Electrical resistance tomography (ERT) provides images of the Electrical properties of subsurface materials leading to the distinction of different Earth’s interior structures. The accuracy of Electrical resistance imaging is strongly affected by the topographical variations so that the lack of incorporation of topography information into the inversion process may produce erroneous anomalies in the resistivity section. Owing to the significance of the topography effects on the resistivity measurements, we use a Schwarz-Christoffel transformation approach to incorporate the irregular surface into the 2.5-dimensional forward solution in the framework of the finite difference method. This approach is implemented on synthetic cases to illustrate how the resistivity measurements are dependent on the topographic irregularities. Numerical experiments demonstrate that in the presence of topographic features between current and potential electrodes, the resistivity response does not reflect the realistic resistivity values of the subsurface even in the case of a homogeneous resistivity distribution.

Introduction: Electrical impedance tomography (EIT) is a non-invasive technique utilized in various medical applications, including brain imaging and other neurological diseases. Recognizing the physiological and anatomical characteristics of organs based on their Electrical properties is one of the main applications of EIT, as each variety of tissue structure has its own Electrical characteristics. The high potential of brain EIT is established in real-time supervision and early recognition of cerebral brain infarction, hemorrhage, and other diseases. In this paper, we review the studies on the neurological applications of EIT. Methods: EIT calculates the internal Electrical conductivity distribution of an organ by measuring its surface impedance. A series of electrodes are placed on the surface of the target tissue, and small alternating currents are injected. The related voltages are then observed and analyzed. The Electrical permittivity and conductivity distributions inside the tissue are reconstructed by measuring the electrode voltages. Results: The Electrical characteristic of biological tissues is remarkably dependent on their structures. Some tissues are better Electrical conductors than the others since they have more ions that can carry the Electrical charges. This difference is attributed to changes in cellular water content, membrane properties, and destruction of tight junctions within cell membranes. Conclusion: EIT is an extremely practical device for brain imaging, capturing fast Electrical activities in the brain, imaging epileptic seizures, detecting intracranial bleeding, detecting cerebral edema, and diagnosing stroke.

Electrical Capacitance tomography (ECT) is an imaging technique that maps the Electrical permittivity contrast of the object. This paper studies an image and a shape reconstruction method for ECT. For image reconstruction, a regularized Gauss-Newton method has been implemented, based on the inverse finite element technique. For shape reconstruction, a . narrow band level set method has been developed. Using experimental ECT data, a comparative study of these two techniques is the main objective of this paper.

Electrical Impedance tomography (EIT), is one of the safest medical imaging technologies and can be used in industrial process monitoring. In this method, image of Electrical conductivity (or Electrical impedance) distribution of the inner part of a conductive subject can be reconstructed. The image reconstruction process is done by injecting an accurate current into the boundary of a volume conductor (W), measuring voltages around the boundary ( ¶W) and transmitting them to a computer, and processing on acquired data with software (e.g. MATLAB).The image would be reconstructed from the measured peripheral data by using an iterative algorithm. A precise instrumentation (EIT hardware) plays a very important and vital role in the quality of reconstructed images. In this paper, we have proposed a practical design of a low-cost precise EIT hardware including, a high output impedance VCCS (Voltage-Controlled Current Source) with pulse generation part, precise voltage demodulator and measuring parts, a high performance multiplexer module, and a control unit. All the parts have been practically and accurately tested with successful results, and finally the proposed design was assembled on PCB.The quality of experimental results at the end of this paper, (reconstructed images by using the implemented system), confirms the accuracy of the proposed EIT hardware.