Showing papers by "Tushar Kanti Bera published in 2012"

A multifrequency Electrical Impedance Tomography (EIT) system for biomedical imaging

Abstract: Multifrequency Electrical Impedance Tomography (EIT) is preferred for imaging of biomedical objects to study their wide range of tissue conductivity profiles among different type of subjects under test. In this direction, a multifrequency EIT system is developed for biomedical imaging and the resistivity imaging of a practical phantom is studied at different frequencies. Practical biological phantoms are developed with NaCl solution as the bathing medium and vegetable tissue cylinders as the inhomogeneity. A sinusoidal constant current is injected to the boundary of the practical phantoms at different frequency levels and the surface potentials are measured. Resistivity images are reconstructed from the boundary potential data using EIDORS and images are analyzed with image contrast parameters. Results show that the instrumentation part of the developed EIT system injects constant current at different frequency levels and measures the boundary potential data. Boundary data are successfully generated for all the frequencies and found suitable for image reconstruction. CNR, PCR and COC of the resistivity images show that the resistivity images are efficiently reconstructed from the boundary data acquired from the multifrequency EIT system.

Common Ground Method of Current Injection in Electrical Impedance Tomography

Abstract: Surface electrodes are essentially required to be switched for boundary data collection in electrical impedance tomography (Ell). Parallel digital data bits are required to operate the multiplexers used, generally, for electrode switching in ELT. More the electrodes in an EIT system more the digital data bits are needed. For a sixteen electrode system. 16 parallel digital data bits are required to operate the multiplexers in opposite or neighbouring current injection method. In this paper a common ground current injection is proposed for EIT and the resistivity imaging is studied. Common ground method needs only two analog multiplexers each of which need only 4 digital data bits and hence only 8 digital bits are required to switch the 16 surface electrodes. Results show that the USB based data acquisition system sequentially generate digital data required for multiplexers operating in common ground current injection method. The profile of the boundary data collected from practical phantom show that the multiplexers are operating in the required sequence in common ground current injection protocol. The voltage peaks obtained for all the inhomogeneity configurations are found at the accurate positions in the boundary data matrix which proved the sequential operation of multiplexers. Resistivity images reconstructed from the boundary data collected from the practical phantom with different configurations also show that the entire digital data generation module is functioning properly. Reconstructed images and their image parameters proved that the boundary data are successfully acquired by the DAQ system which in turn indicates a sequential and proper operation of multiplexers.

Switching of a Sixteen Electrode Array for Wireless EIT System Using a RF-Based 8-Bit Digital Data Transmission Technique

Abstract: Surface electrode switching of 16-electrode wireless EIT is studied using a Radio Frequency (RF) based digital data transmission technique operating with 8 channel encoder/decoder ICs. An electrode switching module is developed the analog multiplexers and switched with 8 bit parallel digital data transferred by transmitter/receiver module developed with radio frequency technology. 8 bit parallel digital data collected from the receiver module are converted to 16 bit digital data by using binary adder circuits and then used for switching the electrodes in opposite current injection protocol. 8 bit parallel digital data are generated using NI USB 6251 DAQ card in LabVIEW software and sent to the transmission module which transmits the digital data bits to the receiver end. Receiver module supplies the parallel digital bits to the binary adder circuits and adder circuit outputs are fed to the multiplexers of the electrode switching module for surface electrode switching. 1 mA, 50 kHz sinusoidal constant current is injected at the phantom boundary using opposite current injection protocol. The boundary potentials developed at the voltage electrodes are measured and studied to assess the wireless data transmission.