生物阻抗的测量方法

通过对生物阻抗的测量来监测生理功能和检测病理事件 ,已成为近年来研究者非常关注的一个研究方向。本文介绍三种生物阻抗的测量方法 ,它们分别是阻抗断层摄影成像技术 ( electricalimpedance tomography,EIT)、基于磁共振成像 ( magnetic resonance imaging,MRI)的方法和阻抗谱测量 ( impedance spectrometry)技术 ,并分别简要介绍了各自的应用     

一种新的六电极人体阻抗测量方法

目前的阻抗分段测量方法是人体成分测量比较精确的办法,但这种测量方法比较复杂,费时较长而且电极费用较高。新方法只需人站在脚踏板上,双手抓住手握架,解决了上述问题,对二十四个人采用同一台阻抗测量仪用新方法与旧方法进行对比实验,结果一致性很好。     

生物阻抗技术概述

简要叙述了人体组织阻抗特性、生物阻抗技术的基本原理和测量方法,全面介绍了生物阻抗技术在细胞测量、体积测量、人体组织结构分析、组织监测、人体成分分析、生物阻抗成像等各方面的应用.     

生物电阻抗技术研究进展

本文从生物电阻抗血流图(bioimpedance rheohepatogram)、生物电阻抗测量(bioimpedance measurement)、生物组织阻抗频谱特性(bioimpedance spextroscopy)、生物电阻抗成像(electrical impedance imaging)等方面结合自己的研究工作,较全面地介绍并讨论了生物电阻抗技术的研究进展情况.     

小儿整体生物电阻抗测量方法的研究

本文以１２名小儿为对象，对小儿整体生物电阻抗（ＷＢＩ）测量的方法条件进行研究。在一般测量方法的基础上，对电极与皮肤接触面处理，测量时限要求、Ｚ代表值的选择等方面进行修订。用修订后的方法测量小儿上、下午和连续５天的ＷＢＩ，上、下午的Ｚ均值间以及连续５天的Ｚ均值均无显著性差异，个体连续５天Ｚ的变异系数的平均数为０．６１％，证明了用该法测量小儿ＷＢＩ的稳定性。     

电阻抗与EIT 测量微系统设计

以微系统结构、高稳定性为设计目标,构建一套基于ATmega16单片机和AD5933的电阻抗与EIT测量微系统。AD5933芯片内部集成了DDS部分、滤波放大部分、12位A/D转换部分和片上的DSP离散傅里叶变换解调部分,避免了各个模块时序不一致造成的误差,提高了系统的稳定性和抗干扰性。基于Matlab平台开发图形用户界面(GUI),实现了数据无线通讯、阻抗图谱绘制、特征参数计算、EIT图像重建。对均匀场进行100次数据采集,系统信噪比达70 dB。对高精度电阻、离体猪肉分别进行阻抗测试,根据Cole-Cole理论,绘制了阻抗圆图,测量结果与最小二乘算法拟合效果相符。针对16电极实验槽中不同位置和不同数量的有机玻璃棒分布,采用高斯牛顿重建算法进行电阻抗图像重建,成像效果良好,验证了系统的有效性与可行性。     

人体区域电阻抗测量的研究现状

生物电阻抗技术作为无创性人体信息检测方法，已在临床检查和监护中得到一定的应用，但为了获得良好的空间定位信息，需要提高空间分辨率，因此人体区域阻抗的测量一直是人们关心的问题。本文扼要介绍了近年人体区域阻抗测量的研究现状，涉及了电阻抗成像技术和采用保护电极法、补偿法和外加磁场法进行区域电阻抗测量的技术。     

生物阻抗测量技术及其临床应用研究进展

生物阻抗技术是利用细胞外液和细胞内液的电学性质测量人体成分及器官变化的一种较新的医学诊断技术。因其具有无创、安全、有效及功能信息丰富等优点,广泛应用于疾病的动态检测。本文阐述了在临床中生物阻抗的测量方法、电极大小形状及贴放位置等的技术研究,并总结了生物阻抗在人体成分分析、心脑血管系统疾病的动态监测、消化系统疾病和肺部疾病的监测,以及乳腺癌检测中的应用。     

基于鸽局部场电位信号的数字字符图像重建研究

利用鸽视顶盖神经元对视觉图像刺激产生的局部场电位信号(LFP),重建刺激数字字符图像。采用微电极阵列记录数字图像扫屏刺激下的神经元LFP信号,对其进行傅里叶变换并提取幅值、相位特征,然后利用逆滤波器算法构造重建模型,重建数字图像,并采用互相关系数进行评价。研究结果发现,在最优通道组合下,依据单因素重建试验,确定重建模型下神经元对视觉刺激的响应延迟时间为0.01 s,响应持续时间为0.55 s,频带范围为1 Hz< f₁<30 Hz、140 Hz< f₂<240 Hz。在各单因素最优的条件下,通过重建模型重建4只鸽子8组数据的10幅数字字符图像(0～9),与原始图像相比,其互相关系数均超过了0.90,总体互相关系数为0.935±0.01。总之,数字图像的扫屏视觉刺激模式所诱发的神经元响应可以以信息积累的方式重建该视觉刺激图像,同时也表明LFP信号的幅值、相位特征可较好地表征视觉刺激图像。     

基于电阻抗技术的多通道呼吸监测系统

目的为及时检测到早期呼吸系统疾病引起的呼吸功能的改变,本研究开发了一套采用生物电阻抗技术同时监测胸部和腹部的呼吸电阻抗信号的多通道呼吸监测系统。方法本系统主要分为3个单元：电阻抗数据采集单元、多通道开关单元和控制单元。电阻抗数据采集单元完成生物电阻抗数据高精度的检测,多通道开关单元完成不同部位数据采集通道之间的转换,控制单元采用LabVIEW编程实现对电阻抗数据采集单元和多通道开关单元的控制、同步采集、数据的显示及存储。利用本系统采集5名健康人长跑5000m前后胸部和腹部的同步呼吸电阻抗信号,采用一种新的参数定量描述胸部和腹部的呼吸电阻抗信号的同步程度。结果长跑前后胸部和腹部同步呼吸电阻抗信号的同步程度具有显著差异（P〈0．01）。结论基于电阻抗技术的多通道呼吸监测系统能够有效用于多个部位呼吸电阻抗信号的同步监测,为早期呼吸系统疾病的检测提供辅助诊断信息。     

Accuracy of an optically isolated tetra-polar impedance measurement system

Accurate electrical transfer impedance measurement at the high frequencies (>1 MHz) required to characterise blood and intracellular structures is very difficult, owing to stray capacitances between lead wires. To solve this problem, an optically isolated measurement system has been developed using a phaselocked-loop technique for synchronisation between current injection (drive) and voltage measurement (receive) circuits. The synchronisation error between drive and receive circuits was less than 1 ns. The accuracy and reproducibility of the developed system was examined using a tissue equivalent Cole model consisting of two resistors and one capacitor. The absolute value Z and phase shift θ in impedance of the Cole model was measured at 1.25 MHz by both an LCR meter and the isolated measurement system. The difference between the values measured by the isolated measurement system and those measured by the LCR meter was less than 0.27 Ω (2.9%) in Z and 0.79 degree in θ. The standard deviation was less than 0.09Ω in Z and 0.60 degree in θ.     

多道阻抗胃动力信息采集和分析方法

目的构建一种多道阻抗胃动力检测与评价方法,研究胃运动的空间传导关系。方法研发了四通道胃动力检测系统,采用超声辅助定位方法提高电极位置的准确性和有效性;采用小波多分辨率分析处理方法获取无干扰的阻抗胃动力信号．并进行了健康自愿者阻抗胃动力检测实验验证。结果主频为3次／min的阻抗胃动力信号波形幅值自近端胃体向幽门方向传导呈增强趋势,胃运动的前向传导和逆向传导时相关系明显,交替存在。当前向传导和逆向传导相遇时会出现一传导失耦联,随即出现前向或逆向的交替,发生明显的传导延迟。结论多通道阻抗胃动力检测方法从空间传导的角度研究胃动力,分析阻抗胃动力信息的幅值、频率变化和空间传导关系,是一种有效的、立足体表电极的多通道胃动力评价方法。     

应用阻抗心动图测量脉搏波传导时间

为了研究射血前时间对用脉搏波传导时间进行连续血压测量的影响,本文设计并实现一种用阻抗心动图确定脉搏波起始点计算脉搏波传导时间的方法,在深呼使血压产生波动的过程中,采用此方法与心电R波峰值作起始点的方法进行对比实验.实验结果表明,用这种方法测量脉搏波传导时间随呼吸的变化曲线与血压变化的规律相一致.与用心电R波法相比,阻抗心电图法可以有效避免射血前时间变化对PWTT测量结果的影响,是一种准确测量脉搏波传导时间的方法.     

Simulation method for cardiac stroke volume estimation by intracardiac electrical impedance measurement

Using the electrical impedance measurement technique to investigate stroke volume estimation, three models of the ventricle were simulated. A four-electrode impedance catheter was used; two electrodes to set up an electric field in the model and the other two to measure the potential difference. A new approach, itself an application of the quasi-static case of a method used to solve electromagnetic field problems, was used to solve the electric field in the model. The behaviour of the estimation is examined with respect to the electrode configuration on the catheter and to catheter location with respect to the ventricle walls. Cardiac stroke volume estimation was found to be robust to catheter location generating a 10 per cent error for an offset of 40 per cent of the catheter from the chamber axis and rotation of 20° with respect to the axis. The electrode configuration has a dominant effect on the sensitivity and accuracy of the estimation. Certain configurations gave high accuracy, whereas in others high sensitivity was found with lower accuracy. This led to the conclusion that the electrode configuration should be carefully chosen according to the desired criteria.     

利用生物电阻抗法分析西藏藏族青少年肌肉发育特点

目的 利用生物电阻抗分析法,通过测量得出西藏藏族青少年身体各部肌肉质量的数值,提出适合于西藏藏族青少年的肌肉质量基准值,进而探讨西藏藏族青少年的肌肉发育特点与规律。方法 在知情同意的情况下,整体随机抽取西藏藏族的健康青少年作为研究对象,其父母均为藏族,共选取1427人(男性710、女性717),应用体成分分析仪对所有受试者进行检测,得出全身肌肉量、躯干肌肉量、左上肢、右上肢、左下肢、右下肢肌肉量。所有结果输入SPSS19.0统计软件包,进行独立样本t 检验和方差分析统计学处理。 结果 西藏藏族青少年各年龄段的全身肌肉量、躯干肌肉量、左上肢、右上肢、左下肢、右下肢肌肉量,在12岁之前有性别差异,
但不明显;12岁之后,以上各项数据均出现性别间差异的显著性,均表现为男性大于女性（P <0.05或P <0.01）,而且随着年龄增长,这种差异越趋明显。12岁之后,女性的增长幅度出现显著下降,而男性在15岁之后,增长趋势才开始下降,而女性此时几乎进入肌肉生长发育的平台期。结论 西藏藏族青少年的肌肉含量随年龄变化特点与体内激素分泌水平有关,体现了不同发育时期的生理特点。     

人体容抗测量的方法与实现

本文根据相位测量电路和阻抗测量电路设计一种人体容抗测量电路。该电路输入阻抗大于１０ＭΩ,输出直流信号,最小输入信号的电压经是５ｍＶ／Ω,容抗的测量范围是：１￣５０Ω,精度是：０．１Ω,电路用于人体容抗的测量,精度和稳定度都达到０．１Ω。     

Effect of skin impedance on image quality and variability in electrical impedance tomography: a model study

A computer simulation is used to investigate the relationship between skin impedance and image artefacts in electrical impedance tomography. Sets of electrode impedance are generated with a pseudo-random distribution and used to introduce errors in boundary voltage measurements. To simplify the analysis, the non-idealities in the current injection circuit are replaced by a fixed common-mode error term. The boundary voltages are reconstructed into images and inspected. Where the simulated skin impedance remains constant between measurements, large impedances (>2kΩ) do not cause significant degradation of the image. Where the skin impedances ‘drift’ between measurements, a drift of 5% from a starting impedance of 100Ω is sufficient to cause significant image distortion. If the skin impedances vary randomly between measurements, they have to be less than 10 Ω to allow satisfactory images. Skin impedances are typically 100–200 Ω at 50 kHz on unprepared skin. These values are sufficient to cause image distortion if they drift over time. It is concluded that the patient's skin should be abraded to reduce impedance, and measurements should be avoided in the first 10 min after electrode placement.     

A simple technique for on-line measurement of contractions of single smooth muscle fibers under current or voltage clamp

This paper describes a simple technique for routine on-line measurement of length and unloaded, isotonic contractions of single smooth muscle fibers during electrophysiological experiments. The fiber is held by the recording electrode itself, stretched straight in a fastflowing stream of solution. The video image of the fiber is measured on-line by a simple computer program. Unlike other optical methods of tracking fiber length, the technique does not require a rigid one-dimensional contraction of the fiber. The technique is reliable and easy to use, and readily compatible with current clamp, voltage clamp, and rapid reversible application of neurotransmitters and drugs.     

生物电阻抗法无创测量颅内压的理论探讨

本文探讨了用生物电阻抗法无创测量颅内压的原理,分析了当颅内压变化时,颅内脑血流及脑脊液的变化情况,并初步推导出通过测量脑阻抗和颈阻抗来监护颅内压的方法     

Microfluidic device for cell capture and impedance measurement

This work presents a microfluidic device to capture physically single cells within microstructures inside a channel and to measure the impedance of a single HeLa cell (human cervical epithelioid carcinoma) using impedance spectroscopy. The device includes a glass substrate with electrodes and a PDMS channel with micro pillars. The commercial software CFD–ACE+ is used to study the flow of the microstructures in the channel. According to simulation results, the probability of cell capture by three micro pillars is about 10%. An equivalent circuit model of the device is established and fits closely to the experimental results. The circuit can be modeled electrically as cell impedance in parallel with dielectric capacitance and in series with a pair of electrode resistors. The system is operated at low frequency between 1 and 100 kHz. In this study, experiments show that the HeLa cell is successfully captured by the micro pillars and its impedance is measured by impedance spectroscopy. The magnitude of the HeLa cell impedance declines at all operation voltages with frequency because the HeLa cell is capacitive. Additionally, increasing the operation voltage reduces the magnitude of the HeLa cell because a strong electric field may promote the exchange of ions between the cytoplasm and the isotonic solution. Below an operating voltage of 0.9 V, the system impedance response is characteristic of a parallel circuit at under 30 kHz and of a series circuit at between 30 and 100 kHz. The phase of the HeLa cell impedance is characteristic of a series circuit when the operation voltage exceeds 0.8 V because the cell impedance becomes significant.