In Situ Characterization of the Degradation of PLGA Microspheres in Hyaluronic Acid Hydrogels by Optical Coherence Tomography

The polymeric implant material poly(lactide-co-glycolide) (PLGA) degrades by a process of bulk degradation, which allows it to be used for the controlled release of therapeutic molecules from implants and microspheres. The temporal characterization of PLGA microsphere degradation has been limited by the need to destructively monitor the samples at each time point. In this study, a noninvasive imaging technology, optical coherence tomography (OCT), was utilized to characterize the in situ degradation of PLGA microspheres suspended within photo-crosslinked hyaluronic acid (HA) hydrogels. Microspheres with differing degradation rates were loaded with bovine serum albumin (BSA) as a marker protein, and temporal release of protein was correlated with morphological changes observed during 3-D OCT imaging. As proof-of-principle, a microsphere-loaded hydrogel scaffold was implanted in a modified rat calvarial critical size defect model and imaged using OCT. This animal model presents the opportunity to monitor microsphere degradation over time in living animals.      

Differential absorption optical coherence tomography with strong absorption contrast agents of gold nanorods

Plasmon-resonant gold nanorods (GNRs) are demonstrated as strong absorption contrast agents for optical coherence tomography (OCT). OCT imaging of tissue phantoms doped with GNRs of different resonant wavelengths and concentrations is studied. To utilize the high absorption property of GNRs, a differential absorp-tion OCT imaging is introduced to retrieve the absorption information of GNRs from conventional backscattered signals. It is shown that the contrast of the OCT image can be enhanced significantly when the plasmon resonant wavelength of the GNRs matches the central wavelength of the OCT source.     

基于光谱光学相干层析技术的膜系反射光谱测量

根据光谱光学相干层析(OCT)技术的原理,建立了光谱光学相干层析系统,并利用该系统测量了膜系的反射光谱。该方法通过傅里叶变换实现了光学相干层析信号光谱信息的提取,克服了传统反射测量方法测量结果不直观、受非测量面干扰等问题。测量所得的光谱反射率,与商业仪器的测量值吻合较好,均方差仅为0.0488。     

Localized measurement of optical attenuation coefficients of atherosclerotic plaque constituents by quantitative optical coherence tomography

Optical coherence tomography (OCT) is a novel, high-resolution diagnostic tool that is capable of imaging the arterial wall and plaques. The differentiation between different types of atherosclerotic plaque is based on qualitative differences in gray levels and structural appearance. We hypothesize that a quantitative data analysis of the OCT signal allows measurement of light attenuation by the local tissue components, which can facilitate quantitative spatial discrimination between plaque constituents. High-resolution OCT images (at 800 nm) of human atherosclerotic arterial segments obtained at autopsy were histologically validated. Using a new, simple analysis algorithm, which incorporates the confocal properties of the OCT system, the light attenuation coefficients for these constituents were determined: for diffuse intimal thickening (5.5 +/- 1.2 mm(-1)) and lipid-rich regions (3.2 +/- 1.1 mm(-1)), the attenuation differed significantly from media (9.9 +/- 1.8 mm(-1)), calcifications (11.1 +/- 4.9 mm(-1) ) and thrombi (11.2 +/- 2.3 mm(-1)) (p < 0.01). These proof of principle studies show that simple quantitative analysis of the OCT signals allows spatial determination of the intrinsic optical attenuation coefficient of atherosclerotic tissue components within regions of interest. Combining morphological imaging by OCT with the observed differences in optical attenuation coefficients of the various regions may enhance discrimination between various plaque types.     

不同结构生物组织光透明作用比较

为了了解生物组织不同结构对光透明进程的影响,利用光相干断层成像术(OCT)和近红外光谱(NIR)对肌肉组织(猪骨骼肌)和上皮组织(猪胃黏膜)经丙三醇处理后的光透明效果进行了比较研究。结果表明,这两种组织的光相干断层成像术成像深度和内层次结构的成像对比度均得到改善;肌肉组织和胃黏膜组织的光透射率分别增加了21%和16%,而漫反射率分别降低了33%和21%;这两种结构组织的光透明效果(肌肉组织较好)和进程(肌肉组织较快)与各自的失水率和失水动力学成正相关,肌肉组织失水过程为先快后慢;胃黏膜组织的失水过程为先慢后快;肌肉组织的总失水率大于胃黏膜组织。这表明结构不同的生物组织的光透明效果存在差异,必须考虑其内部结构的影响。     

Injectable Peptide Decorated Functional Nanofibrous Hollow Microspheres to Direct Stem Cell Differentiation and Tissue Regeneration

Injectable microspheres are attractive stem cell carriers for minimally invasive procedures. For tissue regeneration, the microspheres need to present the critical cues to properly direct stem cell differentiation. In natural extracellular matrix (ECM), growth factors (GFs) and collagen nanofibers provide critical chemical and physical cues. However, there have been no reported technologies that integrate synthetic nanofibers and GFs into injectable microspheres. In this study, functional nanofibrous hollow microspheres (FNF‐HMS), which can covalently bind GF‐mimicking peptides, are synthesized. Two different GF‐mimicking peptides, Transforming Growth Factor‐β1 mimicking peptide Cytomodulin (CM) and Bone Morphogenetic Protein‐2 mimicking peptide P24, are separately conjugated onto the FNF‐HMS to induce distinct differentiation pathways of rabbit bone marrow‐derived mesenchymal stem cells (BMSCs). While no existing biomaterials are reported to successfully deliver CM to induce chondrogenesis, the developed FNF‐HMS are shown to effectively present CM to BMSCs and successfully induced their chondrogenesis for ­cartilage formation in both in vitro and in vivo studies. In addition, P24 is conjugated onto the newly developed FNF‐HMS and is capable of retaining its bioactivity and inducing ectopic bone formation in nude mice. These results demonstrate that the novel FNF‐HMS can effectively deliver GF‐mimicking peptides to modulate stem cell fate and tissue regeneration.     

软组织超声散射子频率特性的研究

由于生物软组织对超声波的衰减、吸收等作用,组织超声背散射射频(RF)信号的中心频率会发生偏移,利用超声背散射RF信号中心频率的偏移量来估计软组织超声特征散射子的粒径等特征成为可能.该文在软组织超声背散射RF信号功率谱理论分析的基础上,制作了4种不同散射子粒径的实验仿体,并对实验仿体进行了信号采集和数据处理,研究其频率特性.研究结果表明,生物软组织超声背散射RF信号的中心频率随超声特征散射子粒径的增大而向低频方向移动,且越来越接近发射超声信号的中心频率.     

Ultralow error rate and dispersion-free transmission of 2.5 Gbit/s SONET for gigabit networks

It is demonstrated that for an NRZ modulated 1310 nm optical transmitter, dispersion-free transmission can be achieved up to approximately 250 km using dispersion-shifted singlemode fibre (DS-SMF) and optical pulse compression. This result implies that DS-SMFs have a potential advantage over standard SMFs for dual-window (1310/1550 nm) multigigabit per second transmission systems. Results on the long-term error performance of experimental prototype 2.5 Gbit/s SONET optical transmission systems are presented with measured error rates smaller than 10/sup -15/.<>     

光子嫩肤热损伤的光学相干层析成像动态监控

提出了一种基于光学相干层析成像(PCT)的动态监控光子嫩肤热损伤的系统.利用OCT测试系统的非入侵性无损检测的技术特点进行实时测量光子嫩肤治疗过程中皮肤的光学参数,并根据所获得的光学参数变化量来反映热损伤程度.采用小鼠动物模型,并用不同剂量的激光照射小鼠背部皮肤,得到了皮肤组织的衰减系数将随着光剂量的增大而减小的关系.实验结果表明,衰减系数的变化量反映了热损伤的严重程度.     

Spectroscopic detection of gastrointestinal dysplasia using optical microsensors

The detection of dysplasia in the gastrointestinal tract can be performed using optical microsensors based on thin-film optical filters and silicon photodiodes. This paper describes two optical microsensors that can be used for spectroscopy data collection in two different spectral bands (one in the violet/blue region and the other in the green region) for which two optical filters were designed and fabricated. An empirical analysis of gastrointestinal spectroscopic data using these specific spectral bands is performed. The obtained results show that it is possible to accurately differentiate dysplastic lesions from normal tissue, with a sensitivity and specificity of 77.8% and 97.6%, respectively. Therefore, the developed filters can be used as a tool to aid in diagnosis. The small size of the optical microsensors can enable, in the future, integration in endoscopic capsules.     

OCT技术在生物组织中的应用

基于光学低相干反射测量而发展起来的光学相干层析技术（Ｏｐｔｉｃａｌ Ｃｏｈｅｒｅｎｃｅ Ｔｏｍｏｇｒａｐｈｙ,简称ＯＣＴ）是一种新型的成像技术,它能对高散射介质如生物组织实施非侵入性的快速成像,因而在在体生物组织的微结构分析和疾病诊断等方面有重要应用。本文概述了ＯＣＴ技术在生物组织的成像、特性参数测量、双折射特性测量及流体测速等方面的应用情况。     

5-Gbit/s BER performance on an all fiber-optic add/drop devicebased on a taper-resonator-taper structure

We present an all fiber-optic add/drop device based on a taper-resonator-taper structure with improved characteristics. Several gigahertz bandwidths are observed using microspheres having diameters ranging from 30 to 50 μm. Extinction ratios as high as 26 dB of the dropped channel are obtained due to nearly ideal coupling and phase matching between the fiber tapers and the small resonator. This is the first time that bit-error rate (BER) measurements have been performed on such couplers. For a device with an optical bandwidth of 3.8 GHz, the BER shows less than 2-dB penalty at 5 Gbit/s and no signs of an error floor     

光学相干层析成像技术在器官疾病诊断上的应用

在现代医学中,核扫描、正电子发射断层扫描( Positron Emission Tomography, PET) 和磁共振成像(Magnetic Resonance Imaging, MRI)技术已被广泛应用于提供组织形态和功能信息。但是这些技术在分辨率或成像深度上各有缺点,而一种基于低相干干涉原理的新型光学检测技术则可以同时实现高分辨率和大深度成像,该技术称为光学相干层析成像技术(Optical Coherence Tomography,OCT)。OCT技术是一种将高纵向分辨率和高横向分辨率结合的非接触、非侵入、无损伤影像技术,可以实现与活体组织病理学观察相同的作用。OCT采用低能量的近红外光源作为探测光,并结合显微镜头、手持式探头或内窥镜等非损伤方式进行常规检测,不会对生物组织造成损伤。同时OCT结合发展迅速的图像采集分析处理技术,可实现实时三维成像,从中提取对诊断有用的信息进行定量分析,为医生的诊断提供便利。该综述重点介绍经典OCT成像技术及其相关医疗应用技术,如SD-OCT、SS-OCT、aOCT、PS-OCT和D-OCT,在呼吸系统、口腔、脑组织和肾脏等其他主要器官疾病检测中的应用。     

纹理分析在生物组织光学相干层析图像信息提取和特征识别中的应用

随着光学相干层析(OCT)技术在生物医学成像领域日趋广泛的应用,分析和提取OCT图像中所包含的生物组织信息、对相关特征加以识别,并最终应用于疾病的辅助诊断和诊疗效果的追踪,已经成为一个重要的研究方向.国内外研究者就此提出了多种不同的方法,其中纹理分析方法得到了最为充分的研究,显示出良好的实用性.对纹理分析在生物组织光学...     

利用测量温度对介质光衰减系数影响的方法

本文的目标是研究一种无损检测温度对介质特别是生物组织光学特性影响的新方法。以牛奶作为样品,将其从低温开始加热,温度跨度从20-35℃,利用光学相干层析成像仪(OCT,中心波长为850nm)每隔5℃对牛奶进行一次成像取得对应的OCT信号强度数据。经过分析发现,当温度升高时,OCT系统探测到信号的衰减系数随之增大。这是一种研究温度对生物组织光学衰减系数影响的新方法。     

双波长光学相干层析成像

组建了具有980nm和1300nm两个波长光源的光学相干层析(OCT)成像系统。利用此系统,分别在两个波长、不同光源功率下,对新鲜猪肉组织进行OCT成像。比较了同一波长、不同功率和不同波长、同一功率下的OCT图像,并比较了同一波长、不同功率和不同波长、同一功率下OCT信号强度随深度变化的曲线。对曲线进行线性拟合,分析了两个波长下生物组织散射系数的变化规律。发现提高光源功率会使探测深度有限提高,而探测深度会随波长增大而增加,并分析了波长变化对OCT系统各参数的影响和进行对比的图像产生差异的原因。     

Optical resonances in dielectric microspheres for transverse magnetic wave

Optical resonances for Transverse Magnetic (TM) wave based on Whispering Gallery Modes (WGM) have been presented with comprehensive mathematical formulations. The present study is characterized both theoretically and experimentally by considering the fact that the size parameter of the dielectric microspheres is very large at optical wavelengths. An asymptotic expression has been developed based on electromagnetic theory for large size parameter. The developed expressions for optical resonance condition of TM wave are very simple and can accurately characterize resonances in dielectric microspheres. The theoretical development is mathematically robust and significantly less complicated than existing approaches based on quantum physics presented in the literatures. The theoretical result of size parameter for consecutive morphology dependent resonance (MDR) peaks is validated by experimental data. The comparisons are shown to be very accurate for large size parameters.     

并行频域OCT图像预处理系统

鉴于传统的时域光学相干层析成像(TDOCT)扫描过程复杂以及基于计算机的数据处理系统速度低,设计了基于ADI公司的双核、高速视频处理芯片ADSP-BF561的并行频域OCT(PSDOCT)图像预处理系统,无需横向和轴向扫描直接得到二维层析图像.实验结果表明:基于实序列IFFT算法、插值查表取模算法、双核并行处理技术及流水线处理技术的软件设计提高了系统的图像处理速度.该系统对横向扫描宽度为2.5 mm的1帧图像(180×512)进行处理需要的时间约为9 ms,轴向分辨率和横向分辨率分别达到17.4μm、14.1μm,灰度值误差为0.205%.满足实时精确成像的要求.     

采用频域光延迟线的光学相干层析成像

频域光延迟线是一种光学扫描结构,其基本组成是一个衍射光栅、一个透镜和一个扫描镜.把频域光延迟线应用到光学相干层析成像系统中,可以使参考臂扫描速率至少达到数m/s以上,从而实现视频速率的图像获取.从几何光学的角度分析了频域光延迟线的工作原理,分析结果表明在扫描角很小的情况下,入射光的光程或相位变化频率与扫描角频率有较好的线性关系.基于这一结构的光学相干层析成像的结果证明可以避免活体生物组织位移引入的图像模糊.另外,还提出了一种基于微执行器的新扫描装置.     

OCT纵向图像形成分析

光学相干层析成像能够直接对物体的纵深方向成像。本文对ＯＣＴ系统测量生物组成的纵向图像形成进行了理论研究，推导了系统相干传递函数，研究了系统的纵深分辨力。