• Journal of Biomedical Engineering Research
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• v.33 no.1
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• pp.39-46
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• 2012

Electrical impedance tomography(EIT) can produce functional images with conductivity distributions associated with physiological events such as cardiac and respiratory cycles. EIT has been proposed as a clinical imaging tool for the detection of stroke and breast cancer, pulmonary function monitoring, cardiac imaging and other clinical applications. However EIT still suffers from technical challenges such as the electrode interface, hardware limitations, lack of animal or human trials, and interpretation of conductivity variations in reconstructed images. We improved the KHU Mark2 EIT system by introducing an EIT electrode interface consisting of nano-web fabric electrodes and by adding a synchronized biosignal measurement system for gated conductivity imaging. ECG and respiration signals are collected to analyze the relationship between the changes in conductivity images and cardiac activity or respiration. The biosignal measurement system provides a trigger to the EIT system to commence imaging and the EIT system produces an output trigger. This EIT acquisition time trigger signal will also allow us to operate the EIT system synchronously with other clinical devices. This type of biosignal gated conductivity imaging enables capture of fast cardiac events and may also improve images and the signal-to-noise ratio (SNR) by using signal averaging methods at the same point in cardiac or respiration cycles. As an example we monitored the beat by beat cardiac-related change of conductivity in the EIT images obtained at a common state over multiple respiration cycles. We showed that the gated conductivity imaging method reveals cardiac perfusion changes in the heart region of the EIT images on a canine animal model. These changes appear to have the expected timing relationship to the ECG and ventilator settings that were used to control respiration. As EIT is radiation free and displays high timing resolution its ability to reveal perfusion changes may be of use in intensive care units for continuous monitoring of cardiopulmonary function.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.39-46
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• 2016

This paper describes the third order feedforward delta-sigma modulator with inverter-based integrators and a 1.5bit comparator for the application of audio signal processing. The proposed 3rd-order delta-sigma modulator is multi-bit structure using 1.5 bit comparator instead of operational amplifier. This delta-sigma modulator has high SNR compared with single-bit 4th-order delta-sigma modulator in a low OSR. And it minimizes power consumes and simplified circuit structure using inverter-based integrator and using inverter-based integrator as analogue adder. The modulator was designed with 0.18um CMOS standard process and total chip area is $0.36mm^2$. The measured power cosumption is 28.8uW in a 0.8V analog supply and 66.6uW in a 1.8V digital supply. The measurement result shows that the peak SNDR of 80.7 dB, the ENOB of 13.1bit and the dynamic range of 86.1 dB with an input signal frequency of 2.5kHz, a sampling frequency of 2.56MHz and an oversampling rate of 64. The FOM (Walden) from the measurement result is 269 fJ/step, FOM (Schreier) was calculated as 169.3 dB.

• Journal of radiological science and technology
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• v.37 no.4
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• pp.307-313
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• 2014

The purpose of this study is that in coronary artery angiography computed tomography (coronary CTA), to gain high quality of image and to use low dose radiation by administrating normal saline and converting the mode of scanning heart rate (HR) characteristics before infusing contrast media. All patients data (total specimens: 200, male: 108, female: 92) were measured by using appropriate mode of scanning the heart rate (HR) after injection of saline. in addition we measured radiation dose (CTDIvol, effective dose) in all examinations. CT number and noise, and blurring of coronary artery (proximal RCA, middle RCA, proximal LCA) were measured and compared. The result of this study after injection of saline, mean heart rate was decreased about $4.8{\pm}0.3bpm$ (beats per minute). 33 patients (13%) got converting scan mode due to reducing heart rate (HR). In prospective gating mode, radiation dose were measured less $6.0{\pm}1.0mSv$ (54.1%) than retrospective gating mode. Also showed a significant difference in heart rate decrease in image evaluation.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.8
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• pp.939-944
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• 2014

Traffic accidents caused by the attention dispersion are increasing and the behavior of the attention dispersion affects the front-observing rate, road keeping ability, and reaction time for a dangerous situation. Many drivers listen to a radio broadcast and they have to change the frequency for continuously listening a radio broadcast of the specific broadcasting station in case of crossing a boundary of the particular area. In this situation, the possibility of a car accident increases, because the attention dispersion of a driver might be occurred. Especially, the risk of a car accident caused by changing the frequency of a radio is more serious in the highway, due to the high speed of a vehicle. In order to reduce the risk of a car accident caused by handling a radio during driving car, in this paper, we propose an automatic frequency conversion algorithm for vehicle radio, which saves normal system frequencies of primary broadcasting stations in a database and determines new frequency of the changed area using the location information obtained from a navigation system in a boundary of the specific area. After determining new frequency, the proposed algorithm selects a frequency with better receiving rate comparing signal-to-noise ratios (SNRs) of two signals corresponding previous and new frequencies.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.2
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• pp.217-225
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• 2020

Concrete waste accounts for approximately 70~80% of the total waste generated during the decommissioning of nuclear power plants (NPPs). Based upon the concentration of each radionuclide, the concrete waste from the decommissioning can be used in the determination of the clearance threshold used to classify waste as radioactive. To reduce the cost of radioactive concrete waste disposal, it is important to perform decontamination before self-disposal or limited recycling. Therefore, it is necessary to estimate the internal radioactivity distribution of radioactive concrete waste to ensure effective decontamination. In this study, the performance metrics of various Compton reconstruction algorithms were compared in order to identify the best strategy to estimate the internal radioactivity distribution in concrete waste during the decommissioning of NPPs. Four reconstruction algorithms, namely, simple back-projection, filtered back-projection, maximum likelihood expectation maximization (MLEM), and energy-deconvolution MLEM (E-MLEM) were used as Compton reconstruction algorithms. Subsequently, the results obtained by using these various reconstruction algorithms were compared with one another and evaluated, using quantitative evaluation methods. The MLEM and E-MLEM reconstruction algorithms exhibited the best performance in maintaining a high image resolution and signal-to-noise ratio (SNR), respectively. The results of this study demonstrate the feasibility of using Compton images in the estimation of the internal radioactive distribution of concrete during the decommissioning of NPPs.

• Journal of radiological science and technology
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• v.39 no.2
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• pp.227-236
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• 2016

Dynamic positron emission tomography(dPET) is widely used medical imaging modality that can provide both physiological and functional neuro-image for diagnosing various brain disease. However, dPET images have low spatial-resolution and high noise level during spatio-temporal analysis (three-dimensional spatial information + one-dimensional time information), there by limiting clinical utilization. In order to overcome these issues for the spatio-temporal analysis, a novel computational technique was introduced in this paper. The computational technique based on singular value decomposition classifies multiple independent components. Signal components can be distinguished from the classified independent components. The results show that signal to noise ratio was improved up to 30% compared with the original images. We believe that the proposed computational technique in dPET can be useful tool for various clinical / research applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.10
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• pp.1142-1149
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• 2007

In this paper, the development of wideband MIMO channel sounder and a pilot measurement result is described for research on the multi antenna radio propagation characteristics considering urban environment at microwave frequencies. We developed $4{\times}4$ MIMO(BW:100 MHz) channel sounder using the high speed switching mechanism and periodic pseudo random binary signals method considering next generation mobile communication system. A pilot measurement campaign at the urban area of Bundang is presented for confirmation of system performance. From the analysis of measurement data, wideband path loss exponent of 3.7 and 8 GHz band is 1.79 and 1.76. Average RMS delay spread is 200 ns and 42 ns respectively. From the experiment results, operation of this measurement system is confirmed considering research for a coverage, SNR and channel capacity in urban environment at microwave frequencies.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.1
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• pp.23-30
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• 2007

We observed the NaCl concentration of solutions using a near-field microwave microprobe(NFMM). Instead of the usual technique, we take advantage of the noncontact evaluation capabilities of a NFMM. A NFMM with a high Q dielectric resonator allows observation of small variations of the permittivity due to changes in the NaCl concentration. The changes of NaCl concentration due to a change of permittivity of the NaCl solution were investigated by measuring the microwave reflection coefficient $S_{11}$ of the resonator. The NaCl sensor consisted of a dielectric resonator coupled to a probe tip at an operating frequency of about f=4 GHz. The change of the NaCl concentration is directly related to the change of the reflection coefficient due to a near field electromagnetic interaction between the probe tip and the NaCl solution. In order to determine the probe selectivity, we measured a mixture solution of NaCl and glucose.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.3
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• pp.78-86
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• 2017

In this paper, we propose hidden object detection system using parametric array based on acoustic signal that is harmless to human body. A transmit signal of the proposed detection system uses a high directive chirp signal generated from parametric array phenomenon, which uses technique to improve a signal to noise (SNR) of a received signal and a distance resolution trough the dechirp processing. The transmit sensor array is constructed as $8{\times}2$ and has a horizontal beam width of $7^{\circ}$ and vertical beam width of $26^{\circ}$. To verify the detection and visualization of the proposed system, a 2-axis driving control system based on linear stage was constructed, and A-scan, B-scan, and C-scan experiments was addressed for hidden object. From experimental results, we detected and visualized the hidden bronze plate and pipe by cloth and the visualized shapes was confirmed. Especially, the obtained errors was $0.015m^2$ for bronze plate, and $0.046m^2$ for pipe.

• Progress in Superconductivity
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• v.7 no.1
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• pp.28-35
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• 2005

We propose a method to measure atrial arrhythmias (AA) such as atrial fibrillation (Afb) and atrial flutter (Afl) with a SQUID magnetocardiograph (MCG) system. To detect AA is one of challenging topics in MCG. As the AA generally have irregular rhythm and atrio-ventricular conduction, the MCG signal cannot be improved by QRS averaging; therefore a SQUID MCG system having a high SNR is required to measure informative atrial excitation with a single scan. In the case of Afb, diminished f waves are much smaller than normal P waves because the sources are usually located on the posterior wall of the heart. In this study, we utilize an MCG system measuring tangential field components, which is known to be more sensitive to a deeper current source. The average noise spectral density of the whole system in a magnetic shielded room was $10\;fT/{\surd}Hz(a)\;1\;Hz\;and\;5\;fT/{\surd}Hz\;(a)\;100\;Hz$. We measured the MCG signals of patients with chronic Afb and Afl. Before the AA measurement, the comparison between the measurements in supine and prone positions for P waves has been conducted and the experiment gave a result that the supine position is more suitable to measure the atrial excitation. Therefore, the AA was measured in subject's supine position. Clinical potential of AA measurement in MCG is to find an aspect of a reentry circuit and to localize the abnormal stimulation noninvasively. To give useful information about the abnormal excitation, we have developed a method, separative synthetic aperture magnetometry (sSAM). The basic idea of sSAM is to visualize current source distribution corresponding to the atrial excitation, which are separated from the ventricular excitation and the Gaussian sensor noises. By using sSAM, we localized the source of an Afl successfully.