生物电阻抗方法测量液体胃排空的研究

目的：为寻找方便、有效的无损伤胃排空测量手段，尝试建立一种生物电阻抗测量新方法以获取液体胃排空曲线，测量半排空时间。 方法：研制了4电极法电阻抗胃排空测量系统，系统由正弦信号发生器、恒流源、电极、前置放大器、解调滤波电路、数据采集单元和上位PC机构成。进行了24例正常人液体胃排空实验，年龄20~21岁。上午空腹，试餐为37 ℃纯净水400 mL，测量时间约30 min。通过阻抗胃排空曲线计算半排空时间。受试者对实验均知情同意。 结果：所有健康志愿者的阻抗胃排空曲线均显示饮水前基础阻抗稳定，在饮水400 mL后阻抗急剧升高，然后先快速下降，再缓慢变化，趋近基础阻抗值。24例纯净水胃排空实验的半排空时间均值为（8.78±1.76） min。 结论：胃阻抗法虽然受到胃液分泌、试验餐成分等多种因素的影响，但是选用对胃内影响较小、电导率低的非营养性液体可以获得阻抗信号和胃容积变化的对应关系。电阻抗法能实现液体胃排空信号的提取，为临床胃排空功能研究提供一种无创测量的新途径。     

数字化外科：生物电阻抗测量技术辅助临床外科的操作**☆

生物电阻抗测量（Bioelectric Impedance Measurement Method,BEI）技术是生物医学工程学的一个飞速发展的领域,利用各种组织、器官不同的电导参数(阻抗、导纳、介电常数等),提取相关的生物医学信息,识别不同组织、器官的无损伤检测技术[1]。这种技术具有无创、廉价、安全、无毒害、操作简单和信息丰富等特点,具有广泛的应用前景。国际上已经开发出了多种基于BEI技术的无创、实时的测量和监控手段,部分产品已成功应用于辅助临床操作,值得关注     

电阻抗断层成像技术对小猪蛛网膜下腔出血早期监护作用的初步研究

目的 观察实验性蛛网膜下腔出血时脑部生物电阻抗断层(EIT)成像的变化规律,探讨其机制及临床应用价值.方法 采用枕大池单次注血模型模拟自发性蛛网膜下腔出血,应用脑EIT成像系统进行连续动态监护,得出蛛网膜下腔出血后脑EIT成像的动态变化.结果 成功建立模型8例,EIT监护图像变化显示注血早期颅脑前部阻抗降低明显,后部电阻抗轻度降低;注射结束后全脑电阻抗逐渐升高,颅脑后部增高明显.结论 脑EIT成像对实验性蛛网膜下腔出血后的电阻抗变化具有敏感性,并对出血部位有一定的定位作用,具有一定的临床应用价值.     

生物电阻抗技术分析人体脂肪成分与心血管病危险因素的相关性

目的：利用生物电阻抗技术探讨人体脂成分与多项心血管病危险因素之间的相互关系，为心血管疾病的预防提供理论依据。 方法:纳入2005-01/06在解放军总医院健康体检中心进行体检的符合入选条件者856名，其中男601例，女255例，平均年龄（45.2±8.7）岁。采用生物电阻抗技术分析受试者的人体成分组成，主要参数指标包括体脂肪量、去脂肪量、体脂肪率等，同时测定血糖、血脂、血液流变学等生化指标并计算体质量指数和腰/臀围比，对测定结果进行相关分析。 结果: ①人体去脂肪量与血液生化和血液流变学指标显著相关，而且这种相关程度远远高于体脂肪量、体质量指数及腰/臀围比与上述指标的相关性。②体脂肪率升高者的空腹血糖、三酰甘油、总胆固醇及低密度脂蛋白胆固醇高于体脂肪率正常者（P < 0.05），高密度脂蛋白胆固醇低于体脂肪率正常者（P < 0.05），此外，体脂肪率升高者的国际标准化比率低于体脂肪率正常者，纤维蛋白原水平高于体脂肪率正常者（P < 0.05）；以上变化还体现在腰/臀围比正常与腰/臀围比升高人群之间；但是，体质量指数的正常和体质量指数升高人群之间则无此变化。 结论：①体脂肪率与心血管风险因子相关，且相关程度高于体质量指数和腰臀围比。②与体质量指数和腰臀围比，体脂肪量、体脂肪率等人体成分测量指标在判定机体是否肥胖和评估血液流变学及血液凝集功能方面更加灵敏。     

基于梯度误差电阻抗断层成像技术的图像评价

国内目前的电阻抗断层成像技术工作重点是针对确定应用目标的实用化应用基础研究，电阻抗断层成像技术系统评价方法是从方法学基础向应用基础和临床应用研究过渡必须解决的关键问题之一。文章通过引入结构偏离度，提出了一种基于梯度误差的电阻抗断层成像技术图像重建评价函数。评价实验基于直径10 cm的16电极盐水槽装置，采用相邻激励、相邻测量模式，由等位线反投影算法重建图像，在实验室建立的电阻抗断层成像仿真实验系统研究平台上进行。采用传统评价参数图像清晰度和交叉熵，与结构偏离度的对比仿真评价结果表明，结构偏离度参数比传统的图像评价参数更具优势。文章提出的基于Sobel算子的梯度误差评价方法，能很好地反映图像的边缘变化和组织纹理结构信息，具有很好的电阻抗断层成像技术图像质量评价性能，可以更有效地反映电阻抗断层成像图像重建效果。     

功能性磁共振导航结合皮质电极描记切除功能区及其附近的癫痫灶

目的探讨利用fMRI导航结合皮质电极描记切除功能区及其附近癫痫灶的临床疗效。方法回顾性分析11例癫痫灶起源于功能区及其附近的癫痫病人的手术经验。病人术前发作频率（2．63±1．68）次／月。术前利用fMRI检查确定功能区位置并与导航图像进行融合,术中使用皮质电极描记标记出癫痫波的位置,通过导航系统了解功能区与癫痫波起源的关系。在保留功能区皮质的基础上,将病灶和癫痫波起源处皮质切除,而位于功能区皮质上的癫痫波起源处则给予小功率皮质热灼。结果皮质发育不全8例,灰质异位症2例,脑外伤后局部皮质软化1例。术后随访6～12个月,癫痫发作完全消失9例,术后3-6d内发作1次2例,随后未再出现癫痫发作。术后未出现明显的神经功能损害加重的情况。术后3个月复查脑电图显示基本正常。结论fMRI导航结合皮质电极描记切除起源于功能区及其附近的癫痫灶是一种微侵袭的手术方法,在切除癫痫灶的同时能最大限度地保留功能区的神经功能。     

参考桩钉修正曲面断层片垂直向的测量值*

背景：牙周病的诊断和治疗过程中常需测量牙槽骨高度和牙根长度,用曲面断层片对其进行定量测量的可靠性一直存在争议。 目的：验证用参考桩钉修正曲面断层片垂直向测量值的可行性。 方法：采用20例正畸患者的寄存模,在模型中的磨牙区、双尖牙区、尖牙区和切牙区嵌入5.00 mm钢珠作为测量对象,并在与钢珠相应的位置放置10.0 mm桩钉作参照物。拍摄模型的曲面断层片,测量钢珠影像垂直径,用桩钉校准和修正测量结果,比较钢珠影像测量值和真实值的差异。 结果与结论：用单一部位的参照物和1组参照物的平均值来校准,不同区域和不同桩钉放置方法测量结果的失真率不同,部分区域的失真率≥5%。在测量区域相应的部位放置完全垂直于牙合 平面的参考桩钉来修正测量值,可提高各区域测量结果的准确性,其失真率皆<1%,修正后的结果不受参照物的影响。而用贴在模型牙槽骨表面的参考桩钉来修正测量值,所得结果不理想。     

基于体素的MRI形态学测量对遗忘型轻度认知障碍和轻度阿尔茨海默病脑灰质萎缩的研究

目的：利用磁共振3DT1WI成像研究遗忘型轻度认知障碍（aMCI）、轻度阿尔茨海默病（AD）患者相对于正常老年人灰质体积改变的特点。方法：采用3．0T磁共振,对33例aMCI患者（aMCI组）、32例轻度AD患者（轻度AD组）及31名正常老年人（对照组）进行3DT1WI扫描,利用基于SPM5的DARTEL工具箱对扫描获得的结构图像进行预处理,再对aMCI组、轻度AD组和对照组的全脑灰质体积进行基于体素的统计学比较。结果：与对照组比较,aMCI组左侧海马、海马旁回、舌回、颞上回,双侧岛叶和颞中回等结构的灰质体积萎缩,其差异有显著统计学意义（P〈0．01,FDR corrected,K〉50体素）。轻度AD组的双侧海马、海马旁回及杏仁核、双侧丘脑、双侧颞顶叶皮质等结构灰质体积萎缩,额叶和枕叶皮质也出现灰质萎缩,其差异也有统计学意义（P〈0．05,FDR corrected,K≥50体素）。结论：基于体素的MRI形态学测量能够客观揭示AD早期阶段的脑灰质萎缩改变,对左侧海马萎缩的识别有助于AD的早期诊断。     

基于体素的MRI形态学测量及ApoE基因检测在遗忘型轻度认知障碍诊断中的应用

目的 应用基于体素的核磁共振(MRI)形态学测量技术及基因检测技术,分析遗忘型轻度认知障碍(aMCI)相对于正常老年人脑灰质体积改变的特点、载脂蛋白E(ApoE)基因多态性并探讨上述改变与aMCI发病机制可能的相关性,为aMCI的早期诊断、早期干预提供依据。方法 临床招募年龄、性别、族别、文化程度、生活背景等相互匹配并确定无血缘关系的14例aMCI患者、15例正常老年人,用3.0T磁共振进行三维T₁WI扫描,利用基于SPM12的DARTEL工具箱对扫描获得的结构图像进行预处理,再对aMCI组和对照组的全脑灰质体积进行基于体素的统计学比较。通过检测静脉血中ApoE基因,鉴定每个样本ApoE基因的等位基因及基因型。将上述所得数据进行相关统计学分析。结果 aMCI组中ε3/ε4基因型与正常对照组相比差异有统计学意义(P<0.05)。aMCI组与对照组比较,脑灰质萎缩主要位于左侧顶上小叶、左侧岛叶、岛叶前部、中央后回、腹内侧前额叶,右侧角回。结论 证实了aMCI患者患病与ApoE基因多态性存在联系,ApoEε4可能为aMCI的危险因素,aMCI患者灰质萎缩主要位于顶...     

Limitation of impedance plethysmography in assessing efficacy of dihydroergotamine-heparin prophylaxis of deep vein thrombosis

The sensitivity of impedance plethysmography (IPG) for diagnosing deep vein thrombosis was evaluated in the presence of dihydroergotamine, an agent with significant venoconstrictor activity. In a prospective, randomized, controlled clinical trial, 105 patients undergoing total hip replacement surgery were investigated to evaluate the thromboprophylactic efficacy of DHE-Heparin using IPG and 125I-Fibrinogen Leg Scanning to monitor the incidence of DVT. Retrospective analysis of the IPG data indicated that DHE-Heparin impaired the sensitivity of impedance plethysmography by decreasing venous capacitance and venous outflow. Although the patient sample size was relatively small, the results showed trends which suggested that the utility of impedance plethysmography for diagnosing DVT was limited in the presence of a vasoactive agent. Alternate noninvasive diagnostic methods may need to be considered in select patients receiving concomitant medications possessing venoconstrictor activity.     

Noninvasive measurement of cerebral bioimpedance for detection of cerebral edema in the neonatal piglet

The association of sustained cerebral edema with poor neurological outcome following hypoxia-ischaemia in the neonate suggests that measurement of cerebral edema may allow early prediction of outcome in these infants. Direct measurements of cerebral impedance have been widely used in animal studies to monitor cerebral edema, but such invasive measurements are not possible in the human neonate. This study investigated the ability of noninvasive cerebral impedance measurements to detect cerebral edema following hypoxia-ischaemia. One-day-old piglets were anaesthetized, intubated and ventilated. Hypoxia was induced by reducing the inspired oxygen concentration to 4-6% O(2). Noninvasive cerebral bioimpedance was measured using gel electrodes attached to the scalp. Cerebral bioimpedance was also measured directly by insertion of two silver-silver chloride electrodes subdurally. Noninvasive and invasive measurements were made before, during and after hypoxia. Whole body impedance was measured to assess overall fluid movements. Intracranial pressure was measured continuously via a catheter inserted subdurally, as an index of cerebral edema. There was good agreement between noninvasive and invasive measurements of cerebral impedance although externally obtained responses were attenuated. Noninvasive measurements were also well correlated with intracranial pressure. Whole body impedance changes did not account for increases in noninvasively measured cerebral impedance. Results suggest that noninvasive cerebral impedance measurements do reflect intracranial events, and are able to detect cerebral edema following hypoxia-ischaemia in the neonate.     

Electrical impedance myography at 50 kHz in the rat: Technique, reproducibility, and the effects of sciatic injury and recovery

ObjectiveTo describe a refined technique for performing electrical impedance myography (EIM) in the rat and assess its reproducibility, long-term stability, and the effects of sciatic nerve injury.MethodsEIM at 50 kHz was performed on the gastrocnemius–soleus complex of the rat hind limb in 12 rats, followed from 6 weeks of age for up to 6 months. Eight additional rats underwent sciatic nerve crush and 6 underwent a sham procedure.ResultsThe EIM variables of resistance, reactance and phase demonstrated substantial change with growth until approximately 14 weeks of age, at which point the measurements stabilized, giving mean values of 6.0 ± 5.7 Ω, 22.1 ± 2.1 Ω, and 16.5 ± 1.1°, respectively, at 16 weeks of age. Immediate reproducibility of technique was high with an intraclass correlation coefficient of 0.91 and higher for all three parameters. Sciatic crush produced marked reductions in the reactance and phase that reversed over a several week period.ConclusionsThese results support that 50 kHz EIM can be performed effectively in adult rat models of neuromuscular disease with a straightforward experimental technique and that it is sensitive to neurogenic injury.SignificanceEIM can serve as a new approach to the study of neuromuscular disease in the rat.     

Determination of body fluid compartments by impedance measurements: Differences in the repartition of water between Duchenne muscular dystrophy and some neurological diseases

Summary Body fluid volumes were determined by impedance measurements in several groups of patients. Boys with Duchenne muscular dystrophy had decreased intracellular and extracellular fluid volumes. Patients with severe sequelae of poliomyelitis and with other severely disabling neurological diseases did not exhibit such profound alterations of their body fluid compartments.

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Zusammenfassung Die Volumina der Körperflüssigkeit wurden durch Widerstandsmessungen in verschiedenen Patientengruppen gemessen. Knaben mit einer Duchennschen Muskeldystrophie haben verminderte intra- und extrazelluläre Flüssigkeitsvolumina. Patienten mit schwerwiegenden Folgen einer Poliomyelitis und mit verschiedenen anderen invalidisierenden neurologischen Erkrankungen zeigen keine so tiefgreifenden Veränderungen in den Kompartimenten der Körperflüssigkeit.

     

The measurement of change in endogenous affective disorders

Summary Psychopathological syndromes, as originally revealed by clinical observation, can also be detected by multivariate statistical analyses of symptom ratings. Changes in the course of psychiatric syndromes may be rated simply by improvement scales or by consecutive quantifications of symptoms and their comparison in chronological order. For the latter approach, which is less liable to bias, clinical ratings of psychopathology by staff members, self-ratings by the patients, analyses of patients' overt behavior (including video and speech records), or objective measurements of psychological and/or physiological variables can be used. Advantages and limitations of these different methods are discussed and illustrated by examples from ongoing clinical research in affective disorders. Generally, the combined use of different rating procedures is recommended. Self-ratings are economical, but they may represent aspects of psychopathology other than clinical ratings. In endogenous depression, mood scales are valid (supplementary) tools for the quantification of long-term as well as short-term changes, including diurnal variations. In severe conditions of mania, however, clinical rating has been—until now—the only valid basis for quantifying the degree of psychopathology and its changes with time. Precise evaluation of changes in psychopathology is essential in longitudinal investigations of endogenous affective disorders, since psychopathology up to now seems to have been the most sensitive and the most specific indicator of the hypothetical underlying abnormalities of cerebral functioning.Paper presented at a symposium on The Measurement of Change in Psychopathology at the VI World Congress of Psychiatry, Honolulu, USA, August 1977     

The importance of measurement invariance in neurocognitive ability testing

Objective: Neurocognitive test batteries such as recent editions of the Wechsler’s Adult Intelligence Scale (WAIS-III/WAIS-IV) typically use nation-level population-based norms. The question is whether these batteries function in the same manner across different subgroups based on gender, age, educational background, socioeconomic status, ethnicity, mother tongue, or race. Here, the author argues that measurement invariance is a core issue in determining whether population-based norms are valid for different subgroups. Method: The author introduces measurement invariance, argues why it is an important topic of study, discusses why invariance might fail in cognitive ability testing, and reviews a dozen studies of invariance of commonly used neurocognitive test batteries. Results: In over half of the reviewed studies, IQ batteries were not found to be measurement invariant across groups based on ethnicity, gender, educational background, cohort, or age. Apart from age and cohort, test manuals do not take such lack of invariance into account in computing full-scale IQ scores or normed domain scores. Conclusions: Measurement invariance is crucial for valid use of neurocognitive tests in clinical, educational, and professional practice. The appropriateness of population-based norms to particular subgroups should depend also on whether measurement invariance holds with respect to important subgroups.     

A new method for noninvasive measurement of short-term cerebrospinal fluid pressure changes in humans

Summary Changes in cerebrospinal fluid (CSF) pressure were shown to be reflected by changes in tympanic membrane (TM) tension. Impedance audiometry measures mechanical tension on the TM and was used to detect changes during jugular vein compression in normal students. CSF and perilymph communicate through the cochlear aqueduct, permitting increases in CSF pressure to result in increased pressure on the stapes footplate. This is transmitted to the TM by the ossicles and detected by impedance audiometry. TM tension was also proportional to CSF pressure in cadavers, where CSF pressure was manipulated by saline injection through a lumbar puncture.