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

Abstract

BackgroundNon-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.MethodsWe 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.ResultsThe 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.ConclusionThe 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.

Three‐Dimensional (3D) cell culture monitoring: Opportunities and challenges for impedance spectroscopy

“…Likewise, a more complex setup of electrodes was designed with the intention of monitoring 3D cultures using EIT (Lee et al, 2014). The quality of the designed device (Figure 8) was assessed using performance metrics such as crosstalk, amplitude stability error, total harmonic distortion, and signal to noise ratio.…”

“…The electrode design shows the placement of current injecting electrodes on parallel walls and the placement of voltage sensing electrodes on the bottom surface as well as the two parallel walls. Reproduced with permission (Lee et al, 2014). Copyright Lee et al; licensee BioMed Central Ltd. 2014 [Color figure can be viewed at wileyonlinelibrary.com]…”

Tactile Sensor for Minimally Invasive Surgery Using Electrical Impedance Tomography

“…Reducing the point spread function of the reconstruction would improve the localisation accuracy and shape estimation. This could be achieved through reconfiguration of the FPC to include internal electrodes [12]- [14] or a full grid [10], [15], [16] to better distribute the sensitivity across the plane of the electrodes. However, these may not sufficiently address the decrease in out of plane sensitivity towards the deformable contact surface.…”

Exploring the Potential of Electrical Impedance Tomography for Tissue Engineering Applications

“…Alternatively, increasing the number of independent measurements also allows a higher sensitivity to the changes of local conductivity. It could be achieved by using new sensor patterns such as the sensor with an increased number of electrodes [ 39 , 40 ]. Otherwise, rotational electrodes can be implemented to the sensor [ 41 ] so that the number of measurements can be increased while the size of the electrodes can be guaranteed, which minimizes the impact of contact impedance [ 42 ] to the voltage data.…”