Showing papers by "Tushar Kanti Bera published in 2009"
05 May 2009
TL;DR: In this paper, a sinusoidal current generator and signal conditioner are used for electrical impedance tomography (EIT) and the EIT forward problem is studied using the forward solver.
Abstract: 16-electrode phantoms are developed and studied with a simple instrumentation developed for electrical impedance tomography. An analog instrumentation is developed with a sinusoidal current generator and signal conditioner circuit. Current generator is developed with modified Howland constant current source fed by a voltage controlled oscillator and the signal conditioner circuit consisting of an instrumentation amplifier and a narrow band pass filter. Electronic hardware is connected to the electrodes through a DIP switch based multiplexer module. Phantoms with different electrode size and position are developed and the EIT forward problem is studied using the forward solver. A low frequency low magnitude sinusoidal current is injected to the surface electrodes surrounding the phantom boundary and the differential potential is measured by a digital multimeter. Comparing measured potential with the simulated data it is intended to reduce the measurement error and an optimum phantom geometry is suggested. Result shows that the common mode electrode reduces the common mode error of the EIT electronics and reduces the error potential in the measured data. Differential potential is reduced up to 67 mV at the voltage electrode pair opposite to the current electrodes. Offset potential is measured and subtracted from the measured data for further correction. It is noticed that the potential data pattern depends on the electrode width and the optimum electrode width is suggested. It is also observed that measured potential becomes acceptable with a 20 mm solution column above and below the electrode array level.
41 citations
06 Mar 2009
TL;DR: A Finite Element Method based forward solver is developed for solving the forward problem of a 2D-Electrical Impedance Tomography and it is attempted to find the sources of errors to improve data quality for better image reconstruction.
Abstract: A Finite Element Method based forward solver is developed for solving the forward problem of a 2D-Electrical Impedance Tomography The Method of Weighted Residual technique with a Galerkin approach is used for the FEM formulation of EIT forward problem The algorithm is written in MatLAB70 and the forward problem is studied with a practical biological phantom developed EIT governing equation is numerically solved to calculate the surface potentials at the phantom boundary for a uniform conductivity An EIT-phantom is developed with an array of 16 electrodes placed on innerthe surface of the phantom tank filled with KCl solution A sinusoidal current is injected through the current electrodes and the differential potentials across the voltage electrodes are measured Measured data is compared with the differential potential calculated for known current and solution conductivity Comparing measured voltage with the calculated data it is attempted to find the sources of errors to improve data quality for better image reconstruction
37 citations
22 Aug 2009
TL;DR: A simple analog instrumentation for Electrical Impedance Tomography is developed and calibrated using the practical phantoms to acquire the voltage data suitable for better image reconstruction.
Abstract: A simple analog instrumentation for Electrical Impedance Tomography is developed and calibrated using the practical phantoms. A constant current injector consisting of a modified Howland voltage controlled current source fed by a voltage controlled oscillator is developed to inject a constant current to the phantom boundary. An instrumentation amplifier, 50 Hz notch filter and a narrow band pass filter are developed and used for signal conditioning. Practical biological phantoms are developed and the forward problem is studied to calibrate the EIT-instrumentation. An array of sixteen stainless steel electrodes is developed and placed inside the phantom tank filled with KCl solution. 1 mA, 50 kHz sinusoidal current is injected at the phantom boundary using adjacent current injection protocol. The differential potentials developed at the voltage electrodes are measured for sixteen current injections. Differential voltage signal is passed through an instrumentation amplifier and a filtering block and measured by a digital multimeter. A forward solver is developed using Finite Element Method in MATLAB7.0 for solving the EIT governing equation. Differential potentials are numerically calculated using the forward solver with a simulated current and bathing solution conductivity. Measured potential data is compared with the differential potentials calculated for calibrating the instrumentation to acquire the voltage data suitable for better image reconstruction.
30 citations
01 Jan 2009
TL;DR: Measured boundary potentials are compared with the simulated data generated by a finite element method based forward solver, intended to modify the phantom design parameters for better image reconstruction.
Abstract: Boundary data profile of practical phantom is studied for two dimensional Medical Electrical Impedance Tomography using different electrode geometries. A sinusoidal current is injected to the phantom boundary for generating surface potential data using neighboring current injection protocol. Boundary data are collected for different electrode area and bathing solution heights using a common mode electrode with different diameters. Measured boundary potentials are compared with the simulated data generated by a finite element method based forward solver. Comparing the measured potential with simulated data it is intended to modify the phantom design parameters for better image reconstruction.
25 citations