共查询到20条相似文献,搜索用时 31 毫秒
1.
《IEEE transactions on bio-medical engineering》2009,56(12):2762-2772
2.
3.
A three-dimensional reconstruction algorithm in electrical impedance imaging is presented for determining the conductivity distribution beneath the surface of a medium, given surface voltage data measured on a rectangular array of electrodes. Such an electrode configuration may be desirable for using electrical impedence tomography to detect tumors in the human breast. The algorithm is based on linearizing the conductivity about a constant value. Here, we describe a simple implementation of the algorithm on a four-electrode--by-four-electrode array and the reconstructions obtained from numerical and experimental tank data. The results demonstrate significantly better spatial resolution in the plane of the electrodes than with respect to depth. 相似文献
4.
5.
Neural prostheses for restoring lost functions can benefit from selective activation of nerves with limited number and density of electrodes. Here, we show by simulations and animal experiments that multipoint simultaneous stimulation with a surface electrode array can selectively activate nerves in a bundle at a desired location in between the array or at a desired depth, which are referred to as lateral or depth-wise gating stimulation, respectively. The stimulation broadly generates action potentials with cathodic source electrodes, and simultaneously blocks unnecessary propagation with downstream anodic gate electrodes. In general, stimulation with a small diameter electrode can affect a nearly hemispherical region, while a large electrode is effective at a more vertically compressed region, i.e., a surface of nerve bundle. The gating stimulation takes advantage of the size effects by utilizing an asymmetrical electrode array. The array of the lateral gating stimulation is designed to have four electrodes; a pair of large source electrodes and a pair of small gate electrodes. The depth-wise gating stimulation array consists of two electrodes; a large gate and small source electrodes. The simulation first demonstrated that appropriate combination of currents at the source and gate electrodes can change recruitment patterns of nerves with lateral or depth-wise selectivity as desired. We then applied the lateral gating stimulation on the rat spinal cords and obtained a preliminary support for the feasibility. 相似文献
6.
介绍了多元高温超导探测器的电极制备,对电极制备过程中的几个关键问题进行了研究,确定了最佳工艺条件,制备出的电极质量良好,又保持了原超导膜的超导性。采用该电极结构制备了12元高温超导探测器,已有较好的光电性能,初步验证了高温超导探测器。可应用于热成象。 相似文献
7.
Newell J.C. Isaacson D. Gisser D.G. 《IEEE transactions on bio-medical engineering》1990,37(7):735-738
Electrical impedance imaging is the technique for producing images of the resistivity of internal body structures based on measurements of voltage and current from electrodes applied to the body's surface. When a multiplicity of electrodes are applied in one or more rows around a body structure such as the thorax or limb, it is useful to be able to rapidly assess the general status of the electrode-body interface to determine if the skin has been suitably prepared, and that electrode and skin impedance are suitably low. In addition, assessment of the impedance of individual electrodes should precede acquisition of data for image formation. This communication presents techniques for assessing the overall skin and electrode impedances relative to the impedance of the body interior, and for assessing the integrity of each electrode's contact impedance. 相似文献
8.
Yoo SK Wang G Collison F Rubinstein JT Vannier MW Kim HJ Kim NH 《IEEE transactions on bio-medical engineering》2004,51(5):838-846
Three-dimensional (3-D) localization of individual cochlear implant electrodes within the inner ear is of importance for modeling the electrical field of the cochlea, designing the electrode array, and programming the associated speech processor. A 3-D reconstruction method of cochlear implant electrodes is proposed to localize individual electrodes from two X-ray views in combination with the spiral computed tomography technique. By adapting epipolar geometry to the configuration of an X-ray imaging system, we estimate individual electrode locations in the least square sense without using a patient attachment required by an existing stereophotogrammetry technique. Furthermore, our method does not require any knowledge of the intrinsic and extrinsic parameters of the imaging system. The performance of our method is studied in numerical simulation and with patient data and is found to be sufficiently accurate for clinical use. The maximum root mean-square errors measured are 0.0445 and 0.214 mm for numerical simulation and patient data, respectively. 相似文献
9.
10.
为了获得目标区域的高精度3-D距离图像,采用自研带读出电路的雪崩光电二极管(APD)面阵探测器组件,研制了一台非扫描激光主动成像雷达。雷达采用波长1.064μm脉冲激光泛光照射目标区域,APD面阵探测器组件接收目标漫反射激光回波信号,经信息处理获得目标区域3-D距离图像,对典型目标开展了3-D成像实验研究。结果表明,所研制的非扫描激光主动成像雷达可获得较好的目标区域3-D距离图像,成像距离达1.2km,距离分辨率为0.45m,成像帧频为20Hz。基于APD面阵探测器组件的非扫描激光主动成像雷达技术取得突破。 相似文献
11.
We have developed a new approach for imaging cardiac transmembrane potentials (TMPs) within the three-dimensional (3-D) myocardium by means of an anisotropic heart model. The cardiac TMP distribution is estimated from body surface electrocardiograms by minimizing objective functions of the "measured" body surface potential maps (BSPMs) and the heart-model-generated BSPMs. Computer simulation studies have been conducted to evaluate the present 3-D TMP imaging approach using pacing protocols. Simulations of single-site pacing at 24 sites throughout the ventricles, as well as dual-site pacing at 12 pairs of sites in the vicinity of atrio-ventricular ring were performed. The present simulation results show that the correlation coefficient (CC) and relative error (RE) between the "true" and inversely estimated TMP distributions were 0.9915 +/- 0.0041 and 0.1266 +/- 0.0326, for single-site pacing, and 0.9889 +/- 0.0034 and 0.1473 +/- 0.0237 for dual-site pacing, respectively, when 10 microV Gaussian white noise (GWN) was added to the BSPMs. The effects of heart and torso geometry uncertainty were also evaluated by shifting the heart position by 10 mm and altering the torso size by 10%. The CC between the "true" and inversely estimated TMP distributions was above 0.97 when these geometry uncertainties were considered. The present simulation results demonstrate the feasibility of noninvasive estimation of TMP distribution throughout the ventricles from body surface electrocardiographic measurements, and suggest that the present method may become a useful alternative in noninvasive imaging of distributed cardiac electrophysiological processes within the 3-D myocardium. 相似文献
12.
本文报道一种32×48元高灵敏非致冷混合式焦平面探测器厚膜阵列.提出了一种采用掺杂钛酸锶钡厚膜作为敏感材料的硅基微机械加工电容式红外探测器像元结构,对其工作原理、器件性能优化设计与制作工艺流程进行了分析,得出了优化的结构参数.分析了影响器件性能的关键因素,给出了器件所用铁电材料的基本物理和电学特性参数以及器件的热隔离技术和相应参数.本结构的像元电容值增量接近相同敏感面的体材料红外探测器,减小了像元与衬底电极引线的寄生电容.采用这种结构的红外探测器阵列对电路的精度要求低,便于研制集成电路.该红外探测器阵列结构的设计思路,符合大阵列红外焦平面像元结构设计的发展趋势,为开展非致冷红外焦平面阵列探测器研究奠定了基础. 相似文献
13.
太赫兹辐射能够穿透大多数对可见光和近红外光不透明的物质。提高成像质量是成像系统的关键,尤其对探测器性能较低的面阵成像更为重要。通过数字图像处理方法改善成像质量是一条重要的解决途径。应用非局部均值(NLM)分别对真实的透射扫描、反射扫描和透射面阵、反射面阵的太赫兹图像进行了去噪处理,选取不同的控制参数进行了对比分析,同时对比了均值滤波处理结果。实验结果表明:非局部均值能够较好地去除连续太赫兹图像噪声、提高成像质量,对噪声严重的面阵成像去噪效果最明显。非局部均值去噪并保持边缘能力明显好于均值滤波。 相似文献
14.
Body surface Laplacian ECG mapping 总被引:5,自引:0,他引:5
A new noninvasive approach has been developed to resolve spatially distributed cardiac electrical activity by measuring the surface Laplacian of the body surface potential. Computer simulations demonstrate the ability of the Laplacian map compared with the potential map to image spatially distributed dipole sources embedded in a semi-infinite volume conductor. Body surface Laplacian mapping has been implemented in human subjects utilizing dry bipolar Laplacian electrodes and compared with potential maps obtained using the central terminal of each bipolar Laplacian electrode. The body surface Laplacian ECG distribution was found to provide better spatial resolution than the body surface potential distribution. The body surface Laplacian map appears to resolve depolarization and repolarization of different regions of the heart. Further improvements of the body surface Laplacian mapping may permit noninvasive mapping of spatially distributed intracardiac events. 相似文献
15.
H. B. Barber H. H. Barrett F. L. Augustine W. J. Hamilton B. A. Apotovsky E. L. Dereniak F. P. Doty J. D. Eskin J. P. Garcia D. G. Marks K. J. Matherson J. M. Woolfenden E. T. Young 《Journal of Electronic Materials》1997,26(6):765-772
Previous work has shown that hybrid semiconductor detector arrays similar to those used in infrared focal-plane arrays are
very attractive for use in nuclear medicine and other gamma-ray imaging applications. In this paper, we describe the development
of a 64 × 64 readout multiplexer specifically for use in gamma-ray imaging; we also describe the construction of 64 × 64 CdZnTe
hybrid detector arrays using the new readout. The readout and detector array are both about one inch square (2.5 cm × 2.5
cm) and have 380 μm pixel pitch. Some initial assembly problems have been resolved by stabilizing the hybrids with epoxy.
Preliminary testing results are presented that verify that the 64 × 64 CdZnTe arrays perform as excellent imaging spectrometers. 相似文献
16.
针对传统红外面阵探测器成像存在分辨率低、视场范围窄、非均匀性的问题,提出一种基于红外点元探测器的扫描成像方法。该方法首先利用微型电机驱动扫描镜依次获取物体表面的红外热斑,经光学镜头聚焦到红外点元探测器,进行光电转换;然后经信号处理板采集、处理后生成红外灰度图像;最后利用多阈值分割的伪彩色映射模型,将灰度图像转换成伪彩色图像。实验结果表明:红外点元探测器扫描成像方法能够实现红外场景的大视场、高分辨率成像,且点元探测器加工制造简单,价格低廉,有效突破了传统大面阵成像的高昂成本限制,更加有利于红外成像技术的推广和应用。 相似文献
17.
Messnarz B Tilg B Modre R Fischer G Hanser F 《IEEE transactions on bio-medical engineering》2004,51(2):273-281
The single-beat reconstruction of electrical cardiac sources from body-surface electrocardiogram data might become an important issue for clinical application. The feasibility and field of application of noninvasive imaging methods strongly depend on development of stable algorithms for solving the underlying ill-posed inverse problems. We propose a novel spatiotemporal regularization approach for the reconstruction of surface transmembrane potential (TMP) patterns. Regularization is achieved by imposing linearly formulated constraints on the solution in the spatial as well as in the temporal domain. In the spatial domain an operator similar to the surface Laplacian, weighted by a regularization parameter, is used. In the temporal domain monotonic nondecreasing behavior of the potential is presumed. This is formulated as side condition without the need of any regularization parameter. Compared to presuming template functions, the weaker temporal constraint widens the field of application because it enables the reconstruction of TMP patterns with ischemic and infarcted regions. Following the line of Tikhonov regularization, but considering all time points simultaneously, we obtain a linearly constrained sparse large-scale convex optimization problem solved by a fast interior point optimizer. We demonstrate the performance with simulations by comparing reconstructed TMP patterns with the underlying reference patterns. 相似文献
18.
金属/碲镉汞电极接触是红外焦平面探测器的重要组成部分,对器件的性能与稳定性影响较大。然而在碲镉汞金属化过程中,金属离子能量较高将有可能对碲镉汞表面造成损伤。本文采用了离子束沉积系统生长金属电极,探究了束流、束压以及热处理等条件对碲镉汞红外探测器接触性能的影响。研究表明,碲镉汞在生长电极后表面会受到一定程度的损伤;随着离子能量的升高,对材料表面损伤加剧。在I-V曲线中,电极沉积损伤较大的器件表现出软击穿现象;在热处理后,在一定程度上可以修复电极沉积时能量过大造成的损伤,提高了电极接触性能。 相似文献
19.