Portable Electrical Impedance Tomography Research Articles

Development and Validation of a Portable EIT System for Real-Time Respiratory Monitoring.

This work contributes to the improvement of novel medical technologies for the prevention and treatment of diseases. Electrical impedance tomography (EIT) has gained attention as a valuable tool for non-invasive monitoring providing real-time insights. The purpose of this work is to develop and validate a novel portable EIT system with a small form factor for respiratory monitoring. The device uses a 16-electrode architecture with adjacent stimulation and measurement patterns, an integrated circuit current source and a single high-speed ADC operating with multiplexers to stimulate and measure across all electrodes. Tests were conducted on 25 healthy subjects who performed a pulmonary function test with a flowmeter while using the EIT device. The results showed a good performance of the device, which was able to recognize all respirations correctly, and from the EIT signals and images, correlations of 96.7% were obtained for instantaneous respiratory rate and 96.1% for tidal volume prediction. These results validate the preliminary technical feasibility of the EIT system and demonstrates its potential as a reliable tool for non-invasive respiratory assessment. The significance of this work lies in its potential to democratize advanced respiratory monitoring technologies, making them accessible to a wider population, including those in remote or underserved areas.

A Blockchain-Based Secure Sharing Scheme for Electrical Impedance Tomography Data

Real-time electrical impedance tomography (EIT) data sharing is becoming increasingly necessary, due to the extensive use of EIT technology in various sectors, including material analysis, biomedicine, and industrial process monitoring. The prevalence of portable EIT equipment and remote imaging technology has led to a predominance of centralized storage, Internet protocol transmission, and certificates from certificate authorities (CA) in telemedicine data. This has resulted in compromised data security, network communication delays, high CA maintenance costs, increased risks of medical data privacy breaches, and low security. Therefore, this paper offers a consortia blockchain-based method for exchanging EIT data that addresses security and integrity concerns during data storage and exchange, while maintaining transparency and traceability. Proprietary re-encryption techniques are employed to guarantee traceability when exchanging anonymous data, enabling precise control over data access. This scheme serves to protect both data and identity privacy, as well as to trace the actual identity of potential malicious users, while also thwarting any coordinated efforts between partially trusted parties and data requesters seeking unauthorized access to confidential information. Additionally, a combination of blockchain and InterPlanetary File System (IPFS) distributed storage technology is utilized to ease the burden of EIT data storage. The feasibility and effectiveness of the proposed solution were validated through a series of experiments, demonstrating its ability to effectively prevent data tampering and misuse, reduce data management costs, and enhance the efficiency and quality of data sharing.

Portable electrical impedance tomography (EIT) system stages non-alcoholic fatty liver disease for potential screening and monitoring at home.

This study demonstrates the feasibility of predicting NAFLD using multi-spectral electrical impedance tomography (EIT), group source separation, constant reference EIT and anthropometric measures. Vibration-controlled Transient Elastography (VCTE) Controlled Attenuated Parameter (CAP; n = 121) and magnetic resonance imaging-proton density fat fraction (MRI-PDFF; n = 34) achieved a sensitivity of 70.9% and specificity of 73.8% with our CAP predicting model and sensitivity of 77.8% and specificity of 80.0% with our MRI-PDFF predicting model. In summary, a portable EIT can be a cost-effective and self-administrable alternative for widespread home-based and community-based diagnostic screening and treatment monitoring of NAFLD.Clinical Relevance- Portable multi-spectral EIT system has the sensitivity and specificity to potentially unlock biomedical imaging in telemedicine for home-based and community-based screening, staging and monitoring for NAFLD.

CLOSE-TO-EFFORTLESS BREATHING PARADIGM MAPS GLOBAL AND REGIONAL LUNG FUNCTION USING ELECTRICAL IMPEDANCE TOMOGRAPHY CROSS SECTIONALLY AND LONGITUDINALLY

CLOSE-TO-EFFORTLESS BREATHING PARADIGM MAPS GLOBAL AND REGIONAL LUNG FUNCTION USING ELECTRICAL IMPEDANCE TOMOGRAPHY CROSS SECTIONALLY AND LONGITUDINALLY

A new portable electrical impedance tomography system for measuring two-dimensional stem water content distribution

Stem water content (StWC) is an important parameter for characterizing plant–water relations. Most sensors and methods can measure only one-dimensional StWC, and those measuring two-dimensional (2D) StWC distributions are expensive. In this study, we developed a low-cost and portable electrical impedance tomography (EIT) system to measure 2D StWC distributions in vivo. The performance of the EIT system was tested in a laboratory setting. An analog stem made of gypsum and two true stems cut from apple trees were used to calibrate the relationship between the average StWC (θv¯) and average change in electrical conductivity (Δσ¯) determined by the EIT system during the stepwise drying procedure. Evaporation experiments were conducted in the laboratory with hollow analog and cut stems to detect variations in StWC (Δθv) and its 2D distribution. Finally, the EIT system was installed in an apple tree for the in vivo monitoring of the diurnal variation of the 2D StWC distribution. The results indicated that the optimal measurement frequency of the EIT system was 47 kHz. After correcting for the effect of temperature, the average relative error of the measurement was reduced (approximately 80.21%). The effective height of the volume sensitivity of the EIT system was approximately 6 cm. The relationship between θv¯ and Δσ¯ showed a strong positive correlation, with all R2 values higher than 0.9808 for the analog stem and two cut stems. Moreover, the actual and EIT-estimatedθv¯ of the analog and cut stems during the evaporation experiments agreed well (R2 = 0.9367 and 0.9610, respectively), which validated the feasibility of the EIT system for StWC measurements. Furthermore, the in vivo EIT-estimated Δθv distribution of the apple tree was highly consistent with the regulation of diurnal variation in StWC in a greenhouse under irrigation and drought stress conditions. The new portable EIT system was able to measure the 2D StWC distribution and has great potential for application in drought monitoring of plant in the near future.

MO380: Bio-Conductivity Measurement for Electrical Impedance Tomography (EIT) in Chronic Kidney Disease—A Non-Invasive and Portable Monitoring Approach

Abstract BACKGROUND AND AIMS Chronic kidney disease (CKD) is an escalating global health concern, and non-invasive means for early CKD detection is eagerly awaited. Kidneys are water- and electrolytes-rich organs with good bio-conductivity. Kidney fibrosis and tubular atrophy are characteristic pathological changes in CKD [1], and is associated with restricted blood perfusion, fluid diffusion [2,3] and hence reduced bio-conductivity. Electrical impedance tomography (EIT) emerges as a non-invasive, ionizing radiation-free imaging technique measuring dielectric properties of the body parts [4]. This study investigated the relationship of EIT indices and renal function in patients with various stages of CKD. METHOD We prospectively recruited 98 patients with different stages of CKD (Stage 1, n = 16; Stage 2, n = 15; Stage 3, n = 20, Stage 4, n = 36 and Stage 5, n = 11). EIT measurements were performed at two frequencies (33.6 and 100 kHz) using a portable EIT device with an electrode belt consisting of 16 gel electrodes. EIT data was pre-processed and reconstructed as mean conductivity maps. Frequency differencing was then performed between conductivity maps at two frequencies. Kidney-related dielectric parameters were extracted around the kidney region located at lower one-third of the frequency differencing conductivity map. Conductivity changes between frequencies were then computed and further regressed with individual biometrics. Predicted eGFR values was then computed and compared with the standard eGFR scores to evaluate its effectiveness on classifying CDK stages. RESULTS The detected mean bio-conductivity changes were −3.9, −67.5, −133.5, −212.6 and −294.7 (a.u.) in patients with CKD Stage 1, 2, 3, 4 and 5, respectively (Fig. 1A). Patients with more advanced stages of CKD tend to show more reduction in bio-conductivity, and eGFR correlated positively with reduction in bio-conductivity (R2 = 0.37, P < 0.001) (Fig. 1B). EIT-predicted eGFR (eGFREIT) was further computed by the captured conductivity changes and individual biometrics (Fig. 2). eGFREIT showed significant correlation with eGFR measured by blood tests (R2 = 0.54, P < 0.001). CONCLUSION EIT showed good correlation with renal function changes in CKD patients, and thus holds promise to be developed into a non-invasive and portable device for early CKD detection in both clinical and community settings.

Respiration monitoring in PACU using ventilation and gas exchange parameters

The importance of perioperative respiration monitoring is highlighted by high incidences of postoperative respiratory complications unrelated to the original disease. The objectives of this pilot study were to (1) simultaneously acquire respiration rate (RR), tidal volume (TV), minute ventilation (MV), SpO2 and PetCO2 from patients in post-anesthesia care unit (PACU) and (2) identify a practical continuous respiration monitoring method by analyzing the acquired data in terms of their ability and reliability in assessing a patient’s respiratory status. Thirteen non-intubated patients completed this observational study. A portable electrical impedance tomography (EIT) device was used to acquire RREIT, TV and MV, while PetCO2, RRCap and SpO2 were measured by a Capnostream35. Hypoventilation and respiratory events, e.g., apnea and hypopnea, could be detected reliably using RREIT, TV and MV. PetCO2 and SpO2 provided the gas exchange information, but were unable to detect hypoventilation in a timely fashion. Although SpO2 was stable, the sidestream capnography using the oronasal cannula was often unstable and produced fluctuating PetCO2 values. The coefficient of determination (R2) value between RREIT and RRCap was 0.65 with a percentage error of 52.5%. Based on our results, we identified RR, TV, MV and SpO2 as a set of respiratory parameters for robust continuous respiration monitoring of non-intubated patients. Such a respiration monitor with both ventilation and gas exchange parameters would be reliable and could be useful not only for respiration monitoring, but in making PACU discharge decisions and adjusting opioid dosage on general hospital floor. Future studies are needed to evaluate the potential clinical utility of such an integrated respiration monitor.

Dry Wearable Textile Electrodes for Portable Electrical Impedance Tomography.

Electrical impedance tomography (EIT), a noninvasive and radiation-free medical imaging technique, has been used for continuous real-time regional lung aeration. However, adhesive electrodes could cause discomfort and increase the risk of skin injury during prolonged measurement. Additionally, the conductive gel between the electrodes and skin could evaporate in long-term usage and deteriorate the signal quality. To address these issues, in this work, textile electrodes integrated with a clothing belt are proposed to achieve EIT lung imaging along with a custom portable EIT system. The simulation and experimental results have verified the validity of the proposed portable EIT system. Furthermore, the imaging results of using the proposed textile electrodes were compared with commercial electrocardiogram electrodes to evaluate their performance.

Development of a Portable Electrical Impedance Tomography Device for Online Thrombus Detection in Extracorporeal-Circulation Equipment

A portable Electrical Impedance Tomography (EIT) device has been developed for online thrombus detection in extracorporeal-circulation equipment. For the portable EIT device, circuits of multiplexer module are designed to expend channels, pipeline processing mechanism is introduced to increase processing speed, and data acquisition rate reaches 50 Frames Per Second (FPS) and the online tomography rate reaches 40 FPS with 8-electrode sensor. To test the characteristics of the proposed EIT device, a series of experiments are conducted. Firstly, small sensors with different size and plastic phantoms are used to test the static properties of the device. Testing results show that the quality of the reconstructed images is related to the diameter of sensor, and Image Correlation (IC) reaches 0.75 when diameter of sensor is 30 mm. Secondly, swine blood is used for making thrombus to verify the EIT device's image reconstruction ability of thrombus in stationary conditions instead of human blood. Experiments show that the reconstructed image error is 8.07% when diameter of the sensor is 10 mm, and it reduces to 1.49% when diameter is 30 mm. Finally, experiments are conducted to measure the position of flowing thrombus. Euclidean distance between voltage data is used to judge the occurrence of thrombus. Experimental results indicate that thrombus is clearly distinguished from the background solution in fluids. As a conclusion, the proposed EIT device is of great significance for online thrombus detection in extracorporeal-circulation system.

An Optimal Electrical Impedance Tomography Drive Pattern for Human-Computer Interaction Applications.

In this article, we presented an optimal Electrical Impedance Tomography (EIT) drive pattern based on feature selection and model explanation, and proposed a portable EIT system for applications in human-computer interaction for gesture recognition and contact detection, which can reduce the measurement time and realize a performance trade-off between the accuracy and the time response. In our experiment, eleven hand gestures were designed to verify the proposed approach and EIT system. Compared to the traditional eight-electrode method, the optimal electrode drive pattern achieved a recognition accuracy of 97.5% with seven electrodes and the measurement time was reduced by 60%. To illustrate the universality of this method, we performed a contact detection experiment. By setting seven labels on the conductive panel and using optimal electrode drive pattern, the detection accuracy reached 100% with seven electrodes and the measurement time was reduced by 85%.

Design of low-cost and high-speed portable two-dimensional electrical impedance tomography (EIT)

Electrical Impedance Tomography (EIT) is a non-invasive of biomedical imaging technique that used constant electric current as a signal modality. The main proposed study was to design two-dimensional EIT system that could support high speed for detection of anomalies inside the practical phantom and has a low cost in fabrication. High-speed portable two-dimensional EIT has been successfully designed and fabricated to generate a reconstructed image from data acquisition in the practical phantom with 16 electrodes. The manufactured EIT equipped with a 7-inch screen as monitoring display, Raspberry Pi 3 Model B and Arduino Uno as controlling and processing units. The system was also used Gauss-newton method for image reconstruction that using Phyton programming which embedded into Raspberry Pi 3 Model B. The results showed that the portable EIT system produced a high-speed data acquisition and image reconstruction with a process is less than 7 seconds. The manufactured EIT revealed that the system had a potential application for medical imaging.  Â

Development of a Portable Electrical Impedance Tomography System for Biomedical Applications

A portable electrical impedance tomography (EIT) system has been developed with Red Pitaya STEMlab for biomedical applications. The Red Pitaya STEMlab is a portable device to realize voltage generation and data acquisition for the EIT system. The EIT system includes a modified howland circuit as a voltage-controlled current source, a high-speed analogy multiplexer module, an 8-electrode array, and a personal computer. The generalized vector sampled pattern matching algorithm and the Tikhonov regularization algorithm are used to reconstruct the image generated by the EIT system. The reconstructed images by using Red Pitaya STEMlab are compared with a commercial impedance analyzer IM3570 within the frequencies of $f = 100$ KHz. The results show that the maximum difference of the image correlation between Red Pitaya STEMlab and IM3570 is 5.36%. Finally, the EIT system is used to image the conductivity of eggs during heating process. These results verified that the developed portable EIT system with Red Pitaya STEMlab could measure the biological tissue in a high accuracy at low cost.

Non-Invasive Electrical Impedance Tomography for Multi-Scale Detection of Liver Fat Content.

Introduction: Obesity is associated with an increased risk of nonalcoholic fatty liver disease (NAFLD). While Magnetic Resonance Imaging (MRI) is a non-invasive gold standard to detect fatty liver, we demonstrate a low-cost and portable electrical impedance tomography (EIT) approach with circumferential abdominal electrodes for liver conductivity measurements.Methods and Results: A finite element model (FEM) was established to simulate decremental liver conductivity in response to incremental liver lipid content. To validate the FEM simulation, we performed EIT imaging on an ex vivo porcine liver in a non-conductive tank with 32 circumferentially-embedded electrodes, demonstrating a high-resolution output given a priori information on location and geometry. To further examine EIT capacity in fatty liver detection, we performed EIT measurements in age- and gender-matched New Zealand White rabbits (3 on normal, 3 on high-fat diets). Liver conductivity values were significantly distinct following the high-fat diet (p = 0.003 vs. normal diet, n=3), accompanied by histopathological evidence of hepatic fat accumulation. We further assessed EIT imaging in human subjects with MRI quantification for fat volume fraction based on Dixon procedures, demonstrating average liver conductivity of 0.331 S/m for subjects with low Body-Mass Index (BMI < 25 kg/m²) and 0.286 S/m for high BMI (> 25 kg/m²).Conclusion: We provide both the theoretical and experimental framework for a multi-scale EIT strategy to detect liver lipid content. Our preliminary studies pave the way to enhance the spatial resolution of EIT as a marker for fatty liver disease and metabolic syndrome.

A Fidelity-Embedded Regularization Method for Robust Electrical Impedance Tomography.

Electrical impedance tomography (EIT) provides functional images of an electrical conductivity distribution inside the human body. Since the 1980s, many potential clinical applications have arisen using inexpensive portable EIT devices. EIT acquires multiple trans-impedance measurements across the body from an array of surface electrodes around a chosen imaging slice. The conductivity image reconstruction from the measured data is a fundamentally ill-posed inverse problem notoriously vulnerable to measurement noise and artifacts. Most available methods invert the ill-conditioned sensitivity or the Jacobian matrix using a regularized least-squares data-fitting technique. Their performances rely on the regularization parameter, which controls the trade-off between fidelity and robustness. For clinical applications of EIT, it would be desirable to develop a method achieving consistent performance over various uncertain data, regardless of the choice of the regularization parameter. Based on the analysis of the structure of the Jacobian matrix, we propose a fidelity-embedded regularization (FER) method and a motion artifact reduction filter. Incorporating the Jacobian matrix in the regularization process, the new FER method with the motion artifact reduction filter offers stable reconstructions of high-fidelity images from noisy data by taking a very large regularization parameter value. The proposed method showed practical merits in experimental studies of chest EIT imaging.

Parametric EIT for monitoring cardiac stroke volume

The bio-impedance technique appears appropriate for non-invasive cardiac stroke volume (SV) measurement, as the thoracic conductivity distribution is altered during the cardiac cycle due to the heart contraction and blood perfusion. In the present work, the feasibility of a parametric electrical impedance tomography (EIT) for assessing the cardiac SV was studied. An impedance model of the thorax was constructed from segmented axial MRI images along 19 phases of the cardiac cycle. The heart was simulated as an ellipsoid, with its axes' lengths set as the reconstruction parameters, while all other tissues' geometry and conductivity values were kept fixed. A Newton–Raphson parametric optimization scheme was utilized, yielding a correlation between the reconstructed and anatomical left ventricular volumes of 0.97 (p = 2 × 10−11). An analysis of noise sensitivity showed that the proposed algorithm requires an SNR greater than 65 dB. The simulation results were compared to physical data, collected with a portable EIT system (PulmoTrace™, CardioInspect). The validation study was employed for a group of N = 28 healthy patients, and a comparison with impedance cardiography measurements (BioZ®, Cardiodynamics) was made, showing a correlation of r = 0.86 (p = 4 ×10−9). The preliminary results demonstrate that parametric EIT has the potential to measure SV, and may be applicable for both clinical and home environment usage.

Design and performance of the UCLH Mark 1b 64 channel electrical impedance tomography (EIT) system, optimized for imaging brain function

The UCLH Mark 1b is a portable EIT system that can address up to 64 electrodes, which has been designed for imaging brain function with scalp electrodes. It employs a single impedance-measuring circuit and multiplexer so that electrode combinations may be addressed flexibly using software. It operates in the relatively low frequency band between 225 Hz and 77 kHz, as lower frequencies produce larger changes during brain activity, and has a videocassette-sized headbox on a lead 10 m long, connected to a base box the size of a video recorder, and notebook PC, so that recordings may be made in ambulant subjects.Its performance was assessed using a resistor–capacitor network, and two saline-filled tanks—a cylindrical Perspex one and a latex one which contained a human skull. System signal-to-noise ratio was better than 50 dB and the maximum reciprocity error less than 10% for most frequencies. The CMMR was better than 80 dB at 38 kHz and a sponge, 20 mm across, which caused a local 12% impedance increase, was correctly localized in images. This suggests that the system has adequate performance to image impedance changes of 5–50% known to occur in the brain during normal activity, epilepsy or stroke; clinical trials to image these conditions are in progress.