Laser Speckle Contrast Analysis Research Articles

Endoscopic laser speckle contrast analysis: A novel method to assess blood flow in gynecologic surgery

Endoscopic laser speckle contrast analysis: A novel method to assess blood flow in gynecologic surgery

Detecting relative speed changes of moving objects through scattering medium by using wavefront shaping and laser speckle contrast analysis.

Imaging through a scattering medium has been a main challenge in modern optical imaging field. Recently, imaging through scattering medium based on wavefront shaping has been reported. However, it has not been clearly investigated to apply the optical memory effect based iterative wavefront shaping technique in speed estimation of a moving object through scattering medium. Here, we proposed to combine the iterative wavefront shaping technique with laser speckle contrast analysis method to detect the relative speed changes of moving objects through scattering medium. Phantom experiments were performed to validate our method.

Cocaine-Induced Abnormal Cerebral Hemodynamic Responses to Forepaw Stimulation Assessed by Integrated Multi-Wavelength Spectroimaging and Laser Speckle Contrast Imaging

Simultaneous imaging of cerebral hemodynamic changes in response to functional activation during drug intoxication provides a valuable strategy to assess cocaine induced neurovascular dysfunction. However, this requires tools with sufficient spatiotemporal resolution and adequate signal to noise ratio (SNR). Though several technologies have been developed to address this demand during functional brain activation, their spatiotemporal resolution has been compromised to preserve SNR. In this study, we combine spatiotemporal-domain laser speckle contrast analysis and image correlation techniques to integrate multi-wavelength spectroimaging and laser speckle contrast imaging (MW-LSCI). Experimental results show that optimized spatiotemporal resolution with enhanced SNR were achieved that enabled simultaneous measurement of multiple hemodynamic responses (i.e., ΔHbO2, ΔHbR, ΔHbT and ΔCBF) during cocaine administration. Specifically, cocaine-induced functional cerebral hemodynamic changes were accessed by measuring the activation responses to forepaw electrical stimulation at different times after cocaine administration. With improved spatiotemporal resolution and SNR, the system was able to differentiate the heterogeneity of cocaine's effects on the cerebral vasculature and on tissue metabolism, demonstrating the unique capability of MW-LSCI for various brain functional and pharmacological studies.

Post-occlusive reactive hyperaemia (POHR) in systemic sclerosis: very early disease (VEDOSS) represents a separate entity compared to established disease

Objectives: Vascular involvement is a key feature of systemic sclerosis (SSc). Vascular changes are central to the pathogenesis of the disease and the assessment of vascular involvement has a prognostic value. This assessment therefore has a pivotal role in the management of SSc patients. The aim of our study was to evaluate post-occlusive reactive hyperaemia (PORH) in consecutive SSc patients and to test whether a PORH test might be a useful tool for the early diagnosis of SSc.Method: Between April 2011 and April 2015, 60 consecutive SSc patients (mean age 56 ± 15 years, females:males = 18:1) were enrolled in the study. The patients were divided into those with full-blown SSc (n = 50) and those with very early diagnosis of SSc (VEDOSS) (n = 10) according to the literature. Laser speckle contrast analysis (LASCA) was used to assess PORH.Results: A statistically significant difference was detected in the post-ischaemic hyperaemic peak flow between VEDOSS and established SSc (424% vs. 137%, p = 0.0011). PORH peak flow decreased according to the capillaroscopic pattern (early = 419%, active = 163%, late = 145%, p = 0.0027). Moreover, a correlation between capillary density and peak flow was revealed (rho = 0.33, p < 0.01).Conclusions: These data show a different pattern of vascular involvement in VEDOSS compared to established disease that mirrors capillaroscopic changes. Functional features of very early and established disease seem to be the physiological counterpart of abnormalities detected by capillaroscopy. The POHR test might be a useful aid for further characterization of vascular involvement in SSc. In particular, blunted POHR might prove a tool to separate pre-clinical from full-blown SSc.

Correlations between skin blood perfusion values and nailfold capillaroscopy scores in systemic sclerosis patients

ObjectivesTo correlate blood perfusion (BP) values assessed by laser speckle contrast analysis (LASCA) in selected skin areas of hands and face with nailfold capillary damage scores in systemic sclerosis (SSc) patients. MethodsSeventy SSc patients (mean SSc duration 6±5years) and 70 volunteer healthy subjects were enrolled after informed consent. LASCA was performed at different areas of the face (forehead, tip of nose, zygomas and perioral region) and at dorsal and volar regions of hands. Microvascular damage was assessed and scored by nailfold videocapillaroscopy (NVC) and the microangiopathy evolution score (MES) was calculated. ResultsSSc patients showed a significantly lower BP than healthy subjects at fingertips, periungual areas and palm of hands (p<0.0001), but not at the level of face and dorsum of hands. A gradual decrease of BP at fingertips, periungual and palm areas, was found in SSc patients with progressive severity of NVC patterns of microangiopathy (“early”, “active”, or “late”) (p<0.01). A negative correlation was observed between MES and BP values, as well as between loss of capillaries and BP, at the same areas (p<0.001 and p<0.01, respectively). Patients with diffuse cutaneous SSc (dcSSc) showed lower BP than those with limited cutaneous SSc (p<0.04). ConclusionsLASCA detects a significant reduction of BP only in those areas usually affected by Raynaud's phenomenon (fingertips, periungual and palm areas), especially in dcSSc patients, and BP values significantly correlate with the nailfold capillaroscopy scores of microangiopathy.

Improvement of Speckle Contrast Image Processing by an Efficient Algorithm.

We demonstrate an efficient algorithm for the temporal and spatial based calculation of speckle contrast for the imaging of blood flow by laser speckle contrast analysis (LASCA). It reduces the numerical complexity of necessary calculations, facilitates a multi-core and many-core implementation of the speckle analysis and enables an independence of temporal or spatial resolution and SNR. The new algorithm was evaluated for both spatial and temporal based analysis of speckle patterns with different image sizes and amounts of recruited pixels as sequential, multi-core and many-core code.

Abstract 19443: Riociguat for the Treatment of Raynaud’s Phenomenon: A Single-dose, Double-blind, Randomised, Placebo-controlled Cross-over Study (DIGIT)

Background: Raynaud’s phenomenon (RP) is a digital ischemia caused by vasoconstriction in the digital blood vessels. Triggers of RP include cold and stress. Medical therapy for RP is unsatisfactory, with many patients not responding to treatment. Here we investigated the safety, efficacy and pharmacokinetics of riociguat, a soluble guanylate cyclase stimulator, in patients with RP. Methods: Patients who had primary RP or secondary RP associated with systemic sclerosis (SSc), and a symptom duration of ≥1 year, were randomized to receive a single oral dose of riociguat 2 mg or placebo. Digital blood flow (DBF) in the right index finger was determined by Laser Speckle Contrast Analysis at room temperature (RT) and after 5 minutes of cold water exposure (CWE), both at baseline and 2 hours after study drug administration. Results: In the patients valid for evaluation (n=20), treatment with riociguat led to an increase in DBF versus baseline of 40.6% at RT and 15.1% after CWE. Based on predefined criteria, patients were considered responders if the placebo-corrected DBF after CWE increased by ≥10% versus baseline at 2 hours after drug intake. This was the case in 12/20 (60%) patients. The highest response rates were seen in patients with primary RP and limited cutaneous SSc, whereas patients with RP associated with diffuse cutaneous SSc responded less well. In responders, riociguat led to an increase in DBF versus baseline of 135.7% at RT and 38.9% after CWE. Riociguat Cmax (SD) 2 hours after drug intake was 76 (1.5) μg/ml, which is in the range previously seen in healthy volunteers and patients with pulmonary hypertension. Comparable Cmax values were observed in responders (81 [1.5] μg/ml) and non-responders (71 [1.6] μg/ml). AEs were reported in 5 patients receiving riociguat (headache, n=4; dyspepsia, n=1) and 1 patient receiving placebo (malaise). No serious AEs were reported. Conclusions: In this small pilot study, riociguat was well tolerated in patients with primary and secondary RP, and improved DBF versus placebo in 60% of patients after cold exposure.

Monitoring capillary blood flow using laser speckle contrast analysis with spatial and temporal statistics

Laser Speckle Contrast Imaging (LSCI) is a simple and powerful technique that is used for full-field imaging of blood flow. The technique analyzes fluctuations in a dynamic speckle pattern to detect the movement of particles. In this article Laser speckle contrast analysis based on spatial and temporal correlations (sLASCA and tLASCA) were used to provide a velocity map of the area of interest in real time without the need for scanning. Spatial and temporal laser speckle contrast analysis have been shown to be a viable real-time method for detecting variations in blood flow. The results of some initial experiments on volunteers are presented. Both the techniques namely sLASCA and tLASCA are able to pick up changes in blood flow, which may arise due to various physiological conditions. Further, more blood flow reflected due to less skin thickness was sensed by the tLASCA technique which can be put to good use in the follow-up of the treatment of certain diseases which may cause decreased blood flow. Thus, both the techniques can be used to compare differences in blood flow values at region in normal subjects and in diseased subjects.

Application of full field optical studies for pulsatile flow in a carotid artery phantom.

A preliminary comparative measurement between particle imaging velocimetry (PIV) and laser speckle contrast analysis (LASCA) to study pulsatile flow using ventricular assist device in a patient-specific carotid artery phantom is reported. These full-field optical techniques have both been used to study flow and extract complementary parameters. We use the high spatial resolution of PIV to generate a full velocity map of the flow field and the high temporal resolution of LASCA to extract the detailed frequency spectrum of the fluid pulses. Using this combination of techniques a complete study of complex pulsatile flow in an intricate flow network can be studied.

OC24.07: Use of endoscopic laser speckle contrast analysis to assess uterine perfusion and blood flow in a uterine transplantation model

OC24.07: Use of endoscopic laser speckle contrast analysis to assess uterine perfusion and blood flow in a uterine transplantation model

Short-term follow-up of digital ulcers by laser speckle contrast analysis in systemic sclerosis patients

ObjectiveTo monitor in systemic sclerosis (SSc) the evolution of digital ulcer (DU) status by analysing blood perfusion (BP) using laser speckle contrast analysis (LASCA). MethodsHand BP was recorded by LASCA in twenty SSc patients with recent onset fingertip DUs before and after 10days of local/systemic treatment. Regions of interest (ROIs) to analyse BP were created al the level of ulcer, peri-ulcer, periungual and fingertip areas. Visual analogue pain scale (VAS) was also administered to patients before and after follow-up. ResultsA statistically significant increase of BP was observed from T0 to T1 in the ROIs created at the level of the ulcer area (p<0.0001), as well as a significant decrease of BP was observed in the peri-ulcer area (p<0.0001). A statistically significant decrease of both ulcer size (p<0.0001) and VAS (p=0.001) was observed, whereas no significant variation of both periungual and fingertip BP was detected. ConclusionsLASCA may safely monitor DU evolution in SSc patients, by evaluating its blood perfusion and area during standard treatment. This may be useful to monitor DU evolution during treatment in clinical trials.

Enhancements on multi-exposure LASCA to reveal information of speed distribution

Laser Speckle Contrast Analysis (LASCA) has been proven to be a highly useful tool for the full-field determination of the blood perfusion of a variety of tissues. Some of the major advantages of this technique are its relatively high spatial and temporal resolution as well as its good or excellent accordance to Doppler systems. However, traditionally it is only able to report a single characteristic speed regarding to the actual range of interest. This might be misleading if multiple characteristic speeds are present (e. g. tremor and perfusion in skin) or if several kinds of tissues are mixed (e. g. parenchyma and vessels in brain). Here we present two relatively simple extensions of LASCA for these problems. The application of multiple autocorrelation functions (combined with the usage of multiple exposure times) can help in the separation of multiple characteristic speeds. We also present a useful method for the separation of information those originate from a mixture of different tissues. The latter method can be also implemented to single-exposure systems.

Methods for the morphological and functional evaluation of microvascular damage in systemic sclerosis.

Systemic sclerosis is a connective tissue disease characterized by alterations in microvascular structure and function. In these patients, numerous studies have demonstrated a relationship between capillary morphology and peripheral blood perfusion. Nailfold videocapillaroscopy reveals the peripheral microvascular morphology and thus allows classification and scoring of capillary abnormalities with respect to different microangiopathy patterns (early, active, and late). Laser Doppler flowmetry and laser speckle contrast analysis can be used to estimate cutaneous blood flow through microvessels and to assess and quantify blood perfusion at peripheral sites. These two methods are also used to identify changes in digital blood perfusion after the infusion of vasodilators.

Entropy analysis reveals a simple linear relation between laser speckle and blood flow.

Dynamic laser speckles contain motion information of scattering particles which can be estimated by laser speckle contrast analysis (LASCA). In this work, an entropy-based method was proposed to provide a more robust estimation of motion speed. An in vitro flow simulation experiment confirmed a simple linear relation between entropy, exposure time, and speed. A multimodality optical imaging setup is developed to validate the advantages of the entropy method based on laser speckle imaging, green light imaging, and fluorescence imaging. The entropy method overcomes traditional LASCA with less noisy interference, and extracts more visible and detailed vasculatures in vivo. Furthermore, the entropy method provides a more accurate estimation and a stable pattern of blood flow activations in the rat's somatosensory area under multitrial hand paw stimulations.

In vivo laser speckle imaging by adaptive contrast computation for microvasculature assessment

Interference of light backscattered from a diffused surface leads to speckle formation in laser speckle imaging. These time integrated speckle patterns can be statistically analyzed to study the flow profile of moving scatterers. Simple speckle contrast analysis techniques have limited ability to distinguish thin structures due to presence of corrupting speckles. This paper presents a high resolution imaging technique by adaptive computation of contrast for laser speckle contrast analysis (adLASCA). Speckle images of retinal microvasculature in mice model are acquired during normal and reduced blood flow conditions. Initially, the speckle images are registered to compensate for movements, associated with heart beating and respiration. Adaptive computation is performed using local image statistics, estimated within a spatially moving window over successive time frames. Experimental evidence suggests that adLASCA outperforms other contrast analysis methods, substantiating significant improvement in contrast resolution. Fine vessels can be distinguished more efficiently with reduced fluctuations in contrast level. Quantitative performance of adLASCA is evaluated by computing standard deviation, corresponding to speckle fluctuations due to unwanted speckles. There is a significant reduction in standard deviation compared to other methods. Therefore, adLASCA can be used for enhancing microvasculature in high resolution perfusion imaging with reduced effect of corrupting speckles for effective assessment.

SAT0174 Follow-Up of Digital Ulcers with Local Laser Speckle Contrast Analysis in Systemic Sclerosis Patients

BackgroundSystemic sclerosis (SSc) is a chronic disorder characterized by damage of microcirculation and progressive tissue hypoperfusion that increase the risk for digital ulcers (DU) (1,2). Both local and systemic treatments...

FRI0480 Laser Speckle Contrast Analysis Assessment of Blood Perfusion in Several Skin Areas of Systemic Sclerosis Patients Looking for Correlations with Nailfold Microangiopathy Extent

BackgroundIn systemic sclerosis (SSc), blood perfusion (BP) may be evaluated by laser speckle contrast analysis (LASCA), as well as nailfold microangiopathy may be assessed by nailfold videocapillaroscopy (NVC) (1-3).ObjectivesTo investigate...

Separation of cortical arteries and veins in optical neurovascular imaging

Separation of arteries and veins in the cerebral cortex is of significant importance in the studies of cortical hemodynamics, such as the changes of cerebral blood flow, perfusion or oxygen concentration in arteries and veins under different pathological and physiological conditions. Yet the cerebral vessel segmentation and vessel-type separation are challenging due to the complexity of cortical vessel characteristics and low spatial signal-to-noise ratio. In this work, we presented an effective full-field method to differentiate arteries and veins in cerebral cortex using dual-modal optical imaging technology including laser speckle imaging (LSI) and optical intrinsic signals (OIS) imaging. The raw contrast images were acquired by LSI and processed with enhanced laser speckle contrast analysis (eLASCA) algorithm. The vascular pattern was extracted and segmented using region growing algorithm from the eLASCA-based LSI. Meanwhile, OIS images were acquired alternatively with 630 and 870 nm to obtain an oxyhemoglobin concentration map over cerebral cortex. Then the separation of arteries and veins was accomplished by Otsu threshold segmentation algorithm based on the OIS information and segmentation of LSI. Finally, the segmentation and separation performances were assessed using area overlap measure (AOM). The segmentation and separation of cerebral vessels in cortical optical imaging have great potential applications in full-field cerebral hemodynamics monitoring and pathological study of cerebral vascular diseases, as well as in clinical intraoperative monitoring.

Skin blood perfusion and cellular response to insertion of insulin pen needles with different diameters.

Today most research on pen needle design revolves around pain perception statements through clinical trials, but these are both costly, timely, and require high sample sizes. The purpose of this study was to test if tissue damage, caused by different types of needles, can be assessed by evaluating skin blood perfusion response around needle insertion sites. Three common sized pen needles of 28G, 30G, and 32G as well as hooked 32G needles, were inserted into the neck skin of pigs and then removed. Laser Speckle Contrast Analysis was used to measure skin blood perfusion for 20 minutes after the insertions. Seven pigs were included in the study and a total of 118 randomized needle insertions were conducted. Histology was made of tissue samples inserted with 18G, 28G, and 32G needles, and stained to quantify red and white blood cell response. Based on area under curve, calculated for each individual blood perfusion recording and grouped according to needle type, skin blood perfusion response relates to needle diameter. The response was significantly higher after insertions with 28G and hooked 32G needles than with 30G (P < .05) and 32G (P < .01) needles. Histology results were not significant, but there was a trend of an increased response with increasing needle diameter. Skin blood perfusion response to pen needle insertions rank according to needle diameter, and the tissue response caused by hooked 32G needles corresponds to that of 28G needles. The relation between needle diameter and trauma when analyzing histology was also suggested.

Strategical steering of the immune system: induction of leukocyte vascular chaperoning increases functional blood flow responses in ischemic muscle (670.6)

BACKGROUND: The role of leukocytes in angiogenesis is emerging. This study investigates leukocytes recruited to ischemic muscle and if vascular repair can be accelerated by induction of local chemokine production.METHODS: Plasmids encoding CCL2 or CXCL12 were expressed in the cremaster muscle or in ischemic hindlimb muscle in wild‐type, CX3CR1‐GFP and RAGE‐/‐ mice. Functional tissue perfusion was measured during heat‐induced hyperemia in the hindlimb using Laser Doppler Flowmetry or in foot pads using Laser Speckle Contrast Analysis. The role of macrophages was challenged by clodronate liposome depletion. Vascular function, leukocyte phenotypes and position were studied in single vessels of ischemic muscle using intravital confocal microscopy. Effects of chemokine overexpression in the injured muscle on leukocyte subsets, perfused vessels and vascular densities were quantified.RESULTS: Plasmid expression peaked at day 2 and was detected for 4 weeks following injection. Ischemic limbs expressing pCXCL12 showed improved heat‐induced hyperemia response and higher density of perfused capillaries 3 and 7 days post ischemia induction. pCXCL12‐expressing ischemic muscles contained increased number of macrophages (CX3CR1+F4/80+), which were polarized towards the pro‐angiogenic phenotype (F4/80+MRC1+) and found to chaperone perfused vessels. The importance of this observation was demonstrated in mice depleted of macrophages, in which functional blood flow response was not improved by pCXCL12. The blood flow effect of pCXCL12 was blunted in RAGE‐/‐ mice despite increased M2 macrophage density, indicating downstream RAGE involvement. Overexpression of pCCL2 did not expand the leukocyte population or improve vascular functional blood flow in this system.CONCLUSION: Overexpression of pCXCL12 but not pCCL2 in ischemic muscle accelerates restoration of functional blood flow responses by retaining macrophages chaperoning the vasculature.