Capacitance Tomography Research Articles

Adversarial Resolution Enhancement for Electrical Capacitance Tomography Image Reconstruction.

High-quality image reconstruction is essential for many electrical capacitance tomography (CT) applications. Raw capacitance measurements are used in the literature to generate low-resolution images. However, such low-resolution images are not sufficient for proper functionality of most systems. In this paper, we propose a novel adversarial resolution enhancement (ARE-ECT) model to reconstruct high-resolution images of inner distributions based on low-quality initial images, which are generated from the capacitance measurements. The proposed model uses a UNet as the generator of a conditional generative adversarial network (CGAN). The generator’s input is set to the low-resolution image rather than the typical random input signal. Additionally, the CGAN is conditioned by the input low-resolution image itself. For evaluation purposes, a massive ECT dataset of 320 K synthetic image–measurement pairs was created. This dataset is used for training, validating, and testing the proposed model. New flow patterns, which are not exposed to the model during the training phase, are used to evaluate the feasibility and generalization ability of the ARE-ECT model. The superiority of ARE-ECT, in the efficient generation of more accurate ECT images than traditional and other deep learning-based image reconstruction algorithms, is proved by the evaluation results. The ARE-ECT model achieved an average image correlation coefficient of more than and an average relative image error about .

Two High-Precision Proximity Capacitance CMOS Image Sensors with Large Format and High Resolution.

This paper presents newly developed two high-precision CMOS proximity capacitance image sensors: Chip A with 12 μm pitch pixels with a large detection area of 1.68 cm2; Chip B with 2.8 μm pitch 1.8 M pixels for a higher resolution. Both fabricated chips achieved a capacitance detection precision of less than 100 zF (10−19 F) at an input voltage of 20 V and less than 10 zF (10−20 F) at 300 V due to the noise cancelling technique. Furthermore, by using multiple input pulse amplitudes, a capacitance detection dynamic range of up to 123 dB was achieved. The spatial resolution improvement was confirmed by the experimentally obtained modulation transfer function for Chip B with various line and space pattens. The examples of capacitance imaging using the fabricated chips were also demonstrated.

Multi-Parametric Imaging of Etruscan Chamber Tombs: Grotte Di Castro Case Study (Italy)

A multi-parametric approach that involves the use of different geophysical methods coupled with geochemical data allowed us to identify undiscovered archeological burials in a funerary area of the Grotte di Castro Etruscan settlement. In particular, we tested the suitability of the capacitive resistivity method and the presence of Radon in soil for the identification of burials calibrating their outcomes over coincident survey profiles with standard geophysical techniques routinely applied for archaeological prospections. Soil Radon data were acquired both in a grid and along a profile to highlight anomalous gas concentrations, whereas electrical resistivity and ground-penetrating radar measurements were conducted on overlapping profiles to depict the electrical and electromagnetic subsurface distribution. Data integration showed a series of anomalies, suggesting the presence of multiple burials starting from a depth of approximately 1.5 m below the terrain surface. Slight anomalies of Radon in the soil were found to correspond to most of the recovered geophysical ones. Our results pointed out the effectiveness of geophysical method integration in archeological prospecting with the novelty of the joint use of Radon in soil measurements and capacitive resistivity tomography. The latter provided reliable results and can be considered as a standalone technique in archaeological surveys.

High Capacitive Secure Image Transmission Over Wireless Channels

Expansion of internet connectivity and its usage globally has increased various demands of providing security for the data transmission. Telemedicine is a modern way of medical care that can be extended to any remote place across the globe. This medical care practice is a result of the deployment of communication systems and information technology into healthcare system. With this technology the diagnosed data can be shared with physician and take his consultation remarks and also physicians can access to diagnostic archive and share for medical practice and learning. However, this exchange of information is confined with several risks of data theft when they are shared in open networks and hence they are to be protected with high security algorithms. This paper provides a high capacitive security algorithm for protecting the images with hidden confidential information. The approach provides a two-way security by encrypting the clinical information initially and embedding it imperceptibly in the concerned image so that the user on other can obtain both the visual and text data at same instance

An optimization method of planar array capacitance imaging

Planar array capacitance imaging technology is a kind of nondestructive testing technology applied to defect detection of composite materials. In the imaging process, the image quality is often poor due to the environment noise and the ill-posed of inverse problem solving. In this paper, an image reconstruction optimization method is proposed. Based on the analysis of the sensitive region of a single pair of electrodes and the contribution of capacitance value to each solution unit, an optimization matrix which is calculated by adjusting the contribution coefficient of each capacitance value to different solution units is proposed to optimize the sensitive field. Finally, simulation and experiment results are presented to show the effectiveness of the proposed method. Through the average relative error of each pixel of the reconstructed image before and after optimization, it can be seen that the error of reconstructed images at two different positions are reduced by an average of 3.22 % and 1.62 % respectively, while verified this method can effectively improve the reconstructed image and improve the anti-noise ability of the image.

Planar array capacitance imaging based on adaptive Kalman filter

Planar array capacitance imaging system has the characteristics of uneven distribution of sensitive field, serious ill posed problem and measurement data vulnerable to external interference, and these characteristics will make the image artifacts particularly serious, affect the quality of the reconstructed image, and even determine the number of defects with difficulty. In order to solve the problem that the edge electric field and ill conditioned characteristics of planar array electrode seriously affect the quality of capacitance image reconstruction, an improved image reconstruction algorithm based on adaptive Kalman filter is proposed to reduce the noise of capacitance data and dielectric constant matrix. On the basis of constructing the state model of planar array capacitance imaging with noise, the maximum likelihood criterion is used to estimate and modify the noise variance matrix of dielectric constant matrix on-line, and the noise variance matrix of dielectric constant matrix is modified in real time. In order to restrain the filtering divergence and accelerate the convergence speed, different weighting coefficients are provided for the error covariance matrix with time going by. Through designing four kinds of samples from simple to complex structure, the defect detection experiment of composite structure is carried out. The experimental results show that compared with linear back projection (LBP), Tikhonov regularization (TR) algorithm and Kalman filtering algorithm, the image error of adaptive Kalman filtering algorithm can be reduced by about 20%, the image correlation coefficient is as high as 0.79 and the convergence speed can be improved by about 15%, the image artifacts of the four samples are greatly reduced. The experimental data show that the proposed adaptive Kalman filter image reconstruction algorithm can effectively reduce the noise of capacitance and permittivity matrix, enhance the stability of planar array capacitance imaging, and reduce the image error, so that the quality of the image can be significantly improved. This study provides a strong technical basis for improving the quantization accuracy of planar array capacitance imaging detection. In the future, we will further consider the image reconstruction under the condition of complex object field.

An imaging algorithm of planar array capacitance sensor for defect detection

Planar array capacitance imaging is a feasible solution for detecting defects in composite components. However, the coplanar arrangement of electrodes in the imaging system renders a soft field effect, which results in unstable or susceptible imaging. The inverse problem of a planar array capacitance sensor system is ill-posed. Hence, a wavelet fusion combined multi-objective threshold programming imaging algorithm is proposed for a planar array capacitive imaging system. Furthermore, initial values of conjugate gradient (CG) and Newton–Raphson (NR) algorithms are optimized using the Tikhonov regularization algorithm. Subsequently, wavelet fusion is introduced to fuse images obtained using the CG and NR algorithms to acquire more detailed information. To further improve the reconstructed quality, a multi-objective threshold programming strategy is proposed. The final reconstruction image is obtained using the optimal threshold. Experimental results show a significantly improved quality of the reconstructed image, thereby verifying the effectiveness of the presented algorithm.

Multichannel Capacitive Imaging of Gas Vortex in Swirling Two-Phase Flows Using Parametric Reconstruction

Swirl-based inline phase separation is a promising approach in the process industry with potential application in oil and gas separation in petroleum industry. To increase the efficiency of the separation, the process may be controlled. In this direction, the position and the diameter of the gas vortex are two parameters that can be used in the control loop, provided that they can be non-intrusively estimated. This article presents a capacitive sensor-based imaging method to extract these geometrical parameters. The proposed method consists in obtaining high-temporal resolution capacitance measurements at the pipe boundary of a test rig, which in turn are used in a reconstruction and extracting the targeted parameters of the gas vortex. The calculated parameters are then used to visually present the swirling flow. The measurement system was evaluated quantitatively by performing experiments with different phantoms of known diameters and positions in the sensing area. Dynamic measurements were also performed in a test rig for liquid-gas swirling flow. The capacitive imaging system is capable of detecting characteristics of the flow for a wide range of gas and liquid flow rates. A qualitative analysis was also carried out by comparing time series of the capacitive images with high-speed camera recording. The geometrical parameters obtained by the proposed approach presents a good agreement with the real data, with a root mean square deviation of 0.76mm for diameter and 0.88mm for vortex position. It can be utilized in future work as an alternative or complementary input for the controlled inline liquid-gas separation system.

Applications of Capacitive Imaging in Human Skin Texture and Hair Analysis

This article focuses on the extraction of information from human skin and scalp hair for evaluation of a subject’s condition in the cosmetic and pharmaceutical industries. It uses capacitive images from existing hand-held research equipment and it applies image processing algorithms to expand their possible applications. The literature review introduces the readers into the field of skin research, and it highlights pieces of information that can be extracted by in vivo skin and ex vivo hair measurements. Then, the selected scientific equipment is presented, and Maxwell-based electrostatic simulations are employed to evaluate the measurement apparatus. Image analysis algorithms are suggested for (a) the detection of polygons on the human skin texture, (b) the estimation of wrinkles length and (c) the observation of hair water sorption capabilities by capacitive imaging systems. Finally, experiments are conducted to evaluate the performance of the presented algorithms and the results are compared with the literature. The results indicate that capacitive imaging systems can be used for skin age classification, detection and tracking of skin artifacts (e.g., wrinkles, moles or scars) and calculation of water content in hair samples.

A capacitive-inductive dual modality imaging system for non-destructive evaluation applications

Abstract For many non-destructive evaluation (NDE) applications, more information can be obtained by using different techniques, especially when the techniques are sensitive to different types of defects. However separate inspections are not always practical due to time and cost constraints. Therefore, an inspection system combing more than one modalities would have many advantages. A dual modality imaging system is thus proposed which can automatically switch between capacitive imaging and inductive imaging modes. Instead of using a physical combination of two sensors, the proposed system employs a coplanar coil pair as a sensor, and the modality switching is done by changing the wiring schemes through program-controlled switch box. After a single scan over the specimen under test, two types of images, namely capacitive and inductive, can be obtained by the proposed system. For an insulated metallic structure, the capacitive image contains the defect information in the insulation layer and on the top surface of the conducting layer, while the inductive image contains the defect information within the conducting region. The proposed integration of the two imaging modalities in a single system does not introduce any interference between the modes and provides more information on the defects with a reduced testing time and production cost on hardware and software compared to using two NDE techniques separately. A theoretical explanation of the imaging mechanisms for the capacitive and inductive modes are provided. The results of finite element modelling show perturbation of the probing fields due to defects in the two imaging modes. Experimental results from a dual modality imaging system are also presented, demonstrating detection of defects in insulator-metal hybrid structures to verify the effectiveness of this approach.

Capacitance imaging for the discrimination of lipid region in atherosclerotic plaque ex vivo using polypyrrole-coated multi-walled carbon nanotube multi-electrode array

We have developed a capacitance imaging technique using polypyrrole (PPy)-coated multi walled carbon nanotube multi electrode array (PPy-MWCNT-MEA) for the discrimination of lipid region in atherosclerotic plaque ex vivo. The lipid region in the atherosclerotic plaque ex vivo, derived from apolipoprotein-E receptor-deficient mice, exhibits higher capacitance than does the lipid-free region. This consequently allows the capacitance imaging of the lipid region. The results from this research are consistent with an earlier study, which reported that a relatively high capacitance was measured from free fatty acid-treated adipocyte cells. Compared to the titanium nitride multi electrode array, the PPy-MWCNT-MEA yields better capacitance imaging of the lipid region, which can be ascribed to the improved contact between the PPy-MWCNTs and the atherosclerotic plaque ex vivo.

Flow pattern visualization and nonlinear analysis of gas-liquid mixing process with top-blowing gas stirring

The evaluation of the mixing effect of gas-liquid two-phase flow during the top-blown gas agitation mixing is one of the difficulties in the testing field, especially in the process of using the model method to study the metallurgical top-blowing process. In order to evaluate the effect of gas-liquid two-phase flow mixing, a gas chromatography simulation based on capacitance tomography was used to visualize the flow pattern and analyze the mixed characteristics. A gas top-blown agitation test rig was set up, the gas phase was air-selected, and the liquid phase was selected from synthetic heat-conducting oil. The top-blown stirring test process was measured and imaged by electrical capacitance tomography (ECT) equipment from ECT Instruments Ltd (UK). The MATLAB program was used to identify the mixing areas of the images to obtain the distribution of gas-liquid two-phase. The flow pattern of the gas-liquid mixing region was obtained. The chaotic detection of the gas-liquid mixing process was performed by the three-state test method; the images were processed by the counting box dimension-corrosion method to obtain the mixing uniformity time of gas-liquid flow. Results show that it is feasible to use the capacitance tomography technique to visualize the gas-liquid two-phase distribution. The uniformity time quantification of the gas-liquid mixing process is also achieved.

Calcium Channels Gate Calcium-Independent But Voltage-Dependent Secretion in Mammalian Cells

The somata of primary sensory neurons, including dorsal root ganglion (DRG) neurons, release neurotransmitters and neuropeptides. Following physiological action potentials, in addition to Ca2+-dependent secretion, we have discovered and studied Ca2+-independent but voltage-dependent secretion (CiVDS) in somata of freshly isolated DRG neurons. Major open question of CiVDS is the molecular mechanism, including 3 components: fusion-pore machinery, voltage-sensor and the linker of fusion-pore and voltage-sensor. Here we report, by using exocytosis assays of membrane capacitance and single vesicle imaging, CiVDS is jointly contributed by (1) SNARE protein SNAP-25 for fusion pore, (2) voltage gated Ca channel (VGCC) Cav2.2 for Ca sensor; (3) and the “synprint”, which is Cav2.2 intracellular loop718-963aa, as the linker between fusion pore and voltage sensor; (4) CiVDS presents in both somata and axons. Following automatic knockdown of CiVDS by 3d-culture of DRG neurons, CiVDS is rescued by overexpressing any component of SNAP-25 or Cav2.2. On other hand, CiVDS is inhibited by blockers against SNAP-25, Cav2.2 and synprint. CiVDS is blocked by Cav2.2-RNAi-KD in DRG pre-transfected in vivo (Chai et al, Neuron, 2017). Importantly, our recent new evidences show that CiVDS presents and functions also robustly in other essential cells, implicating that CiVDS may impact mammalian physiology and disease much more than previously thought.

Unprecedented sensing of interlayer defects in three-dimensionally printed polymer by capacitance measurement

Interlayer defects in a three-dimensionally (3D) printed structure are expected from the residual stress and commonly observed warpage, but their detection has been challenging and elusive. They are to be distinguished from intralayer defects (e.g., discernible voids), which can be quite easily detected. Interlayer defects in the form of local inadequate interlayer bonding in a 3D-printed polymer structure have been unprecedentedly shown in this work to be detectible by capacitance measurement. The interlayer defects are artificially obtained and judiciously positioned. The printing involves conventional stereolithography, using an acrylate resin. Two coplanar electrical contacts are positioned on the exterior surface of the structure. The capacitance decreases monotonically with increasing number of defects at a given layer, and with decreasing N, where N is the number of layers above the defect, thus providing an effective indicator of the presence and location defects. However, the capacitance can be the same for different numbers of defects if N is different. This issue may be circumvented in future work by having additional electrical contacts at various layers. The maximum value of N that allows capacitance-based defect detection exceeds 210. The fractional decrease in capacitance due to the defects (relative to the case of no defect) increases monotonically with increasing number of defects at a given layer, but it essentially does not vary with N. Thus, the fractional decrease in capacitance indicates the presence of defects, but is not an effective indicator of the defect location. The capacitance increases with N, due to the larger depth of penetration of the current when N is higher. The greater is the number of defects at a layer, the more is the reduction in the depth of current penetration by these defects. The technique of this work may be extended to the detection of the 3D positions of defects by capacitance tomography.

Scanning Capacitance Microscopy of Triglycine Sulfate Crystals with the Profile Chromium Distribution

The spatial capacitance distribution, domain wall configuration, and impurity composition of triglycine sulfate TGS–TGS + Cr crystals with a growth periodic impurity structure have been investigated using scanning capacitance microscopy and X-ray fluorescence and topography. The chromium ion concentration in the strips emerging to the surface has been determined, and the periodic impurity distribution has been established. The difference between the chromium concentrations in nominally pure and impurity strips was found to be ~0.08 wt %, which is reflected in a variation in the capacitance image contrast by 0.17%. It is shown that capacitance images carry information about localization of the impurity gradient regions and domain walls and make it possible to establish a correlation between the defect and domain structures of a ferroelectric crystal.

Effects of capacitance ratio on the image linearity of capacitive division image readout

Capacitive division readout anode has the advantages of simple manufacture technology and high spatial resolution. Linearity of the restored image is limited by the relationship between the values of C (charge divide capacitor), Cs (parasitic capacitor), Cd (capacitor introduced by diagonal electrode) and Cp (perimeter capacitor). This paper describes a discrete capacitance matrix to investigate the dependence of image linearity on capacitor ratios, including C/Cs, C/C d and(N-1)C/C p (N is the number of nodes in each row of the capacitance matrix). Results presents that image nonlinearity varies monotonically with C/Cs, C/C d and(N-1)C/Cp. The effect of these capacitors on the linearity of image can be negligible when C/Cs is greater than 100, C/Cd is greater than 10 and (N-1)C/Cp is smaller than 0.1. The reliability of the simulation results is verified by experiments. The RMS nonlinearity of capacitive anode is expected to less than 0.71%.

Local carrier distribution imaging on few-layer MoS2 exfoliated on SiO2 by scanning nonlinear dielectric microscopy

We demonstrate that scanning nonlinear dielectric microscopy (SNDM) can be used for the nanoscale characterization of dominant carrier distribution on atomically thin MoS2 mechanically exfoliated on SiO2. For stable imaging without damaging microscopy tips and samples, SNDM was combined with peak-force tapping mode atomic force microscopy. The identification of dominant carriers and their spatial distribution becomes possible even for single and few-layer MoS2 on SiO2 using the proposed method allowing differential capacitance (dC/dV) imaging. We can expect that SNDM can also be applied to the evaluation of other two-dimensional semiconductors and devices.

Visualization of Gas–Oil–Water Flow in Horizontal Pipeline Using Dual-Modality Electrical Tomographic Systems

Employing dual-modality tomography inherently involves data from multiple dimensions, and thus a coherent approach is required to fully exploit the information from various dimensions. This paper describes a novel approach for dual-modality electrical resistance and capacitance tomography (ERT-ECT) to visualize gas–oil–water flow in horizontal pipeline. Compared with the conventional methods with dual-modality tomographic systems, the approach based on thresholding takes the account of multi-dimensional data, which therefore is capable of providing insights into investigated flow in both spatial and temporal terms. The experimental results demonstrate the feasibility of the approach, by which six common flow regimes in horizontal pipeline flow are visualized based on the multi-dimensional data with ERT-ECT systems, including (wavy) stratified flow, plug flow, slug flow, annular flow, and bubbly flow. Although the present approach is proposed for data acquired with an ERT-ECT system, it is potentially adaptable to other dual-modality tomographic systems that use concentration tomograms as inputs.

Dielectric imaging for differentiation between cancer and inflammation in vivo

In this study, we develop an in vivo dielectric imaging technique that measures capacitance using pin-type electrode arrays. Compared to normal tissues, cancer tissues exhibit higher capacitance values, allowing us to image the cancer region and monitor the chemotherapeutic effects of cancer in real-time. A comparison with the histopathological results shows that the in vivo dielectric imaging technique is able to detect small tumors (<3 mm) and tumor-associated changes. In addition, we demonstrate that cancer and inflammation may be distinguished by measuring the capacitance images at different frequencies. In contrast, the positron emission tomography using 2-[18F]-fluoro-2-deoxy-D-glucose was not capable of discriminating between cancer and inflammation.

Understanding the effects of topography on skin moisturization measurement via two-dimensional capacitance imaging.

Methods which assess skin moisturization based on changes in its electrical properties are widely used in both cosmetic and medical research industries. However, the devices themselves often give results which are significantly different to each other. Recently two-dimensional imaging moisturization systems have become commercially available, which have the capability to provide a more detailed assessment of what is contributing to measured skin moisturization. Presented here is a new in vitro method for preparing textured model test substrates for use with these devices, and results of their use to provide a clearer insight into the devices operation. A variety of different textured model test substrates were measured using a commercially available skin moisturization measurement device, the Epsilon. The response of the Epsilon was also tested against conventional skin moisturization devices. Surface morphology of model test substrates was found to have a significant influence on the measurement of its electrical properties with both the conventional and two-dimensional skin moisturization measurement devices. Through modification of the areas of the image being assessed for the two-dimensional moisturization mapping device, the parts of the model test substrate in contact with the device were indentified and analysed separately to areas not in contact with the sensor. This provided a more robust assessment of the electrical properties of substrate itself, rather than being influenced by texture like the conventional skin moisturization measurement devices. While the two-dimensional moisturization mapping systems can be used like a conventional electrical skin measurement device giving a simple overall reading of skin moisturization for the test area, their true value over existing electrical measures comes from its ability to isolate the skin itself from areas which are not in contact with the sensor.