Laser Speckle Technique Research Articles

Effect of pulsed electromagnetic fields on the blood circulation in ischemic skin models: A pilot study

ABSTRACTThe aim of this study was to investigate the effect of pulsed electromagnetic fields (PEMFs) on the blood circulation in an ischemic skin model using a laser-speckle contrast-imaging technique. Four rats were divided into a control group and a PEMF group. A cranially based skin flap (5 × 10 cm2) was elevated on the back of the rat. The skin flap was not sutured and the blood velocity of the entire medial surface was measured for 90 min, using a laser-speckle contrast-imaging system. For the PEMF group, a PEMF (1 Hz, 10 mT) was applied to this area during the measurement. The blood flow in the control group continued decreasing from immediately after the operation until after 90 min. However, in the PEMF group, the blood flow decreased more than in the control group until after 60 min. The blood flow increased after 90 min, but it did not recover the initial condition. However, the blood flow in certain vessels in the PEMF group increased more than in the initial condition. In conclusion, we found that a PEMF (1 Hz, 10 mT) may improve blood circulation.

Dynamic laser speckle technique as an alternative tool to determine hygroscopic capacity and specific surface area of microporous zeolites

Adsorption phenomena have several technological applications such as desiccants, catalysts, and separation of gases. Their uses depend on the textural properties of the solid adsorbent and the type of the adsorbed liquid or gas. Therefore, it is important to determine these properties. The most common measurement methods are physicochemical based on adsorption of N2 to determine the surface area and the distribution of pores size. However these techniques present certain limitations for microporous materials. In this paper we propose the use of the Dynamic Laser Speckle (DLS) technique to measure the hygroscopic capacity of a microporous natural zeolite and their modified forms. This new approach based on the adsorption of water by solids allows determine their specific surface area (S). To test the DLS results, we compared the obtained S values to those calculated by different conventional isotherms using the N2 adsorption-desorption method.

Laser Speckle Modeling and Simulation for Biophysical Dynamics: Influence of Sample Statistics

Laser speckle is a statistical phenomenon and should be treated as such when establishing experimental parameters for using laser speckle techniques to infer information about the dynamics of a coherently illuminated medium, such as biological tissue. Herein, we demonstrate that when sampling (imaging) speckle patterns, it is critical that the sampled speckle patterns are unbiased estimators of the underlying random speckle field. If this condition is not met, the quality of the results will be compromised. Specifically, this study examines the effects of first and second order spatial statistics of speckle intensity images on laser speckle contrast imaging results. Finally, it is recommended that when using speckle techniques such as laser speckle contrast imaging, investigators should examine the first and second order spatial statistics of a speckle image prior to collecting actual data. If this examination reveals that the imaged speckle intensity image is not an unbiased estimator of the underlying random speckle field, then adjustments should be made to ensure that the images taken are unbiased estimators of the true speckle field.

Assessment of biological activity in RAW 264.7 cell line stimulated with lipopolysaccharide using dynamic laser speckle

Dynamic laser speckle (DLS) technique or biospeckle is a noninvasive approach that can sensitively monitor the dynamics of a biological material such as the metabolism of cells. In turn, stimulation of cell activity is widely used in microbiology: it can be done by means of many agents, such as lipopolysaccharide (LPS), which is the most common component within the cell wall of Gram-negative bacteria, and it has been extensively used in in vitro models studying inflammation. The main challenge is to monitor the change of behavior inside the cells during their stimulation. This work tested the viability of the BSL to monitor the change in the metabolism of RAW cells when LPS is applied. The results show different answers of cells to distinct concentrations of LPS, and the inflammatory process promoted by the LPS could be best distinguished from the RAW cells alone in a concentration of 10 ng/mL. This proved the ability of the DLS to monitor the agent stimulus.

Laser speckle technique to study the effect of chemical pre-treatment on the quality of minimally processed apples

In the present study, the laser speckle technique has been used for the quality evaluation of chemically treated cut apples. Chemical pre-treatment includes 1% (w/v) solution of citric acid (CA), sodium chloride (SC), and a combination of CA and sodium chloride (CS). The variation in weight loss, respiration rate, total soluble solids (TSS), titratable acidity (TA), and absorbance of chemically treated cut apples stored at 5 °C was monitored for 11 d. The speckle grain size was calculated by an autocovariance method from the speckled images of freshly cut chemically treated apples. The effect of chemicals on TSS and the TA content variation of the cut apples were well correlated to the linear speckle grain size. Circular degree of polarization confirms the presence of a small scatterer and hence Rayleigh diffusion region. For all the treated cut apples, a decrease in the concentration of small particles nearly after the mid-period of storage results in the fast decay of circular degree of polarization. For non-invasive and fast analysis of the chemical constituent of fruits during minimal processing, the laser speckle can be practically used in the food industry.

Study on Particle Size and Concentration Using Laser Speckle Technique in Light Scattering Liquid Medium

A high coherent Laser beam is scattered from a colloidal medium of liquid (milk) due to the movement of sedimentation and Brownian motion and a random grainy image known as speckle pattern is formed in the observation plane. The resultant speckle having a statistical distribution of the intensity and it is dynamic in nature. Sequential laser speckle images were recorded for different concentrations and the time evolution of this interference image carries information about the dynamics of the scattering particles. The aim of this work is to evaluate the use of dynamic speckle for the assessment of particle size and corresponding speckle size for different concentration with the help of image processing technique.

Hydro-Adsorption Study by Dynamic Laser Speckle of Natural Zeolite for Adsorbent and Fertilizer Applications

The dynamic behavior caused by hydro-adsorption process of materials based on a rich mineral clinoptilolite together with their acidic, basic and calcinated forms has been studied by the dynamic laser speckle (DLS) technique. We propose a modified Peleg’s equation to improve fitting of DLS data. Textural (BET), structural (XRD) and spectroscopic (FTIR) properties were also studied and compared. We demonstrated that DLS was the most sensitive, simple and inexpensive method for comparing the performance of adsorptive materials with slightly modified surfaces. It also allowed the correlation with physicochemical properties.

Following the drying process of Fevicol (adhesive) by dynamic speckle measurement

This work presents the study of drying of Fevicol (adhesive) using dynamic laser speckle technique. Dynamic laser speckle analysis is a non-invasive method that does not disturb the drying process. A low power laser light illuminates the sample and corresponding speckle images of the sample resulting from the phenomenon of interference are registered. If the sample shows activity, the speckle pattern changes in time. Following this evolution, we can analyze the drying process by means of image processing algorithms. In this work, the application of dynamic speckle technique to follow the drying process of Fevicol with different drying times is presented. Results obtained using numerical methods of Inertia Moment and cross-correlation show that quantitative evaluation of spatial temporal speckle activities can be used to monitor Fevicol drying process. The approaches such as auto-correlation and speckle contrast using temporal correlation allowed differentiating different stages of drying. In addition, the techniques allowed their applicability to follow the slow streaming of Fevicol from the coin surface.

Mapping transverse velocity of particles in capillary vessels by time-varying laser speckle through perturbation analyses.

We propose a cross-correlation method to map the transverse velocities of particles moving in capillary vessels using full-field time-varying laser speckle technique. The mapping is achieved by a semi-random perturbation model that describes the intensity fluctuation of time-varying laser speckle signals. When passing through probing volume, moving particles encode a random perturbation into the observed laser speckle pattern. We calculate the transverse flow velocity by cross-correlating the temporal envelopes of the perturbation signals. The proposed method is experimentally verified by the use of polymer microsphere suspension in a glass capillary.

Characterization of Bacillus thuringiensis parasporal crystals using laser speckle technique: effect of crystal concentration and dimension

In this paper, we report experimental results where laser speckle grain size and degree of light polarization are used to distinguish different sizes of Bacillus thuringiensis spherical crystals and different concentration within fermentation products. Three strains of Bacillus thuringiensis, isolated from the Lebanese soil, are selected. After fermentation, crystals and spores are separated using a technique based on flotation in order to obtain large quantities of relatively pure crystals. Crystals are then embedded in an agarose matrix gel and illuminated by a laser. Speckle patterns are recorded and analyzed. Results show that when crystal concentrations increase in the sample, the values of the degree of light linear polarization and speckle grain size decrease, and the negative values of light circular polarization degree increase. A transition from a Rayleigh scattering regime to a Mie regime is also observed. Furthermore, when the diameter of spherical crystals increases, the normalized value of the light linear polarization degree and the grain size diminish drastically for a given concentration of crystals in the matrix, whereas the normalized value of light circular polarization degree increases. This optical characterization constitutes an unambiguous signature of spherical crystals produced by fermentations of different Bacillus thuringiensis strains and shows that speckle may potentially be used at an industrial scale as a low-cost and noninvasive technique in order to characterize crystal geometry and to evaluate the yield of crystal production within fermentation.

Depth measurement of a blood flow region based on speckle decorrelation

Laser speckle technique is a useful means for imaging blood flow in living bodies and, it has been utilized for analyzing the condition of living bodies or the health state. However, depth of a blood flow region has not been measured yet by this method. In the present study, we investigate use of a decorrelation in a pair of speckle patterns in a temporal sequence for measuring depth of the blood flow region. Blood flow is also measured simultaneously by means of a spatio-temporal difference of the same pair of speckle patterns as that used for depth measurement. Experiments are conducted for reference and sample models using ground-glass plates and a silicone layer and for a human finger, to confirm the feasibility of the proposed method.

Force–frequency analysis of contraction using a novel laser-speckle contrast techniques in iPS-derived cardiomyocytes, Repro Cardio2™

Force–frequency analysis of contraction using a novel laser-speckle contrast techniques in iPS-derived cardiomyocytes, Repro Cardio2™

Pointwise implementation of dynamic laser speckle technique

The paper proposes pointwise implementation of correlation-based algorithms for processing time sequences of 2D dynamic speckle patterns of a diffuse object illuminated with a laser light in order to obtain a spatial map of physical or biological activity across its surface. Both temporal correlation and structure functions were studied with and without the pointwise normalization by the variance of intensity fluctuations in time. The performance of the algorithms was checked by simulation of dynamic speckle patterns at a given spatial distribution of the temporal correlation radius of activity and by dynamic speckle measurement of a test object. The obtained set of high contrast and high spatial resolution activity maps proves the efficiency of the normalized correlation-based algorithms to indicate regions of varying activity even at non-uniform illumination and reflectivity across the object.

Feasibility study of hidden flow imaging based on laser speckle technique using multiperspectives contrast images

This paper demonstrates the insertion of lens array in the front of a CCD camera in a laser speckle imaging (LSI) like-technique to acquire multiple speckle reflectance projections for imaging blood flow in an intact biological tissue. In some of LSI applications, flow imaging is obtained by thinning or removing of the upper tissue layers to access blood vessels. In contrast, with the proposed approach flow imaging can be achieved while the tissue is intact. In the system, each lens from an hexagonal lens array observed the sample from slightly different perspectives and captured with a CCD camera. In the computer, these multiview raw images are converted to speckled contrast maps. Then, a self-deconvolution shift-and-add algorithm is employed for processing yields high contrast flow information. The method is experimentally validated first with a plastic tube filled with scattering liquid running at different controlled flow rates hidden in a biological tissue and then extensively tested for imaging of cerebral blood flow in an intact rodent head experience different conditions. A total of fifteen mice were used in the experiments divided randomly into three groups as follows: Group 1 (n=5) consisted of injured mice experience hypoxic ischemic brain injury monitored for ~40min. Group 2 (n=5) injured mice experience anoxic brain injury monitored up to 20min. Group 3 (n=5) experience functional activation monitored up to ~35min. To increase tissue transparency and the penetration depth of photons through head tissue layers, an optical clearing method was employed. To our knowledge, this work presents for the first time the use of lens array in LSI scheme.

Determination of maize hardness by biospeckle and fuzzy granularity

In recent years there has been renewed interest in the development of novel grain classification methods that could complement traditional empirical tests. A speckle pattern occurs when a laser beam illuminates an optically rough surface that flickers when the object is active and is called biospeckle. In this work, we use laser biospeckle to classify maize (Zea mays L.) kernel hardness. A series of grains of three types of maize were cut and illuminated by a laser. A series of images were then registered, stored, and processed. These were compared with results obtained by floating test. The laser speckle technique was effective in discriminating the grains based on the presence of floury or vitreous endosperm and could be considered a feasible alternative to traditional floating methods. The results indicate that this methodology can distinguish floury and vitreous grains. Moreover, the assay showed higher discrimination capability than traditional tests. It could be potentially useful for maize classification and to increase the efficiency of processing dry milling corn.

Blood perfusion effect of acupuncture on acute facial paralysis observed by laser speckle technique

To observe effect of acupuncture for acute facial paralysis patients with ocular skin blood perfusion, and to explore the safety and effectiveness of acupuncture in treating acute facial paralysis. Thirty patients with acute facial paralysis were enrolled and acupunctured in facial points and bilateral Hegu (LI 14), and the PeriCam laser speckle flow video monitoring system was used not only for recording ocular skin blood perfusion condition in both normal and affected sides before acupuncture, at 15 min after acupuncture and after removing needles immediately, but also for calculating reduction ratio of ocular skin average perfusion in the affected side face compared with the healthy side. Compared with the healthy side of face, the ocular skin blood perfusion of the affected side after acupuncture was significantly different from that before intervention. The blood perfusion levels after 15-minute acupuncture and at the time of remaining needles were significantly different from the basic line (all P<0.01). Acupuncture can significantly improve eye blood perfusion of the acute facial paralysis, enhance metabolic activity of the affected facial tissues, and promote the recovery of facial nerve function.

Non-contact in vivo measurement of ocular microtremor using laser speckle correlation metrology

Ocular microtremor (OMT) is a small involuntary eye movement present in all subjects. In this paper we present the results of in vivo OMT measurement using a novel non-contact laser speckle technique. OMT signals have not previously been measured from the sclera using this laser speckle correlation technique. To verify the system's ability to record eye movements, it is first tested using a large angle eye rotation. Next, the system is tested with a group of 20 subjects and OMT parameters are extracted. The results of OMT measurements gave a mean frequency of 78 ± 3.86 Hz and peak-to-peak amplitude of 21.42 ± 7.01 µrad, these values are consistent with known values from eye-contacting methods.

Frame-rate analysis of arterial blood flow in human and rat using laser speckle image sensing

In imaging of blood flow by means of a laser speckle technique, we have proposed so far an estimation parameter based on the spatial contrast of speckle patterns observed for the blood flow in skin tissue and a blood vessel. This parameter enable us to image a relative blood flow distribution from a single speckle pattern, thus, it analyzes the blood flow with a frame-rate of an imaging device used. In this study, we investigated availability of this parameter for detecting changes in arterial blood flow caused by medication and cold stimulation to the skin tissue. Experiments were conducted for an anesthetized rat and a human wrist to confirm the feasibility of the present parameter.

Dai Huang Fu Zi Tang could ameliorate intestinal injury in a rat model of hemorrhagic shock by regulating intestinal blood flow and intestinal expression of p-VASP and ZO-1

BackgroundDai Huang Fu Zi Tang (DHFZT), an oriental herbal formula, has long been used clinically in treatment of intestinal obstruction, acute pancreatitis, cholecystalgia and chronic diarrhea for thousands of years. Recent studies have demonstrated that DHFZT can reduce intestinal pathological injury and the concentration of enterogenous endotoxin in an animal model. But the underlying mechanism has not been fully elucidated.MethodsSD male rats in adult were used to model HS and treated with DHFZT. The serum concentration of endotoxin were analyzed by dynamic turbidimetric method. In addition, the blood flow of small intestine were measured using laser speckle technique. Phosphorylated vasodilator-stimulated phosphoprotein (p-VASP) and zonula occludens (ZO)-1 protein, intestinal fatty acid binding protein (IFABP) were measured by Western Blotting, RT-PCR, ELISA respectively.ResultsPresent study showed that DHFZT markedly elevated the blood flow of small intestine, protected the intestinal barrier function by up-regulating the expression of ZO-1 protein and down-regulating expression of p-VASP, and notely decreased serum concentration of IFABP and endotoxin in HS.ConclusionsThese results reveal that DHFZT improves intestinal blood flow, protects the intestinal barrier function, and ameliorates intestinal endotoxaemia in rats with HS.

Two-wavelengths laser-speckle technique for thickness determination of transparent layers on rough surfaces

In this work, a non-contacting laser-speckle technique and two different implementations thereof for measuring the thickness of thin transparent liquid layers on optically rough surfaces are presented. The optical system allows large stand-off distances and can be used in harsh environments and industrial applications. The thickness of the (oil) coating can be measured down into the μm range, which is below that of the surface roughness. The distribution of the coating depends on adhesive and cohesive forces, the temperature and primarily on the surface topography itself. The thickness of transparent coatings can be evaluated statistically considering wavelengths and roughness. We describe the two measurement principles and the data processing, present measurement results and discuss the advantages and disadvantages of both methods. For a better understanding, the theoretical considerations of the diffraction of sinusoidal phase gratings in the Fraunhofer region will be given.