Laser speckle contrast imaging to predict the effect of temporary spinal cord stimulation in postherpetic neuralgia patients: A prospective observational study

Temporary spinal cord stimulation(tSCS)can effectively reduce the pain and severity of postherpetic neuralgia(PHN).However,there are no effective and objective methods for predicting the effects of tSCS on PHN.Laser speckle contrast imaging(LSCI)is frequently used in neurology to evaluate the effectiveness of treatment.To assess the accuracy of LSCI in predicting the impact of tSCS on PHN,14 adult patients receiving tSCS treatments for spinal nerve-innervated(C6-T2)PHN participated in this observational study.Visual analog scale(VAS)assessments and LSCI bloodflow images of the-ngers were recorded after the tSCS procedure.The results showed that the VAS scores of all patients decreased signi-cantly.Moreover,the bloodflow index(BFI)values were signi-cantly higher than they were before the procedure.Increased bloodflow and pain alleviation were positively correlated.The-ndings indicated that spinal nerve PHN(C6-T2)was signi-cantly reduced by tSCS.Pain alleviation by tSCS was positively correlated with increased bloodflow in the hand.The effect of tSCS on PHN may thus be predicted using an independent and consistent indicator such as LSCI.

Transmissive multifocal laser speckle contrast imaging through thick tissue

Laser speckle contrast imaging(LSCI)is a powerful tool for monitoring blood flow changes in tissue or vessels in vivo,but its applications are limited by shallow penetration depth under reflective imaging configuration.The traditional LSCI setup has been used in transmissive imaging for depth extension up to 2l_(t)–3l_(t)(l_(t)is the transport mean free path),but the blood flow estimation is biased due to the depth uncertainty in large depth of field(DOF)images.In this study,we propose a transmissive multifocal LSCI for depth-resolved blood flow in thick tissue,further extending the transmissive LSCI for tissue thickness up to 12lt.The limited-DOF imaging system is applied to the multifocal acquisition,and the depth of the vessel is estimated using a robust visibility parameter V_(r)in the coherent domain.The accuracy and linearity of depth estimation are tested by Monte Carlo simulations.Based on the proposed method,the model of contrast analysis resolving the depth information is established and verified in a phantom experiment.We demonstrated its effectiveness in acquiring depth-resolved vessel structures and flow dynamics in in vivo imaging of chick embryos.

Laser speckle contrast imaging for monitoring of acutepancreatitis at ischemia-reperfusion injury of thepancreas in rats

The influence of ischemia-reperfusion(I/R)action on pancreatic blood flow(PBF)and the development of acute pancreatitis(AP)in laboratory rats is evaluated in vivo by using the laser speckle contrast imaging(LSCI).Additionally,the optical properties in norm and under condition of AP in rats were assessed using a modied integrating sphere spectrometer and inverse Monte Carlo(IMC)software.The results of the experimental study of microcirculation of the pancreas in 82 rats in the ischemic model are presented.The data obtained conrm the fact that local ischemia and changes in the blood°ow velocity of the main vessels cause and provoke acute pancreatitis.

Application of Laser Speckle Technology on the Detection of Agricultural Products

[Objective] The research aimed at investigating the application of laser speckle technology in agricultural products detection.[Method] This article described the basic principle of the laser speckle technology,provided a review of application development of the laser speckle technology in agricultural products detection,analyzed the problems in agriculture products detection using laser speckle technology and described the prospects of laser speckle technology in agricultural products detection.[Result] The laser speckle technology is a non-destructive detection technology for quality determination of agricultural products,which can be used to classify the agricultural products reasonably according to the quality of agricultural products.[Conclusion] The article provided reference and consult for laser speckle detection technology research.

A New Method for Evaluating Regional Cerebral Blood Flow Changes:Laser Speckle Contrast Imaging in a C57BL/6J Mouse Model of Photothrombotic Ischemia

The present study aimed to improve the processing of data acquired from laser speckle contrast imaging（LSCI） to provide a standardization method to explore changes in regional cerebral blood flow（r CBF） and to determine the correlations among r CBF, cerebral ischemic lesion volume and microvascular density over time in a focal ischemic region. C57BL/6J mice were subjected to focal photothrombotic（PT） ischemia. r CBF was measured using LSCI at different time points before and after PT ischemia through an intact skull. Standardized r CBF（Sr CBF）, defined as the ratio of r CBF measured in the ipsilateral region of interest（ROI） to that in the corresponding contralateral region, was calculated to evaluate potential changes. In addition, the volume of the ischemic lesion and the microvascular density were determined using Nissl staining and immunofluorescence, respectively. The relationships among the ischemic lesion volume, microvascular density and Sr CBF were analyzed over time. The results showed that the cortical r CBF measured using LSCI following PT ischemia in the C57BL/6J mice gradually increased. Changes in the cerebral ischemic lesion volume were negatively correlated with Sr CBF in the ischemic region. Changes in the microvascular density were similar to those observed in Sr CBF. Our findings indicate that LSCI is a practical technique for observing changes in murine cortical r CBF without skull opening and for analyzing the relationships among the ischemic lesion volume, microvascular density and Sr CBF following focal cerebral ischemia. Preliminary results also suggest that the use of LSCI to observe the formation of collateral circulation is feasible.

Confocal laser speckle autocorrelation imaging of dynamic flow in microvasculature

Laser speckle imaging has been widely used for in-vivo visualization of blood perfusion in biological tissues.However,existing laser speckle imaging techniques suffer from limited quantification accuracy and spatial resolution.Here we re-port a novel design and implementation of a powerful laser speckle imaging platform to solve the two critical limitations.The core technique of our platform is a combination of line scan confocal microscopy with laser speckle autocorrelation imaging,which is termed Line Scan Laser Speckle Autocorrelation Imaging(LS-LSAI).The technical advantages of LS-LSAI include high spatial resolution(~4.4μm)for visualizing and quantifying blood flow in microvessels,as well as video-rate imaging speed for tracing dynamic flow.

Improving sampling depth of laser speckle imaging by topical optical clearing:A theoretical and in vivo study

The effect of optical cleaning method combined with laser speckle imaging(LSI)was discussed to improve the detection depth of LSI due to high scattering characteristics of skin,which limit its clinical application.A double-layer skin tissue model embedded with a single blood vessel was established,and the Monte Carlo method was used to simulate photon propagation under the action of light-permeating agent.808 nm semiconductor and 632.8 nm He–Ne lasers were selected to study the e®ect of optical clearing agents(OCAs)on photon deposition in tissues.Results show that the photon energy deposition density in the epidermis increases with the amount of tissue°uid replaced by OCA.Compared with glucose solution,polyethylene glycol 400(PEG 400)and glycerol can considerably increase the average penetration depth of photons in the skin tissue,thereby raising the sampling depth of the LSI.After the action of glycerol,PEG 400,and glucose,the average photon penetration depth is increased by 51.78%,51.06%,and 21.51%for 808nm,68.93%,67.94%,and 26.67%for 632.8 nm lasers,respectively.In vivo experiment by dorsal skin chamber proves that glycerol can cause a substantial decrease in blood°ow rate,whereas PEG 400 can signicantly improve the capability of light penetration without a®ecting blood velocity,which exhibits considerable potential in the monitoring of blood°ow in skin tissues.

ASSESSMENT OF OPTICAL CLEARING INDUCED IMPROVEMENT OF LASER SPECKLE CONTRAST IMAGING

Laser Speckle Contrast Imaging(LSCI)plays an important role in studying blood flow,but suffers from limited penetration depth of light in turbid tissue.The strong scattering of tissue obviously reduces the image contrast which decreases the sensitivity to flow velocity.Some image processing or optical clearing methods have been proposed to lessen the deficiency,but quantitative assessment of improvement is seldom given.In this study,LSCI was applied to monitor the blood flow through a capillary embedded within various tissue phantoms at depths of 0.25,0.45,0.65,0.85 and 1.05 mm,and the flow velocity in capillary was controllable from 0 to 4mm/s.Here,glycerol,a common optical clearing agent,was mixed with Intralipid at different volume ratio to make the reduced scattering coefficient of tissue phantom decrease from 13.00 to 0.50 cm−1.The quantitative analysis demonstrates that the optical clearing method can obviously enhance the image contrast,imaging depth,and sensitivity to blood flow velocity.Comparing the Laser Speckle Contrast Analysis methods and the optical clearing method,we find that for typical turbid tissue,the sensitivity to velocity estimated by the Laser Speckle Temporal Contrast Analysis(LSTCA)is twice of that by the Laser Speckle Spatial Contrast Analysis(LSSCA);while the sensitivity to velocity estimated by using the two analysis methods has a 10-fold increase,respectively,if addition of glycerol makes the reduced scattering coefficient of tissue phantom decrease by 30%.Combining the LSTCA and the optical clearing method,the sensitivity to flow velocity will be further enhanced.

Measurement of the surface morphology of plasma facing components on the EAST tokamak by a laser speckle interferometry approach

The laser speckle interferometry approach provides the possibility of an in situ optical noncontacted measurement for the surface morphology of plasma facing components(PFCs),and the reconstruction image of the PFC surface morphology is computed by a numerical model based on a phase unwrapping algorithm.A remote speckle interferometry measurement at a distance of three meters for real divertor tiles retired from EAST was carried out in the laboratory to simulate a real detection condition on EAST.The preliminary surface morphology of the divertor tiles was well reproduced by the reconstructed geometric image.The feasibility and reliability of this approach for the real-time measurement of PFCs have been demonstrated.

LASER SPECKLE MOVEMENT CAUSED BY SURFACE DEFORMATION AND LIGHT WAVELENGTH CHANGE

When a surface is illuminated by laser,the field of diffusing reflective light can be described by Fresnel-Kirchhoff integration in the region of Fresnel.If the correlation,before and after the change of intensity field,is analysed by statistical method,three governing equations for variations of intensity field and speckle movement formulas can be obtained.In these equations,the surface motion,deformation and wavelength change are all considered to cause the speckle movement.

IN VIVO MAPPING BRAIN MICROCIRCULATION BY LASER SPECKLE CONTRAST IMAGING:A MAGNETIC RESONANCE PERSPECTIVE OF THEORETICAL FRAMEWORK

The fundamental limitations of most vascular-based functional neuroimaging techniques are placed by the fact how fine the brain regulates the blood supply system.In vivo mapping of the cerebral microcirculation with high resolution and sensitivity hence becomes unprecedentedly compelling.This paper reviews the theoretical background of the laser speckle contrast imaging(LSCI)technique and attempts to present a complete framework stemming from a simple biophysical model.Through the sensitivity analysis,more insights into the tool optimization are attained for in vivo applications.Open questions of the technical aspects are discussed within this unified framework.Finally,it concludes with a brief perspective of future research in a way analogous to the magnetic resonance imaging(MRI)technique.Such exploration could catalyze their development and initiate a technological fusion for precise assessment of blood flow across various spatial scales.

Hidden stage of intracranial hemorrhage in newborn rats studied with laser speckle contrast imaging and wavelets

Using the laser speckle contrast imaging and wavelet-based analyses,we investigate a latent("hidden")stage of the development of intracranial hemorrhages(ICHs)in newborn rats.We apply two measures based on the continuous wavelet-transform of blood flow velocity in the sagittal sinus,namely,the spectral energy in distinct frequency ranges and a multiscality degree characterizing complexity of experimental data.We show that the wavelet-based multifractal formalism reveals changes in the cerebrovascular blood flow at the development of ICH.

Modified Laser Speckle Imaging with Adaptive Window

One of the advantages of laser speckle is detecting microvascular through image processing. This paper proposes a new image processing method for laser speckle, adaptive window method that adaptively processes laser speckle images in the space. Disadvantage of conventional fixed window method is that it uses the same window size regardless of target areas. Inherently laser speckle contains undesired noise. Thus a large window is helpful for removing the noise, but it results in low resolution of image. Otherwise a small window may detect micro vascular but it has limits in noise removal. To overcome this trade-off, the concept of adaptive window method is newly introduced to conventional laser speckle image analysis. In addition, the modified adaptive window method applied to other selection images. We have compared conventional Laser Speckle Contrast Analysis （LASCA） and its variants with the proposed method in terms of image quality and processing complexity, Moreover compared the result of the accompamed changing sdection images have also been compared.

Laser speckle contrast imaging based on uniting spatiotemporal Fourier transform

We propose a laser speckle contrast imaging method based on uniting spatiotemporal Fourier transform.First,the raw speckle images are entirely transformed to the spatiotemporal frequency domain with a three-dimensional(3D)fast Fourier transform.Second,the dynamic and static speckle components are extracted by applying 3D low-pass and high-pass filtering in the spatiotemporal frequency domain and inverse 3D Fourier transform.Third,we calculate the time-averaged modulation depth with the average of both components to map the two-dimensional blood flow distribution.The experiments demonstrate that the proposed method could effectively improve computational efficiency and imaging quality.

Research on dynamic measurement method of speckle in laser display

Laser display technology is the most promising display technology in the market and is widely used in many fields. However, laser speckle has been troubling the application and expansion of this technology in some fields. In order to better evaluate the speckle, speckle measurement methods must be studied. In this study, a dynamic measurement method for laser speckles is proposed according to the optical superposition characteristics of speckle, which can reduce the influence of non-coherent factors on the speckle measurement results. The feasibility of the dynamic speckle measurement method is verified by designing an experimental scheme.

Laser speckle grayscale lithography:a new tool for fabricating highly sensitive flexible capacitive pressure sensors

Achieving a high sensitivity for practical applications has always been one of the main developmental directions for wearable flexible pressure sensors.This paper introduces a laser speckle grayscale lithography system and a novel method for fabricating random conical array microstructures using grainy laser speckle patterns.Its feasibility is attributed to the autocorrelation function of the laser speckle intensity,which adheres to a first-order Bessel function of the first kind.Through objective speckle size and exposure dose manipulations,we developed a microstructured photoresist with various micromorphologies.These microstructures were used to form polydimethylsiloxane microstructured electrodes that were used in flexible capacitive pressure sensors.These-1 sensors exhibited an ultra-high sensitivity:19.76 kPa for the low-pressure range of 0-100 Pa.Their minimum detection threshold was 1.9 Pa,and they maintained stability and resilience over 10,000 test cycles.These sensors proved to be adept at capturing physiological signals and providing tactile feedback,thereby emphasizing their practical value.

Facile fabrication of microstructured surface using laser speckle for high-sensitivity capacitive pressure sensors

The design of a maskless exposure system for fabricating the microstructured surface based on the grainy light illumination generated by laser speckle is reported. Upon combining with soft lithography, we obtained microstructured polydimethylsiloxane electrodes with microstructure sizes of 20 μm and 40 μm and microstructure fill factors ranging from 10% to 90%. The feasibility of using this method in fabricating high-sensitivity capacitive pressure sensors was demonstrated. The sensor shows the highest sensitivity of 2.14 k Pa-1under 0–100 Pa pressures, the low detection limit of 4.9 Pa, and the excellent stability and durability of 10000 cycles. The method of employing laser speckle in fabricating microstructures with different morphologies is simple and robust, which is superior to other methods such as traditional photolithography.

In vivo monitoring of microneedle-based transdermal drug delivery of insulin

Soluble microneedles(MNs)have recently become an eficient and minimally invasive tool in transdermal drug delivery because of their excellent biocompatibility and rapid dissohution.However,direct monitoring of structural and functional changes of MNs in vivo to estimate the efficieancy of insulin delivery is difficult.We monitored the dissolution of MNs to obtain structural imaging of MNs'changes by using optical coherence tomography(OCT).We also observed the effect of MNs on microvascular conditions with laser speckle contrast imaging(LSCIT)and measured the blood perfusion of skin to obtain functional imaging of MNs.We determined the performance of two soluble MN arrays made from polyvinyi alcohol(PVA)and polyvinyl alco-hol/polyvinylpyrolidone(PVA/PVP)by calculating the cross sectional areas of the micro-channels in mouse skin as a function of time.Moreover,the change in blood glucose before and after using MNs loaded with insulin was evaluated as an auxiliary means to demonstrate the ability of the soluble MNs to deliver insulin.Results showed that the structural imaging of these MNs could be observed in vivo via OCT in real time and the fumctional imaging of MNs could be showed using LSCI OCT and LSCI are potential tools in monitoring MNs structural and functional changes.

DETECTING CEREBRAL ARTERIES AND VEINS:FROM LARGE TO SMALL

In this paper,a model-based reconstruction technique is proposed to simultaneously measure the relative deoxyhemoglobin concentration and the relative blood flow velocity in cerebral cortex.With the help of this model-based reconstruction technique,artifacts due to nonuniform laser illumination and curvature of cortex are efficiently corrected.The results of relative deoxyhemoglobin concentration and relative blood flow velocity are then used to detect and distinguish cerebral arteries and veins.In an experimental study on rat,cerebral blood vessels are segmented from the reconstructed blood flow image by Otsu multiple threshold method.Afterwards,arteries and veins are distinguished by a simple fuzzy criterion based on the information of relative deoxyhemoglobin concentration.

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 con-centration 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 seg-mented using region growing algorithm from the eLASCA-based LSI.Meanwhile,OIS imageswere acquired altermatively with 630 and 870 nm to obtain an oxy hemoglobin concentration mapover cerebral cortex.Then the separation of arteries and veins was accomplished by Otsuthreshold 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.