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。     

实时在位皮肤光学吸收系数与优化散射系数规律的研究

为了解皮肤光学吸收系数和散射系数的规律,利用双通道血氧测试仪(OXI Meter)对志愿者上表皮肤进行实时在位光学参数测量,得到了光学吸收系数与优化散射系数的变化规律.通过对不同个体的不同部位研究,发现皮肤光学参数与性别、年龄、体态和肤色有密切关系,为皮肤病的诊断和美容提供了重要的参考依据.     

基于CST的乳腺癌组织介电常数成像探究

目的：研究乳腺癌组织的介电常数成像的可行性及成像效果,并初步确立合适的成像参数。方法：根据已有文献中正常乳房组织与乳腺癌组织介电常数的数据差异,利用CST微波工作室软件建立正常乳房组织、乳腺癌组织及原测量同轴探头仿真模型,通过改变癌变组织半径及在正常乳房组织中的深度这两个参数,得到不同条件下的散射参数,并将其转化为阻抗信息后进行成像,通过分别固定癌变组织半径和深度,对另一参数下得到的不同成像图形进行比较分析,最终确定扫描成像的最优分辨率及深度。结果：在0.5 GHz-9.5 GHz频段,对本文所建立的乳腺癌组织模型进行介电常数成像可以得到清晰的成像图像,其分辨率为1 mm;其中,阻抗值实部的成像效果要明显优于阻抗值虚部的成像效果,在频率为5.89 GHz时,最佳的成像参数为：乳腺癌组织半径r=2 mm,距正常乳房组织表面深度h=1 mm。结论：本文分析了乳房X线照相术与超声检测的优缺点,并对乳腺癌组织仿真模型进行介电常数成像,成像结果具有较高的分辨率,验证了介电常数成像的可行性,为乳腺癌组织检测提供了新的思路。     

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。     

免疫病理诊断大疱性皮肤病

皮肤免疫病理是以皮肤病为对象，用免疫技术研究皮肤组织病变免疫学特征的一个免疫学或组织病理学的分支。在临床诊断和实验研究中常用的方法为免疫荧光技术，免疫酶标技术和免疫电镜技术。免疫病理技术在皮肤病中主要用于大疱性皮肤病，结缔组织病，皮肤血管炎，银屑病，...     

近红外光断层成像逆问题的优化算法

我们给出了近红外光断层成像逆问题的求解方法,建模和仿真可以获得生物组织的光学系数分布.根据有限元求解玻尔兹曼方程的正向问题方法,利用有限元方法多物理场耦合分析软件包(Femlab)进行建模和正向问题的求解,将此结果作为优化仿真时的数据;把成像逆问题的求解转化为一个优化问题来处理.通过仪器测量数据与理论数据构造标准差优化函数进行光学参数的优化,多参数无约束优化算法主要采用了多种编码的多群体遗传算法.最后给出了利用Femlab和遗传算法求解近红外光断层成像逆同题的完整步骤和仿真结果,验证了本文的方法准确地解决了近红外光断层成像的逆问题.     

脑皮层功能活动与病理状态光学检测方法研究进展

光学成像方法具备高时间、空间分辨率和多参数的信息获取能力，在神经科学研究中发挥着重要的作用，受到广泛关注。简要介绍和评述了用于脑皮层功能检测的主要光学成像方法，并重点讨论了其中两种方法——内源光信号成像与激光散斑成像的基本原理、技术进展，以及在脑功能活动与病理状态检测中的应用。     

近红外荧光散射断层成像的研究进展

近红外荧光光学断层成像(FODT)是以合适的荧光探针作为标记物或对比剂，用特定波长的红光激发荧光染料，使其发出波长长于激发光的近红外荧光，通过测量媒质边界处有限点的荧光强度，考虑光子在组织中传播的散射特性，来重建出组织内部的荧光光学特性的分布图像以及组织光学参数。这种成像方式具有无电离辐射、染料稳定、可长期监测和设备简单、成本低等优点，在肿瘤检测、基因表达、蛋白质分子检测和药物受体定位等方面有着很大的应用潜力。在给出近红外荧光散射断层成像典型系统的基础上，详述了近红外荧光在组织中的频域传播模型和重建算法；介绍了两家研究机构在此领域的研究进展；讨论了将该成像方法应用于临床的进一步的发展方向。     

皮肤T淋巴细胞归巢

淋巴细胞再循环和组织特异性归巢是其发挥各种生物学功能的基础，Ｔ细胞归巢至皮肤的过程由其表面的皮肤归巢受体和内皮细胞表面的粘附分子相互作用来完成，同时又受到组织微环境、细胞因子和超抗原等多种因素的调节。归巢至皮肤的Ｔ淋巴细胞在过敏性皮肤病、炎症皮肤病及皮肤肿瘤等多种皮肤疾病的发生发展中发挥着重要作用。     

一种新型算法在组织光学参数测量系统中的应用

无创测量确定生物组织的光学特性参数在医学诊断和治疗领域中有着广泛的应用前景.目前确定组织参数的方法多建立在单层模型条件下,而实际的许多生物组织均具有分层结构,比如在肌肉、颅骨等.因此在多层模型条件下反演计算组织参数具有更大的实际意义.近年许多研究者针对以上问题提出了各种解决方法,如最小二乘法、神经网络方法等,但这些方法都存在需要时间过长或者误差较大的缺点.本文在组织参数测量领域引入数据挖掘办法--支持向量机(support vector machines,SVM),对双层模型中四个待定组织光学参数的确定进行了研究.结果 表明,利用SVM方法确定组织光学参数具有很好的准确性和实时性.     

几种乳腺疾病的电阻抗扫描的频率特性

利用电阻抗扫描技术,研究人体乳腺在疾病状态下电导参数随激励频率的变化规律,为进一步的乳腺疾病检查打下基础。获得了浸润性导管癌、瘤样增生和乳腺腺病等三种乳腺疾病的电导参数的频率特性曲线,并与病变周围正常组织进行了对比,可以得出病变组织具有与正常组织不同的频率特性,而且上述三种不同种类疾病的频率特性也各有差异。因此提示可以根据频率特性的特征,来辨别病变的种类。     

Methods for imaging the structure and function of living tissues and cells: 2. Fluorescence lifetime imaging

This second article in the series shows how fluorescence lifetime imaging allows natural biochemical and physiological properties of tissues to act as contrast agents and so provide a basis for distinguishing normal and diseased tissue components. When combined with methods for imaging through non-transparent tissues and tomographic reconstruction it shows promise as a new optical biopsy technique. In addition to this, specially designed vital fluorescent probes of specific biochemical, secondary messenger and receptor activity in living cells may be imaged using FLIM. This is the youngest of the techniques covered in these review articles on imaging, the first FLIM images of cells having been produced in 1994.     

Effects of motion on optical properties in the spatial frequency domain

Spatial frequency domain imaging (SFDI) is a noncontact and wide-field optical imaging technology currently being used to study the optical properties and chromophore concentrations of in vivo skin including skin lesions of various types. Part of the challenge of developing a clinically deployable SFDI system is related to the development of effective motion compensation strategies, which in turn, is critical for recording high fidelity optical properties. Here we present a two-part strategy for SFDI motion correction. After verifying the effectiveness of the motion correction algorithm on tissue-simulating phantoms, a set of skin-imaging data was collected in order to test the performance of the correction technique under real clinical conditions. Optical properties were obtained with and without the use of the motion correction technique. The results indicate that the algorithm presented here can be used to render optical properties in moving skin surfaces with fidelities within 1.5% of an ideal stationary case and with up to 92.63% less variance. Systematic characterization of the impact of motion variables on clinical SFDI measurements reveals that until SFDI instrumentation is developed to the point of instantaneous imaging, motion compensation is necessary for the accurate localization and quantification of heterogeneities in a clinical setting.     

Terahertz pulsed imaging of freshly excised human colonic tissues

We present the results from a feasibility study which measures properties in the terahertz frequency range of excised cancerous, dysplastic and healthy colonic tissues from 30 patients. We compare their absorption and refractive index spectra to identify trends which may enable different tissue types to be distinguished. In addition, we present statistical models based on variations between up to 17 parameters calculated from the reflected time and frequency domain signals of all the measured tissues. These models produce a sensitivity of 82% and a specificity of 77% in distinguishing between healthy and all diseased tissues and a sensitivity of 89% and a specificity of 71% in distinguishing between dysplastic and healthy tissues. The contrast between the tissue types was supported by histological staining studies which showed an increased vascularity in regions of increased terahertz absorption.     

Optical non-invasive technique for vessel imaging: I. Experimental results

This paper investigates some prerequisites for vessel imaging based on diffuse reflectance measurements in order to develop an optical non-invasive method for the imaging and monitoring of vessels. The method utilizes near-infrared (NIR) radiation (890 nm) from a light emitting diode. The light is guided into the tissue via an optical fibre (diameter 1.0 mm). The backscattered light is collected by an optical fibre of the same type and detected by an optical power meter. The fibres are moved over the skin in two directions with the aid of two motors operated by a microcomputer. Spatially resolved reflectance at the skin surface could be presented as a vessel-map in a colour-coded form on a computer screen. Experimental results indicate that the vessel imaging facility depends upon source-detector separation, relative position and vessel depth, and does not depend essentially on the radiant power from the light source. It is shown that, by a proper choice of probe parameters, one can improve the vessel identification ability. After vessel imaging the technique can potentially be used to monitor several physiological parameters on a selected vascular bed or to distinguish between injured and healthy tissue by monitoring local blood flow, oxygen saturation and the recirculation, pre- and post-operatively.     

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...     

Near-infrared diffuse optical tomography

Diffuse optical tomography (DOT) is emerging as a viable new biomedical imaging modality. Using near-infrared (NIR) light, this technique probes absorption as well as scattering properties of biological tissues. First commercial instruments are now available that allow users to obtain cross-sectional and volumetric views of various body parts. Currently, the main applications are brain, breast, limb, joint, and fluorescence/bioluminescence imaging. Although the spatial resolution is limited when compared with other imaging modalities, such as magnetic resonance imaging (MRI) or X-ray computerized tomography (CT), DOT provides access to a variety of physiological parameters that otherwise are not accessible, including sub-second imaging of hemodynamics and other fast-changing processes. Furthermore, DOT can be realized in compact, portable instrumentation that allows for bedside monitoring at relatively low cost. In this paper, we present an overview of current state-of-the -art technology, including hardware and image-reconstruction algorithms, and focus on applications in brain and joint imaging. In addition, we present recent results of work on optical tomographic imaging in small animals.     

MRI-based three-dimensional thermal physiological characterization of thyroid gland of human body

This article is dedicated to present a MRI (magnetic resonance imaging) based three-dimensional finite element modeling on the thermal manifestations relating to the pathophysiology of thyroid gland. An efficient approach for identifying the metabolic dysfunctions of thyroid has also been demonstrated through tracking the localized non-uniform thermal distribution or enhanced dynamic imaging. The temperature features over the skin surface and thyroid domain have been characterized using the numerical simulation and experimental measurement which will help better interpret the thermal physiological mechanisms of the thyroid under steady-state or water-cooling condition. Further, parametric simulations on the hypermetabolism symptoms of hyperthyroidism and thermal effects within thyroid domain caused by varying breathing airflow in the trachea and blood-flow in artery and vein were performed. It was disclosed that among all the parameters, the airflow volume has the largest effect on the total heat flux of thyroid surface. However, thermal contributions caused by varying the breathing frequency and blood-flow velocity are negligibly small. The present study suggests a generalized way for simulating the close to reality physiological behavior or process of human thyroid, which is of significance for disease diagnosis and treatment planning.     

Dielectric properties of female human breast tissue measured in vitro at 3.2 GHz.

Complex permittivities of in vitro diseased and undiseased human female breast tissues have been measured at 3.2 GHz using a resonant cavity technique. Ranges of dielectric properties and water contents of these tissues are presented. Experimental data are compared with models predicted from mixture equations. Measured permittivity data lie within limits set by two-phase mixture theory, but some conductivity data are in excess of those expected for a mixture of saline and protein. At any particular microwave frequency in all tissue of a given type, the relationship between permittivity and conductivity may be parametrized using the Debye relaxation equations. For each breast tissue type a characteristic relaxation frequency was calculated and found to be lower than that of physiological saline at the same temperature. It is concluded that the dielectric relaxation of tissue water is not the only dispersive process occurring at this frequency: dielectric relaxation of bound water and the tail end of a beta-dispersion may also contribute to the dielectric properties. The similarity of the dielectric properties of benign and malignant breast tumours measured in this work suggest that in vivo dielectric imaging methods will not be capable of distinguishing them.