实验探索非靶组织光学参数对超声调制光的影响

生物组织是一种复杂的多层高散射介质,探索光在超声作用下的生物组织中的传播规律是超声调制光学成像术必须解决的一个基本问题,关系到最终进行图像处理与重建。通过实验探索超声调制光信号在双层和三层组织中的传播规律。实验结果表明非靶组织的光学属性（吸收系数和散射系数）和组织结构（单层或多层）都不影响超声调制光信号的调制深度。调制深度只与超声焦区介质（即靶组织）的声光属性有关,具有较佳的抗干扰性,适合用于图像重构。     

生物组织的超声调制光学成像技术

具有超声定位的高空间分辨率和光学检测的高灵敏度的超声调制光学成像技术是一种有前途的无损的生物组织成像技术。文章阐述了该技术的成像原理,评述了前人在散射介质中声光作用机制的理论研究;介绍了该领域在技术路线上的最新研究进展;最后总结了超声调制光学成像技术的优点并展望了其在生物医学领域的应用前景。     

生物光子成像专题序言

本专题刊由八篇有关生物组织光学成像方面的邀稿 (Invited papers)及一些常规文章组成。近年来 ,在高散射介质中 (尤其在生物组织中 )光输运问题被越来越广泛和深入的研究。这些研究可以开发一些新的无损而又廉价的医学光学成像技术。光学成像因其可以提供生理学功能型的医学影像 ,而引起学术界广泛的关注。光学成像主要包括漫射光断层成像、相干光断层成像 (OCT)、早到光子技术、超声调制技术、磁光调制技术、偏振调制技术、漫射光断层成像等等方面。另一方面 ,荧光标记成像、单分子探测等等手段 ,拓展了研究范围 ,提供了更多的处理方法…     

生物光学成像专刊征文通知

本专刊主要由有关生物组织光学成像方面的邀稿和投稿组成。近年来 ,在高散射介质中 (尤其在生物组织中 )光输运问题被越来越广泛和深入的研究。这些研究可以开发一些新的无损而又廉价的医学光学成像技术。光学成像因其可以提供生理学功能型的医学影像 ,而引起学术界广泛的关注。光学成像主要包括漫射光断层成像、相干光断层成像 ( OCT)、早到光子技术、超声调制技术、磁光调制技术、偏振调制技术等等方面。在这些技术中 ,相干光断层成像具有较高的空间分辨率 ,技术相对比较成熟 ,但其检测深度有限。漫射光断层成像的空间分辨率是比较低的 …     

生物光学成像专题征文通知

本专刊主要由有关生物组织光学成像方面的邀稿和投稿组成。近年来 ,在高散射介质中 (尤其在生物组织中 )光输运问题被越来越广泛和深入的研究。这些研究可以开发一些新的无损而又廉价的医学光学成像技术。光学成像因其可以提供生理学功能型的医学影像 ,而引起学术界广泛的关注。光学成像主要包括漫射光断层成像、相干光断层成像 ( OCT)、早到光子技术、超声调制技术、磁光调制技术、偏振调制技术等等方面。在这些技术中 ,相干光断层成像具有较高的空间分辨率 ,技术相对比较成熟 ,但其检测深度有限。漫射光断层成像的空间分辨率是比较低的 …     

用去卷积法提高超声调制光学成像的空间分辨率

超声调制光学成像的空间分辨率取决于光在组织中的散射程度和扫描超声束的聚焦大小。由于组织是强散射介质,实际应用中的超声束都有一定的聚焦宽度(通常是毫米数量级),所以该技术成像空间分辨率一直无法提高。针对这个问题,首次将去卷积图像处理法运用在超声调制光学成像技术中,有效地解决了扫描超声束带来的信号展开,分辨率下降的影响。理论和防真结果表明,处理后的成像分辨率大大提高,图像质量明显改善。该方法无须对系统装置做任何改动,只利用适当的数据处理,就实现了成像超分辨,具有应用价值。     

Wigner-Ville分布法估计生物组织散射元平均间距

生物组织散射元平均间距是描述生物组织微观结构和超声散射特性的重要参数。文中构造了生物组织散射元一维超声散射模型,提出用Ｗｉｇｎｅｒ－Ｖｉｌｅ分布函数方法估计生物组织散射元平均间距,仿真结果表明这一方法具有良好的空间分辨率,能检测出生物组织散射元平均间距细微的非均匀性变化,且有良好的抗噪声性等一系列优良特性     

生物组织超声散射系数与温度相关性的研究

在随机起伏介质超声散射理论基础上,根据生物非均匀介质中声波动方程,推导出散射系数与温度的关系,然后分别采用了回波直接截取、经验模态分层（EDM）两种方法进行实验验证分析.结果表明超声散射系数与温度有依次递增的对应关系,可以运用它从超声回波信号中有效地提取组织温度信息.经验模态分层法的数据处理结果一致性要好些,总体趋势更接近理论分析.     

生物组织散射元平均间距估计的一种新方法

生物组织散射元平均间中划描述生物组织微观结构特性和生物组织超微散射特性的重要参数。本文在对生物组织超声背向散射随机模的基础上,提出了基于生物组织超声背向散射信号突变点检测的工用射元平均间距估计的新方法。该方法是生物组织超声散射分析的有效方法。     

反卷积在生物组织光传输特性研究中的应用

生物组织中的光传输特性可以以点扩散函数表征,即在线状光束入射条件下,生物组织中某一深度层面上的光强度场分布。为获得点扩散函数的具体形式,已发展了多种理论分析方法,其中以Monte Carlo模拟方法最具代表性。但现有理论计算方法都要以生物组织的光学参数已知为前提,而光学参数的准确度直接影响着计算的精度。从线性平移不变系统理论出发,生物组织内一定深度层面上的光强分布被看成是光源强度分布与点扩散函数的卷积,从而提出通过测量在轴对称的准直扩展光源照射条件下,组织中特定层面上的光强度分布,利用反卷积重建生物组织的点扩散函数的方法,并将这种方法应用于典型生物组织透射面上点扩散函数的重建,得到了相应的点扩散函数。实验结果与Monte Carlo模拟的结果吻合较好,表明该方法从实验上获得生物组织点扩散函数的正确性和有效性。     

Multiangle light scattering flow photometry of cultured human fibroblasts: comparison of normal cells with a mutant line containing cytoplasmic inclusions.

Multi-angle light scattering flow photometry was used to study the light scattering properties of normal cultured fibroblasts and a mutant fibroblast line containing cytoplasmic lysosomal inclusions. The effect of glutaraldehyde fixation on the light scattering properties of the cells was also examined and correlated with their ultrastructure. Normal fibroblasts showed uniform organelle distribution with few vacuoles or dense bodies in the cytoplasm while the mutant line showed abnormal cytoplasmic inclusions of varying morphology, density and lucency. As predicted by light scattering theory, the mutant cells containing the cytoplasmic inclusions scattered more light at large angles (greater than theta = 1.85 degrees) than did the normal cells. Glutaraldehyde fixation decreased light scattering at small angles (less than theta = 1.85 degrees), increased light scattering at larger angles (greater than theta = 1.85 degrees) in both normal and mutant cells and enhanced resolution of the light scattering signatures. The mutant line scattered 2-3 times more light at a wide angle (greater than theta = 12.74 degrees) than did the normal cells. These data suggest that abnormal lysosomal storage inclusion bodies in the cytoplasm of the cells can be detected by differential light scattering methods.     

Comparison of lipid binding and kinetic properties of normal, variant, and gamma-carboxyglutamic acid modified human factor IX and factor IXa

The abilities of normal and three abnormal factor IXa molecules to activate factor X and to bind to phospholipid membranes have been compared to define the contributions of protein-lipid interactions and factor IXa light chain-heavy chain interactions to the functioning of this protein. The abnormal proteins studied had altered amino acid residues in their light chains. The heavy-chain regions, containing the active site serine and histidine residues, were normal in the abnormal proteins on the basis of titration by antithrombin III. The binding constants (Kd) for normal (N), variant [Chapel Hill (CH) and Alabama (AL)], and gamma-carboxyglutamic acid (Gla) modified (MOD) factors IX and IXa to phosphatidylserine (PS)/phosphatidylcholine (PC) small, unilamellar vesicles (SUV) were measured by 90 degrees light scattering. The Kd values for factor IXN binding were quite sensitive to the PS content of the membrane but less sensitive to Ca2+ concentrations between 0.5 and 10 mM. The zymogen and activated forms of both normal and abnormal factor IX bound with similar affinities to PS/PC (30/70) SUV. In the cases of factor IXaN and factor IXaAL, but not factor IXaCH or factor IXaMOD, irreversible changes in scattering intensity suggested protein-induced vesicle fusion. Since the activation peptide is not released from factor IXaCH, the normal interaction of factor IXa with a membrane must require the release of the activation peptide and the presence of intact Gla residues. The rate of factor X activation by normal and abnormal factor IXa was obtained by using a chromogenic substrate for factor Xa in the presence of PS/PC (30/70) SUV and 5 mM Ca2+.     

Complexity analysis of electrocardiographic signals

Two types of electrocardiographic data series were investigated using appropriate tests based on a selection of semi-quantitative analysis algorithms. Distribution histograms, power spectra, auto-correlation functions, state-space portraits, Lyapunov exponents and wavelet transformations were applied to electrocardiograms of normal and stressed subjects. Statistical analysis using the Student's t-test revealed significant and non-significant alterations in stress-loaded cases compared to normal ones. Higher levels of adrenaline may account for a more complex dynamics (deterministic chaos) revealed in the stressed subjects.     

Spectral densities of nitrogen nuclei in Escherichia coli ribonuclease HI obtained by 15N NMR relaxation and molecular dynamics

Summary Spectral densities of the ¹⁵N amide in Escherichia coli ribonuclease HI, obtained from NMR relaxation experiments, were compared with those calculated using a molecular dynamics (MD) simulation. All calculations and comparisons assumed that the auto-correlation function describing the internal motions of the molecule was independent of the auto-correlation function associated with overall rotational diffusion. Comparisons were limited to those residues for which the auto-correlation function of internal motions rapidly relaxed and reached a steady state within 205 ps. The results show the importance of frequency components as well as amplitudes of internal motions in order to obtain a meaningful comparison of MD simulations with NMR data.     

Wide‐field optical property mapping and structured light imaging of the esophagus with spatial frequency domain imaging

As the incidence of esophageal adenocarcinoma continues to rise, there is a need for improved imaging technologies with contrast to abnormal esophageal tissues. To inform the design of optical technologies that meet this need, we characterize the spatial distribution of the scattering and absorption properties from 471 to 851 nm of eight resected human esophagi tissues using Spatial Frequency Domain Imaging. Histopathology was used to categorize tissue types, including normal, inflammation, fibrotic, ulceration, Barrett's Esophagus and squamous cell carcinoma. Average absorption and reduced scattering coefficients of normal tissues were 0.211 ± 0.051 and 1.20 ± 0.18 mm^?1, respectively at 471 nm, and both values decreased monotonically with increasing wavelength. Fibrotic tissue exhibited at least 68% larger scattering signal across all wavelengths, while squamous cell carcinoma exhibited a 36% decrease in scattering at 471 nm. We additionally image the esophagus with high spatial frequencies up to 0.5 mm^?1 and show strong reflectance contrast to tissue treated with radiation. Lastly, we observe that esophageal absorption and scattering values change by an average of 9.4% and 2.7% respectively over a 30 minute duration post‐resection. These results may guide system design for the diagnosis, prevention and monitoring of esophageal pathologies.      

Diagnosing colorectal abnormalities using scattering coefficient maps acquired from optical coherence tomography

Optical coherence tomography (OCT) has shown potential in differentiating normal colonic mucosa from neoplasia. In this study of 33 fresh human colon specimens, we report the first use of texture features and computer vision-based imaging features acquired from en face scattering coefficient maps to characterize colorectal tissue. En face scattering coefficient maps were generated automatically using a new fast integral imaging algorithm. From these maps, a gray-level cooccurrence matrix algorithm was used to extract texture features, and a scale-invariant feature transform algorithm was used to derive novel computer vision-based features. In total, 25 features were obtained, and the importance of each feature in diagnosis was evaluated using a random forest model. Two classifiers were assessed on two different classification tasks. A support vector machine model was found to be optimal for distinguishing normal from abnormal tissue, with 94.7% sensitivity and 94.0% specificity, while a random forest model performed optimally in further differentiating abnormal tissues (i.e., cancerous tissue and adenomatous polyp) with 86.9% sensitivity and 85.0% specificity. These results demonstrated the potential of using OCT to aid the diagnosis of human colorectal disease.     

Monte Carlo simulation of photon scattering in biological tissue models

Monte Carlo simulation of photon scattering, with and without abnormal tissue placed at various locations in the rectangular, semi-circular and semi-elliptical tissue models, has been carried out. The absorption coefficient of the tissue considered as abnormal is high and its scattering coefficient low compared to that of the control tissue. The placement of the abnormality at various locations within the models affects the transmission and surface emission of photons at various locations. The scattered photons originating from deeper layers make the maximum contribution at farther distances from the beam entry point. The contribution of various layers to photon scattering provides valuable data on variability of internal composition. Introduction.     

基于景观结构的北京市顺义区生态风险时空特征

以1997、2001、2005、2009和2013年遥感影像为基础数据,对快速城市化地区——北京市顺义区进行景观分类,构建基于景观干扰度和景观脆弱度的生态风险指数,利用GS⁺和ArcGIS软件进行空间自相关和地统计学分析,研究景观生态风险的时空变化特征.结果表明:研究区内的生态风险指数存在一定的空间正相关关系,随着粒度的增大,呈现下降的趋势;在一定的粒度范围内(<12 km),空间自相关性具有明显的尺度依赖特征.1997—2013年,空间异质性中的随机变异均小于空间自相关变异,由空间自相关部分引起的空间异质性占据主导地位.研究期间,研究区生态风险水平一直以中等生态风险程度为主,较高生态风险和较低生态风险区域面积增加,而中等生态风险区域面积逐渐减少.低生态风险区主要位于顺义区机场区域及东南部的林地;高生态风险区主要位于水域景观区域,如潮白河两岸.     

Cross- and auto-correlation in early vision

Neurons that respond selectively to the orientation of visual stimuli were discovered in V1 more than 50 years ago, but it is still not fully understood how or why this is brought about. We report experiments planned to show whether human observers use cross-correlation or auto-correlation to detect oriented streaks in arrays of randomly positioned dots, expecting that this would help us to understand what David Marr called the 'computational goal' of V1. The streaks were generated by two different methods: either by sinusoidal spatial modulation of the local mean dot density, or by introducing coherent pairs of dots to create moiré patterns, as Leon Glass did. A wide range of dot numbers was used in the randomly positioned arrays, because dot density affects cross- and auto-correlation differently, enabling us to infer which method was used. This difference stems from the fact that the cross-correlation task is limited by random fluctuations in the local mean density of individual dots in the noisy array, whereas the auto-correlation task is limited by fluctuations in the numbers of randomly occurring spurious pairs having the same separation and orientation as the deliberately introduced coherent pairs. After developing a new method using graded dot luminances, we were able to extend the range of dot densities that could be used by a large factor, and convincing results were obtained indicating that the streaks generated by amplitude modulation were discriminated by cross-correlation, while those generated as moiré patterns were discriminated by auto-correlation. Though our current results only apply to orientation selectivity, it is important to know that early vision can do more than simple filtering, for evaluating auto-correlations opens the way to more interesting possibilities, such as the detection of symmetries and suspicious coincidences.