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B. Ulker Karbeyaz

Bio: B. Ulker Karbeyaz is an academic researcher. The author has contributed to research in topics: Electromagnetic coil. The author has an hindex of 1, co-authored 1 publications receiving 79 citations.

Papers
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Journal ArticleDOI
TL;DR: The field profiles obtained by scanning a biological tissue show the potential of this methodology for clinical applications, and images obtained from isolated conducting tubes show that it is possible to distinguish two tubes separated 17 mm from each other.
Abstract: A data-acquisition system has been developed to image electrical conductivity of biological tissues via contactless measurements. This system uses magnetic excitation to induce currents inside the body and measures the resulting magnetic fields. The data-acquisition system is constructed using a PC-controlled lock-in amplifier instrument. A magnetically coupled differential coil is used to scan conducting phantoms by a computer controlled scanning system. A 10000-turn differential coil system with circular receiver coils of radii 15 mm is used as a magnetic sensor. The transmitter coil is a 100-turn circular coil of radius 15 mm and is driven by a sinusoidal current of 200 mA (peak). The linearity of the system is 7.2% full scale. The sensitivity of the system to conducting tubes when the sensor-body distance is 0.3 cm is 21.47 mV/(S/m). It is observed that it is possible to detect a conducting tube of average conductivity (0.2 S/m) when the body is 6 cm from the sensor. The system has a signal-to-noise ratio of 34 dB and thermal stability of 33.4 mV//spl deg/C. Conductivity images are reconstructed using the steepest-descent algorithm. Images obtained from isolated conducting tubes show that it is possible to distinguish two tubes separated 17 mm from each other. The images of different phantoms are found to be a good representation of the actual conductivity distribution. The field profiles obtained by scanning a biological tissue show the potential of this methodology for clinical applications.

84 citations


Cited by
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PatentDOI
TL;DR: In this article, a magnetic induction tomography (MIT) apparatus comprises an excitation signal generator (70), a primary excitation coil (50), an active reference source (175), and a signal distribution network (115).
Abstract: A magnetic induction tomography (MIT) apparatus comprises an excitation signal generator (70) for generating an excitation signal; a primary excitation coil (50) arranged to receive the excitation signal from the excitation signal generator (70) and to convert the excitation signal into electromagnetic radiation and to emit said radiation to excite a sample having at least one of an electrical conductivity distribution, an electrical permittivity distribution or a magnetic permeability distribution; a primary receiver coil (60) arranged to receive electromagnetic radiation from the excited sample and to convert the received radiation into a detection signal; and a signal distribution network (115) arranged to receive the detection signal from the primary receiver coil (60). The apparatus further comprises a passive reference detector arranged to detect the excitation signal and to convert the detected signal into a passive reference signal. The apparatus further comprises an active reference signal generator (230) for generating an active reference signal; and an active reference source (175) arranged to receive the active reference signal from the active reference signal generator (230) and to supply the active reference signal to the signal distribution network (115).

531 citations

Journal ArticleDOI
TL;DR: Using a time-lapse image acquired from a CCD camera, a non-contact and non-invasive device, which could measure both the respiratory and pulse rate simultaneously was developed, which successfully measured heart rate and respiratory rate simultaneously.

368 citations

Journal ArticleDOI
TL;DR: Results show that when individual subject MR head images are not available to construct subject-specific head models, accurate EEG source localization should employ a four- or five-layer BEM template head model incorporating an accurate skull conductivity estimate and warped to 64 or more accurately 3-D measured and co-registered electrode positions.
Abstract: Subject-specific four-layer boundary element method (BEM) electrical forward head models for four participants, generated from magnetic resonance (MR) head images using NFT ( www.sccn.ucsd.edu/wiki/NFT ), were used to simulate electroencephalographic (EEG) scalp potentials at 256 recorded electrode positions produced by single current dipoles of a 3-D grid in brain space. Locations of these dipoles were then estimated using gradient descent within five template head models fit to the electrode positions. These were: a spherical model, three-layer and four-layer BEM head models based on the Montreal Neurological Institute (MNI) template head image, and these BEM models warped to the recorded electrode positions. Smallest localization errors (4.1-6.2 mm, medians) were obtained using the electrode-position warped four-layer BEM models, with largest localization errors (~20 mm) for most basal brain locations. When we increased the brain-to-skull conductivity ratio assumed in the template model scalp projections from the simulated value (25:1) to a higher value (80:1) used in earlier studies, the estimated dipole locations moved outwards (12.4 mm, median). We also investigated the effects of errors in co-registering the electrode positions, of reducing electrode counts, and of adding a fifth, isotropic white matter layer to one individual head model. Results show that when individual subject MR head images are not available to construct subject-specific head models, accurate EEG source localization should employ a four- or five-layer BEM template head model incorporating an accurate skull conductivity estimate and warped to 64 or more accurately 3-D measured and co-registered electrode positions.

223 citations

Journal ArticleDOI
TL;DR: A 16-channel magnetic induction tomography (MIT) system has been constructed for imaging samples with low conductivities (<10 S m−1) such as biological tissues or ionized water in pipelines as mentioned in this paper.
Abstract: A 16-channel magnetic induction tomography (MIT) system has been constructed for imaging samples with low conductivities (<10 S m−1) such as biological tissues or ionized water in pipelines The system has a fixed operating frequency of 10 MHz and employs heterodyne downconversion of the received signals, to 10 kHz, to reduce phase instabilities during signal distribution and processing The real and imaginary components of the received signal, relative to a synchronous reference, are measured using a digital lock-in amplifier Images are reconstructed using a linearized reconstruction method based on inversion of a sensitivity matrix with Tikhonov regularization System performance measurements and images of a pipeline phantom and a human leg in vivo are presented The average phase precision of the MIT system is 17 millidegrees

107 citations

Journal ArticleDOI
TL;DR: In this paper, the authors provide a thorough review of the advances in sensor technology for measurement of common water quality parameters (pH, turbidity, free chlorine, dissolved oxygen, and conductivity) in drinking water distribution systems.
Abstract: Online drinking water quality monitoring technologies have made significant progress for source water surveillance and water treatment plant operation. The use of these technologies in the distribution system has not been favorable due to the high costs associated with installation, maintenance, and calibration of a large distributed array of monitoring sensors. This has led to a search for newer technologies that can be economically deployed on a large scale. This paper includes a brief description of important parameters for drinking water and current available technologies used in the field. The paper also provides a thorough review of the advances in sensor technology for measurement of common water quality parameters (pH, turbidity, free chlorine, dissolved oxygen, and conductivity) in drinking water distribution systems.

104 citations