电阻抗断层成像技术研究进展

电阻抗断层成像(EIT)是一种重要的医学成像方法,通过对物体表面的分布电测量来获知物体内部的电特性图像,有着良好的应用前景.本文对EIT的硬件系统和成像算法的研究进展作了全面的描述.首先对硬件部分的信号源和驱动模式进行了介绍,并对目前使用的EIT系统作了简要的分析;然后介绍了成像算法,从二维和三维成像两个方面对目前EIT的重建算法进行阐述.最后,对EIT进行了讨论和总结.     

神经肌肉电刺激下小腿肌肉的电学特性研究

目的 采用电阻抗成像（electrical impedance tomography,EIT）方法研究神经肌肉电刺激（neuromuscular electrical stimulation,NMES）下小腿肌肉的电学特性,旨在将EIT作为一种长期监测方法,从而可视化NMES训练对人类小腿肌肉的训练效果。方法 16名实验对象被随机分配到对照组（control group,CG,n=8）和最佳电压强度的NMES训练组（optimal voltage intensity training group,OG,n=8）。对照组保持正常生活方式并不进行NMES和其他的肌肉训练;NMES训练组中使用商业NMES设备对实验对象右小腿进行23 min的NMES训练,每周3次,为期5周。应用EIT测量在每周一训练开始前的电导率分布。并且采用生物电阻抗分析（bioelectrical impedance analysis,BIA）方法测量右腿细胞外含水量与身体总含水量的比率（ECW/TBW） βrl,及身体总含水量（TBW）τ。为了量化NMES在肌肉训练过程中的作用,使用配对样本t检验分析EIT重建图像的...     

电阻抗断层成像技术进展

电阻抗断层成像技术分为:静态EIT(以电阻抗分布的绝对值为成像目标)和动态EIT(以电阻抗分布的相对值为成像目标),它是近年来国内外生物医学工程研究的比较热门的一种成像技术。因为与已有的X射线成像、计算机断层扫描成像(CT)、核磁共振成像(MRI)及超声成像相比,这种新的成像技术不仅具有解剖学的特征信息,还有功能性成像的性质。又因为它的无创、简单、便宜、容易应用等特点,在临床有着很好的应用前景。本文通过数学、物理以及应用上的论述并结合了最新的国内外科研动态。介绍了电阻抗断层成像技术的数学计算(包括算法和算法分析),物理基础(激励方式,激励频率,驱动模式),揭示了电阻抗断层成像技术的基本原理,并展示了此项技术的临床应用情况。     

体外循环血栓非侵入在线电阻抗成像方法

目的 在体外循环系统中,血栓的在线检测和可视化具有重要意义。本文提出了基于电阻抗成像（EIT）的体外循环血栓非侵入在线检测方法。方法 首先通过联合仿真研究了传感器尺寸对成像效果的影响。其次,根据仿真结果设计了直径为20 mm的16铜质电极EIT传感器,搭建了循环流动实验平台,并设计了静态和循环流动实验。使用尺寸为3～6 mm的猪血块代替血栓,将血块置于新鲜猪血样本中,采用Tikhonov正则化算法进行成像。将3 mm和5 mm的血块分别置于循环系统中,重建血块在传感器截面的大小和位置图像,并与高速相机拍摄结果进行对比。结果 仿真结果显示当目标物与传感器面积比（AR）不小于0.01时,传感器直径为20 mm和30 mm对应的图像相关系数（IC）均大于0.06,成像效果较好。静态成像结果显示,相对尺寸覆盖率误差（RCR）小于等于0.1。循环流动实验显示,血块经过传感器时,检测到归一化后的相对电导率变化值分别为80和200,结果显示该方法能够检测到循环系统中的血块。结论 该方法具有实时性和非侵入的优点,有望应用于体外血栓的检测。     

右美托咪定联合肺保护性通气策略对肺癌根治术患者氧化应激、炎症反应和免疫功能的影响

摘要 目的：探讨右美托咪定联合肺保护性通气策略对肺癌根治术患者氧化应激、炎症反应和免疫功能的影响。方法：选择我院行肺癌根治术患者110例,入选患者根据信封抽签法分为A组和B组,各为55例。A组接受右美托咪定联合传统通气策略,B组接受右美托咪定联合肺保护性通气策略,观察两组患者的氧合指数（OI）、氧化应激指标[超氧化物歧化酶（SOD）、丙二醛（MDA）]、炎症反应指标[白介素-6（IL-6）、肿瘤坏死因子-α（TNF-α）]、免疫功能变化以及术后肺部并发症发生率。结果：B组单肺通气前即刻（T2）~恢复双肺通气15 min（T6）时间点OI高于A组（P<0.05）。B组术后72 h（T7）时间点CD3⁺、CD4⁺、CD4⁺/CD8⁺高于A组,CD8⁺低于A组（P<0.05）。B组T7时间点SOD水平高于A组,MDA水平低于A组（P<0.05）。B组T7时间点IL-6、TNF-α水平低于A组（P<0.05）。两组术后肺部并发症发生率组间对比无统计学差异（P>0.05）。结论：右美托咪定联合肺保护性通气策略可改善肺癌根治术患者氧合和炎症反应,有效减轻免疫抑制及氧化应激反应。     

基于生物阻抗谱的生物细胞活性免标记检测方法

目的 基于生物阻抗谱（bioelectrical impedance spectroscopy,BIS）技术,提出一种免标记的生物细胞活性实时检测方法。该方法依据不同浓度、生理、病理状态下细胞组织的电学特性差异来判断细胞是否具有活性,以协助医师在临床手术中快速精准定位患者烫伤组织并实现有效切除。方法 使用具有活性的斑马鱼胚胎干细胞来模拟人体烫伤组织,采用生物阻抗谱技术来鉴别细胞组织的生理状态。结果 在不同状态下,细胞的阻抗幅值变化有显著的差异,可以从中发现同等浓度下活性细胞的阻抗幅值比死亡细胞平均高出17.25%,活性细胞发生弛豫频率的时间也比死亡细胞早25%。结论 实验数据表明,生物阻抗谱法能有效区分胚胎干细胞的两类生理状态;从聚类区域中可以看出,BIS检测法具有明显的细胞活性及浓度区分能力,理论上能够快速地协助医师完成对患者烫伤组织检测。     

人类小腿肌肉对运动训练生理响应的电学特性研究

目的 运动训练已被证明能够改善许多慢性肌肉功能疾病,被用于治疗衰老型肌萎缩。本文采用电阻抗成像(electrical impedance tomography,EIT)研究人类小腿肌肉对运动训练生理响应的电学特性,旨在使用EIT方法可视化运动训练对人类小腿响应肌肉隔室内肌肉纤维体积增加的效果。方法 实验对象被要求在连续5个实验日进行左、右腿单侧提踵训练,应用EIT检测每日运动训练前和运动训练后小腿肌肉的电导率分布。为了定量分析运动训练对响应肌肉隔室的作用,使用配对样本t检验分析EIT重建图像的空间平均电导率<σ>。结果 运动训练后,由小腿腓肠肌组成的M₁肌肉隔室空间平均电导率<σ>_M1显著增加。此外,连续5个实验日的EIT测量结果显示,运动训练前的空间平均电导率<σ^pre>_M1呈上升趋势。所有实验对象在实验日1早晨进行实验前的腿部瘦体重与<σ>_M1呈线性关系,即<σ>_M1随腿部瘦体重增加而增加;运...     

木麻黄根乙酸乙酯部位化学成分研究

为阐明木麻黄（Casuarina equisetifolia）的化学成分,采用有机溶剂提取、萃取及多种分离技术,从其根中分离得到14个化合物。经光波谱分析,其结构分别鉴定为5-hydroxy-3-methoxyphenyl-6-O-syringoyl-β-d-glucopyranoside （1）,高良姜苷A （2）,heterophylloside C （3）、6''-O-vanilloylisotachioside （4）、3,4,5-trimethoxyphenyl-6-O-syringoyl-β-d-glucopyranoside （5）、香草醛（6）、丁香醛（7）、3,4-二羟基苯甲醛（8）、齐墩果酸（9）、桦木酸（10）、胡萝卜苷（11）、胡萝卜苷亚油酸酯（12）、（±）-lyoniresinol 2-O-a-rhamnoside （13）和（-）-9-acetyl-isolariciresinol 9''-O-a-l-rhamnopyranoside （14）,其中化合物14为新的木脂素。     

严重急性呼吸综合征冠状病毒2膜蛋白对宿主细胞pre-mRNA 3"UTR加工的影响

目的 研究严重急性呼吸综合征冠状病毒2（SARS-CoV-2）膜蛋白对宿主细胞mRNA前体（pre-mRNA）3"非翻译区（UTR）加工的影响。方法 本研究以人肺上皮细胞系A549为模型，利用瞬时转染在细胞内过表达SARS-CoV-2膜蛋白；利用RNA-Seq测序技术及生物信息学分析方法，系统性描绘宿主细胞选择性多聚腺苷酸化（alternative polyadenylation，APA）事件；Metascape数据库对发生显著APA变化的基因进行功能富集分析；RT-qPCR验证靶基因3"UTR长度变化；蛋白质免疫印迹（Western blot）检测目的蛋白表达水平。结果 SARS-CoV-2膜蛋白外源表达后宿主细胞内共813个基因发生显著APA变化。GO和KEGG分析显示，差异APA基因广泛参与有丝分裂细胞周期、调节细胞应激等生物过程，涉及病毒感染和蛋白质加工等。从中进一步筛选出AKT1基因，在IGV软件中显示3"UTR延长；RT-qPCR验证AKT1基因的3"UTR长度变化趋势；Western blot结果显示AKT1蛋白磷酸化水平增加。结论 SARS-CoV-2膜蛋白潜在影响宿主pre-mRNA的3"UTR加工，其中参与多种病毒性生物过程的AKT1基因 3"UTR延长，且其编码的蛋白质功能在细胞内被激活。     

间歇性θ节律经颅磁刺激改善大鼠工作记忆的海马与前额叶跨脑区神经网络效应研究

目的 间歇性θ节律刺激（iTBS）作为一种新型的经颅磁刺激模式，已经广泛应用于探索大脑认知功能和神经调控等方面，但其电生理调控机制尚不清晰，探索iTBS对大脑认知功能的影响及其电生理机制，对脑疾病的治疗和磁刺激的临床应用具有重要意义。方法 本文利用iTBS制备磁刺激大鼠模型，采集记录大鼠在执行工作记忆（WM）任务过程中腹侧海马（vHPC）和内侧前额叶皮层（mPFC）的局部场电位（LFPs）信号，应用格兰杰因果网络分析方法，研究了iTBS对大鼠WM过程中vHPC与mPFC跨脑区神经网络协同和信息交互的影响。结果 iTBS增强了大鼠的学习记忆能力，使其完成工作记忆任务所需时长减少（2.67±1.63）d（P<0.05），iTBS显著改善了大鼠的行为学表现；同时iTBS增强了大鼠在WM期间vHPC与mPFC脑区的自因果网络连接，增加了网络连接强度、连接密度和全局效率（P<0.05）；并且iTBS增强了vHPC与mPFC脑区的跨脑区网络连接，增加了vHPC-mPFC跨脑区的节点度和因果流向（P<0.05）。结论 iTBS磁刺激对大鼠工作记忆行为学及相关脑区神经网络均有显著的积极作用，iTBS可以促进大鼠认知能力，提高大脑神经网络的信息交互和传递效率，iTBS的神经调控机制可能是通过增强大脑vHPC与mPFC之间的网络连接和信息交互来提高工作记忆能力。     

Functional Regions of Interest in Electrical Impedance Tomography: A Secondary Analysis of Two Clinical Studies

Introduction

Patients with acute respiratory distress syndrome (ARDS) typically show a high degree of ventilation inhomogeneity, which is associated with morbidity and unfavorable outcomes. Electrical impedance tomography (EIT) is able to detect ventilation inhomogeneity, but it is unclear which method for defining the region of interest (ROI) should be used for this purpose. The aim of our study was to compare the functional region of interest (fROI) method to both the lung area estimation method (LAEM) and no ROI when analysing global parameters of ventilation inhomogeneity. We assumed that a good method for ROI determination would lead to a high discriminatory power for ventilation inhomogeneity, as defined by the area under the receiver operating characteristics curve (AUC), comparing patients suffering from ARDS and control patients without pulmonary pathologies.

Methods

We retrospectively analysed EIT data from 24 ARDS patients and 12 control patients without pulmonary pathology. In all patients, a standardized low-flow-pressure volume maneuver had been performed and was used for EIT image generation. We compared the AUC for global inhomogeneity (GI) index and coefficient of variation (CV) between ARDS and control patients using all EIT image pixels, the fROI method and the LAEM for ROI determination.

Results

When analysing all EIT image pixels, we found an acceptable AUC both for the GI index (AUC = 0.76; 95% confidence interval (CI) 0.58–0.94) and the CV (AUC = 0.74; 95% CI 0.55–0.92). With the fROI method, we found a deteriorating AUC with increasing threshold criteria. With the LAEM, we found the best AUC both for the GI index (AUC = 0.89; 95% CI 0.78–1.0) and the CV (AUC = 0.89; 95% CI 0.78–1.0) using a threshold criterion of 50% of the maximum tidal impedance change.

Conclusion

In the assessment of ventilation inhomogeneity with EIT, functional regions of interest obscure the difference between patients with ARDS and control patients without pulmonary pathologies. The LAEM is preferable to the fROI method when assessing ventilation inhomogeneity.     

Regional lung perfusion estimated by electrical impedance tomography in a piglet model of lung collapse

The assessment of the regional match between alveolar ventilation and perfusion in critically ill patients requires simultaneous measurements of both parameters. Ideally, assessment of lung perfusion should be performed in real-time with an imaging technology that provides, through fast acquisition of sequential images, information about the regional dynamics or regional kinetics of an appropriate tracer. We present a novel electrical impedance tomography (EIT)-based method that quantitatively estimates regional lung perfusion based on first-pass kinetics of a bolus of hypertonic saline contrast. Pulmonary blood flow was measured in six piglets during control and unilateral or bilateral lung collapse conditions. The first-pass kinetics method showed good agreement with the estimates obtained by single-photon-emission computerized tomography (SPECT). The mean difference (SPECT minus EIT) between fractional blood flow to lung areas suffering atelectasis was -0.6%, with a SD of 2.9%. This method outperformed the estimates of lung perfusion based on impedance pulsatility. In conclusion, we describe a novel method based on EIT for estimating regional lung perfusion at the bedside. In both healthy and injured lung conditions, the distribution of pulmonary blood flow as assessed by EIT agreed well with the one obtained by SPECT. The method proposed in this study has the potential to contribute to a better understanding of the behavior of regional perfusion under different lung and therapeutic conditions.     

Assessment of Regional Ventilation Distribution: Comparison of Vibration Response Imaging (VRI) with Electrical Impedance Tomography (EIT)

Background

Vibration response imaging (VRI) is a bedside technology to monitor ventilation by detecting lung sound vibrations. It is currently unknown whether VRI is able to accurately monitor the local distribution of ventilation within the lungs. We therefore compared VRI to electrical impedance tomography (EIT), an established technique used for the assessment of regional ventilation.

Methodology/Principal Findings

Simultaneous EIT and VRI measurements were performed in the healthy and injured lungs (ALI; induced by saline lavage) at different PEEP levels (0, 5, 10, 15 mbar) in nine piglets. Vibration energy amplitude (VEA) by VRI, and amplitudes of relative impedance changes (rel.ΔZ) by EIT, were evaluated in seven regions of interest (ROIs). To assess the distribution of tidal volume (V_T) by VRI and EIT, absolute values were normalized to the V_T obtained by simultaneous spirometry measurements. Redistribution of ventilation by ALI and PEEP was detected by VRI and EIT. The linear correlation between pooled V_T by VEA and rel.ΔZ was R² = 0.96. Bland-Altman analysis showed a bias of −1.07±24.71 ml and limits of agreement of −49.05 to +47.36 ml. Within the different ROIs, correlations of V_T-distribution by EIT and VRI ranged between R² values of 0.29 and 0.96. ALI and PEEP did not alter the agreement of V_T between VRI and EIT.

Conclusions/Significance

Measurements of regional ventilation distribution by VRI are comparable to those obtained by EIT.     

Mechanical strain promotes osteoblast ECM formation and improves its osteoinductive potential

Background

Hyperpolarised helium MRI (He3 MRI) is a new technique that enables imaging of the air distribution within the lungs. This allows accurate determination of the ventilation distribution in vivo. The technique has the disadvantages of requiring an expensive helium isotope, complex apparatus and moving the patient to a compatible MRI scanner. Electrical impedance tomography (EIT) a non-invasive bedside technique that allows constant monitoring of lung impedance, which is dependent on changes in air space capacity in the lung. We have used He3MRI measurements of ventilation distribution as the gold standard for assessment of EIT.

Methods

Seven rats were ventilated in supine, prone, left and right lateral position with 70% helium/30% oxygen for EIT measurements and pure helium for He3 MRI. The same ventilator and settings were used for both measurements. Image dimensions, geometric centre and global in homogeneity index were calculated.

Results

EIT images were smaller and of lower resolution and contained less anatomical detail than those from He3 MRI. However, both methods could measure positional induced changes in lung ventilation, as assessed by the geometric centre. The global in homogeneity index were comparable between the techniques.

Conclusion

EIT is a suitable technique for monitoring ventilation distribution and inhomgeneity as assessed by comparison with He3 MRI.     

Ventilation distribution in rats: Part I - The effect of gas composition as measured with electrical impedance tomography

ABSTRACT: The measurement of ventilation distribution is currently performed using inhaled tracer gases for multiple breath inhalation studies or imaging techniques to quantify spatial gas distribution. Most tracer gases used for these studies have properties different from that of air. The effect of gas density on regional ventilation distribution has not been studied. This study aimed to measure the effect of gas density on regional ventilation distribution. METHODS: Ventilation distribution was measured in seven rats using electrical impedance tomography (EIT) in supine, prone, left and right lateral positions while being mechanically ventilated with either air, heliox (30% oxygen, 70% helium) or sulfur hexafluoride (20% SF6, 20% oxygen, 60% air). The effect of gas density on regional ventilation distribution was assessed. RESULTS: Gas density did not impact on regional ventilation distribution. The non-dependent lung was better ventilated in all four body positions. Gas density had no further impact on regional filling characteristics. The filling characteristics followed an anatomical pattern with the anterior and left lung showing a greater impedance change during the initial phase of the inspiration. CONCLUSION: It was shown that gas density did not impact on convection dependent ventilation distribution in rats measured with EIT.     

Monitoring changes in lung air and liquid volumes with electrical impedance tomography

Adler, A., R. Amyot, R. Guardo, J. H. T. Bates, and Y. Berthiaume. Monitoring changes in lung air and liquid volumes withelectrical impedance tomography. J. Appl.Physiol. 83(5): 1762-1767, 1997.Electricalimpedance tomography (EIT) uses electrical measurements at electrodesplaced around the thorax to image changes in the conductivitydistribution within the thorax. This technique is well suited tostudying pulmonary function because the movement of air, blood, andextravascular fluid induces significant conductivity changes within thethorax. We conducted three experimental protocols in a total of 19 dogsto assess the accuracy with which EIT can quantify changes in thevolumes of both gas and fluid in the lungs. In the first protocol, lungvolume increments from 50 to 1,000 ml were applied with a largesyringe. EIT measured these volume changes with an average error of 27 ± 6 ml. In the second protocol, EIT measurements were made at endexpiration and end inspiration during regular ventilation with tidalvolume ranging from 100 to 1,000 ml. The average error in the EITestimates of tidal volume was 90 ± 43 ml. In the third protocol,lung liquid volume was measured by instilling 5% albumin solution intoa lung lobe in increments ranging from 10 to 100 ml. EIT measured thesevolume changes with an average error of 10 ± 10 ml and was alsoable to detect into which lobe the fluid had been instilled. These results indicate that EIT can noninvasively measure changes in thevolumes of both gas and fluid in the lungs with clinically usefulaccuracy.

     

Lung tumors on multimodal radiographs derived from grating-based X-ray imaging – A feasibility study

PurposeThe purpose of this study was to assess whether grating-based X-ray imaging may have a role in imaging of pulmonary nodules on radiographs.Materials and methodsA mouse lung containing multiple lung tumors was imaged using a small-animal scanner with a conventional X-ray source and a grating interferometer for phase-contrast imaging. We qualitatively compared the signal characteristics of lung nodules on transmission, dark-field and phase-contrast images. Furthermore, we quantitatively compared signal characteristics of lung tumors and the adjacent lung tissue and calculated the corresponding contrast-to-noise ratios.ResultsOf the 5 tumors visualized on the transmission image, 3/5 tumors were clearly visualized and 1 tumor was faintly visualized in the dark-field image as areas of decreased small angle scattering. In the phase-contrast images, 3/5 tumors were clearly visualized, while the remaining 2 tumors were faintly visualized by the phase-shift occurring at their edges. No additional tumors were visualized in either the dark-field or phase-contrast images. Compared to the adjacent lung tissue, lung tumors were characterized by a significant decrease in transmission signal (median 0.86 vs. 0.91, p = 0.04) and increase in dark-field signal (median 0.71 vs. 0.65, p = 0.04). Median contrast-to-noise ratios for the visualization of lung nodules were 4.4 for transmission images and 1.7 for dark-field images (p = 0.04).ConclusionLung nodules can be visualized on all three radiograph modalities derived from grating-based X-ray imaging. However, our initial data suggest that grating-based multimodal X-ray imaging does not increase the sensitivity of chest radiographs for the detection of lung nodules.     

Functional Validation and Comparison Framework for EIT Lung Imaging

Introduction

Electrical impedance tomography (EIT) is an emerging clinical tool for monitoring ventilation distribution in mechanically ventilated patients, for which many image reconstruction algorithms have been suggested. We propose an experimental framework to assess such algorithms with respect to their ability to correctly represent well-defined physiological changes. We defined a set of clinically relevant ventilation conditions and induced them experimentally in 8 pigs by controlling three ventilator settings (tidal volume, positive end-expiratory pressure and the fraction of inspired oxygen). In this way, large and discrete shifts in global and regional lung air content were elicited.

Methods

We use the framework to compare twelve 2D EIT reconstruction algorithms, including backprojection (the original and still most frequently used algorithm), GREIT (a more recent consensus algorithm for lung imaging), truncated singular value decomposition (TSVD), several variants of the one-step Gauss-Newton approach and two iterative algorithms. We consider the effects of using a 3D finite element model, assuming non-uniform background conductivity, noise modeling, reconstructing for electrode movement, total variation (TV) reconstruction, robust error norms, smoothing priors, and using difference vs. normalized difference data.

Results and Conclusions

Our results indicate that, while variation in appearance of images reconstructed from the same data is not negligible, clinically relevant parameters do not vary considerably among the advanced algorithms. Among the analysed algorithms, several advanced algorithms perform well, while some others are significantly worse. Given its vintage and ad-hoc formulation backprojection works surprisingly well, supporting the validity of previous studies in lung EIT.     

Benign-malignant pulmonary nodule classification in low-dose CT with convolutional features

PurposeLow-Dose Computed Tomography (LDCT) is the most common imaging modality for lung cancer diagnosis. The presence of nodules in the scans does not necessarily portend lung cancer, as there is an intricate relationship between nodule characteristics and lung cancer. Therefore, benign-malignant pulmonary nodule classification at early detection is a crucial step to improve diagnosis and prolong patient survival. The aim of this study is to propose a method for predicting nodule malignancy based on deep abstract features.MethodsTo efficiently capture both intra-nodule heterogeneities and contextual information of the pulmonary nodules, a dual pathway model was developed to integrate the intra-nodule characteristics with contextual attributes. The proposed approach was implemented with both supervised and unsupervised learning schemes. A random forest model was added as a second component on top of the networks to generate the classification results. The discrimination power of the model was evaluated by calculating the Area Under the Receiver Operating Characteristic Curve (AUROC) metric.ResultsExperiments on 1297 manually segmented nodules show that the integration of context and target supervised deep features have a great potential for accurate prediction, resulting in a discrimination power of 0.936 in terms of AUROC, which outperformed the classification performance of the Kaggle 2017 challenge winner.ConclusionEmpirical results demonstrate that integrating nodule target and context images into a unified network improves the discrimination power, outperforming the conventional single pathway convolutional neural networks.