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Design of a microscopic electrical impedance tomography system for 3D continuous non-destructive monitoring of tissue culture.

Lee EJ, Wi H, McEwan AL, Farooq A, Sohal H, Woo EJ, Seo JK, Oh TI - Biomed Eng Online (2014)

Bottom Line: We developed a new micro-EIT system and report on simulation and experimental results of its macroscopic model.From numerical and experimental results, we estimate that at least 20 × 40 electrodes with 120 μm spacing are required to monitor the complex shape of ingrowth neotissue inside a scaffold with 300 μm pore.Future challenges include manufacturing a bioreactor-compatible container with a dense array of electrodes and a larger number of measurement channels that are sensitive to the reduced voltage gradients expected at a smaller scale.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering and Impedance Imaging Research Center, Kyung Hee University, 46-701 Yongin, Korea. tioh@khu.ac.kr.

ABSTRACT

Background: Non-destructive continuous monitoring of regenerative tissue is required throughout the entire period of in vitro tissue culture. Microscopic electrical impedance tomography (micro-EIT) has the potential to monitor the physiological state of tissues by forming three-dimensional images of impedance changes in a non-destructive and label-free manner. We developed a new micro-EIT system and report on simulation and experimental results of its macroscopic model.

Methods: We propose a new micro-EIT system design using a cuboid sample container with separate current-driving and voltage sensing electrodes. The top is open for sample manipulations. We used nine gold-coated solid electrodes on each of two opposing sides of the container to produce multiple linearly independent internal current density distributions. The 360 voltage sensing electrodes were placed on the other sides and base to measure induced voltages. Instead of using an inverse solver with the least squares method, we used a projected image reconstruction algorithm based on a logarithm formulation to produce projected images. We intended to improve the quality and spatial resolution of the images by increasing the number of voltage measurements subject to a few injected current patterns. We evaluated the performance of the micro-EIT system with a macroscopic physical phantom.

Results: The signal-to-noise ratio of the developed micro-EIT system was 66 dB. Crosstalk was in the range of -110.8 to -90.04 dB. Three-dimensional images with consistent quality were reconstructed from physical phantom data over the entire domain. From numerical and experimental results, we estimate that at least 20 × 40 electrodes with 120 μm spacing are required to monitor the complex shape of ingrowth neotissue inside a scaffold with 300 μm pore.

Conclusion: The experimental results showed that the new micro-EIT system with a reduced set of injection current patterns and a large number of voltage sensing electrodes can be potentially used for tissue culture monitoring. Numerical simulations demonstrated that the spatial resolution could be improved to the scale required for tissue culture monitoring. Future challenges include manufacturing a bioreactor-compatible container with a dense array of electrodes and a larger number of measurement channels that are sensitive to the reduced voltage gradients expected at a smaller scale.

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Design of the sample container included voltage sensing electrodes and current driving electrodes for the Kyung Hee University (KHU) Mark2 micro-EIT system. The EIT system injects current on surface electrodes and senses voltages on an additional set of surface electrodes. (a) The dimensions of a sample container and each 3 × 3 current driving electrodes on the current source plane and the current sink plane. (b) 24 × 15 voltage sensing electrodes on three imaging planes and dimensions for each sensing electrode. (c) Simulation of the voltage distributions subject to the primary current  and (d and e) simulation results for two secondary currents, , .
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Fig1: Design of the sample container included voltage sensing electrodes and current driving electrodes for the Kyung Hee University (KHU) Mark2 micro-EIT system. The EIT system injects current on surface electrodes and senses voltages on an additional set of surface electrodes. (a) The dimensions of a sample container and each 3 × 3 current driving electrodes on the current source plane and the current sink plane. (b) 24 × 15 voltage sensing electrodes on three imaging planes and dimensions for each sensing electrode. (c) Simulation of the voltage distributions subject to the primary current and (d and e) simulation results for two secondary currents, , .

Mentions: In order to obtain the most information of internal impedance from surface measurements, we installed arrays of small voltage sensing electrodes and large current driving electrodes on five sides of the sample container. The top was left open for tissue manipulations. Larger electrodes are required for current driving to reduce the contact impedance and improve current density uniformity. Figure 1(a) and (b) show the sample container and the location of the current driving electrodes and voltage sensing electrodes. Let Pk, k = 1,⋯,9 and k = 11,⋯,19, be the large square current driving electrodes placed on both shorter ends of the container in Figure 1(a). We refer to the longer container sides with voltage sensing electrodes as the imaging planes 1, 2, and 3. These are respectively, the front, back, and bottom sides of the container.Figure 1


Design of a microscopic electrical impedance tomography system for 3D continuous non-destructive monitoring of tissue culture.

Lee EJ, Wi H, McEwan AL, Farooq A, Sohal H, Woo EJ, Seo JK, Oh TI - Biomed Eng Online (2014)

Design of the sample container included voltage sensing electrodes and current driving electrodes for the Kyung Hee University (KHU) Mark2 micro-EIT system. The EIT system injects current on surface electrodes and senses voltages on an additional set of surface electrodes. (a) The dimensions of a sample container and each 3 × 3 current driving electrodes on the current source plane and the current sink plane. (b) 24 × 15 voltage sensing electrodes on three imaging planes and dimensions for each sensing electrode. (c) Simulation of the voltage distributions subject to the primary current  and (d and e) simulation results for two secondary currents, , .
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4196084&req=5

Fig1: Design of the sample container included voltage sensing electrodes and current driving electrodes for the Kyung Hee University (KHU) Mark2 micro-EIT system. The EIT system injects current on surface electrodes and senses voltages on an additional set of surface electrodes. (a) The dimensions of a sample container and each 3 × 3 current driving electrodes on the current source plane and the current sink plane. (b) 24 × 15 voltage sensing electrodes on three imaging planes and dimensions for each sensing electrode. (c) Simulation of the voltage distributions subject to the primary current and (d and e) simulation results for two secondary currents, , .
Mentions: In order to obtain the most information of internal impedance from surface measurements, we installed arrays of small voltage sensing electrodes and large current driving electrodes on five sides of the sample container. The top was left open for tissue manipulations. Larger electrodes are required for current driving to reduce the contact impedance and improve current density uniformity. Figure 1(a) and (b) show the sample container and the location of the current driving electrodes and voltage sensing electrodes. Let Pk, k = 1,⋯,9 and k = 11,⋯,19, be the large square current driving electrodes placed on both shorter ends of the container in Figure 1(a). We refer to the longer container sides with voltage sensing electrodes as the imaging planes 1, 2, and 3. These are respectively, the front, back, and bottom sides of the container.Figure 1

Bottom Line: We developed a new micro-EIT system and report on simulation and experimental results of its macroscopic model.From numerical and experimental results, we estimate that at least 20 × 40 electrodes with 120 μm spacing are required to monitor the complex shape of ingrowth neotissue inside a scaffold with 300 μm pore.Future challenges include manufacturing a bioreactor-compatible container with a dense array of electrodes and a larger number of measurement channels that are sensitive to the reduced voltage gradients expected at a smaller scale.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering and Impedance Imaging Research Center, Kyung Hee University, 46-701 Yongin, Korea. tioh@khu.ac.kr.

ABSTRACT

Background: Non-destructive continuous monitoring of regenerative tissue is required throughout the entire period of in vitro tissue culture. Microscopic electrical impedance tomography (micro-EIT) has the potential to monitor the physiological state of tissues by forming three-dimensional images of impedance changes in a non-destructive and label-free manner. We developed a new micro-EIT system and report on simulation and experimental results of its macroscopic model.

Methods: We propose a new micro-EIT system design using a cuboid sample container with separate current-driving and voltage sensing electrodes. The top is open for sample manipulations. We used nine gold-coated solid electrodes on each of two opposing sides of the container to produce multiple linearly independent internal current density distributions. The 360 voltage sensing electrodes were placed on the other sides and base to measure induced voltages. Instead of using an inverse solver with the least squares method, we used a projected image reconstruction algorithm based on a logarithm formulation to produce projected images. We intended to improve the quality and spatial resolution of the images by increasing the number of voltage measurements subject to a few injected current patterns. We evaluated the performance of the micro-EIT system with a macroscopic physical phantom.

Results: The signal-to-noise ratio of the developed micro-EIT system was 66 dB. Crosstalk was in the range of -110.8 to -90.04 dB. Three-dimensional images with consistent quality were reconstructed from physical phantom data over the entire domain. From numerical and experimental results, we estimate that at least 20 × 40 electrodes with 120 μm spacing are required to monitor the complex shape of ingrowth neotissue inside a scaffold with 300 μm pore.

Conclusion: The experimental results showed that the new micro-EIT system with a reduced set of injection current patterns and a large number of voltage sensing electrodes can be potentially used for tissue culture monitoring. Numerical simulations demonstrated that the spatial resolution could be improved to the scale required for tissue culture monitoring. Future challenges include manufacturing a bioreactor-compatible container with a dense array of electrodes and a larger number of measurement channels that are sensitive to the reduced voltage gradients expected at a smaller scale.

Show MeSH
Related in: MedlinePlus