemetry and simple burn photographs are the best option, that for research purposes a wide range of different techniques can be used but that, most importantly, for the actual treatment decisions, laser Doppler imaging is the only technique that has been shown to accurately predict wound outcome with a large weight of evidence. Moreover this technique has been approved for burn depth assessment by regulatory bodies including the FDA.
Current concepts on burn wound conversion-a review of recent advances in understanding the secondary progressions of burns
- A A Salibian
- Atd Rosario
- Lam Severo
- L Nguyen
- D A Banyard
- J D Toranto
Salibian AA, Rosario ATD, Severo LAM, Nguyen L, Banyard DA,
Toranto JD. Current concepts on burn wound conversion-a
review of recent advances in understanding the secondary
progressions of burns. Burns 2016;42(August (5)):1025-35, doi:
http://dx.doi.org/10.1016/j.burns.2015.11.007.
Phenomenon of progressive deepening in burn wounds. Chinese burn surgery
- Z Yang
Yang Z. Phenomenon of progressive deepening in burn
wounds. Chinese burn surgery. Netherlands: Springer; 2015,
doi:http://dx.doi.org/10.1007/978-94-017-8575-4 p. 210.