Laser Speckle Contrast Analysis Research Articles

Use of Laser Speckle Contrast Analysis during pelvic surgery in a uterine transplantation model.

Aim:Uterine transplantation (UTx) is proposed for treatment of uterine factor infertility. Our aim was to assess whether Endoscopic Laser Speckle Contrast Analysis (eLASCA) could evaluate pelvic blood flow at anastomotic sites required for sheep and rabbit UTx.Results/methodology:eLASCA detected blood flow in rabbit UTx #7 and #9. In sheep UTx #2, #3 and #5, the results allowed us to conclude that blood flow was present in the uterine graft following transplantation; and post-UTx, the animal had heart and respiratory rates, and oxygen saturation compatible with a normal hemodynamic status.Conclusion:These preliminary results establish the potential of Laser Speckle Contrast Analysis as noncontact and real-time tool for observation of spatially-resolved blood flow from which other parameters can be derived.

Effects of hepatic blood inflow on liver ultrastructure and regeneration after extensive liver resection in rats with cirrhosis.

The aim of the present study was to investigate the effects of hepatic blood inflow on liver function, liver ultrastructure and the regeneration of future liver remnant (FLR) following major hepatectomy in rats with liver cirrhosis. A rat model of cirrhosis was established through intraperitoneal injection of carbon tetrachloride for 8 consecutive weeks. Extensive liver resection and different blood inflow models by portal vein (PV) and/or hepatic artery (HA) stenosis were conducted on the cirrhosis rats. Animal models were constructed as follows: Control (group A), low-flow PV + high-flow HA (group B), low-flow PV + low-flow HA (group C), high-flow PV + high-flow HA (group D) and high-flow PV + low-flow HA (group E). Hepatic blood inflow was detected by laser speckle contrast analysis, liver function and pathological changes were analyzed, Masson staining was used to identify the fibrosis of the liver and Periodic acid-Schiff staining was used to identify glycogen synthesis and hepatocyte function. The liver cell ultrastructure was evaluated by transmission electron microscopy, and the expression of Ki-67 in hepatocytes and the weight of the FLR were recorded to determine the regeneration of the FLR. Five days after major hepatectomy and liver blood inflow modulation, pathological examination of the livers from groups B and C revealed less congestion and less extensive hepatocellular injury. The serum alanine aminotransferase level of group B at 1, 3 and 5 days after hepatectomy and blood inflow modulation was 460.9±31.7, 331.0±22.0 and 285.6±15.8 U/l, respectively (control group: 676.9±41.7, 574.9±28.0 and 436.1±32.7 U/l, respectively; P<0.05); the total bilirubin of group B at 1, 3 and 5 days was 20.4±1.5, 16.1±1.0 and 13.5±0.6 µmol/l, respectively (control group: 30.3±1.4, 26.5±0.8 and 22.1±1.2 µmol/l, respectively; P<0.05). The size of the endoplasmic reticulum in the low-flow PV groups increased significantly and the mitochondrial swelling was alleviated. The positive rate of Ki-67 in the hepatocytes of groups B, C and D was 23.9±3.6, 15.7±2.3 and 12.9±2.4%, respectively (control group: 10.1±2.1%, P<0.05), and the positive rate of Ki-67 in group E was 6.1±1.4% (compared with that of the control group, P<0.05). The remnant liver weight of group B was 15.4±1.0 g (compared with that of the control group, P<0.05). Therefore, decreased portal blood flow combined with increased hepatic arterial blood flow alleviated the congestion in the liver following major hepatectomy in cirrhotic rats, improved the pathological status and liver function, increased the expression of Ki-67 and promoted liver regeneration.

Is laser speckle contrast analysis (LASCA) the new kid on the block in systemic sclerosis? A systematic literature review and pilot study to evaluate reliability of LASCA to measure peripheral blood perfusion in scleroderma patients

A reliable tool to evaluate flow is paramount in systemic sclerosis (SSc). We describe herein on the one hand a systematic literature review on the reliability of laser speckle contrast analysis (LASCA) to measure the peripheral blood perfusion (PBP) in SSc and perform an additional pilot study, investigating the intra- and inter-rater reliability of LASCA. A systematic search was performed in 3 electronic databases, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. In the pilot study, 30 SSc patients and 30 healthy subjects (HS) underwent LASCA assessment. Intra-rater reliability was assessed by having a first anchor rater performing the measurements at 2 time-points and inter-rater reliability by having the anchor rater and a team of second raters performing the measurements in 15 SSc and 30 HS. The measurements were repeated with a second anchor rater in the other 15 SSc patients, as external validation. Only 1 of the 14 records of interest identified through the systematic search was included in the final analysis. In the additional pilot study: intra-class correlation coefficient (ICC) for intra-rater reliability of the first anchor rater was 0.95 in SSc and 0.93 in HS, the ICC for inter-rater reliability was 0.97 in SSc and 0.93 in HS. Intra- and inter-rater reliability of the second anchor rater was 0.78 and 0.87. The identified literature regarding the reliability of LASCA measurements reports good to excellent inter-rater agreement. This very pilot study could confirm the reliability of LASCA measurements with good to excellent inter-rater agreement and found additionally good to excellent intra-rater reliability. Furthermore, similar results were found in the external validation.

REAL TIME ASSESSMENT OF MICROCIRCULATION IN HYPERTENSION USING LASER SPECKLE CONTRAST ANALYSIS

Objective: Skin microcirculation has been suggested as a model of generalized microvascular function. It has also been used as a window to access endothelial function in the microvasculature. In this study we evaluated endothelial dysfunction of skin microcirculation in hypertensive patients compared to healthy, normotensive individuals using Laser Speckle Contrast Analysis (LASCA), a novel tool to assess microcirculation non-invasively, in real time and with high reproducibility. Design and method: We studied a group of 26 untreated hypertensive patients with new-onset essential hypertension without cardiovascular comorbidities, mean age 50.5 ± 15.7 years and 13 healthy individuals matched for age, sex and body mass index. In all subjects, forearm skin blood flow was recorded under standardized conditions using a laser speckle contrast imager (PeriCam PSI NR System, Perimed, Järfälla, Sweden). Post-occlusive reactive hyperemia (PORH) was assessed following a standardized protocol and data were analyzed with signal processing software (PIMSoft, Perimed). The amplitude of PORH responses was expressed as a percentage increase between peak and baseline perfusion (%), baseline Cutaneous Vascular Conductance (CVC), peak CVC and peak CVC minus baseline CVC. The CVC was calculated as the flux divided by mean arterial pressure and expressed in perfusion units (PU)/mmHg. Results: Baseline perfusion was similar between the two groups. However, during PORH patients with hypertension showed significantly lower percentage increase from baseline to peak perfusion (145.9 ± 9.72 vs 181.68 ± 12.35 %, p = 0.019). In addition, baseline CVC (0.34 ± 0.019 vs 0.43 ± 0.03 PU/mmHg, p = 0.009) and peak CVC (0.82 ± 0.04 vs 1.2 ± 0.06 PU/mmHg, p < 0.001) were significantly lower in hypertensive patients compared to controls. Finally, PORH amplitude as expressed by peak CVC minus baseline CVC (0.48 ± 0.03 vs 0.76 ± 0.04 PU/mmHg, p < 0.001) was significantly lower in hypertensive patients compared to normotensives. Conclusions: Using LASCA, a non-contact, real-time, highly reproducible and sensitive technique for the assessment of skin microcirculation, we showed that hypertensive patients demonstrate impaired microvascular responses to stimulation tests. Endothelial dysfunction is present in the very early stages of essential hypertension, long before the establishment of overt cardiovascular disease, and LASCA may represent a novel, valuable tool for its assessment.

Improving temporal resolution and speed sensitivity of laser speckle contrast analysis imaging based on noise reduction with an anisotropic diffusion filter

The fluctuation of contrast caused by statistical noise degenerates the temporal/spatial resolution of laser speckle contrast imaging (LSCI) and limits the maximum speed when imaging. In this study, we investigated the application of the anisotropic diffusion filter (ADF) to temporal LSCI and found that the edge magnitude parameter of the ADF can be determined by the mean of the contrast image. Because the edge magnitude parameter is usually denoted as K, we term this the K-constant ADF (KC-ADF) and show that temporal sensitivity is improved when imaging because of the enhanced signal-to-noise ratio when using the KC-ADF in small-animal experiments. The cardiac cycle of a rat as high as 390 bpm can be imaged with an industrial camera.

Increased visceral tissue perfusion with heated, humidified carbon dioxide insufflation during open abdominal surgery in a rodent model.

Tissue perfusion during surgery is important in reducing surgical site infections and promoting healing. This study aimed to determine if insufflation of the open abdomen with heated, humidified (HH) carbon dioxide (CO2) increased visceral tissue perfusion and core body temperature during open abdominal surgery in a rodent model. Using two different rodent models of open abdominal surgery, visceral perfusion and core temperature were measured. Visceral perfusion was investigated using a repeated measures crossover experiment with rodents receiving the same sequence of two alternating treatments: exposure to ambient air (no insufflation) and insufflation with HH CO2. Core body temperature was measured using an independent experimental design with three treatment groups: ambient air, HH CO2 and cold, dry (CD) CO2. Visceral perfusion was measured by laser speckle contrast analysis (LASCA) and core body temperature was measured with a rectal thermometer. Insufflation with HH CO2 into a rodent open abdominal cavity significantly increased visceral tissue perfusion (2.4 perfusion units (PU)/min (95% CI 1.23–3.58); p<0.0001) compared with ambient air, which significantly reduced visceral blood flow (-5.20 PU/min (95% CI -6.83- -3.58); p<0.0001). Insufflation of HH CO2 into the open abdominal cavity significantly increased core body temperature (+1.15 ± 0.14°C) compared with open cavities exposed to ambient air (-0.65 ± 0.52°C; p = 0.037), or cavities insufflated with CD CO2 (-0.73 ± 0.33°C; p = 0.006). Abdominal visceral temperatures also increased with HH CO2 insufflation compared with ambient air or CD CO2, as shown by infrared thermography. This study reports for the first time the use of LASCA to measure visceral perfusion in open abdominal surgery and shows that insufflation of open abdominal cavities with HH CO2 significantly increases visceral tissue perfusion and core body temperature.

Temporal and Spatial Quantification of Pain- Related Small Fiber Functionality Assessed Using Laser Speckle Contrast Analysis.

This study aimed to establish a practical method for assessing pain symptomatology and develop criteria for quantifying small fiber functions using laser speckle contrast analysis (LASCA). Axon flare responses, which reflect small fiber functions, were induced either by histamine or capsaicin applied to the volar surface of the skin of the left forearm. To inhibit small fiber function, local anesthetic cream was applied to the skin of right forearm. The effects on pain symptomatology (severity/timing) and axon flare responses (temporal/spatial characteristics) were measured using LASCA. To highlight the clinical relevance, this method was applied to 3 different types of patients with small fiber dysfunction. Forty-four forearms of 22 healthy volunteers were tested. Eutectic mixture local anesthetic cream reduced the severity and duration of pain, abolishing or prolonging the latency to reach 3-fold higher levels of basal skin microcirculation levels, and decreasing the area and intensity of flare responses. There were positive correlations between pain symptomatology and flare response characteristics in the control forearm. Similar results were confirmed in neuropathic pain patients. Pain-related small fiber functions and symptomatology (two-in-one method) can be assessed via histamine- or capsaicin-evoked axon flare responses in as little as 15 minutes. The reduction of small fiber functions are characterized by decrease in flare size/intensity at 5 minutes after stimulation and prolongation/abolishment of the latency to reach 3-fold higher levels of baseline skin microcirculation. LASCA may be applied in the clinic to aid early diagnosis, monitor disease progression, and objectively assess treatment efficacy in patients with neuropathic pain.

Stem cells enhance reperfusion following ischemia: Validation using laser speckle imaging in predicting tissue repair.

The lack of real-time assessment of vascular perfusion changes remains a major weakness in assessing the efficacy of bone marrow stromal cells (BMSC) therapeutic ischemia reperfusion (I/R) injury. This study provides for the first time the real-time in vivo perfusion monitoring in I/R mice with BMSC therapy. Animal model. Surgically created cutaneous flaps perfused by the inferior epigastric vessels were subjected to 3.5 hours of ischemia/reperfusion. Wound healing and vascular perfusion were assessed by Image-J and laser speckle contrast analysis (LSCA) in three groups (sham, I/R, and I/R + BMSC). BMSC tracking was quantified in an additional two groups (with/without I/R) using intravital fluorescent microscopy. The histopathology of skin flaps was examined by hematoxylin and eosin stain. Infiltrated macrophages were analyzed by confocal immunofluorescent microscopy. Postischemic tissues treated with BMSC demonstrated significantly greater survival than I/R control. On days 3 to 7 postreperfusion, both proximal and distal areas in BMSC-treated flaps demonstrated greater levels of perfusion than untreated I/R flaps (P < 0.05). Intravital fluorescent microscopy revealed that numbers of labeled BMSC were significantly increased in the distal area compared to the proximal area in both with and without ischemic mice. Histological examination showed lower necrosis and infiltrated inflammatory cells in I/R + BMSC-treated mice versus I/R controls. BMSC accumulated in I/R flaps and exerted beneficial effects including: 1) improving vascular perfusion and 2) attenuating inflammatory cell infiltration. LSCA facilitates monitoring of the real-time restitution of perfusion during flap wound healing in experimental animals and could also similarly applied in clinical investigations. NA. Laryngoscope, 128:E198-E205, 2018.

Use of Laser-Speckle Contrast Analysis in the Study of “Non Healing” Leg Ulcers-A Preliminary Study

Use of Laser-Speckle Contrast Analysis in the Study of “Non Healing” Leg Ulcers-A Preliminary Study

Pathophysiological and behavioral deficits in developing mice following rotational acceleration-deceleration traumatic brain injury.

ABSTRACTAbusive head trauma (AHT) is the leading cause of death from trauma in infants and young children. An AHT animal model was developed on 12-day-old mice subjected to 90° head extension-flexion sagittal shaking repeated 30, 60, 80 and 100 times. The mortality and time until return of consciousness were dependent on the number of repeats and severity of the injury. Following 60 episodes of repeated head shakings, the pups demonstrated apnea and/or bradycardia immediately after injury. Acute oxygen desaturation was observed by pulse oximetry during respiratory and cardiac suppression. The cerebral blood perfusion was assessed by laser speckle contrast analysis (LASCA) using a PeriCam PSI system. There was a severe reduction in cerebral blood perfusion immediately after the trauma that did not significantly improve within 24 h. The injured mice began to experience reversible sensorimotor function at 9 days postinjury (dpi), which had completely recovered at 28 dpi. However, cognitive deficits and anxiety-like behavior remained. Subdural/subarachnoid hemorrhage, damage to the brain-blood barrier and parenchymal edema were found in all pups subjected to 60 insults. Proinflammatory response and reactive gliosis were upregulated at 3 dpi. Degenerated neurons were found in the cerebral cortex and olfactory tubercles at 30 dpi. This mouse model of repetitive brain injury by rotational head acceleration-deceleration partially mimics the major pathophysiological and behavioral events that occur in children with AHT. The resultant hypoxia/ischemia suggests a potential mechanism underlying the secondary rotational acceleration-deceleration-induced brain injury in developing mice.

Pericyte implantation in the brain enhances cerebral blood flow and reduces amyloid-β pathology in amyloid model mice

Pericytes are a major component of cerebrovasculature playing a key role in maintaining cerebrovascular homeostasis. These cells have also been suggested to regulate brain metabolism of amyloid-β (Aβ), disturbances of which are believed to contribute to the pathogenesis of Alzheimer's disease (AD). To examine the effects of pericytes on brain Aβ metabolism, C3H/10T1/2 mouse mesenchymal stem cells were differentiated into pericytes and stereotaxically injected into the brains of amyloid AD model APP/PS1 mice at the age of 18 to 20months. Consistent with a role of pericytes in modulating cerebrovascular function, brain microcirculation in the pericyte-injected hemisphere of the mice was increased 3weeks after implantation compared to the contralateral hemisphere when measured by laser speckle contrast analysis technology. Importantly, enzyme-linked immunosorbent assay revealed that the levels of insoluble Aβ40 and Aβ42 were significantly lower in the hippocampus of the pericyte-injected hemisphere of the APP/PS1 mice than that of the contralateral side. Consistently, immunohistochemical analysis demonstrated that the pericyte implantation reduced Aβ deposition in the hippocampus. When brain slices from the APP/PS1 mice were incubated with C3H/10T1/2 cell-derived pericytes, Aβ42 levels were significantly reduced in a manner that depends on the expression of a major Aβ endocytic receptor, the low-density lipoprotein receptor-related protein 1 (LRP1). While LRP1 mediated the cellular uptake of Aβ in the pericytes, the amounts of major Aβ-degrading enzymes were not affected by LRP1 knockdown. Together, our findings indicate that mesenchymal stem cell–derived pericytes have the capacity to reduce brain Aβ and related pathology, and suggest that cell-based therapy through transplantation of pericytes may be a promising approach to prevent and/or treat AD.

Assessment of treatment effects on digital ulcer and blood perfusion by laser speckle contrast analysis in a patient affected by systemic sclerosis.

Laser speckle contrast analysis (LASCA) is a good tool to evaluate the variation in peripheral blood perfusion during long-term follow-up and is able to safely monitor digital ulcer evolution in scleroderma patients. It evaluates blood perfusion in different areas within the skin lesions and surrounding them during standard treatment.

An international SUrvey on non-iNvaSive tecHniques to assess the mIcrocirculation in patients with RayNaud's phEnomenon (SUNSHINE survey).

To canvas opinion concerning the role of non-invasive techniques in the assessment of patients with Raynaud's phenomenon (Rp) in clinical and research settings: four nailfold capillaroscopy methods [videocapillaroscopy (NVC), dermoscopy, stereomicroscopy, digital USB microscopy], four laser Doppler methods (laser Doppler flowmetry, imaging, anemometry/velocimetry, laser speckle contrast analysis), thermographic imaging, and upper limb arterial Doppler ultrasound. Emails with a link to the survey were sent to physicians from the European Scleroderma Trials and Research group (EUSTAR), the EULAR Study Group on Microcirculation in Rheumatic Diseases (SG_MC/RD) and members of the pediatric rheumatology Email board. The main descriptive analysis related to physicians looking after adult patients, with some analysis also of opinions from paediatric rheumatologists. 106 'adult physicians' responded (a response rate of 25.8%), of whom 68.9% were European, and 81.1% practising for more than 10years. Nineteen paediatricians responded. The most widely available technique was NVC (72.7%). Nailfold capillaroscopy was most frequently performed by the physician him/herself, using different types of equipment relating to availability. Most rheumatologists reported high levels of appropriateness for NVC in both clinical and research settings for global assessment and differential diagnosis of Rp. Other techniques were less used. Of all the different techniques, nailfold capillaroscopy was the one most used in both clinical and research settings by adult physicians, the majority of whom use NVC in their everyday practice. The low proportion of clinicians using other techniques suggests that these are currently mainly research tools, available only in specialist centres.

Correlations between blood perfusion and dermal thickness in different skin areas of systemic sclerosis patients

ObjectiveTo identify possible correlations between skin blood perfusion (BP) and dermal thickness (DT) in different skin areas of systemic sclerosis (SSc) patients. MethodsSixty-two SSc patients, according to 2013 EULAR/ACR criteria, and 62 healthy subjects (CNT) were enrolled. Skin BP was analysed by laser speckle contrast analysis (LASCA) at the level of dorsum of the middle phalanx of the third fingers, dorsal aspect of the hands and zygoma. DT was assessed by both skin high frequency ultrasound (US) and modified Rodnan skin score (mRSS) in the same above reported areas. All patients were studied also by nailfold videocapillaroscopy (NVC) to assess the proper pattern of microvascular damage (“Early”, “Active”, or “Late”). ResultsAt the level of finger dorsum a statistically significant negative correlation was observed in SSc patients between skin BP and both ultrasound-DT (p=0.0005 r=0.43) and mRSS (p=0.0007 r=0.42), but not at the level of hand dorsum and zygoma. No statistically significant correlation was present between skin BP and ultrasound-DT at any level in CNT. In detail, SSc patients, compared to CNT, showed a statistically significant lower BP only at level of fingers (median PU 72.6 vs 136.1 respectively, p<0.0001) and a statistically significant higher ultrasound-DT at the level of dorsum of 3th finger bilaterally (median mm 0.9 vs 0.7, p<0.0001), dorsum of hands (median mm 0.9 vs 0.7, p<0.0001) and zygoma (median mm 0.8 vs 0.7, p<0.0001). A significant positive correlation between ultrasound-DT and mRSS was observed in SSc patients at level of the three areas (dorsum of fingers p<0.0001 r=0.51; dorsum of hands p=0.03 r=0.27; zygoma p=0.0001 r=0.45). A progressive decrease of skin BP and increase of ultrasound-DT was found correlated with the progression of the severity of NVC patterns. ConclusionsThis study demonstrates for the first time in SSc patients a significant inverse relationship between skin BP, measured by LASCA, and DT, evaluated by both US and mRSS, at the level of dorsum of the middle phalanx of the third fingers.

AAT – A Novel Cartilage‐Protective Mediator

IntroductionThe resolution of inflammation is a process that ensures repair and restoration of tissue physiology. Using integrated approach with proteomic analyses and bio‐assays with human chondrocytes and experimental arthritis, we identified α1‐Antitrypsin(AAT), the chief neutrophil elastase(NE) inhibitor, as a novel chondroprotective protein produced in resolving exudates.MethodsResolving rat pleural exudates (24h post‐carrageenan injection) were run for mass spectrometry using ion‐trap mass analyzer (MS/MS LTQ Orbitrap XL). Human C28/I2 chondrocytes were grown in high‐density micromass(MM)1 incubated with AAT with/without catabolic stimuli interleukin(IL)‐1β (20ng/ml) or osteoarthritic synovial fluids (OASF; 1:100) for 48h. Glycosaminoglycans (GAG) deposition was assessed using Alcian Blue(AB) staining. Gene expression was quantified by qPCR. Data are expressed as 2−ΔΔCt equation–relative amount of target genes, normalized to GAPDH and vehicle, with expression set to 1.0 (N=3). Inflammatory arthritis was induced though K/BxN serum transfer model2. Knee joint structure and cartilage integrity were determined 48h after intra‐articular(i.a.) or intra‐peritoneal(i.p.) injection of AAT (n=8) by the GAG‐sensitive toluidine blue staining of knee sections. Knee inflammation (diameter; n=14), changes in leukocyte kinetics (number of rolling and adherent leukocytes; intravital microscopy; n=8), blood perfusion (Laser Speckle Contrast Analysis; n=8), and pain (von Frey algesiometry; n=8) were evoked by i.a. injection of NE (5μg)3 with/without AAT(100ng) and quantified 4h post‐injection. One‐way ANOVA, or student's T‐test were applied for stats.ResultsProteomics identified AAT in pro‐resolving (24h post‐carrageenan) exudates. Exogenous AAT abrogated the effect of IL‐1β on MMP13 (p&lt;0.05). Incubation of chondrocyte MM with OASF augmented IL6 and MMP13 mRNA, with concomitant down‐regulation of COL2A1 and ACAN gene products: tested at 3–10 μg/ml, AAT significantly attenuated these effects (p&lt;0.01). GAG deposition confirmed the chondroprotection afforded by AAT: ~80% reduction by OASF and reversal to control levels with AAT (p&lt;0.01).In the model of arthritis, knee joint cartilage was eroded by ~65% (GAG content; p&lt;0.05). Intra‐articular injection of AAT(100ng) recovered cartilage integrity by 52% compared to vehicle‐injected contralateral joints (p&lt;0.05). Systemic AAT (10μg i.p.) reduced cartilage destruction by ~30%, compared to vehicle‐injected animals (p&lt;0.05).NE induced acute inflammation and pain in knee joints of mice: it caused a marked increase in knee diameter, synovial microcirculation, vascular response with increased leukocyte kinetics and a decrease in hindpaw withdrawal threshold (p&lt;0.01). Co‐administration of NE and AAT(100ng) significantly counteracted NE‐induced knee inflammation (p&lt;0.01) and potently reverted the NE‐induced pain (p&lt;0.01).ConclusionUsing resolving exudates as a bio‐source, we identified the neutrophil elastase inhibitor AAT as a novel tissue‐protective protein with a broad spectrum of activities, thus paving the way for new strategies to prevent joint pain and repair/restore compromised cartilage functions.

Retooling Laser Speckle Contrast Analysis Algorithm to Enhance Non-Invasive High Resolution Laser Speckle Functional Imaging of Cutaneous Microcirculation

Cutaneous microvasculopathy complicates wound healing. Functional assessment of gated individual dermal microvessels is therefore of outstanding interest. Functional performance of laser speckle contrast imaging (LSCI) systems is compromised by motion artefacts. To address such weakness, post-processing of stacked images is reported. We report the first post-processing of binary raw data from a high-resolution LSCI camera. Sharp images of low-flowing microvessels were enabled by introducing inverse variance in conjunction with speckle contrast in Matlab-based program code. Extended moving window averaging enhanced signal-to-noise ratio. Functional quantitative study of blood flow kinetics was performed on single gated microvessels using a free hand tool. Based on detection of flow in low-flow microvessels, a new sharp contrast image was derived. Thus, this work presents the first distinct image with quantitative microperfusion data from gated human foot microvasculature. This versatile platform is applicable to study a wide range of tissue systems including fine vascular network in murine brain without craniotomy as well as that in the murine dorsal skin. Importantly, the algorithm reported herein is hardware agnostic and is capable of post-processing binary raw data from any camera source to improve the sensitivity of functional flow data above and beyond standard limits of the optical system.

Analysis of Critically Perfused Tissues by Laser Speckle Contrast Analysis (LASCA) Perfusion Imaging

Background: The success of tissue transplantation and long-term tissue stability after wound healing depends on sufficient tissue perfusion. Laser Doppler-supported procedures allow for an objective measurement of relative tissue perfusion. The development of Speckle-based Laser Doppler imaging now enables a real-time representation of tissue perfusion. The perfusion of tissues relevant in plastic surgery such as scars, phalangeal replantations and burn wounds were systematically analysed by Laser Speckle Contrast Analysis (LASCA) imaging. Method: Perfusion of skin, scars, replanted fingers and different burn wound degrees (IIa, IIb and III) were systematically examined by LASCA imaging. Baseline perfusion of control tissue and perfusion values of compromised tissues were quantified and compared. Results: LASCA imaging shows significant differences in baseline perfusion of skin compared to atrophic scars, hypertrophic scars and keloids. Finger replantations with subsequent replantation failure show a characteristic and significant hypoperfusion in line with the expected clinical feature. A significant difference in tissue perfusion is seen in superficial (IIa) and superficial deep (IIb) burns, which are hard to distinguish on clinical examination. Deep burns (III) are characterised by hypoperfusion, which differs significantly from grade IIa and IIb burn wound perfusion, but not from baseline skin perfusion. Furthermore, the characteristic perfusion values of different burn degrees correspond to the varying treatment strategies. Conclusion: LASCA imaging is a robust method of perfusion imaging, which combines high resolution and speed. Hypoperfusion of tissues relevant to plastic surgery such as scars, phalangeal replantations and the different burn degrees (IIa, IIb and III) can be detected by LASCA imaging with high precision. Ease of use and immediate real-time imaging make LASCA imaging a reliable tool for the evaluation of tissue perfusion after plastic surgery procedures, which may influence further treatment decisions.

On the equivalence and differences between laser Doppler flowmetry and laser speckle contrast analysis.

Laser Doppler flowmetry (LDF) and laser speckle contrast analysis (LASCA) both utilize the spatiotemporal properties of laser speckle patterns to assess microcirculatory blood flow in tissue. Although the techniques analyze the speckle pattern differently, there is a close relationship between them. We present a theoretical overview describing how the LDF power spectrum and the LASCA contrast can be calculated from each other, and how both these can be calculated from an optical Doppler spectrum containing various degrees of Doppler shifted light. The theoretical relationships are further demonstrated using time-resolved speckle simulations. A wide range of Monte Carlo simulated tissue models is then used to show how perfusion estimates for LDF and LASCA are affected by changes in blood concentration and speed distribution, as well as by geometrical and optical properties. We conclude that perfusion estimates from conventional single exposure time LASCA are in general more sensitive to changes in optical and geometrical properties and are less accurate in the prediction of real perfusion changes, especially speed changes. Since there is a theoretical one-to-one relationship between Doppler power spectrum and contrast, one can conclude that those drawbacks with the LASCA technique can be overcome using a multiple exposure time setup.

Monitoring of peripheral blood flow in patients with systemic lupus erythematosus by using laser speckle contrast analysis

Objective To noninvasively assess peripheral blood flow changes in patients with systemic lupus erythematosus (SLE) before and after treatments by using laser speckle contrast analysis (LSCA), to compare eripheral blood flow between SLE patients and healthy controls, and to evaluate effects of air temperature, age and gender on peripheral blood flow changes. Methods Clinical data on air temperature at the first visit (groups of ≥ 20 ℃ and < 20 ℃ ), age (groups of < 20, 20-< 40 and ≥ 40 years), gender, blood and urine routine test results, complement levels and immunologic test findings were collected from 47 patients with SLE. The patients' condition was evaluated by systemic lupus erythematosus disease activity index (SLEDAI), and Spearman's correlation analysis was carried out to assess its correlation with peripheral blood flow changes (expressed as changes in speckle flow index [△SFI]values) measured by LSCA. Peripheral blood flow was compared between the 47 patients and 30 healthy human controls. Results Compared with healthy controls, SLE patients showed significantly lower subungual SFI values (7.017 ± 0.356 vs. 9.765 ± 0.337, t = 5.182, P 0.05) compared with those at the baseline. Air temperature affected subungual blood flow significantly (t = 2.415, P 0.05). In addition, neither gender nor age had obvious effects on subungual or periungual blood flow. Conclusions Compared with healthy controls, peripheral blood flow significantly changed in patients with SLE, and was improved to a certain extent after treatment. Air temperature markedly affects subungual blood flow. LSCA may be a supplementary approach to more convenient and quantitative assessment of the severity of SLE. Key words: Lupus erythematosus, systemic; Blood flow velocity; Laser speckle contrast analysis

Cerebral capillary velocimetry based on temporal OCT speckle contrast.

We propose a new optical coherence tomography (OCT) based method to measure red blood cell (RBC) velocities of single capillaries in the cortex of rodent brain. This OCT capillary velocimetry exploits quantitative laser speckle contrast analysis to estimate speckle decorrelation rate from the measured temporal OCT speckle signals, which is related to microcirculatory flow velocity. We hypothesize that OCT signal due to sub-surface capillary flow can be treated as the speckle signal in the single scattering regime and thus its time scale of speckle fluctuations can be subjected to single scattering laser speckle contrast analysis to derive characteristic decorrelation time. To validate this hypothesis, OCT measurements are conducted on a single capillary flow phantom operating at preset velocities, in which M-mode B-frames are acquired using a high-speed OCT system. Analysis is then performed on the time-varying OCT signals extracted at the capillary flow, exhibiting a typical inverse relationship between the estimated decorrelation time and absolute RBC velocity, which is then used to deduce the capillary velocities. We apply the method to in vivo measurements of mouse brain, demonstrating that the proposed approach provides additional useful information in the quantitative assessment of capillary hemodynamics, complementary to that of OCT angiography.