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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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Related in: MedlinePlus

The simulated model with testing objects in the shape of the letters “EIT”. The size of the sample container is scaled down by 10 times from the experimental phantom container used earlier. A material of 1.5 Ω·m resistivity appears on the bottom side as the shape of “EIT” in a homogeneous material of 1 Ω·m resistivity. This material is stacked in a triangular shape from the bottom with a height of 300 μm to simulate the pore space in bone tissue engineering scaffolds where neotissue is grown.
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Fig8: The simulated model with testing objects in the shape of the letters “EIT”. The size of the sample container is scaled down by 10 times from the experimental phantom container used earlier. A material of 1.5 Ω·m resistivity appears on the bottom side as the shape of “EIT” in a homogeneous material of 1 Ω·m resistivity. This material is stacked in a triangular shape from the bottom with a height of 300 μm to simulate the pore space in bone tissue engineering scaffolds where neotissue is grown.

Mentions: Following the phantom experiment, we undertook a numerical simulation using the proposed electrode configuration with an increasing number of electrodes to determine how many voltage sensing electrodes would be required to perform imaging for the tissue culture. We assumed that the container shown in Figure 1(a) was filled with a homogeneous material of 1 Ω·m resistivity. The size of the sample container was scaled down by 10 times. A material of 1.5 Ω·m resistivity appeared on the bottom side in the shape of the letters “EIT”. This material was stacked in a triangular shape from the bottom with a height of 300 μm, as shown in Figure 8. The sizes were based on the scaffolds used for bone tissue engineering that typically have a 100–300 μm pore space where neotissue is grown [28].Figure 8


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)

The simulated model with testing objects in the shape of the letters “EIT”. The size of the sample container is scaled down by 10 times from the experimental phantom container used earlier. A material of 1.5 Ω·m resistivity appears on the bottom side as the shape of “EIT” in a homogeneous material of 1 Ω·m resistivity. This material is stacked in a triangular shape from the bottom with a height of 300 μm to simulate the pore space in bone tissue engineering scaffolds where neotissue is grown.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig8: The simulated model with testing objects in the shape of the letters “EIT”. The size of the sample container is scaled down by 10 times from the experimental phantom container used earlier. A material of 1.5 Ω·m resistivity appears on the bottom side as the shape of “EIT” in a homogeneous material of 1 Ω·m resistivity. This material is stacked in a triangular shape from the bottom with a height of 300 μm to simulate the pore space in bone tissue engineering scaffolds where neotissue is grown.
Mentions: Following the phantom experiment, we undertook a numerical simulation using the proposed electrode configuration with an increasing number of electrodes to determine how many voltage sensing electrodes would be required to perform imaging for the tissue culture. We assumed that the container shown in Figure 1(a) was filled with a homogeneous material of 1 Ω·m resistivity. The size of the sample container was scaled down by 10 times. A material of 1.5 Ω·m resistivity appeared on the bottom side in the shape of the letters “EIT”. This material was stacked in a triangular shape from the bottom with a height of 300 μm, as shown in Figure 8. The sizes were based on the scaffolds used for bone tissue engineering that typically have a 100–300 μm pore space where neotissue is grown [28].Figure 8

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