肝脏和肺组织的太赫兹光谱成像

与红外辐射、X射线、核磁共振、超声波等传统医疗诊断技术相比,太赫兹技术具有能量低、空间分辨力高和带宽宽等独特分析能力,成为人体成像或人体组织癌症诊断技术的补充技术。分别对肝脏和肺的正常组织与肿瘤组织做了太赫兹光谱检测与太赫兹成像研究,通过肝脏的光谱检测与成像实验总结出相关经验,使得肺癌组织太赫兹成像得到了明显的效果,并且发现肺癌肿瘤组织在1.0 THz~1.75 THz频率范围内的太赫兹成像能够明显区分出正常组织与肿瘤组织,且频率越高,成像分辨力越高。     

Nondestructive high-resolution microwave imaging of biomaterials and biological tissues

A high-Q near-field probe based on the 2D microstrip line geometry using defected ground structure (DGS) has been proposed and experimentally evaluated for nondestructive characterization and high-resolution imaging of biomaterials and biological tissues. The unique specifications of the probe are as follows; small size, simple fabrication, non-contact with a sample, excellent de-coupling from surroundings and high microwave power is directly coupled into the tissues. Experimental results show that the probe is able to detect the microwave characteristics of thin lossy biomaterials containing water. High resolution microwave images of leaves with different water content have been obtained with amplitude contrast of about 40–50 dB and spatial resolution of about λ/40. Also, a measurement scenario for detection of lipomas with different sizes has been investigated. Results show that the proposed probe can detect the lipoma of a size larger than 5 mm. Finally, an artificial model to detect skin cancer at the early stage is developed using layers of raw chicken skin. Measurement results show that the probe could accurately detect malignant tumor with at least 15 dB magnitude and more than 100° phase contrast from the healthy skin and with about 8 dB contrast from the benign lesions of the same size.     

Frequency optimization for microwave imaging of biological tissues

Theoretical calculations are provided to show that 2 to 8 GHz represents a frequency region most suited for microwave imaging of biological tissue. The attenuation and spatial resolution are both adequate to yield useful diagnostic information.     

Characterization of linewidth variation for single- and multiple-layer resist systems

The advantages gained by the use of a multilayer resist system were examined by electrical linewidth measurements of polysilicon lines ranging in width from 0.7 to 1.0 µm. Multilayer resist was compared to single-layer resist and quantitative data was obtained regarding the theoretical advantages of reduced reflectivity, improved planarity, and thinner imaging resist inherent to a multilayer resist system. Two different thicknesses of single-layer resist revealed that a thinner imaging layer resulted in improvements of up to 15 percent for linewidth variation and 35 percent for depth of focus, Reducing reflections from the substrate from 33 to 3.5 percent led to improvements of up to 30 percent in linewidth variation and depth of focus. Introduction of a particular type of topography under the polysilicon led to a worsened linewidth variation and depth of focus, by up to 30%.     

Characterization of poly-Si TFT variation using interdigitated method

In this paper, the device variation characteristic of poly-Si TFTs is statistically investigated. First the variation of devices is examined with respect to different device distance. It is found that the device variation would exhibit similar behavior for different device distance. Then, in order to study the method to suppress device variation, the interdigitated layout is adopted. It is found that though the variation behavior of the poly-Si TFTs is much more serious and complicated than MOSFETs, the law of area can still be utilized to describe the variation behavior in the interdigitated layout. The fitting parameters in law of area can provide insights for understanding the intrinsic variation behavior for poly-Si TFTs and the discussion about the variation for the device with various channel width is provided. The variation behavior of poly-Si TFTs is then compared with amorphous silicon TFTs and single crystal silicon MOSFETs. The impacts of poly-Si TFT variation on circuit design and performance is also discussed.     

Laser backscattering and transillumination imaging of human tissues and their equivalent phantoms

Surface backscattering profiles from a human forearm and transmission profiles through a human thumb, of red and near-infrared lasers, were determined. For the preparation of tissue-equivalent phantoms, white paraffin wax mixed with various wax color pigments were used. The surface reflectance profiles of a human forearm were matched with that of the phantom by mixing color pigments in various proportions. The reconstructed surface reflectance image of the phantom prepared by this procedure was similar to that of the human forearm. The transmission tomogram of the human thumb was obtained in fan-beam configuration by a near-infrared laser tomography system. Based on the horizontal scan of this tomogram, a two-layered phantom was made. The color composition of the phantom was so adjusted that its horizontal scan was matched with that of the thumb tomogram. The phantoms of complex tissues, prepared by this procedure, could be used for evaluation and calibration of new optical diagnostic imaging techniques.     

Multislice tomographic imaging and analysis of human breast-equivalent phantoms and biological tissues

A laser transillumination tomographic system, consisting of electrical, optical, mechanical, and software components, to obtain multislice images of tissue-equivalent breast phantoms and biological tissues, is developed. The tissue-equivalent phantoms are prepared from paraffin wax mixed with wax color pigments by matching their surface backscattered profiles as measured by multiprobe laser reflectometer, with that of respective tissues. The optical parameters of these phantoms are determined by matching their reflectance profiles with that as obtained by Monte Carlo simulation of optical scattering. For multislice tomographic analysis conical breast phantoms of height 80.0 mm and 80.0 mm base diameter with inclusions of different optical properties and dimensions are developed. The resolution of the inclusions in the tomograms depends on their sizes and optical parameters. The minimum size of the inclusion as detected by this procedure in a slice of diameter 50.0 mm is 3.0 mm. The structural variation as observed in the tomograms of phantoms of combination of biological tissues indicates its possible applications in detecting the abnormalities developing in human healthy soft tissues.     

Fast and noninvasive fluorescence imaging of biological tissues in vivo using a flying-spot scanner

We have developed a flying-spot scanner (FSS), for fluorescence imaging of tissues in vivo. The FSS is based on the principles of single-pixel illumination and detection via a raster scanning technique. The principal components of the scanner are a laser light source, a pair of horizontal and vertical scanning mirrors to deflect the laser light in these respective directions on the tissue surface, and a photo multiplier tube (PMT) detector. This paper characterizes the performance of the FSS for fluorescence imaging of tissues in vivo. First, a signal-to-noise ratio (SNR) analysis is presented. This is followed by characterization of the experimental SNR, linearity and spatial resolution of the FSS. Finally, the feasibility of tissue fluorescence imaging is demonstrated using an animal model. In summary, the performance of the FSS is comparable to that of fluorescence-imaging systems based on multipixel illumination and detection. The primary advantage of the FSS is the order-of-magnitude reduction in the cost of the light source and detector. However, the primary disadvantage of the FSS its significantly slower frame rate (1 Hz). In applications where high frame rates are not critical, the FSS will represent a low-cost alternative to multichannel fluorescence imaging-systems.     

压缩感知ISAR成像的全变差优化最小算法

对于逆合成孔径雷达(ISAR)目标成像,从少量压缩测量回波数据重建高分辨率运动目标是不适定问题,且观测噪声也会影响重建结果。在频率步进连续波 ISAR系统回波观测模型基础上,结合压缩感知原理,给出了一种基于全变差正则化的 ISAR压缩感知成像模型,通过将该优化模型转化为一系列简单代理函数进行求解,提出了一种快速优化最小算法。最后在不同回波信噪比条件下进行仿真验证。实验结果表明,当回波信噪比大于10 dB 时,本文方法明显优于距离-多普勒算法和基于L1范数的压缩感知成像方法。     

温度变化对光电系统成像模糊的影响研究

针对温度变化使光电系统成像质量下降的问题,从图像模糊程度的角度,分析了温度变化对系统离焦的影响,建立了离焦模糊图像的数学模型,进而揭示了温度变化对成像模糊的影响规律。利用建立的数学模型,对一幅清晰的图像进行仿真实验,仿真结果表明:温度变化越大,光电系统成像越模糊。通过研究温度变化对光电系统成像模糊的影响,为光电系统的环境适应性设计提供了重要的参考。     

Three-dimensional EIT imaging of breast tissues: system design and clinical testing

Results of development and testing of the new medical imaging system are described. The system uses a planar array consisting of 256 electrodes and enables obtaining images of the three-dimensional conductivity distribution in regions below the skin's surface up to several centimeters deep. The developed measuring system and image reconstruction algorithm can be used for breast tissue imaging and diagnostics, in particular for malignant tumor detection. Examples of tomographic images obtained in vivo during clinical tests are presented. The mammary gland, being an organ-target, alters at the background with such physiological events as menstrual cycle, pregnancy, lactation, and postmenopause. The objectives of this paper include estimation of the possibilities of electrical impedance mammography for investigation of mammary glands' state among women with different hormonal status. We found that electrical impedance mammograms from different groups had clear visual distinctions and statistically significant differences in mammary glands' conductivity. Our data on conductivity distribution in the mammary gland during different physiological periods will allow us to use it as normal values in the future, to continue this research on mammary glands with different pathology.     

生物组织单像素成像重构的散射干扰抑制

针对单像素成像重构中的散射介质影响而导致重构图像无法达到最佳效果的问题,研究了有无散射介质的情况下,关联算法和压缩感知算法的图像重构适用性。分析了散射介质在成像光路造成的调制信息空间结构变化和在探测光路造成的信号损耗对成像的影响,建立了近红外单像素成像系统,使用CGI算法和TVAL3算法实现了穿透生物组织散射介质的单像素成像实验。实验发现,在无散射介质时,TVAL3算法的重构时间、峰值信噪比和相似度等均优于CGI算法;而在有散射介质时,CGI算法的三项数值中有两项优于TVAL3算法,其最大重构时间（0.304091 s）小于TVAL3算法最小时间（1.766299 s）,其最小峰值信噪比（9.9831 dB）高于TVAL3算法的最大值（9.170456 dB）,其相似度（0.0982、0.1178）则位于TVAL3算法的范围内（0.099258~0.497622）。结果表明,基于关联成像理论的CGI算法较适合散射介质成像,基于压缩感知理论的TVAL3算法更适合无散射介质成像。     

红外成像灰度随距离变化的李群表达

大气对红外辐射传输的影响引起的红外成像灰度变化,是红外目标跟踪应用需要应对的问题。对红外成像灰度变化规律进行李群建模,对设计高效、鲁棒的目标跟踪算法具有重要意义。首先分析了红外辐射传输模型,并结合红外成像机理,得到红外成像灰度变化模型。进一步从理论上证明了大气影响下红外成像灰度变化规律符合李群结构,提出了红外图像灰度动态变化的一种非欧数学表征。最后根据红外成像灰度变化模型对不同环境下采集到的外场实验数据进行拟合,回归分析结果表明了该模型的准确性,进而说明了对红外成像灰度变化规律进行李群表达的合理性。     

Temperature variation mapping of a microelectromechanical system by thermoreflectance imaging

We present in this letter a cost effective noncontact imaging technique well adapted to measure the temperature variations on microelectromechanical systems. The setup is tested on a microheater constituted of a polysilicon resistor deposited on a dielectric membrane. Results concerning the temperature variations of this device are compared on one hand with simulation predictions, and on the other hand with thermoreflectance point measurements. From thermoreflectance images, we also estimate the values of the thermoreflectance coefficients of the polysilicon and of the dielectric.     

增广拉格朗日双边全变分压缩成像重构算法

针对基于全变分压缩成像算法重构的图像存在虚假边界以及边缘信息对比度低的问题,提出了一种基于全变分成像模型的增广拉格朗日双边全变分压缩成像重构算法。在全变分正则化思想基础上引入双边滤波技术,并加入拉格朗日函数算子,将目标函数转化为增广拉格朗日函数,利用交替方向法求解函数模型的最优解。迭代过程中选用最速下降法对梯度进行求解,对算法进行优化,提高算法运行速度。实验结果表明,算法改进后可以更加精确的重构出原始图像,重构图像的峰值信噪比提高2 dB,重构错误率降低10%,结构相似度提高0.1,并且对噪声具有较好的鲁棒性。     

Electrical and compositional properties of TaSi2 films

Tantalum silicide (TaSi₂) thin films were sputter deposited on p- and n-type silicon substrates using ultrapure TaSi₂ targets. The TaSi₂/Si samples were annealed in nitrogen or forming gas or oxygen containing steam at temperatures in the range of 400–900°C. The sheet resistances of TaSi₂/Si were measured by four-point probe before and after anneal. The structure of these films was investigated using x-ray diffraction (XRD) methods. It has been found that the sheet resistance decreases with the increase in annealing temperature and also with the increase in film thickness. X-ray diffraction patterns show changes in the morphological structure of the films. Oxidation characteristics of the film have been investigated in the temperature range of 400–900°C in oxygen containing steam ambient. The oxidation time ranged from 0.5 to 1.5 h. No oxide formation of the tantalum silicide films was observed in this investigation. This has been attributed to the high purity of TaSi₂ sputter targets used in the preparation of the films.     

Characterization of interfacial thermal resistance by acoustic micrography imaging

In high-power electronics modules, the heat generated by the power devices is transferred to the ambient environment by attaching a heat spreader to the semiconductor package to ensure efficient thermal management. Typical attachment materials introduce interfaces and/or interlayers of finite thickness. Using a scanning acoustic microscope (SAM), a non-destructive inspection tool, we can detect the cracks, voiding, porosity, coplanarity and delamination in the interface layer, which correlate to the measured thermal resistance of an interface. This investigation would result in optimizing the bonding process of the selected interface material, minimizing the void-content to ensure enhanced thermal management of power modules.     

Fiber-optic confocal reflectance microscope with miniature objective for in vivo imaging of human tissues

We have built a fiber-optic confocal reflectance microscope capable of imaging human tissues in near real time. Miniaturization of the objective lens and the mechanical components for positioning and axially scanning the objective enables the device to be used in inner organs of the human body. The lateral resolution is 2 micrometers and axial resolution is 10 micrometers. Confocal images of fixed tissue biopsies and the human lip in vivo have been obtained at 15 frames/s without any fluorescent stains. Both cell morphology and tissue architecture can be appreciated from images obtained with this microscope.     

基于K阶簇分析的乳腺组织拉曼光谱成像研究

采用共焦拉曼光谱仪,测量了正常乳腺组织和浸润性导管癌组织的阵列显微拉曼谱3 000多个,利用自编软件对谱数据进行K阶簇分析(K-means cluster analysis),得到各簇的平均谱以及各谱的簇类别。各簇平均谱与商售的甘油三酸脂、胶原和肌动蛋白等纯生化物质的拉曼谱具有很高的相关性,说明K阶簇分析能够区分细胞质、细胞间质及脂肪等不同组织形态的拉曼谱;依据各谱的簇类别构建阵列拉曼谱的簇分析成像能够显现乳腺上皮组织的生化成分分布及乳腺管结构,与乳腺组织形态模型成像结果相互印证。本文研究预示簇分析是研究乳腺组织拉曼谱及提取诊断信息的有效手段,优势在于不需要知道组织样品的生化信息。     

基于激光热成像方法的奥氏体钢表面缺陷表征

有源热成像是当今广泛使用的无损检测方法,可利用材料热特性完成缺陷表征。本文使用激光作为热成像的激励源,使用激光局部加热试件,产生的球形热流允许以任意方向检测缺陷。在加热过程中,能量扩散完全覆盖缺陷区域,在散热过程中,缺陷的存在会使得激光器的热足迹呈现不对称性,红外热像仪实时监测表面温度场分布,实现表面缺陷的可视化检测。通过实验验证以及对实验结果的图像分析来完成缺陷表征,结果表明:在散热过程中,红外热像仪可实现对缺陷的可视化检测,通过图像锐化处理检测缺陷边界,得到缺陷的形状分布,完成缺陷的定位表征。