A Coupled Double-Layer Electrical Impedance Tomography-Based Sensing Skin for Pressure and Leak Detection.

There is an extensive need for surface sensors for applications such as tactile sensing for robotics, damage and strain detection for structural health monitoring and leak detection for buried structures. One type of surface sensor is electrical impedance tomography (EIT)-based sensing skins, which use electrically conductive coatings applied on the object's surface to monitor physical or chemical phenomena on the surface. In this article, we propose a sensing skin with two electrically coupled layers separated by an insulator. Based on electrical measurements, the spatial distribution of the electrical coupling between the layers is estimated. This coupling is sensitive to both the pressure distribution on the surface and water entering between the layers through a leak. We present simulations and experimental studies to evaluate the feasibility of the proposed method for pressure sensing and leak detection. The results support the feasibility of the proposed method for both of these applications.

A 3 MHz Low-Error Adaptive Howland Current Source for High-Frequency Bioimpedance Applications.

Bioimpedance is a diagnostic sensing method used in medical applications, ranging from body composition assessment to detecting skin cancer. Commonly, discrete-component (and at times integrated) circuit variants of the Howland Current Source (HCS) topology are employed for injection of an AC current. Ideally, its amplitude should remain within 1% of its nominal value across a frequency range, and that nominal value should be programmable. However, the method's applicability and accuracy are hindered due to the current amplitude diminishing at frequencies above 100 kHz, with very few designs accomplishing 1 MHz, and only at a single nominal amplitude. This paper presents the design and implementation of an adaptive current source for bioimpedance applications employing automatic gain control (AGC). The "Adaptive Howland Current Source" (AHCS) was experimentally tested, and the results indicate that the design can achieve less than 1% amplitude error for both 1 mA and 100 µA currents for bandwidths up to 3 MHz. Simulations also indicate that the system can be designed to achieve up to 19% noise reduction relative to the most common HCS design. AHCS addresses the need for high bandwidth AC current sources in bioimpedance spectroscopy, offering automatic output current compensation without constant recalibration. The novel structure of AHCS proves crucial in applications requiring higher ß-dispersion frequencies exceeding 1 MHz, where greater penetration depths and better cell status assessment can be achieved, e.g., in the detection of skin or breast cancer.

The Diagnostic Accuracy of Electrical Impedance Spectroscopy-Assisted Colposcopy, HPV mRNA Test, and P16/Ki67 Immunostaining as CIN2+ Predictors in Greek Population.

OBJECTIVE: To evaluate the diagnostic accuracy of Electrical Impedance Spectroscopy (EIS)-assisted colposcopy in detecting CIN2+ Greek women towards standalone colposcopy, HPV mRNA testing, and p16/Ki67 immunostaining. METHODS: We conducted a cross-sectional observational study at the Cervical Pathology Clinic of the 2nd Obstetrics-Gynecology University Department of Hippokration Hospital Thessaloniki involving 316 patients from January 2022 to August 2023. All participants provided liquid-based cervical samples for cytology, HPV mRNA testing, and p16/Ki67 immunostaining. MAIN OUTCOME MEASURES: Subsequently, participants underwent both standalone colposcopy and EIS/ZedScan-assisted colposcopy, followed by cervical punch biopsies. RESULTS: The incorporation of EIS significantly enhanced the sensitivity of colposcopy, increasing it from 54.17% to 100%, equivalent to that of HPV mRNA testing and p16/Ki67 immunostaining, while achieving a high specificity (95.45%). The specificities observed with EIS/ZedScan-assisted and standalone colposcopy were notably superior to those of HPV-related biomarkers (HPV mRNA test and p16/Ki67 immunostaining). When compared to standalone colposcopy, HPV mRNA testing, and p16/Ki67 immunostaining, EIS/ZedScan-assisted colposcopy demonstrated the most favorable combination of Positive and Negative Predictive Values, at 90.57% and 100%, respectively. The inclusion of EIS/ZedScan in colposcopy led to the detection of 44 additional cases of true CIN2+ (100% of the total CIN2+ confirmed histologically) that were missed by standalone colposcopy. This discovery suggests a 45.83% increase in the detection of CIN2+ cases. CONCLUSIONS: The integration of EIS with colposcopy has demonstrated effectiveness in detecting cervical lesions, resulting in a significant detection increase of CIN2+ cases while offering optimal levels of sensitivity, specificity, and predictive values for CIN2+ detection.

Detection of invasive ductal carcinoma in quadrant breast areas by electrical impedance tomography implemented with gaussian relaxation-time distribution (EIT-GRTD).

Invasive ductal carcinoma (IDC) in breast specimens has been detected in the quadrant breast area: (I) upper outer, (II) upper inner, (III) lower inner, and (IV) lower outer areas by electrical impedance tomography implemented with Gaussian relaxation-time distribution (EIT-GRTD). The EIT-GRTD consists of two steps which are (1) the optimum frequencyfoptselection and (2) the time constant enhancement of breast imaging reconstruction.foptis characterized by a peak in the majority measurement pair of the relaxation-time distribution functionγ,which indicates the presence of IDC.γrepresents the inverse of conductivity and indicates the response of breast tissues to electrical currents across varying frequencies based on the Voigt circuit model. The EIT-GRTD is quantitatively evaluated by multi-physics simulations using a hemisphere container of mimic breast, consisting of IDC and adipose tissues as normal breast tissue under one condition with known IDC in quadrant breast area II. The simulation results show that EIT-GRTD is able to detect the IDC in four layers atfopt= 30, 170 Hz. EIT-GRTD is applied in the real breast by employed six mastectomy specimens from IDC patients. The placement of the mastectomy specimens in a hemisphere container is an important factor in the success of quadrant breast area reconstruction. In order to perform the evaluation, EIT-GRTD reconstruction images are compared to the CT scan images. The experimental results demonstrate that EIS-GRTD exhibits proficiency in the detection of the IDC in quadrant breast areas while compared qualitatively to CT scan images.

Seeing Through Muddy Water: Laser-Induced Graphene for Portable Tomography Imaging.

Due to its outstanding physical and chemical properties, graphene synthesized by laser scribing on polyimide (PI) offers excellent opportunities for photothermal applications, antiviral and antibacterial surfaces, and electrochemical storage and sensing. However, the utilization of such graphene for imaging is yet to be explored. Herein, using chemically durable and electrically conductive laser-induced graphene (LIG) for tomography imaging in aqueous suspensions is proposed. These graphene electrodes are designed as impedance imaging units for four-terminal electrical measurements. Using the real-time portable imaging prototypes, the conductive and dielectric objects can be seen in clear and muddy water with equivalent impedance modeling. This low-cost graphene tomography measurement system offers significant advantages over traditional visual cameras, in which the suspended muddy particles hinder the imaging resolution. This research shows the potential of applying graphene nanomaterials in emerging marine technologies, such as underwater robotics and automatic fisheries.

Absolute values of regional ventilation-perfusion mismatch in patients with ARDS monitored by electrical impedance tomography and the role of dead space and shunt compensation.

BACKGROUND: Assessment of regional ventilation/perfusion (V'/Q) mismatch using electrical impedance tomography (EIT) represents a promising advancement for personalized management of the acute respiratory distress syndrome (ARDS). However, accuracy is still hindered by the need for invasive monitoring to calibrate ventilation and perfusion. Here, we propose a non-invasive correction that uses only EIT data and characterized patients with more pronounced compensation of V'/Q mismatch. METHODS: We enrolled twenty-one ARDS patients on controlled mechanical ventilation. Cardiac output was measured invasively, and ventilation and perfusion were assessed by EIT. Relative V'/Q maps by EIT were calibrated to absolute values using the minute ventilation to invasive cardiac output (MV/CO) ratio (V'/Q-ABS), left unadjusted (V'/Q-REL), or corrected by MV/CO ratio derived from EIT data (V'/Q-CORR). The ratio between ventilation to dependent regions and perfusion reaching shunted units ( V D ' /QSHUNT) was calculated as an index of more effective hypoxic pulmonary vasoconstriction. The ratio between perfusion to non-dependent regions and ventilation to dead space units (QND/ V DS ' ) was calculated as an index of hypocapnic pneumoconstriction. RESULTS: Our calibration factor correlated with invasive MV/CO (r = 0.65, p < 0.001), showed good accuracy and no apparent bias. Compared to V'/Q-ABS, V'/Q-REL maps overestimated ventilation (p = 0.013) and perfusion (p = 0.002) to low V'/Q units and underestimated ventilation (p = 0.011) and perfusion (p = 0.008) to high V'/Q units. The heterogeneity of ventilation and perfusion reaching different V'/Q compartments was underestimated. V'/Q-CORR maps eliminated all these differences with V'/Q-ABS (p > 0.05). Higher V D ' / Q SHUNT correlated with higher PaO2/FiO2 (r = 0.49, p = 0.025) and lower shunt fraction (ρ = - 0.59, p = 0.005). Higher Q ND / V DS ' correlated with lower PEEP (ρ = - 0.62, p = 0.003) and plateau pressure (ρ = - 0.59, p = 0.005). Lower values of both indexes were associated with less ventilator-free days (p = 0.05 and p = 0.03, respectively). CONCLUSIONS: Regional V'/Q maps calibrated with a non-invasive EIT-only method closely approximate the ones obtained with invasive monitoring. Higher efficiency of shunt compensation improves oxygenation while compensation of dead space is less needed at lower airway pressure. Patients with more effective compensation mechanisms could have better outcomes.

All-MXene electronic tongue for neurotransmitters detection.

Neurotransmitters (NTs) are molecules produced by neurons that act as the body's chemical messengers. Their abnormal levels in the human system have been associated with many disorders and neurodegenerative diseases, which makes the monitoring of NTs fundamentally important. Specifically for clinical analysis and understanding of brain behavior, simultaneous detection of NTs at low levels quickly and reliably is imperative for disease prevention and early diagnosis. However, the methods currently employed are usually invasive or inappropriate for multiple NTs detection. Herein, we developed a MXene-based impedimetric electronic tongue (e-tongue) for sensitive NT monitoring, using Nb2C, Nb4C3, Mo2C, and Mo2Ti2C3 MXenes as sensing units of the e-tongue, and Principal Component Analysis (PCA) as the data treatment method. The high specific surface area, distinct electrical properties, and chemical stability of the MXenes gave rise to high sensitivity and good reproducibility of the sensor array toward NT detection. Specifically, the e-tongue detected and differentiated multiple NTs (acetylcholine, dopamine, glycine, glutamate, histamine, and tyrosine) at concentrations as low as 1 nmol L-1 and quantified NTs present in a mixture. Besides, analyses performed with interferents and actual samples confirmed the system's potential to be used in clinical diagnostics. The results demonstrate that the MXene-based e-tongue is a suitable, rapid, and simple method for NT monitoring with high accuracy and sensitivity.

First real-time imaging of bronchoscopic lung volume reduction by electrical impedance tomography.

BACKGROUND: Bronchoscopic lung volume reduction (BLVR) with one-way endobronchial valves (EBV) has better outcomes when the target lobe has poor collateral ventilation, resulting in complete lobe atelectasis. High-inspired oxygen fraction (FIO2) promotes atelectasis through faster gas absorption after airway occlusion, but its application during BLVR with EBV has been poorly understood. We aimed to investigate the real-time effects of FIO2 on regional lung volumes and regional ventilation/perfusion by electrical impedance tomography (EIT) during BLVR with EBV. METHODS: Six piglets were submitted to left lower lobe occlusion by a balloon-catheter and EBV valves with FIO2 0.5 and 1.0. Regional end-expiratory lung impedances (EELI) and regional ventilation/perfusion were monitored. Local pocket pressure measurements were obtained (balloon occlusion method). One animal underwent simultaneous acquisitions of computed tomography (CT) and EIT. Regions-of-interest (ROIs) were right and left hemithoraces. RESULTS: Following balloon occlusion, a steep decrease in left ROI-EELI with FIO2 1.0 occurred, 3-fold greater than with 0.5 (p < 0.001). Higher FIO2 also enhanced the final volume reduction (ROI-EELI) achieved by each valve (p < 0.01). CT analysis confirmed the denser atelectasis and greater volume reduction achieved by higher FIO2 (1.0) during balloon occlusion or during valve placement. CT and pocket pressure data agreed well with EIT findings, indicating greater strain redistribution with higher FIO2. CONCLUSIONS: EIT demonstrated in real-time a faster and more complete volume reduction in the occluded lung regions under high FIO2 (1.0), as compared to 0.5. Immediate changes in the ventilation and perfusion of ipsilateral non-target lung regions were also detected, providing better estimates of the full impact of each valve in place. TRIAL REGISTRATION: Not applicable.

The study of the influence of the geometry of a lateral electric field resonator on its resonant characteristics.

An experimental study of the dependence of the electrical impedance of a lateral electric field resonator on its thickness and the size of the gap between the electrodes was carried out. The resonator was made of PZT-19 piezoceramics in the form of a rectangular parallelepiped with the shear dimensions of 18 × 20 mm2. Two rectangular electrodes with a gap that varied in the range from 4 to 14 mm were applied on one side of the resonator. For each gap width, the frequency dependences of the real and imaginary parts of the electrical impedance were measured using an impedance analyzer. It has been found that increasing the gap width leads to an increase in the resonant frequency and to an increase in the maximum value of the real part of the impedance. Three series of such experiments were carried out for three values of the resonator thickness: 3.02, 2.38 and 1.9 mm. The resonant characteristics of the resonator were also theoretically analyzed by finite element analysis using two models. One resonator model was based on a two-dimensional finite element method. In this case, the vibration modes that existed due to the finite size of the plate in the direction parallel to the gap between the electrodes were not taken into account. The second model of the resonator used a three-dimensional finite element method, which correctly took into account all vibration modes existing in the resonator. Comparison of theory with experiment has shown that the three-dimensional model provides a better agreement between theoretical and experimental results.

A Narrative Review on the Clinical Utility of Electrical Impedance Spectroscopy for Diagnosing High-Grade Cervical Intraepithelial Neoplasia.

Colposcopy constitutes a pivotal step in the diagnosis and management of cervical intraepithelial neoplasia; nevertheless, the method has several inherent and external limitations. Electrical impedance spectroscopic (EIS) has been among the adjuncts that have been developed to increase the diagnostic accuracy of colposcopy. EIS is based on the principle that the trajectory of electrical current alters depending on the consistency of the tissues. In the present study, we investigate the diagnostic accuracy and clinical utility of EIS by means of searching the available evidence. Our search yielded 17 articles during the period 2005-2023. Subsequently, we focused on the performance metrics of the included studies. The general concept is that EIS, in combination with colposcopy, is a method with increased sensitivity and specificity in detecting high-grade cervical intraepithelial neoplasia as compared to colposcopy alone. However, we documented a heterogeneous distribution of these and other metrics, including the positive predictive value, the negative predictive value, and the area under the receiver operating characteristic curve (AUC). Additionally, we located potential confounders that might hamper the measurements of EIS and, as such, warrant further investigation in future research. We conclude that future studies should be directed towards randomized multicentric trials, whereas the advent of artificial intelligence might improve the diagnostic accuracy of the method by helping incorporate a large amount of data.

Impact of extended lung protection during mechanical ventilation on lung recovery in patients with COVID-19 ARDS: a phase II randomized controlled trial.

BACKGROUND: Protective ventilation seems crucial during early Acute Respiratory Distress Syndrome (ARDS), but the optimal duration of lung protection remains undefined. High driving pressures (ΔP) and excessive patient ventilatory drive may hinder lung recovery, resulting in self-inflicted lung injury. The hidden nature of the ΔP generated by patient effort complicates the situation further. Our study aimed to assess the feasibility of an extended lung protection strategy that includes a stepwise protocol to control the patient ventilatory drive, assessing its impact on lung recovery. METHODS: We conducted a single-center randomized study on patients with moderate/severe COVID-19-ARDS with low respiratory system compliance (CRS < 0.6 (mL/Kg)/cmH2O). The intervention group received a ventilation strategy guided by Electrical Impedance Tomography aimed at minimizing ΔP and patient ventilatory drive. The control group received the ARDSNet low-PEEP strategy. The primary outcome was the modified lung injury score (mLIS), a composite measure that integrated daily measurements of CRS, along with oxygen requirements, oxygenation, and X-rays up to day 28. The mLIS score was also hierarchically adjusted for survival and extubation rates. RESULTS: The study ended prematurely after three consecutive months without patient enrollment, attributed to the pandemic subsiding. The intention-to-treat analysis included 76 patients, with 37 randomized to the intervention group. The average mLIS score up to 28 days was not different between groups (P = 0.95, primary outcome). However, the intervention group showed a faster improvement in the mLIS (1.4 vs. 7.2 days to reach 63% of maximum improvement; P < 0.001), driven by oxygenation and sustained improvement of X-ray (P = 0.001). The intervention group demonstrated a sustained increase in CRS up to day 28 (P = 0.009) and also experienced a shorter time from randomization to room-air breathing (P = 0.02). Survival at 28 days and time until liberation from the ventilator were not different between groups. CONCLUSIONS: The implementation of an individualized PEEP strategy alongside extended lung protection appears viable. Promising secondary outcomes suggested a faster lung recovery, endorsing further examination of this strategy in a larger trial. Clinical trial registration This trial was registered with ClinicalTrials.gov (number NCT04497454) on August 04, 2020.

A new label free spiral sensor using impedance spectroscopy to characterize hepatocellular carcinoma in tissue and serum samples.

Hepatocellular carcinoma (HCC) stands as the most prevalent form of primary liver cancer, predominantly affecting patients with chronic liver diseases such as hepatitis B or C-induced cirrhosis. Diagnosis typically involves blood tests (assessing liver functions and HCC biomarkers), imaging procedures such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), and liver biopsies requiring the removal of liver tissue for laboratory analysis. However, these diagnostic methods either entail lengthy lab processes, require expensive imaging equipment, or involve invasive techniques like liver biopsies. Hence, there exists a crucial need for rapid, cost-effective, and noninvasive techniques to characterize HCC, whether in serum or tissue samples. In this study, we developed a spiral sensor implemented on a printed circuit board (PCB) technology that utilizes impedance spectroscopy and applied it to 24 tissues and sera samples as proof of concept. This newly devised circuit has successfully characterized HCC and normal tissue and serum samples. Utilizing the distinct dielectric properties between HCC cells and serum samples versus the normal samples across a specific frequency range, the differentiation between normal and HCC samples is achieved. Moreover, the sensor effectively characterizes two HCC grades and distinguishes cirrhotic/non-cirrhotic samples from tissue specimens. In addition, the sensor distinguishes cirrhotic/non-cirrhotic samples from serum specimens. This pioneering study introduces Electrical Impedance Spectroscopy (EIS) spiral sensor for diagnosing HCC and liver cirrhosis in clinical serum-an innovative, low-cost, rapid (< 2 min), and precise PCB-based technology without elaborate sample preparation, offering a novel non-labeled screening approach for disease staging and liver conditions.

The influence of different spontaneous breathing trials on regional ventilation distribution in patients with prolonged mechanical ventilation.

OBJECTIVE: This study aimed to explore the influence of different spontaneous breathing trials (SBTs) on regional ventilation distribution in patients with prolonged mechanical ventilation (PMV). METHODS: A total of 24 patients with PMV were analyzed retrospectively. They received three different SBT modes which are automatic tube compensation (ATC), continuous positive airway pressure (CPAP), and T-piece (TP), over three days, and every SBT lasted two hours. Electrical impedance tomography (EIT) was used to monitor the SBT process and five-minute EIT data from five periods (pre-SBT which is t0, at the beginning and the end of the first hour SBT are t1 and t2, at the beginning and the end of the second hour SBT are t3 and t4) were analyzed. RESULTS: In all PMV patients, the temporal skew of aeration (TSA) values at t3 were significantly different in three SBTs (ATC: 18.18±22.97; CPAP: 20.42±17.01; TP:11.26±11.79; p=0.05). In the weaning success group, TSA (t1) values were significantly different too (ATC: 11.11±13.88; CPAP: 19.09±15.77; TP: 9.09±12.74; p=0.04). In the weaning failure group, TSA (t4) values were significantly different in three SBTs (ATC: 36.67±18.46; CPAP: 15.38±11.69; TP: 17.65±17.93; p=0.04). The patient's inspiratory effort (Global flow index at t1) in patients with weaning failure under CPAP (3.51±4.31) was significantly higher than that in the ATC (1.15±1.47) and TP (0.89±1.28). The SBT mode with the best ventilation uniformity may be the one that activates the respiratory muscles the most which may be the optimal SBT. The SBT mode of most uniform ventilation distribution settings varies from patient to patient. CONCLUSION: The regional ventilation distribution was different for each individual, making the SBT with the best ventilation distribution of patients need to be personalized. EIT is a tool that can be considered for real-time assessment.

Separation of ventilation and perfusion of electrical impedance tomography image streams using multi-dimensional ensemble empirical mode decomposition.

Objective:In the future, thoracic Electrical Impedance Tomography (EIT) monitoring may include continuous and simultaneous tracking of both breathing and heart activity. However, an effective way to decompose an EIT image stream into physiological processes as a ventilation-related and cardiac-related signal is missing. Approach:This study analyses the potential of Multi-dimensional Ensemble Empirical Mode Decomposition (MEEMD) by application of the Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) and a novel frequency-based combination criterion for de-trending, denoising and source separation of EIT image streams, collected from 9 healthy male test subjects with similar age and constitution. Main results:In this paper, a novel approach to estimate the lung, the heart and the perfused regions of an EIT image is proposed, which is based on the Root Mean Square Error (RMSE) between the index of maximal respiratory and cardiac variation to their surroundings. The summation of the indexes of the respective regions reveals physiologically meaningful time signals, separated into the physiological bandwidths of ventilation and heart activity at rest. Moreover, the respective regions were compared with the relative thorax movement and photoplethysmogram (PPG) signal. In linear regression analysis and in the Bland-Altman plot, the beat-to-beat time course of both the ventilation-related signal and the cardiac-related signal showed a high similarity with the respective reference signal. Significance:Analysis of the data reveals a fair separation of ventilatory and cardiac activity realizing the aimed source separation, with optional de-trending and noise-removal. For all analyses, a feasible correlation of 0.587 to 0.905 was found between the cardiac-related and the PPG signal. .

Evaluating Dielectric Properties for Assessing Water Content at Acupuncture Points: New Methodology.

Importance: Understanding acupuncture point microenvironments is vital for optimizing treatment efficacy. Evaluating changes in water content at these points can provide further insights into the effects of acupuncture on tissues. Objective: This study aimed to measure tissue dielectric constant (TDC) and assess changes in water content, specifically at stomach 36 (ST36, Zusanli) and spleen 6 (SP6, Sanyinjiao) acupuncture points. Methods: In a controlled, blinded, randomized trial, 113 healthy volunteers were divided into six groups based on TDC sensor diameters (XS, M, and L): three control groups and three acupuncture groups. They were assessed at three time points: T1, baseline; T2, 20 min post-needle withdrawal; and T3, 40 min post-needle withdrawal. Electrical impedance (EI) was also analyzed. Significance level was set at p < 0.001. Results: TDC at ST36 and SP6 significantly decreased with the XS probe at T2 and T3 compared with that at T1 (F8, 452: 54.61). TDC did not significantly vary between T2 and T3 with M and L probes. EI data indicated that the current passage increased in the SP (F2, 226: 39.32) and ST (F2, 226: 37.32) groups during T2 and T3 compared with that during T1 within their respective groups and controls. Conclusions: and Relevance: This study demonstrated the efficacy of TDC measurements in detecting water content fluctuations at acupuncture points and their responses to needles. TDC measurements, which were validated against EI, provide valuable insights into acupuncture point microenvironments and thus help optimize treatments.

Occurrence of pendelluft during ventilator weaning with T piece correlated with increased mortality in difficult-to-wean patients.

BACKGROUND: Difficult-to-wean patients, typically identified as those failing the initial spontaneous breathing trial (SBT), face elevated mortality rates. Pendelluft, frequently observed in patients experiencing SBT failure, can be conveniently detected through bedside monitoring with electrical impedance tomography (EIT). This study aimed to explore the impact of pendelluft during SBT on difficult-to-wean patients. METHODS: This retrospective observational study included difficult-to-wean patients undergoing spontaneous T piece breathing, during which EIT data were collected. Pendelluft occurrence was defined when its amplitude exceeded 2.5% of global tidal impedance variation. Physiological parameters during SBT were retrospectively retrieved from the EIT Examination Report Form. Other clinical data including mechanical ventilation duration, length of ICU stay, length of hospital stay, and 28-day mortality were retrieved from patient records in the hospital information system for each subject. RESULTS: Pendelluft was observed in 72 (70.4%) of the 108 included patients, with 16 (14.8%) experiencing mortality by day 28. The pendelluft group exhibited significantly higher mortality (19.7% vs. 3.1%, p = 0.035), longer median mechanical ventilation duration [9 (5-15) vs. 7 (5-11) days, p = 0.041] and shorter ventilator-free days at day 28 [18 (4-22) vs. 20 (16-23) days, p = 0.043]. The presence of pendellfut was independently associated with increased mortality at day 28 (OR = 10.50, 95% confidence interval 1.21-90.99, p = 0.033). CONCLUSIONS: Pendelluft occurred in 70.4% of difficult-to-wean patients undergoing T piece spontaneous breathing. Pendelluft was associated with worse clinical outcomes, including prolonged mechanical ventilation and increased mortality in this population. Our findings underscore the significance of monitoring pendelluft using EIT during SBT for difficult-to-wean patients.

[Research of electrical impedance tomography based on multilayer artificial neural network optimized by Hadamard product for human-chest models].

Electrical impedance tomography (EIT) is a non-radiation, non-invasive visual diagnostic technique. In order to improve the imaging resolution and the removing artifacts capability of the reconstruction algorithms for electrical impedance imaging in human-chest models, the HMANN algorithm was proposed using the Hadamard product to optimize multilayer artificial neural networks (MANN). The reconstructed images of the HMANN algorithm were compared with those of the generalized vector sampled pattern matching (GVSPM) algorithm, truncated singular value decomposition (TSVD) algorithm, backpropagation (BP) neural network algorithm, and traditional MANN algorithm. The simulation results showed that the correlation coefficient of the reconstructed images obtained by the HMANN algorithm was increased by 17.30% in the circular cross-section models compared with the MANN algorithm. It was increased by 13.98% in the lung cross-section models. In the lung cross-section models, some of the correlation coefficients obtained by the HMANN algorithm would decrease. Nevertheless, the HMANN algorithm retained the image information of the MANN algorithm in all models, and the HMANN algorithm had fewer artifacts in the reconstructed images. The distinguishability between the objects and the background was better compared with the traditional MANN algorithm. The algorithm could improve the correlation coefficient of the reconstructed images, and effectively remove the artifacts, which provides a new direction to effectively improve the quality of the reconstructed images for EIT.

Non-Invasive Detection of Early-Stage Fatty Liver Disease via an On-Skin Impedance Sensor and Attention-Based Deep Learning.

Early-stage nonalcoholic fatty liver disease (NAFLD) is a silent condition, with most cases going undiagnosed, potentially progressing to liver cirrhosis and cancer. A non-invasive and cost-effective detection method for early-stage NAFLD detection is a public health priority but challenging. In this study, an adhesive, soft on-skin sensor with low electrode-skin contact impedance for early-stage NAFLD detection is fabricated. A method is developed to synthesize platinum nanoparticles and reduced graphene quantum dots onto the on-skin sensor to reduce electrode-skin contact impedance by increasing double-layer capacitance, thereby enhancing detection accuracy. Furthermore, an attention-based deep learning algorithm is introduced to differentiate impedance signals associated with early-stage NAFLD in high-fat-diet-fed low-density lipoprotein receptor knockout (Ldlr-/-) mice compared to healthy controls. The integration of an adhesive, soft on-skin sensor with low electrode-skin contact impedance and the attention-based deep learning algorithm significantly enhances the detection accuracy for early-stage NAFLD, achieving a rate above 97.5% with an area under the receiver operating characteristic curve (AUC) of 1.0. The findings present a non-invasive approach for early-stage NAFLD detection and display a strategy for improved early detection through on-skin electronics and deep learning.

A preliminary study on the application of electrical impedance tomography based on cerebral perfusion monitoring to intracranial pressure changes.

Background: In intracranial pathologic conditions of intracranial pressure (ICP) disturbance or hemodynamic instability, maintaining appropriate ICP may reduce the risk of ischemic brain injury. The change of ICP is often accompanied by the change of intracranial blood status. As a non-invasive functional imaging technique, the sensitivity of electrical impedance tomography (EIT) to cerebral hemodynamic changes has been preliminarily confirmed. However, no team has conducted a feasibility study on the dynamic detection of ICP by EIT technology from the perspective of non-invasive whole-brain blood perfusion monitoring. In this study, human brain EIT image sequence was obtained by in vivo measurement, from which a variety of indicators that can reflect the tidal changes of the whole brain impedance were extracted, in order to establish a new method for non-invasive monitoring of ICP changes from the level of cerebral blood perfusion monitoring. Methods: Valsalva maneuver (VM) was used to temporarily change the cerebral blood perfusion status of volunteers. The electrical impedance information of the brain during this process was continuously monitored by EIT device and real-time imaging was performed, and the hemodynamic indexes of bilateral middle cerebral arteries were monitored by transcranial Doppler (TCD). The changes in monitoring information obtained by the two techniques were compared and observed. Results: The EIT imaging results indicated that the image sequence showed obvious tidal changes with the heart beating. Perfusion indicators of vascular pulsation obtained from EIT images decreased significantly during the stabilization phase of the intervention (PAC: 242.94 ± 100.83, p < 0.01); perfusion index which reflects vascular resistance increased significantly in the stable stage of intervention (PDT: 79.72 ± 18.23, p < 0.001). After the intervention, the parameters gradually returned to the baseline level before compression. The changes of EIT indexes in the whole process are consistent with the changes of middle cerebral artery velocity related indexes shown in TCD results. Conclusion: The EIT image combined with the blood perfusion index proposed in this paper can reflect the decrease of cerebral blood flow under the condition of increased ICP in real time and intuitively. With the advantages of high time resolution and high sensitivity, EIT provides a new idea for non-invasive bedside measurement of ICP.

Layered Fusion Reconstruction Based on Fuzzy Features for Multi-Conductivity Electrical Impedance Tomography.

In medical imaging, detecting tissue anomalies is vital for accurate diagnosis and effective treatment. Electrical impedance tomography (EIT) is a non-invasive technique that monitors the changes in electrical conductivity within tissues in real time. However, the current challenge lies in simply and accurately reconstructing multi-conductivity distributions. This paper introduces a layered fusion framework for EIT to enhance imaging in multi-conductivity scenarios. The method begins with pre-imaging and extracts the main object from the fuzzy image to form one layer. Then, the voltage difference in the other layer, where the local anomaly is located, is estimated. Finally, the corresponding conductivity distribution is established, and multiple layers are fused to reconstruct the multi-conductivity distribution. The simulation and experimental results demonstrate that compared to traditional methods, the proposed method significantly improves multi-conductivity separation, precise anomaly localization, and robustness without adding uncertain parameters. Notably, the proposed method has demonstrated exceptional accuracy in local anomaly detection, with positional errors as low as 1% and size errors as low as 33%, which significantly outperforms the traditional method with respective minimum errors of 9% and 228%. This method ensures a balance between the simplicity and accuracy of the algorithm. At the same time, it breaks the constraints of traditional linear methods, struggling to identify multi-conductivity distributions, thereby providing new perspectives for clinical EIT.