Dartmouth's next generation EIS system: preliminary hardware considerations

Abstract

Our previous system covered the frequency range of 0 to 1 MHz. In this new design we propose to cover the range from 0 to 10 MHz. The higher frequencies have forced us to reconsider several design decisions in view of both the physics of the problem and the performance of available electronic components. In this presentation we examine in detail the constraints faced by the designer, starting from wiring consideration to measurement techniques. We will also present the solutions we selected to overcome the limitations we discovered. The problems include phase detection, amplitude measurements, system organization and layout and finally system calibration.

Three-dimensional EIT imaging of breast tissues: system design and clinical testing

“…The application of EIT in mammography requires special designs of the measuring system and image reconstruction algorithm. Although there are research projects using common two-dimensional (2-D) EIT with electrodes arranged in a ring [3], we consider the imaging of a three-dimensional (3-D) distribution of conductivity essential to breast diagnostics. This requires applying a 2-D array of electrodes for data acquisition and corresponding reconstruction software, such as suggested in [4], to provide a 3-D image reconstruction.…”

Statistical Estimation of EIT Electrode Contact Impedance Using a Magic Toeplitz Matrix

“…In this section, we apply our gapZ model to the patient breast measurement data using the Dartmouth EIT hardware [8]. The woman is in the lying position with 16 electrodes attached on the periphery of the pending breast.…”

“…Due to the natural heterogeneity of the skin and variation of contact pressure the electrode contact impedance may vary from electrode to electrode. This variation introduces substantial biases and “contact artifacts” in the reconstruction of electric properties of the breast and makes detecting abnormalities difficult.Since breast does not have rigid geometry, the boundary of the governing Laplace partial differential equation (PDE) is not well specified either in the planar design of RPI in which the breast is compressed between two plates [7], or in the Dartmouth circular design in which electrodes are configured radially around the circumference of the pendant breast [8]. An inaccurately specified boundary geometry results in high reproducibility error [9].…”

“…Since breast does not have rigid geometry, the boundary of the governing Laplace partial differential equation (PDE) is not well specified either in the planar design of RPI in which the breast is compressed between two plates [7], or in the Dartmouth circular design in which electrodes are configured radially around the circumference of the pendant breast [8]. An inaccurately specified boundary geometry results in high reproducibility error [9].…”

2D EIT for biomedical imaging: Design, measurement, simulation, and image reconstruction

“…Hartov et al [10,13,14] at Dartmouth College have developed a 2D data acquisition system and image reconstruction algorithms that are able to obtain the spatial distribution of both conductivity and permittivity. Their data acquisition system can be configured as V-mode (voltage source mode) and I-mode (current source mode).…”