在体动物组织复阻抗频谱的测量及初步结果

目的 :探索测量在体动物组织复阻抗频谱的方法。方法 :系统采用频率响应测量原理和四电极法。结果 :实现了生物组织复阻抗频谱的测量系统 ,设计了用于在体组织测量的电极 ;利用这一系统进行了部分在体动物组织复阻抗频谱的测量。初步测量结果表明 :在体动物组织在缺血前后 ,阻抗频谱变化显著。结论 :动物组织复阻抗频谱在供血正常状态及缺血后有显著变化 ,且缺血前后的变化与随离体时间的变化性质完全不同。     

实时电阻抗断层成像系统对离体心脏充盈模型成像的初步结果

目的 :探讨电阻抗断层成像技术 （EIT）在心血管系统成像中的潜在应用价值 ,同时通过对离体动物器官的成像实验改进已有的成像实验系统。方法 :用自行设计的实时电阻抗断层成像系统 ,对离体动物心脏充盈模型进行EIT的实验。结果 :EIT图像对离体心脏充盈模型中各腔室的电阻抗分布的变化敏感。结论 :EIT在心血管系统中有应用前景     

电阻抗断层成像与胃排空和胃动力检测

电阻抗断层成像(EIT)是继形态、结构成像之后,于近20余年发展,出现的新一代医学成像技术,具有功能成像,无损伤和医学图像监护三大突出优势.其在胃肠领域的最多应用是评价通过胃部的食物流动以替代临床仍然视为胃排空测量金标准的核素法.在离体的模型实验中EIT可精确测量玻璃棒/气囊的容积变化.在体实验条件下,EIT能精确测量胃容积(气囊)的变化.EIT胃排空测量与染料稀释法、胃存留法、核素法等有较好的相关性.EIT胃动力测量以置于体表的电极阵列实现无损检测,以实时图像方式直接显示体内胃体的收缩和运动状况,将是胃动力检测与评价手段的重大进步,显示了诱人的应用前景.     

电阻抗断层图象新技术

<正> 电阻抗断层图象技术(EIT:ElectricalImpedance Tomography)是当今生物医学工程学重大研究课题之一.它是继形态、结构成像之后,于最近十余年才出现的新一代更为有效的无损伤功能成像技术.EIT通过配置于人体体表的电极阵,提取与人体生理、病理状态相关的组织或器官的电特性信息,不但反映了解剖学结构,更重要的是可望给出功能性图象结果.因此CT、超声等其他成像技术无法与之相比的.EIT不使用核素或射线,对人体无害,可以多次测量,重复使用,可以成为对病人进行长期、连续监护而不会给病人造成损伤或带来不适的医院监护设备.加之其成本低廉,不要求特殊的工作环境等,因而是一种理想的和具有诱人应用前景的无损伤医学成像技术.     

生物电阻抗断层成象研究的几个关键问题

电阻抗断层成象是一种新的成象技术 ,在临床图象监护和功能成象方面有很好的应用前景 （无创、简单、容易应用等 ）。本文作者在生物电阻抗断层成象基本原理的基础上 ,介绍目前研究中的一些关键问题 ,并进性了讨论     

胸腔电生物阻抗法血流动力学监测技术的临床应用

胸腔电生物阻抗法（thoracic electrical bioimpedance,TEB）血流动力学监测技术于20世纪60年代末美国太空总署首创用于宇航生理研究,至90年代有了较大的突破,特别是波形分析和模式识别软件的改进,结合计算机数字化的技术处理,使其在准确性和可重复性方面有了很大的提高。目前多种型号的国产阻抗法监测仪也相继问世。基于理论和技术的不断完善,近年来TEB血流动力学监测技术的临床应用日益广泛^[1]。本文就其特点及临床应用做一介绍。     

容积测量结合计算机断层成像分级对肝硬化定量诊断的研究

已有研究发现，肝容积的大小与肝细胞数目及肝硬化严重程度有关，但单纯的肝容积测量很难精确反映肝细胞数目的减少程度。本研究试图通过肝硬化计算机断层成像(CT)的形态学变化结合肝脾容积测量，探讨该方法对肝硬化诊断的价值。     

应用心前区电阻抗测量冠心病的左心室舒张功能

近年来，采用直接式阻抗血流仪，以多种小电极短距离引导阻抗图的方法，已证明所记录的心前区阻抗图（LVIG）在检测心脏舒张功能中有一定的应用价值[1]，本文用此方法测定了60例冠心病人，并与50例正常人对照，以探讨心前区阻抗图在左室舒张功能中的临床应用价值。     

Regional ventilation distribution determined by electrical impedance tomography: reproducibility and effects of posture and chest plane

Background and objective: Reliable assessment of regional lung ventilation and good reproducibility of electrical impedance tomography (EIT) data are the prerequisites for the future application of EIT in a clinical setting. The aims of our study were to determine (i) the reproducibility of repeated EIT measurements and (ii) the effect of the studied transverse chest plane on ventilation distribution in different postures. Methods: Ten healthy adult subjects were studied in three postures on two separate days. EIT and spirometric data were obtained during tidal breathing and slow vital capacity (VC) manoeuvres. EIT data were acquired in two chest planes at 13 scans/s. Reproducibility of EIT findings was assessed by Bland‐Altman analysis and Pearson correlation in 16 regions of interest in each plane. Regional ventilation distribution during tidal breathing and deep expiration was determined as fractional ventilation in four quadrants of the studied chest cross‐sections. Results: Our study showed a good reproducibility of EIT measurements repeated after an average time interval of 8 days. Global tidal volumes and VCs determined by spirometry on separate days were not significantly different. Regional ventilation in chest quadrants assessed by EIT was also unaffected. Posture exerted a significant effect on ventilation distribution among the chest quadrants during spontaneous breathing and deep expiration in both planes. The spatial distribution patterns in the two planes were not identical. Conclusions: We conclude that regional EIT ventilation findings are reproducible and recommend that the EIT examination location on the chest is carefully chosen especially during repeated measurements and follow‐up.     

Monitoring patients with left ventricular failure by electrical impedance tomography

Acute left ventricular failure (LVF) is a common medical emergency but detection and monitoring of pulmonary oedema remains problematic. Fluid is an important determinant of tissue impedance. Electrical impedance tomography (EIT) is a non-invasive technique allowing localisation of impedance changes within tissue. We have investigated the relationship between LVF and the electrical impedance of lung tissue. Twenty patients with a clinical diagnosis of acute left ventricular failure were compared with 30 normal subjects. Patients were monitored using serial chest radiographs and electrical impedance tomography measurements of lung impedance during hospital admission. Radiographs were graded according to the severity of pulmonary oedema by two independent radiologists. Lung impedance was significantly (P<0.0001) lower than normal in patients with left ventricular failure. Values returned towards the normal range as LVF resolved. There was a similar improvement in the score of the chest radiographs. The electrical impedance of the lung is low in left ventricular failure and increases following treatment.     

Electrical impedance tomography is able to track changes in respiratory function in endotoxin-challenged rodents

Background and objective:   In order to assess and optimize the effect of new therapies for acute lung injury (ALI) in rodent models, a monitoring technique that continuously assesses the functional state of the lung is mandatory. Electrical impedance tomography (EIT) has been suggested as a technique for quantifying lung inflammation in ALI. However, EIT has not been evaluated in a rodent model of ALI.
Methods:   EIT measurements were compared in ventilated Sprague–Dawley rats ( n  = 14), randomly subjected to intratracheal administration of endotoxin (LPS) or saline (control). Lung mechanics, lung weight wet/dry ratio and inflammatory markers in bronchoalveolar lavage fluid were also evaluated.
Results:   LPS caused a significant decrease in lung compliance and TLC as compared with control (−42.0%, P  = 0.04, and −27.9%, P  = 0.02, respectively). These changes were paralleled by differences in mean impedance changes as detected by EIT (Spearman's rank correlation coefficient: ρ = 0.66 and 0.73, respectively, P  < 0.01). LPS increased the lung weight wet/dry ratio (6.35 ± 0.42 vs 5.15 ± 0.07, P  = 0.003), and the bronchoalveolar lavage total WCC (8.96 ± 1.87 vs 1.16 ± 0.10 × 10⁹/L, P  = 0.002) as compared with control. The lung weight wet/dry ratio was inversely related to the mean impedance change (ρ = −0.76, P  < 0.01).
Conclusions:   This study has demonstrated for the first time that eight-electrode EIT readily tracks the inflammatory response of lung tissue in a rodent model of ALI. EIT may thus provide a promising, non-invasive technique for monitoring the time-course of ALI in rodent models, and for testing novel pharmacological strategies to counter it.     

Chest wall mesenchymal hamartoma in an infant: Evaluation with electrical impedance tomography

Mesenchymal hamartoma of the chest wall is a rare benign nonneoplastic lesion of infancy arising from chondro‐osseous tissue. Although its natural history suggests spontaneous regression, we describe a fatal case in a neonate with significant respiratory compromise. We explored the use of electrical impedance tomography to evaluate the dynamic impact of such space occupying lesions on a ventilated infant.     

Cold pain prolongs gastric emptying of liquid but not solid meal: an electrical impedance tomography (EIT) study

Stressful stimuli are reported to affect gastric emptying. However, methods for measuring gastric emptying are, in themselves, stressful. Electrical impedance tomography (EIT) is a method for measuring gastric emptying noninvasively. We used EIT to measure gastric emptying of liquid and solid meals to determine the effect of cold pain stress on gastric emptying. EIT (DAS-01P APT system; University of Sheffield, UK) was carried out in six healthy women (age, 21.6 ± 0.4 [mean ± SD] years) who had ingested a liquid (potage, 263 g; 139 kcal) or solid (beef patty, 205 g; 435 kcal) test meal. Cold pain stimuli consisted of repeated immersions of the subject's non-dominant hand into ice water (4°C) for 1 min, with a 15-s recovery period between immersions, for a total of 20 min. For the control stimulus, water at 37°C was used. The cold pain stimulus was applied immediately after the ingestion of a test meal. All studies were carried out randomly in each subject at intervals of more than 1 week. With cold pain, the half emptying time of the liquid meal was significantly greater than that with the control stimulus (47.6 ± 26.1 min vs 28.1 ± 10.8 min, P < 0.05). For the solid meal, the half emptying time did not differ between stimuli (101.9 ± 44.8 min with cold pain vs 92.6 ± 30.5 min with control stimulus). There were no significant differences in lag time between the liquid and solid meals. Cold pain stress delayed gastric emptying of liquid but not solid meals. Received: September 28, 1999 / Accepted: February 25, 2000