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.

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.

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.

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.

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.

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.

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 compared with indocyanine green in renal perfusion of a porcine model

Background:When viewed under near-infrared light,indocyanine green(ICG)signal for kidney perfusion can be utilized in partial nephrectomy.Laser speckle contrast imaging(LSCI)uses coherent light to detect perfusion during real-time laparoscopic surgery.Materials and methods:Laser speckle contrast imaging or ActivSight,an imaging sensor adapter,was used during laparoscopy of an anesthetized porcine kidney model.ActivSight's"perfusion mode"and"quantification mode"displayed the blood flow as a heatmap and numerical signal intensity,respectively.Results:After the upper segmental renal artery was clamped,ICG was seen in the lower pole,and LSCI showed low unit(dark color)quantification and perfusion in the upper pole.Indocyanine green was retained in the lower pole after the upper segmental artery was unclamped,and LSCI perfusion was demonstrated in the entire kidney.Conclusions:Laser speckle contrast imaging is a dye-free,repeatable,real-time adjunct for renal parenchymal perfusion assessment applicable to minimally invasive renal surgery to complement the technology of ICG near-infrared fluorescence and advance digital surgery.

激光散斑衬比成像技术在慢性脑缺血动物模型中的应用研究进展

激光散斑衬比成像技术采用可视化、可量化的方法实时动态测量组织或器官的微循环血流量。因其活体检测、实时成像及操作简单等优点,已在微循环检测的多个领域中应用。慢性脑缺血动物模型主要通过减少双侧颈总动脉向大脑输送血流量的方法造模,可造成脑供血长期不足。激光散斑衬比成像技术可通过对慢性脑缺血动物模型皮层脑血流量、侧支循环开放、神经血管耦合反应等进行观察分析,从而判断动物模型造模是否成功及干预方法对其的治疗效果。本文就激光散斑衬比成像技术在慢性脑缺血动物模型中的应用及其优缺点进行总结,以期为临床治疗和科研提供新思路。

应用激光散斑衬比成像探究牙龈生物型对正畸加力下牙龈血流变化的影响

目的:应用激光散斑衬比成像(laser speckle contrast imaging,LSCI)探究牙龈生物型对正畸加力下牙龈血流变化的影响。方法:招募24例符合纳入标准的受试者参与研究,包括薄龈型组12例,厚龈型组12例,随机在每例受试者上颌左侧或右侧的尖牙至第一磨牙间施加150 g的力,并在施力前、施力30 min、1 d、3 d、7 d、14 d分别使用LSCI动态监测施力侧尖牙区牙龈血流灌注。结果:组间比较,薄龈型组与厚龈型组各时间点的血流值比较均存在显著差异,厚龈型血流值显著高于薄龈型(P<0.05);组内比较,每组各时间点的血流值比较也存在显著差异(P<0.05),施力后,局部血流灌注在30 min~1 d内降至最小值,7 d左右上升至最大值,14 d时基本恢复到基线。在没有力值加载的静息状态下,游离龈与牙间乳头的血流值比较存在显著差异(P<0.05),游离龈血流值显著低于牙间乳头。结论:LSCI是正畸加力过程中实时监测牙龈血流灌注的良好工具,薄龈型血液供应显著低于厚龈型。

应用激光散斑衬比成像与磁共振波谱观察针刺穴位局部理化特征

目的观察针刺不同穴位及不同针刺条件下的穴位局部理化特征。方法实验1将24只SD大鼠随机分为4组,每组6只,观察针刺不同经穴及非经非穴的穴位局部理化特征;实验2选取6只SD大鼠,观察肾俞穴针刺不同时长(5 min、10 min、15 min、20 min、30 min)的局部血流灌注量;实验3选取6只SD大鼠,观察肾俞穴在起针后(0 min、5 min、10 min、15 min、20 min、30 min)的局部血流灌注量。结果针刺不同穴位的局部理化特征为,针刺可增加肾俞、百会、足三里穴位局部血流灌注量及穴位局部乳酸(lactic acid,Lac)、丙氨酸(alanine,Ala)、磷酸肌酸(phosphocreatine,PCr)、葡萄糖(glucose,Glu)能量代谢水平。针刺肾俞穴不同时长的穴位局部理化特征为,与针刺前比较,肾俞穴在留针后5 min、10 min其局部血流灌注量明显上升(P<0.01),之后平缓下降但仍较高(P<0.05);与留针5 min、10 min、15 min比较,留针30 min穴位局部血流灌注量降低(P<0.05)。针刺肾俞穴后效应的穴位局部理化特征为,与针刺前比较,肾俞穴在起针后6个时间点血流灌注量均显著升高(P<0.05);且与起针后5 min比较,起针15 min、20 min明显降低(P<0.05,P<0.01)。结论针刺不同穴位其局部血流灌注量与局部组织代谢改变不同,提示穴位的局部理化特征具有位置差异的特异性。针刺时长影响穴位局部血流灌注量,但是针刺时长10 min后穴位局部变化趋于平稳,同时,针刺肾俞穴存在后效应至少可持续30 min,为临床针刺效应提供参考依据。

高灰度级高分辨率激光散斑血流实时成像研究

激光散斑对比成像是一种大测量范围、实时、高分辨率的光学成像方法.现有研究表明,低灰度级(8位)低分辨率(752像素×480像素)照相机可以有效监测血液等散射介质流动,但散粒噪声大、有效成像区域小等缺点难以通过软件弥补,严重影响成像质量.使用高灰度级(16位)高分辨率(2 048像素×2 048像素)照相机监测血液流动会减慢单帧成像速度,并行计算能使图像处理时间减少1/3.研究借助动物血液流动实验,以成像速度与成像质量为评价标准,对比分析高灰度级高分辨率空间激光散斑对比成像与空间近似激光散斑对比成像(sLSCIa)、时间激光散斑对比成像(tLSCI)的结果.结果表明,高灰度级高分辨率空间激光散斑对比成像并行计算兼顾成像质量与成像速度,可以达到临床实时监测血液流动要求.

激光散斑对比成像技术在血流监测中的应用

激光散斑对比成像(LSCI)是一种以宽视场方式监测血流速度的非扫描光学成像技术。LSCI技术具有高时间-空间分辨率、快速实时成像、非接触式、仪器结构简单、无需造影剂等优势。本文简要介绍了LSCI的基本原理,概述了反射式LSCI和透射式LSCI两种结构,综述了LSCI在皮肤血流、大脑皮层和视网膜血流等生物医学应用中的最新研究进展,并对其发展前景做了进一步展望,为血流监测提供理论依据和实践指导。

术中甲状旁腺显影技术的研究进展

随着健康体检与癌症筛查的普及,甲状腺肿瘤的早期检出率逐渐增加。甲状腺肿瘤的治疗通常以手术切除为主,而甲状腺腺体后方的甲状旁腺对机体钙调节和维持内环境平衡至关重要,术中对于甲状旁腺的保护是避免术后发生甲状旁腺功能减退的关键步骤,故甲状腺术中对甲状旁腺的精准识别尤为重要。目前,甲状旁腺的识别在很大程度上依赖手术医生的临床经验和技巧,术中准确而快速识别甲状旁腺的技术可为临床提供重要的辅助治疗手段。最近几年,荧光图像引导手术,得到了广泛的研究,并越来越受欢迎。为此,本文将对术中甲状旁腺荧光显影技术及其最新的研究进展进行简单的如下综述。

Histogram analysis of laser speckle contrast image for cerebral blood flow monitoring

Laser speckle contrast imaging （LSCI） is a powerful tool for blood flow mapping. In this paper, we described a simple algorithm based on histogram analysis of laser speckle contrast image to provide rapid differentiation between macro- and microcirculations. The algorithm was successfully verified by the study of blood flow in rat cortex under functional activation.

精密测量中激光成像系统散斑的抑制因素

对采用激光照明的测量系统中散斑形成的三个重要因素,即入射光束的相干性、相位差和偏振特性进行了详细的理论分析,并给出了这些因素与散斑对比度的变化关系。计算表明,相干长度降到低于1 mm时,散斑对比度减小到0.5左右,得到的图像细节相对比较清楚,易于检测。基于计算分析,提出了相应的解决及优化方法,为抑制散斑、提高激光照明质量和测量准确性提供了理论依据。

基于激光散斑的应力传感系统

激光散斑传感技术具有结构简单、灵敏度高等特点,可以实现对应力、振动、距离、速度、流速等物理量的传感测量,已成为光学传感领域中的研究热点之一。设计了一套基于激光散斑的应力传感系统。该系统使用波长为405 nm激光作为光源,利用音圈电机振动多模光纤,同时采用CCD图像传感采集系统对抛光玻璃表面进行显微成像,通过MATLAB软件对采集到的散斑图像进行分析处理,计算散斑对比度,拟合散斑对比度随时间变化的曲线。结果表明:散斑图像对比度的变化反应了多模光纤应力的变化,通过多模光纤应力变化可以判断是否有入侵者,实现了防盗功能。

光学成像技术在体研究肿瘤的光动力效应

光动力疗法(PDT)已发展成为一种较成熟的肿瘤治疗方法,PDT诱导的血管损伤是杀死肿瘤的重要机制之一.为了在活体肿瘤模型上实时监测PDT导致的血管损伤效应,使用稳定高表达绿色荧光蛋白(GFP)的人涎腺腺样囊性癌细胞株(ACC-M-GFP),建立了基于鸡胚尿囊膜(CAM)的肿瘤模型.应用荧光成像技术对肿瘤的生长位置、大小,以及治疗区域进行方便精确的定位;利用激光散斑成像技术,实时监测CAM上肿瘤周围血管的血液动力学参数.发现不同光动力剂量所导致的血管损伤有显著不同.结果表明,荧光标记的鸡胚尿囊膜肿瘤模型为研究PDT导致的血管损伤效应提供了良好的实验模型,激光散斑成像技术适用于实时监测PDT过程中血管结构、血流速度的变化,由此得出血液灌注率可用以评估PDT对肿瘤周围血管的损伤效应.