1
|
Wang L, Zhu W, Wang R, Li W, Liang G, Ji Z, Dong X, Shi X. Suppressing interferences of EIT on synchronous recording EEG based on comb filter for seizure detection. Front Neurol 2022; 13:1070124. [DOI: 10.3389/fneur.2022.1070124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 11/18/2022] [Indexed: 12/03/2022] Open
Abstract
Background and objectiveThe purpose of this study was to eliminate the interferences of electrical impedance tomography (EIT) on synchronous recording electroencephalography (EEG) for seizure detection.MethodsThe simulated EIT signal generated by COMSOL Multiphysics was superimposed on the clinical EEG signal obtained from the CHB-MIT Scalp EEG Database, and then the spectrum features of superimposed mixed signals were analyzed. According to the spectrum analysis, in addition to high-frequency interference at 51.2 kHz related to the drive current, there was also low-frequency interference caused by switching of electrode pairs, which were used to inject drive current. A low pass filter and a comb filter were used to suppress the high-frequency interference and low-frequency interference, respectively. Simulation results suggested the low-pass filter and comb filter working together effectively filtered out the interference of EIT on EEG in the process of synchronous monitoring.ResultsAs a result, the normal EEG and epileptic EEG could be recognized effectively. Pearson correlation analysis further confirmed the interference of EIT on EEG was effectively suppressed.ConclusionsThis study provides a simple and effective interference suppression method for the synchronous monitoring of EIT and EEG, which could be served as a reference for the synchronous monitoring of EEG and other medical electromagnetic devices.
Collapse
|
2
|
Gallet A, Rigby S, Tallman TN, Kong X, Hajirasouliha I, Liew A, Liu D, Chen L, Hauptmann A, Smyl D. Structural engineering from an inverse problems perspective. Proc Math Phys Eng Sci 2022; 478:20210526. [PMID: 35153609 PMCID: PMC8791046 DOI: 10.1098/rspa.2021.0526] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 12/07/2021] [Indexed: 01/16/2023] Open
Abstract
The field of structural engineering is vast, spanning areas from the design of new infrastructure to the assessment of existing infrastructure. From the onset, traditional entry-level university courses teach students to analyse structural responses given data including external forces, geometry, member sizes, restraint, etc.-characterizing a forward problem (structural causalities → structural response). Shortly thereafter, junior engineers are introduced to structural design where they aim to, for example, select an appropriate structural form for members based on design criteria, which is the inverse of what they previously learned. Similar inverse realizations also hold true in structural health monitoring and a number of structural engineering sub-fields (response → structural causalities). In this light, we aim to demonstrate that many structural engineering sub-fields may be fundamentally or partially viewed as inverse problems and thus benefit via the rich and established methodologies from the inverse problems community. To this end, we conclude that the future of inverse problems in structural engineering is inexorably linked to engineering education and machine learning developments.
Collapse
Affiliation(s)
- A. Gallet
- Department of Civil and Structural Engineering, University of Sheffield, Sheffield, UK
| | - S. Rigby
- Department of Civil and Structural Engineering, University of Sheffield, Sheffield, UK
| | - T. N. Tallman
- School of Aeronautics and Astronautics, Purdue University, West Lafayette, IN, USA
| | - X. Kong
- Department of Physics and Engineering Science, Coastal Carolina University, Conway, SC, USA
| | - I. Hajirasouliha
- Department of Civil and Structural Engineering, University of Sheffield, Sheffield, UK
| | - A. Liew
- Department of Civil and Structural Engineering, University of Sheffield, Sheffield, UK
| | - D. Liu
- School of Physical Sciences, University of Science and Technology of China, Hefei, People’s Republic of China
| | - L. Chen
- Department of Civil and Structural Engineering, University of Sheffield, Sheffield, UK
| | - A. Hauptmann
- Research Unit of Mathematical Sciences, University of Oulu, Oulu, Finland
- Department of Computer Science, University College London, London, UK
| | - D. Smyl
- Department of Civil, Coastal, and Environmental Engineering, University of South Alabama, Mobile, AL, USA
| |
Collapse
|
3
|
Ravagli E, Mastitskaya S, Holder DS, Aristovich KY. Simplifying the hardware requirements for fast neural EIT of peripheral nerves. Physiol Meas 2021; 43. [PMID: 34915462 DOI: 10.1088/1361-6579/ac43c0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 12/16/2021] [Indexed: 11/12/2022]
Abstract
OBJECTIVE The main objective of this study was to assess the feasibility of lowering the hardware requirements for fast neural EIT in order to support the distribution of this technique. Specifically, the feasibility of replacing the commercial modules present in the existing high-end setup with compact and cheap customized circuitry was assessed. APPROACH Nerve EIT imaging was performed on rat sciatic nerves with both our standard ScouseTom setup and a customized version in which commercial benchtop current sources were replaced by custom circuitry. Electrophysiological data and images collected in the same experimental conditions with the two setups were compared. Data from the customized setup was subject to a down-sampling analysis to simulate the use of a recording module with lower specifications. MAIN RESULTS Compound action potentials (573±287µV and 487±279µV, p=0.28) and impedance changes (36±14µV and 31±16µV, p=0.49) did not differ significantly when measured using commercial high-end current sources or our custom circuitry, respectively. Images reconstructed from both setups showed neglibile (<1voxel, i.e. 40µm) difference in peak location and a high degree of correlation (R2=0.97). When down-sampling from 24 to 16 bits ADC resolution and from 100KHz to 50KHz sampling frequency, signal-to-noise ratio showed acceptable decrease (<-20%), and no meaningful image quality loss was detected (peak location difference <1voxel, pixel-by-pixel correlation R2=0.99). SIGNIFICANCE The technology developed for this study greatly reduces the cost and size of a fast neural EIT setup without impacting quality and thus promotes the adoption of this technique by the neuroscience research community.
Collapse
Affiliation(s)
- Enrico Ravagli
- Medical Physics and Biomedical Engineering, University College London, Malet Place Engineering Building, London, WC1E 6BT, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND
| | - Svetlana Mastitskaya
- Medical Physics and Biomedical Engineering, University College London, Malet Place Engineering Building, London, London, WC1E 6BT, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND
| | - David S Holder
- Department of Medical Physics and Bioengineering, University College London, Malet Place Engineering Building, Gower Street, London, London, WC1E 6BT, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND
| | - Kirill Y Aristovich
- Department of Medical Physics and Bioengineering, University College London, Malet Place Engineering Building - Gower Street - London, London, WC1E 6BT, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND
| |
Collapse
|
4
|
Ravagli E, Mastitskaya S, Thompson N, Aristovich K, Holder D. Optimization of the electrode drive pattern for imaging fascicular compound action potentials in peripheral nerve with fast neural electrical impedance tomography. Physiol Meas 2019; 40:115007. [PMID: 31694004 PMCID: PMC7214787 DOI: 10.1088/1361-6579/ab54eb] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
OBJECTIVE The main objective of this study was to investigate which injection pattern led to the best imaging of fascicular compound activity in fast neural EIT of peripheral nerve using an external cylindrical 2 × 14-electrodes cuff. Specifically, the study addressed the identification of the optimal injection pattern and of the optimal region of the reconstructed volume to image fascicles. APPROACH The effect of three different measurement protocol features (transversal/longitudinal injection, drive electrode spacing, referencing configuration) over imaging was investigated in simulation with the use of realistic impedance changes and noise levels. Image-based metrics were employed to evaluate the quality of the reconstructions over the reconstruction domain. The optimal electrode addressing protocol suggested by the simulations was validated in vivo on the tibial and peroneal fascicles of rat sciatic peripheral nerves (N = 3) against MicroCT reference images. MAIN RESULTS Injecting current transversally, with spacing of ⩾4 electrodes apart (⩾100°) and single-ring referencing of measurements, led to the best overall localization when reconstructing on the edge of the electrode array closest to the reference. Longitudinal injection protocols led to a higher SNR of the reconstructed image but poorer localization. All in vivo EIT recordings had statistically significant impedance variations (p < 0.05). Overall, fascicle center-of-mass (CoM) localization error was estimated at 141 ± 56 µm (-26 ± 94 µm and 5 ± 29° in radial coordinates). Significant difference was found (p < 0.05) between mean angular location of the tibial and peroneal CoMs. SIGNIFICANCE This study gives the reader recommendations for performing fast neural EIT of fascicular compound activity using the most effective protocol features.
Collapse
Affiliation(s)
- Enrico Ravagli
- Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
| | | | | | | | | |
Collapse
|
5
|
Hope J, Aqrawe Z, Lim M, Vanholsbeeck F, McDaid A. Increasing signal amplitude in electrical impedance tomography of neural activity using a parallel resistor inductor capacitor (RLC) circuit. J Neural Eng 2019; 16:066041. [PMID: 31536974 DOI: 10.1088/1741-2552/ab462b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE To increase the impedance signal amplitude produced during neural activity using a novel approach of implementing a parallel resistor inductor capacitor (RLC) circuit across the current source used in electrical impedance tomography (EIT) of peripheral nerve. APPROACH The frequency response of the impedance signal was characterized in the range 4-18 kHz, then a frequency range with significant capacitive charge transfer was selected for experiment with the RLC circuit. Design of the RLC circuit was aided by in vitro impedance measurements on nerve and nerve cuff in the range 5 Hz to 50 kHz. MAIN RESULTS The frequency response of the impedance signal across 4-18 kHz showed maximum amplitude at 6-8 kHz, and steady decline in amplitude between 8 and 18 kHz with -6 dB reduction at 14 kHz. The frequency range 17 ± 1 kHz was selected for the RLC experiment. The RLC experiment was performed on four subjects using an RLC circuit designed to produce a resonant frequency of 17 kHz with a bandwidth of 3.6 kHz, and containing a 22 mH inductive element and a 3.45 nF capacitive element with +0.8/- 3.45 nF manual tuning range. With the RLC circuit connected, relative increases in the impedance signal (±3σ noise) of 44% (±15%), 33% (±30%), 37% (±8.6%), and 16% (±19%) were produced. SIGNIFICANCE The increase in impedance signal amplitude at high frequencies, generated by the novel implementation of a parallel RLC circuit across the drive current, improves spatial resolution by increasing the number of parallel drive currents which can be implemented in a frequency division multiplexed (FDM) EIT system, and aids the long term goal of a real-time FDM EIT system by reducing the need for ensemble averaging.
Collapse
Affiliation(s)
- J Hope
- The Department of Mechanical Engineering, The University of Auckland, Auckland, New Zealand. Dodd Walls Centre for Photonic and Quantum Technologies, Dunedin, New Zealand
| | | | | | | | | |
Collapse
|
6
|
Tarotin I, Aristovich K, Holder D. Simulation of impedance changes with a FEM model of a myelinated nerve fibre. J Neural Eng 2019; 16:056026. [DOI: 10.1088/1741-2552/ab2d1c] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
|
7
|
Darnajou M, Dupré A, Dang C, Ricciardi G, Bourennane S, Bellis C. On the Implementation of Simultaneous Multi-Frequency Excitations and Measurements for Electrical Impedance Tomography. SENSORS 2019; 19:s19173679. [PMID: 31450594 PMCID: PMC6749333 DOI: 10.3390/s19173679] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 08/08/2019] [Accepted: 08/20/2019] [Indexed: 11/16/2022]
Abstract
The investigation of quickly-evolving flow patterns in high-pressure and high-temperature flow rigs requires the use of a high-speed and non-intrusive imaging technique. Electrical Impedance Tomography (EIT) allows reconstructing the admittivity distribution characterizing a flow from the knowledge of currents and voltages on its periphery. The need for images at high frame rates leads to the strategy of simultaneous multi-frequency voltage excitations and simultaneous current measurements, which are discriminated using fast Fourier transforms. The present study introduces the theory for a 16-electrode simultaneous EIT system, which is then built based on a field programmable gate array data acquisition system. An analysis of the propagation of uncertainties through the measurement process is investigated, and experimental results with fifteen simultaneous signals are presented. It is shown that the signals are successfully retrieved experimentally at a rate of 1953 frames per second. The associated signal-to-noise ratio varies from 59.6–69.1 dB, depending on the generated frequency. These preliminary results confirm the relevance and the feasibility of simultaneous multi-frequency excitations and measurements in EIT as a means to significantly increase the imaging rate.
Collapse
Affiliation(s)
- Mathieu Darnajou
- CEA Cadarache, 13115 Saint-Paul-lez-Durance, France.
- École Centrale de Marseille, 38 Rue Frédéric Joliot Curie, 13013 Marseille, France.
| | - Antoine Dupré
- Department of Paediatrics, University of Geneva, 1205 Geneva, Switzerland
| | - Chunhui Dang
- CEA Cadarache, 13115 Saint-Paul-lez-Durance, France
- École Centrale de Marseille, 38 Rue Frédéric Joliot Curie, 13013 Marseille, France
| | | | - Salah Bourennane
- École Centrale de Marseille, 38 Rue Frédéric Joliot Curie, 13013 Marseille, France
| | - Cédric Bellis
- Aix Marseille Univ, CNRS, Centrale Marseille, LMA UMR 7031, Marseille, France
| |
Collapse
|
8
|
Avery J, Dowrick T, Witkowska-Wrobel A, Faulkner M, Aristovich K, Holder D. Simultaneous EIT and EEG using frequency division multiplexing. Physiol Meas 2019; 40:034007. [DOI: 10.1088/1361-6579/ab0bbc] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
9
|
Hope J, Aristovich K, Chapman CAR, Volschenk A, Vanholsbeeck F, McDaid A. Extracting impedance changes from a frequency multiplexed signal during neural activity in sciatic nerve of rat: preliminary study in vitro. Physiol Meas 2019; 40:034006. [DOI: 10.1088/1361-6579/ab0c24] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
10
|
|
11
|
Dupré A, Mylvaganam S. A Simultaneous and Continuous Excitation Method for High-Speed Electrical Impedance Tomography with Reduced Transients and Noise Sensitivity. SENSORS 2018; 18:s18041013. [PMID: 29597327 PMCID: PMC5948595 DOI: 10.3390/s18041013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 03/25/2018] [Accepted: 03/26/2018] [Indexed: 11/16/2022]
Abstract
This paper presents a concept for soft field tomographic scan of all the projections of electromagnetic waves emanating from an array of electrodes. Instead of the sequential excitation of all pairs of electrodes in the list of all projections, the new method present here consists of a single and continuous excitation. This excitation signal is the linear combination of the excitation signals in the projection set at different AC frequencies. The response to a given projection is discriminated by selecting the corresponding AC frequency component in the signal spectra of the digitally demodulated signals. The main advantage of this method is the suppression of transients after each projection, which is particularly problematic in electrical impedance tomography due to contact impedance phenomena and skin effect. The second benefit over the sequential scan method is the increased number of samples for each measurement for reduced noise sensitivity with digital demodulation. The third benefit is the increased temporal resolution in high-speed applications. The main drawback is the increased number of signal sources required (one per electrode). This paper focuses on electrical impedance tomography, based on earlier work by the authors. An experimental proof-of-concept using a simple 4-electrodes electrical impedance tomographic system is presented using simulations and laboratory data. The method presented here may be extended to other modalities (ultrasonic, microwave, optical, etc.).
Collapse
Affiliation(s)
- Antoine Dupré
- Private Practice, Jouquetti, 05400 Furmeyer, France.
| | - Saba Mylvaganam
- Department of Electrical Engineering, IT and Cybernetics, Faculty of Technology, Natural Sciences and Maritime Sciences, University College of Southeast Norway, Porsgrunn 3901, Norway.
| |
Collapse
|