定量血管内光学相干层析成像的研究进展

血管内光学相干层析成像(IVOCT)是目前分辨率最高的血管内成像技术,可对冠状动脉血管腔及管壁内膜下病变进行快速、清晰的成像。仅根据组织结构的层析图像无法精确识别粥样硬化斑块成分(如钙化、纤维化、脂质和混合斑块),需要形态结构之外的生理信息的对比机制,获得具有临床诊断价值的组织参数,即定量IVOCT(qIVOCT)。本文针对根据IVOCT原始背向散射信号和灰阶图像定量测量血管壁组织的光学特性参数、弹性参数和血流动力学参数的研究现状进行归纳和总结,分析目前存在的问题,展望可能的发展方向。     

血管内光学相干层析成像技术在冠状动脉粥样硬化斑块检测方面的应用

血管内光学相干层析成像(IVOCT)技术近年来在冠状动脉粥样硬化斑块检测方面发展非常迅速,可实现血管内病变组织高分辨率、无辐射、实时在体成像,在临床诊断方面发挥了重要的作用.本文简要介绍了IVOCT的成像原理、生物组织光学特征参数以及色散系数的计算方法,并对动脉粥样硬化斑块的机器学习算法进行了概述,为构建斑块的智能识别...     

脑功能光学成像技术及医学进展

本文较全面论述了目前发展中的脑功能光学成像技术:脑功能的内禀光学成像、神经元活动相关信号方法、光学相干层析成像、无损伤脑功能内禀光学成像等方法的原理、成像特性及相关最新医学研究进展.     

光相干层析成像中的散斑

由于光相干层析成像中测量的干涉信号空间频带有限 ,因此会产生散斑。在高散射的生物组织图像中 ,散斑具有双重身份 ,即作为噪声源和作为组织微结构的信号载体。本文的前半部分对于光相干层析成像中散斑的产生原因、统计特性以及分类作了综述。通过采样束的相位和振幅扰动可以定义信号载体散斑和信号降低散斑。本文的后半部分讨论了减少散斑的 4种方法 :偏振合成法、空间合成法、频率合成法和数字信号处理方法 ,并且通过举例对每一种方法的有效性作了简单的分析。最后 ,文章提出了需进一步研究的问题     

生物组织非接触光声层析成像EI北大核心CSCD

在光声成像中,超声信号通常需要采用接触传感器探测,这使其在很多应用中受到很大的限制,如脑功能成像。为了替代接触探测器实现非接触的光声层析成像(NCPAT),激光干涉技术被用于远程获取超声信号。本文搭建了非接触光声层析成像系统,系统采用波长为532 nm、能量17.5 m J/cm^2的激光作为光声激发源,激光外差干涉仪作为光声信号的远程探测系统,对实际生物组织模型进行了旋转几何的光声信号探测。利用激光外差干涉仪探测到的光声信号,进行反投影算法的图像重建。实验结果表明在具有组织散射特性的模型中,激光外差干涉仪在2.25 MHz带宽(峰值下15 d B强度的信号宽带)下,NCPAT成像系统可以识别500μm直径的黑色微球,并实现了在强散射介质中多层结构的光学对比成像。这将扩展光声和超声在体成像在生物医学领域的应用范围。     

光学相干层析成像无损监测不同表面处理后树脂充填界面

目的使用光学相干层析成像(OCT)观察不同方法处理牙本质后牙本质-树脂粘接界面的表现差异。方法选取20颗因治疗需要拔除的人前磨牙, 去除牙齿冠方1/3暴露牙本质, 随机分为A、B、C、D共4组, 每组5颗牙。于各组牙齿牙本质表面涂抹粘接剂并光固化后, 保持A组及C组牙齿表面干燥条件下树脂粘接。于B组及D组牙齿牙本质表面喷洒水雾模拟唾液污染后树脂粘接。在牙本质树脂粘接后使用OCT对样本扫描成像。结果牙本质-树脂粘接界面缺陷在OCT图像上显示为显著高亮度影像, 与周围正常组织及粘接区域分界清晰。无论是在激光蚀刻后或是酸蚀剂蚀刻后, 干燥条件下的树脂粘接并不能完全杜绝牙本质-树脂粘接界面缺陷的发生, 水汽污染条件下树脂粘接后的粘接界面缺陷更加明显。结论 OCT系统在牙本质树脂粘接过程中可对牙本质及牙本质-树脂粘接界面进行有效监测, 能准确显示牙本质-树脂粘接界面缺陷, 具有作为临床治疗过程实时监测系统的潜力。相比于激光蚀刻技术, 磷酸酸蚀剂蚀刻操作简便, 且能减少干燥或污染状态下牙本质-树脂粘接界面缺陷的发生。     

生物组织光学层析成像技术的理论研究

本文发展了一种能实现生物组织光学层析成像的理论。文中建立了光在生物组织中的散射模型，并利用格林函数法分析了问题的数学基本解的形式，得到了问题的初始值的解析表达式。利用偏微分方程特征线传播的方法，可以把问题的边界值（即测量值）传递给每层的初始值。然后结合初始值的解析形式，构造出一个目标函数，即可把逐层重构组织光学特性参数的问题转化为逐层控制参数使目标函数具有极小值的优化问题，从而逐层地重构出生物组织的光学特性参数。利用组织光学特性参数重构的结果，借助于计算机的图象处理技术，就可进一步得到组织内部的光学层析结构图象。本文最后给出了一个计算机数值仿真解。     

口腔光学相干计算机断层摄影术

光学相干计算机断层摄影术（optical coherence tomography，OCT），是近10年间迅速发展起来的一种新的生物组织成像技术。文章介绍口腔OCT原理和主要功能，阐述口腔OCT在离体口腔组织断层成像、在体口腔组织的实时断层摄影、龋损牙体组织的早期诊断、牙体修复和窝沟封闭效果的评估、监控龋病发展进程、口腔黏膜疾病的无创诊断、口腔软组织癌前病变的无创早期诊断中的实际应用，并与其他影像设备诊断进行比较，展望OCT的发展。     

基于光学相干层析的生物3D打印人工皮肤量化分析

对人工皮肤3D特征的无损定量检测分析,是研究皮肤打印和诱导培养技术须解决的关键问题。利用谱域光学相干层析成像(SD-OCT),对生物3D打印人工皮肤进行无损成像和量化分析。基于光学相干层析成像(OCT)强度信号的自适应峰值检测算法,量化皮肤3D厚度分布和粗糙度变化,通过计算不同位置的皮肤整体厚度及其波动,定量可视化皮肤的空间分辨结构特征。OCT成像人工皮肤的结构特征与切片的苏木精伊红(H&E)染色结果一致,两者实测皮肤整体厚度差异最大为3. 59μm,可验证该方法的可行性和准确性。通过SD-OCT对人工皮肤在培养周期内的持续检测,2D人工皮肤厚度分布检测可以展示皮肤在不同培养时间的厚度增长曲线,而3D空间分辨厚度分布图和表面粗糙图谱能更直观地显示皮肤生长状态。量化统计结果表明,在气液培养过程中,人工皮肤的整体平均厚度不断增长并趋于稳定,皮肤成熟时整体平均厚度为83. 91μm;皮肤表面粗糙度随角质化程度变化先减后增。基于OCT强度信号量化分析的方法能真实有效反映生物3D打印人工皮肤的结构参数变化,可为人工皮肤制备过程中的质量评估提供一种可靠的监测手段。     

利用双SLD光源提高OCT纵向分辨率的理论研究

提高光学相干层析成像(Optical Coherence Tomography: OCT)系统纵向分辨率的关键是选取合适的光源, 本文将双SLD光源代替传统OCT系统中的单个SLD光源,通过理论分析和计算机仿真,表明双SLD光源能有效提高OCT系统纵向分辨率.     

Stent Evaluation with Optical Coherence Tomography

Optical coherence tomography (OCT) has been recently applied to investigate coronary artery disease in interventional cardiology. Compared to intravascular ultrasound, OCT is able to visualize various vascular structures more clearly with higher resolution. Several validation studies have shown that OCT is more accurate in evaluating neointimal tissue after coronary stent implantation than intravascular ultrasound. Novel findings on OCT evaluation include the detection of strut coverage and the characterization of neointimal tissue in an in-vivo setting. In a previous study, neointimal healing of stent strut was pathologically the most important factor associated with stent thrombosis, a fatal complication, in patients treated with drug-eluting stent (DES). Recently, OCT-defined coverage of a stent strut was proposed to be related with clinical safety in DES-treated patients. Neoatherosclerosis is an atheromatous change of neointimal tissue within the stented segment. Clinical studies using OCT revealed neoatherosclerosis contributed to late-phase luminal narrowing after stent implantation. Like de novo native coronary lesions, the clinical presentation of OCT-derived neoatherosclerosis varied from stable angina to acute coronary syndrome including late stent thrombosis. Thus, early identification of neoatherosclerosis with OCT may predict clinical deterioration in patients treated with coronary stent. Additionally, intravascular OCT evaluation provides additive information about the performance of coronary stent. In the near future, new advances in OCT technology will help reduce complications with stent therapy and accelerating in the study of interventional cardiology.     

Application of Improved Homogeneity Similarity-Based Denoising in Optical Coherence Tomography Retinal Images

Image denoising is a fundamental preprocessing step of image processing in many applications developed for optical coherence tomography (OCT) retinal imaging—a high-resolution modality for evaluating disease in the eye. To make a homogeneity similarity-based image denoising method more suitable for OCT image removal, we improve it by considering the noise and retinal characteristics of OCT images in two respects: (1) median filtering preprocessing is used to make the noise distribution of OCT images more suitable for patch-based methods; (2) a rectangle neighborhood and region restriction are adopted to accommodate the horizontal stretching of retinal structures when observed in OCT images. As a performance measurement of the proposed technique, we tested the method on real and synthetic noisy retinal OCT images and compared the results with other well-known spatial denoising methods, including bilateral filtering, five partial differential equation (PDE)-based methods, and three patch-based methods. Our results indicate that our proposed method seems suitable for retinal OCT imaging denoising, and that, in general, patch-based methods can achieve better visual denoising results than point-based methods in this type of imaging, because the image patch can better represent the structured information in the images than a single pixel. However, the time complexity of the patch-based methods is substantially higher than that of the others.     

Mechanical Analysis of Atherosclerotic Plaques Based on Optical Coherence Tomography

Finite element analysis is a powerful tool for investigating the biomechanics of atherosclerosis and has thereby provided an improved understanding of acute myocardial infarction. Structural analysis of arterial walls is traditionally performed using geometry contours derived from histology. In this paper we demonstrate the first use of a new imaging technique, optical coherence tomography (OCT), as a basis for finite element analysis. There are two primary benefits of OCT relative to histology: 1) imaging is performed without excessive tissue handling, providing a more realistic geometry than histology and avoiding structural artifacts common to histologic processing, and 2) OCT imaging can be performed in vivo, making it possible to study disease progression and the effect of therapeutic treatments in animal models and living patients. Patterns of mechanical stress and strain distributions computed from finite element analysis based on OCT were compared with those from modeling based on "gold standard" histology. Our results indicate that vascular structure and composition determined by OCT provides an adequate basis for investigating the biomechanical factors relevant to atherosclerosis and acute myocardial infarction.     

基于光学相干层析的视网膜图像分割

利用光学相干层析（optical coherence tomography,OCT）技术可以得到清晰的视网膜层状结构,实现视网膜层状结构自动分割功能是解决OCT技术应用于视网膜疾病诊断的一项基础问题。本文通过图像平滑、峰值探测、Snake模型、贪婪算法和样条插值等综合技术,对OCT视网膜图像进行分割,自动提取层状结构轮廓并获取视网膜厚度分布图。将以上算法应用于24例正常人眼底图像,并与专家手动标记轮廓提取的厚度相比,结果证实上述视网膜自动测量算法与专家人工标记取得较好一致性。本文提出的测量算法有望应用于视网膜变异性评估。     

Optical Coherence Tomographic Observation of Morphological Features of Neointimal Tissue after Drug-Eluting Stent Implantation

Purpose

The impacts of different time courses and the degree of neointimal growth on neointimal morphology have not yet been sufficiently investigated. Therefore, we evaluated the morphological features of neointimal tissue after drug-eluting stent (DES) implantation using optical coherence tomography (OCT).

Materials and Methods

The morphological features of neointimal tissue in stented segments with a maximal percentage of cross-sectional area (CSA) stenosis of neointima were evaluated in 507 DES-treated lesions with >100 µm mean neointimal thickness on follow-up OCT. Neointimal tissue was categorized as homogeneous, heterogeneous, layered, or neoatherosclerotic.

Results

In lesions with <50% of neointimal CSA stenosis, homogeneous neointima (68.2%) was predominant, followed by heterogeneous neointima (14.1%) and layered neointima (14.1%). In lesions with ≥50% of neointimal CSA stenosis, layered neointima was most frequently observed (68.3%), followed by neoatherosclerotic neointima (25.2%). In subgroup analysis of lesions with ≥50% of neointimal CSA stenosis, 89.5% of the lesions with a stent age <30 months were layered neointima, while 62.3% of the lesions with a stent age ≥30 months were neoatherosclerotic neointima.

Conclusion

This study suggests that the OCT-detected morphology of DES neointimal tissue was different according to the follow-up time course and degree of neointimal hyperplasia.     

Tissue Elasticity Estimation with Optical Coherence Elastography: Toward Mechanical Characterization of <Emphasis Type="Italic">In Vivo</Emphasis> Soft Tissue

High-resolution imaging provides a significant means for accurate material modulus estimation and mechanical characterization. Within the realm of in vivo soft tissue characterization, particularly on small biological length scales such as arterial atherosclerotic plaques, optical coherence tomography (OCT) offers a desirable imaging modality with higher spatial resolution and contrast of tissue as compared with intravascular ultrasound (IVUS). Based on recent advances in OCT imaging and elastography, we present a fully integrated system for tissue elasticity reconstruction, and assess the benefits of OCT on the distribution results of four representative tissue block models. We demonstrate accuracy, with displacement residuals on the order of 10⁻⁶ mm (more than 3 orders of magnitude less than average calculated displacements), and high-resolution estimates, with the ability to resolve inclusions of 0.15 mm diameter.     

Detection of Occludable Angles with the Pentacam and the Anterior Segment Optical Coherence Tomography

Purpose

To assess efficacy of the Pentacam (PTC) and the anterior segment optical coherence tomography (AOCT) for detection of occludable angles.

Materials and Methods

Fourty-one eyes with gonioscopically diagnosed occludable angles and 32 normal open-angle eyes were included. Anterior chamber angle (ACA) and anterior chamber depth (ACD) were measured with PTC and AOCT. Receiver operating characteristic (ROC) curve was constructed for each parameter and the area under the ROC curve (AUC) was calculated.

Results

Values of ACA and ACD measured by PTC and AOCT were similar not only in normal open angle eyes but also in occludable angle eyes. For detection of occludable angle, the AUCs of PTC with ACA and ACD were 0.935 and 0.969, respectively. The AUCs of AOCT with ACA and ACD were 0.904 and 0.947, respectively.

Conclusion

Both PTC and AOCT allow accurate discrimination between open and occludable angle eyes, so that they may aid to screening the occludable angles.     

Fast Optical Transillumination Tomography with Large-Size Projection Acquisition

Techniques such as optical coherence tomography and diffuse optical tomography have been shown to effectively image highly scattering samples such as tissue. An additional modality has received much less attention: Optical transillumination (OT) tomography, a modality that promises very high acquisition speed for volumetric scans. With the motivation to image tissue-engineered blood vessels for possible biomechanical testing, we have developed a fast OT device using a collimated, noncoherent beam with a large diameter together with a large-size CMOS camera that has the ability to acquire 3D projections in a single revolution of the sample. In addition, we used accelerated iterative reconstruction techniques to improve image reconstruction speed, while at the same time obtaining better image quality than through filtered backprojection. The device was tested using ink-filled polytetrafluorethylene tubes to determine geometric reconstruction accuracy and recovery of absorbance. Even in the presence of minor refractive index mismatch, the weighted error of the measured radius was <5% in all cases, and a high linear correlation of ink absorbance determined with a photospectrometer of R ² = 0.99 was found, although the OT device systematically underestimated absorbance. Reconstruction time was improved from several hours (standard arithmetic reconstruction) to 90 s per slice with our optimized algorithm. Composed of only a light source, two spatial filters, a sample bath, and a CMOS camera, this device was extremely simple and cost-efficient to build.     

Optical Coherence Tomography for the Diagnosis and Evaluation of Human Otitis Media

We report the application of optical coherence tomography (OCT) to the diagnosis and evaluation of otitis media (OM). Whereas conventional diagnostic modalities for OM, including standard and pneumatic otoscopy, are limited to visualizing the surface of the tympanic membrane (TM), OCT effectively reveals the depth-resolved microstructure below the TM with very high spatial resolution, with the potential advantage of its use for diagnosing different types of OM. We examined the use of 840-nm spectral domain-OCT (SD-OCT) clinically, using normal ears and ears with the adhesive and effusion types of OM. Specific features were identified in two-dimensional OCT images of abnormal TMs, compared to images of healthy TMs. Analysis of the A-scan (axial depth scan) identified unique patterns of constituents within the effusions. The OCT images could not only be used to construct a database for the diagnosis and classification of OM but OCT might also represent an upgrade over current otoscopy techniques.

Graphical Abstract

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Optical coherence tomography: technology and applications for neuroimaging

Optical coherence tomography (OCT) is an emerging imaging technology with applications in biology, medicine, and materials investigations. Attractive features include high cellular-level resolution, real-time acquisition rates, and spectroscopic feature extraction in a compact noninvasive instrument. OCT can perform "optical biopsies" of tissue, producing images approaching the resolution of histology without having to resect and histologically process tissue specimens for characterization and diagnosis. This article will review several of the current technological developments in OCT. To illustrate the potential of this technology for neuroimaging, applications for imaging neural development, the neural retina, tumors of the central nervous system, and the microsurgical repair of peripheral nerves will be presented. This technology offers a potential investigative tool for addressing many of the present challenges in neuroimaging.