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.

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.

Generating Proton Beams Exceeding 10 MeV Using High Contrast 60TW Laser

A prototype of a laser driven proton accelerator is built at Peking University. Protons exceeding IOMeV are accelerated from micrometer-thick aluminum targets irradiated by tightly focused laser pulse with 1.8 J energy and 30fs duration. The beam energy spectrum and charge distribution are measured by a Thomson parabola spectrometer and radiochromic fihn stacks. The sensitivity of proton cut-off energy to the focusing of the laser beam, the pulse duration, and the foil thickness are systematically investigated in the experiments. Stable proton beams have been produced with an optimized parameter set, providing a cornerstone for the future applications of laser accelerated protons.

Assessment of contrast sensitivity loss after intrastromal femtosecond laser and LASIK procedure

AIM： To assess the loss of contrast sensitivity （CS） function for INTRACOR or intrastromal femtosecond laser presbyopia procedure to conventional LASIK procedures.METHODS： Patients were recruited from a refractive surgery center for either INTRACOR or conventional LASIK. INTRACOR was performed on 8 eyes and LASIK was performed for 40 eyes in an overlapping period. Pre-operative evaluation and post-operative follow up for up to three months was done. Drops of CS in 4 spatial frequency （3 cpd, 6 cpd, 12 cpd and 18 cpd） right before and 3mo after the surgery were compared by Wilcoxon signed ranks test.RESULTS： For INTRACOR, CS threshold showed significant drop at both glare and non-glare condition, the drop was seen in all 4 spatial frequency. The averaged loss over the 4 spatial frequencies 3mo after surgery was 1.18 for non-glare and 0.71 for glare. For LASIK the CS threshold drop was most significant in 12 cpd for glare.CONCLUSION： INTRACOR procedure produces a gain of near vision for presbyopia patients but also introduces a high lost of contrast sensitivity plus worsen of vision quality. Pre-surgical patient selection and advise should be given with specific regards to night driving and glare conditions.

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.

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.

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.

Low-Spatial Coherence High-Power Electrically Injected 6xx nm Dual-Emitter Laser

Laser-based displays have attracted much attention owing to large-size screen and full-color gamut compared with other displays such as liquid crystal display and light emitting diode. However, there exists a phenomenon, speckle, limits the applications of laser display because of the high coherence of laser. In this work, we developed an electrically injected 6xx nm dual-emitter laser which combines the low-spatial coherence with the high-power. The output power of the dual-emitter laser exceeds 500 mW under 20?C pulse operation. The single emitter consists of D-shaped section used to obtain more independent spatial modes thus reduces coherence and a stripe area to obtain the high power. The radius of the D-shaped cavity is 500 μm and the length of stripe is 1000 μm. We used the standard photolithography and inductively coupled plasma (ICP) process to fabricate the device. The speckle contrast was measured to be 5%. It exhibits a great potential of reducing speckle from the source directly for laser display.

Optical path design of phase contrast imaging on HL-2A tokamak

A phase contrast imaging（PCI） diagnostic has recently been developed on HL-2 A tokamak. It can diagnose plasma density fluctuations with maximum wave number of 15 cm^（-1） and wave number resolution of 2 cm^（-1）. The time resolution reaches 2 μs. A 10.6 μm CO_2 laser is expanded to a beam with a diameter of 30 mm and injected into the plasma as an incident beam,injecting into plasma. The emerging scattered and unscattered beams are contrasted by a phase plate. The ideas of optical path design are presented in this paper, together with the parameters of the main optical components. The whole optical path of PCI is not only carefully designed, but also constructed on HL-2 A. First calibration results show the ability of this system to catch plasma turbulence in a wide frequency domain.

Laser-induced Interstitial Thermotherapy via a Single-needle Delivery System: Optimal Conditions of Ablation, Pathological and Ultrasonic Changes

Summary： This study aimed to examine the optimal conditions of laser-induced interstitial ther- motherapy （LITT） via a single-needle delivery system, and the ablation-related pathological and ultra- sonic changes. Ultrasound （US）-guided LITT （EchoLaser system） was performed at the output power of 2--4 Wattage （W） for 1-10 min in ex vivo bovine liver. Based on the results of the ex vivo study, the output power of 3 and 4 W with different durations was applied to in vivo rabbit livers （n=24）, and VX2 tumors implanted in the hind limbs of rabbits （n=24）. The ablation area was histologically determined by hematoxylin-eosin （HE） staining. Traditional US and contrast enhanced ultrasound （CEUS） were used to evaluate the treatment outcomes. The results showed： （1） In the bovine liver, ablation disruption was grossly seen, including a strip-like ablation crater, a carbonization zone anteriorly along the fiber tip, and a surrounding gray-white coagulation zone. The coagulation area, 1.2 cm in length and 1.0 cm in width, was formed in the bovine liver subjected to the ablation at 3 W for 5 min and 4 W for 4 rain, and it extended slightly with the ablation time. （2） In the rabbit liver, after LITT at 3 W for 3 min and more, the coagulation area with length greater than or equal to 1.2 cm, and width greater than or equal to 1.0 cm, was found. Similar coagulation area was seen in the implanted VX2 carcinoma at 3 W for 5 min. （3） Gross examination of the liver and carcinoma showed three distinct regions： ablation cra- ter/carbonization, coagulation and congestion distributed from the center outwards. （4） Microscopy re- vealed four zones after LITT, including ablation crater/carbonization, coagulation, edema and conges- tion from the center outwards. A large area with coagulative necrosis was observed around a vessel in the peripheral area with edema and hyperemia. （5） The size of coagulation was consistent well to the CEUS findings. It was concluded that EchoLaser system at low power can produce a coagulation area larger than 1.0 cm×1.0 cm during a short time period. The real-time US imaging can be used to effec- tively guide and assess the treatment.

Comparison of the femtosecond Laser and mechanical microkeratome for flap cutting in LASIK

· AIM: To compare refractive results, higher-order aberrations(HOAs), contrast sensitivity and dry eye after laser in situ keratomileusis(LASIK) performed with a femtosecond laser versus a mechanical microkeratome for myopia and astigmatism.·METHODS: In this prospective, non-randomized study,120 eyes with myopia received a LASIK surgery with the Visu Max femtosecond laser for flap cutting, and 120 eyes received a conventional LASIK surgery with a mechanical microkeratome. Flap thickness, visual acuity, manifest refraction, contrast sensitivity function(CSF) curves,HOAs and dry-eye were measured at 1wk; 1, 3, 6mo after surgery.·RESULTS: At 6mo postoperatively, the mean central flap thickness in femtosecond laser procedure was113.05 ±5.89 μm(attempted thickness 110 μm), and148.36 ±21.24 μm(attempted thickness 140 μm) in mechanical microkeratome procedure. An uncorrected distance visual acuity(UDVA) of 4.9 or better was obtained in more than 98% of eyes treated by both methods, a gain in log MAR lines of corrected distance visual acuity(CDVA) occurred in more than 70% of eyes treated by both methods, and no eye lost ≥1 lines of CDVA in both groups. The difference of the mean UDVA and CDVA between two groups at any time post-surgery were not statistically significant(P 】0.05). The postoperative changes of spherical equivalent occurred markedly during the first month in both groups. The total root mean square values of HOAs and spherical aberrations in the femtosecond treated eyes were markedly less than those in the microkeratome treated eyes during 6mo visit after surgery(P 【0.01). The CSF values of the femtosecond treated eyes were also higherthan those of the microkeratome treated eyes at all space frequency(P 【0.01). The mean ocular surface disease index scores in both groups were increased at 1wk, and recovered to preoperative level at 1mo after surgery. The mean tear breakup time(TBUT) of the femtosecond treated eyes were markedly longer than those of the microkeratome treated eyes at postoperative 1, 3mo(P 【0.01).·CONCLUSION: Both the femtosecond laser and the mechanical microkeratome for LASIK flap cutting are safe and effective to correct myopia, with no statistically significant difference in the UDVA, CDVA during 6mo follow-up. Refractive results remained stable after 1mo post-operation for both groups. The femtosecond laser may have advantages over the microkeratome in the flap thickness predictability, fewer induced HOAs, better CSF,and longer TBUT.

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。

The influence of divergence angle on the deposition of neutral chromium atoms using a laser standing wave

The characteristics of neutral chromium atoms in the standing wave field are discussed. Based on a semi-classical model, the motion equation of neutral atoms in the laser standing wave field is analyzed, and the trajectories of the atoms are obtained by simulations with the different divergence angles of the atomic beam. The simulation results show that the full width at half maximum （FWHM） of the stripe is 2.75 nm and the contrast is 38.5 ： 1 when the divergence angle equals 0 mrad, the FWHM is 24.1 nm and the contrast is 6.8：1 when the divergence angle equals 0.2 mrad and the FWHMs are 58.6 and 137.8 nm, and the contrasts are 3.3 ： 1 and 1.6 ： i when the divergence angles equal 0.5 and 1.0 mrad, respectively.

激光投影显示中复合散斑抑制方法的研究

为了有效抑制激光投影显示中的散斑,基于散斑统计理论,建立了光纤长度与光纤末端出射光场衬比度的数值表达式;采用积分散斑统计学方法理论分析了级联位相片散射特性和运动特性对散斑衬比度的影响;实验研究了不同光纤长度下振动光纤前后图像的散斑衬比度;比较了运用散斑抑制技术和复合散斑抑制技术所获得的散斑图像衬比度。结果表明,采用振动10 m多模光纤与旋转级联位相片相结合的复合散斑抑制技术,可将散斑衬比度降低到3.76%;采用复合散斑抑制技术将增加系统自由度,从而更有效地抑制散斑。该研究为激光投影显示中开展复合散斑抑制技术研究工作提供了参考。

不同对比剂浓度对准分子激光消蚀作用的影响:体外研究

目的探讨对比剂浓度对准分子激光消蚀斑块作用的影响。方法采用直径为0.9 mm的激光纤维导管,运用波长为308 nm的氯化氙准分子激光进行斑块模型消蚀实验。在准分子激光消蚀过程中,根据所注射对比剂浓度不同分为5组:生理盐水组、25%浓度组、50%浓度组、75%浓度组、100%浓度组。通过光学相干断层成像评估准分子激光消蚀后斑块管腔面积变化,以评估对比剂浓度对准分子激光消蚀作用的影响。同时,利用水听器测量准分子激光在不同对比剂浓度的液体中产生的冲击波压力,以探讨准分子激光的冲击波压力与其消蚀作用的相关性。结果75%浓度组和100%浓度组的消蚀面积相近(P>0.05),均大于50%浓度组、25%浓度组和生理盐水组(均P<0.001)。50%浓度组的消蚀面积显著大于25%浓度组和生理盐水组(均P<0.001),而25%浓度组则大于生理盐水组(P<0.001)。对比剂浓度对准分子激光冲击波压力的影响也呈现相似的趋势。准分子激光产生的冲击波压力与其消蚀面积之间存在显著正相关(r=0.9987,P<0.001)。结论可以通过改变对比剂浓度来调节准分子激光对斑块组织消蚀作用的强度,为准分子激光联合对比剂注射技术在冠心病治疗中运用提供了指导。

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。

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.

HL-2A装置相衬成像系统的安全连锁与远程监控

通过在相衬成像系统光路中引入电控安全快门控制激光输出,并使用延迟电路实现了安全快门与HL-2A放电运行的同步触发,保障了诊断系统的安全运行,安全快门时间响应为26ms,其抖动误差1ms;利用四象限传感器实现了激光束斑位置的实时监测,获得了HL-2A装置垂直和水平方向的振动数据。所发展的电控快门技术和激光实时监测系统不仅能够大幅提高相衬成像系统的安全性和可靠性,对于HL-2A/2M装置诊断系统的发展和完善也具有重要意义。