Search

Electrical Impedance Tomography (EIT) is a medical imaging technique that is primarily used to monitor the respiration of a patient. Because EIT is based on electrical measurements, it is a safe, non-invasive, and cost-effective imaging technique. However, the EIT image reconstruction is a severely ill-posed problem that gives low spatial resolution where only large variations in tissue conductivity can be visualized. Furthermore, widely used time difference EIT relies on a single frequency alternating current measurement which does not allow for discrimination of different tissues on their conductivity spectra. Here we show the application of a new EIT reconstruction algorithm which correlates measurements taken at different frequencies to include the spectral dependency of the tissue properties. The algorithm is tested on a simulated phantom using data for muscle and lung tissue from the literature. It shows that contrary to a standard EIT image reconstruction, the frequency dependence of the tissues is retained, which can be used to further improve distinguishability in EIT images.

The apnea test (AT) is a critical procedure in determining brain death. It temporarily disconnects the patient from the ventilator for 7 to 10 minutes. This study explores pulsatile Electrical Impedance Tomography (EIT) during AT in 10 patients suspected of brain death to discern physiological changes. Analysis revealed three distinct patterns of pulsatile EIT signal changes: increasing; fluctuating; and decreasing. These findings show the potential of pulsatile EIT monitoring to provide novel insight into cardio-pulmonary dynamics during AT.

Electrical Impedance Tomography is used to image the cross-sectional conductivity of an object. It is clinically used for high-frame-rate imaging of lung ventilation. Most current systems use very limited current injection waveforms and patterns. We have developed a flexible system for researching alternatives. This paper covers our voltage conditioning module’s design and characterisation. The device was shown to work up to the desired 10 MHz. The responses were uniform with minor gain mismatch between all channels after manufacturing variations. The low-frequency (

Electrical Impedance Tomography (EIT) has shown promising results as a low-cost imaging method for visualizing ventilation distribution within the lungs. However, clinical interpretation of EIT images is often hindered by blurred anatomical alignment and reconstruction artifacts. Integrating structural priors into the EIT reconstruction process has the potential to enhance the interpretability of the EIT images. Thus, a patient-specific structural prior mask is introduced in this contribution, which restricts the reconstruction of conductivity changes within the lung regions.We conducted numerical simulations on four finite element models representing four different thorax excursions to investigate the impact of the structural prior mask on EIT images. Simulations were performed under four different ventilation statuses. EIT images were reconstructed using the Gauss-Newton and discrete cosine transform-based EIT algorithms.We conducted a quantitative analysis using figures of merit to evaluate the images of the two reconstruction algorithms. The results show the structural prior mask preserves the morphological structures of the lungs and limits reconstruction artifacts.

Electrical impedance tomography (EIT) has the potential for monitoring perfusion in addition to respiration on the bedside. Several separation methods were reported, e.g. Filtering, ECG-gating and PCA. However, the separation is not trivial, which is why harmonic analysis was introduced in EIT data analysis. It is based on several assumptions and therefore prove of plausibility is necessary. In this contribution a two-dimensional thorax simulation is introduced, which includes simplified lungs and heart with changing shapes and conductivities due to volume variations and lung perfusion. Harmonic analysis was applied on the simulated data. The separation results are in good agreement with the simulation settings. Further investigations will be required due to limitations of the simulation. Nevertheless, harmonic analysis delivered precise results in ideal and strictly defined conditions.

Morphological prior information incorporated with the discrete cosine transformation (DCT) based electrical impedance tomography (EIT) algorithm can improve the interpretability of EIT reconstructions in clinical applications. However, an outdated structural prior can yield a misleading reconstruction compromising the accuracy of the clinical diagnosis and the appropriate treatment decision. In this contribution, we propose a redistribution index scaled between 0 and 1 to quantify the possible error in a DCT-based EIT reconstruction influenced by structural prior information. Two simulation models of different tissue atelectasis and collapsed ratios were investigated. Outdated and updated structural prior information were applied to obtain different EIT reconstructions using this simulated data, with which the redistribution index was calculated and compared. When the difference between prior and reality (the redistribution index) became larger and exceeded a threshold, this was considered as an indicator of an outdated prior information. The evaluation result shows the potential of the redistribution index to detect outdated prior information in a DCT-based EIT algorithm.

The COVID-19 is a viral infection that causes respiratory complications. Infected lungs often present ground glass opacities, thus suggesting that medical imaging technologies could provide useful information for the disease diagnosis, treatment, and posterior recovery. The Electrical Impedance Tomography (EIT) is a non-invasive, radiationfree, and continuous technology that generates images by using a sequence of current injections and voltage measurements around the body, making it very appropriate for the study to monitor the regional behaviour of the lung. Moreover, this tool could also be used for a preliminary COVID-19 phenotype classification of the patients. This study is based on the monitoring of lung compliances of two COVID-19-infected patients: the results indicate that one of them could belong to the H-type, while the other is speculated belongs to L-type. It has been concluded that the EIT is a useful tool to obtain information regarding COVID-19 patients and could also be used to classify different phenotypes.

COVID-19 induced acute respiratory distress syndrome (ARDS) could have two different phenotypes, which might have different response and outcome to the traditional ARDS positive end-expiration pressure (PEEP) treatment. The identification of the different phenotypes in terms of the PEEP recruitment can help improve the patients’ outcome. In this contribution we reported a COVID-19 patient with seven-day electrical impedance tomography monitoring. From the conductivity distribution difference image analysis of the data, a clear course developing trend can be observed in addition to the phenotype identification. This case might suggest that EIT can be a practical tool to identify phenotypes and to provide progressive information of COVID-19 pneumonia.

Purpose: To evaluate a novel structural-functional DCT-based EIT lung imaging method against the classical EIT reconstruction. Method: Taken retrospectively from a former study, EIT data was evaluated using both reconstruction methods. For different phases of ventilation, EIT images are analyzed with respect to the global inhomogeneity (GI) index for comparison. Results: A significant less variant GI index was observed in the DCTbased method, compared to the index from classical method. Conclusion: The DCT-based method generates more accurate lung contour yet decreasing the essential information in the image which affects the GI index. These preliminary results must be consolidated with more patient data in different breathing states.

[Objective] The dispute in the paleogeographic pattern of the carbonate platform and distribution of reservoir facies during the deposition of the Dengying Formation in the middle-upper area, hinders the expansion of the exploration domain from the Mianyang-Changning intracratonic sag to other areas. [Methods] Detailed lithofacies and facies analysis was conducted on more than 30 sections (wells), [Results] further confirming that the mound-shoal is marked by massive peloidal/ooidal dolograinstone and columnar, domal dolostromatolite, which were deposited around the platform (or inner ramp) margin of the Middle-Upper Yangtze Platform gradually shifting outward into tempestite of the middle-outer ramp or slump dolobreccia, argillaceous dolomite and chert of slope-basin facies. Owing to the mound-shoal barrier, its back was dominated by tidal flat and lagoon. Of these, the tidal flat facies were marked by microbial dololaminite, domal dolostromatolite, dolothrombolite with minor peloidal dolograinstone, and dolomudstone, which are commonly arranged into meter-centimeter scale cycles. The lagoon facies were composed mainly of dolomudstone and peloidal dolowackestone. In general, the mound-shoal facies is present in the lower Dengying Formation along the platform to slope transition (or inner ramp to middle ramp transition) . In the Upper Yangtze Platform, it occurs in the Deng 1 (e.g., wells Pengtan 1, Ziyang 1, and sections Qingping, Beidoushan) or Deng 2 members at the Baijiaba, Yulin, and Meiziwan sections, or in both the Deng 1 and Deng 2 members at the Songlin-Yankong areas. On Middle Yangtze Platform, it occurs in the Hamajing (e. g., sections Sancha, Bailuya, and Tianping) or Baimatuo members of the upper Dengying Formation at the Miaohe section. Specifically, the mound- shoal facies shows repeated transgressions and regressions and occurs in different stratigraphic position of the Dengying Formation at many sections (Baiguoping, Xiaofenghe, Dengyingxia, Wushan, Xuejiadian, and Dengjiaya) . In contrast, the tidal flat and lagoon facies are widely present on the whole Middle-Upper Yangtze Platform, commonly associated with the grape-like dolomite at the lower-middle part of the Deng 2 member (or correlated stratigraphy) . The spatiotemporal distributions of these facies show a progradational trend of the Dengying Formation on the Middle- Upper Yangtze Platform, which consists of 2.5 depositional sequences with three progradations (shallowing) and two retrogradations (deepening) . The regressive system tract of Sequence 1 is formed by the lower Dengying Formation (the Deng 1 to middle Deng 2 or Hamajing members), characterized by the upward evolution of lagoon or moundshoal facies into tidal flat facies. On the Upper Yangtze Platform, Sequence 2 occurs in the upper Deng 2 member, marked by the regression of mound-shoal facies and the presence of more lagoonal dolomudstone, followed by the reoccurrence of tidal flat facies. On the Middle Yangtze Platform, Sequence 2 is present in the Shibantan member, represented by the deepening into middle ramp limestone or lagoonal dolomudstone and then shallowing into moundshoal or tidal flat facies. Sequence 3 on the Middle Yangtze Platform shows a similar deepening (transgression) and shallowing (regression) cycle. On the Upper Yangtze Platform, the transgressive systems tract of Sequence 3 is located in the siliciclastic rock of the Deng 3 member and the following transgressive systems tract is marked by the transition of lagoonal dolomudstone to tidal flat dolomicrobialite. [Conclusions] Owing to the denudation of the Dengying Formation at the platform margin-slope area and Upper Yangtze Platform beyond the current plate boundary, the platform marginal mound-shoal facies are locally present in the Deng 4 member. In this case, certain areas (e.g., the Songlin-Yankong area and periphery of the Middle Yangtze Platform) with platform marginal mound-shoal facies in the lower-middle Dengying Formation (Deng 1 to 2 or Hamajing to Shibantan members) are important exploration targets. Moreover, the lower Deng 2 and upper Deng 4 members (or coeval strata) formed during progradations composed of microbial dolomite throughout the Middle-Upper Yangtze Platform (or inner ramp) interior are also important exploration targets. Because the microbial dolomite was widely developed throughout the Middle-Upper Yangtze Platform interior, decoding the formation mechanism and distribution pattern of high-quality reservoir is the key to finding new hydrocarbon provinces. [ABSTRACT FROM AUTHOR]

[Objective] Marine red beds are distributed across various stages in geological history, are often interpreted as products of special environments, and have attracted widespread attention. The Sowa Formation in the Jurassic Qiangtang Basin is a set of sedimentary rocks composed of clastic and carbonate mixed sediments. In the Sowa Formation exposed in Bilocuo, Shuanghu county, Tibet, the red beds are mainly composed of carbonate sediments. [Methods] This study explored the causes of th red color and significance in the deposition and diagenesis of the red beds based on sedimentological, mineralogical, and geochemical methods. [Results] Field sedimentology and downhole thin section identification of these red beds revealed that the rocks are composed of grain-supported limestone, with abundant debris from cephalopods, echinoderms, bivalves, bryozoans, gastropods, and other benthic organisms. Biogenic debris and terrestrial quartz debris are the main components of the ooids, which display characteristics of a high-energy beach environment. Spectroscopic studies and scanning electron microscopy indicate that the main cause of the red color is submicron- to micron-sized pseudo-hexagonal and tetragonal hematite crystals. The coloration minerals are concentrated in the ooid cortex structure, and the cementing material is virtually devoid of coloration minerals. This suggests that during early diagenesis, particularly during the formation of ooids and peloids, iron-loving microorganisms played an important role in capturing iron oxides. Furthermore, the geochemical analysis of carbonate minerals shows that the redness is positively correlated with the flux of terrestrial debris input. Additionally, it exhibits a positive Ce/Ce* anomaly (1.1-1.3) and a pattern of enriched-middle rare earth elements "bulge", indicating that the iron oxides underwent reductive dissolution.[Conclusions] Based on these findings, the study reconstructed the red coloration process of these red beds. The input of terrestrial iron-bearing minerals provided the material basis for the red coloration, and then, during early diagenesis, reductive fluids dissolved the iron-bearing minerals, providing free iron ions for iron-loving microorganisms, allowing them to recrystallize and ultimately form hydroxyl iron and cause red coloration through chemical or biological processes. [ABSTRACT FROM AUTHOR]