• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.3
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• pp.138-141
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• 2006

Blood flow is one of vital signals related to human physiological information. Photoplethysmograph (PPG) has been used to measure indirectly heart rate, blood oxygen saturation ($SpO_2$), and so on. Because PPG signal is weak and sensitive to motion artifacts, it is very important to continuously obtain stable PPG signal during free movement. In this study, we applied the scaled Fourier linear combiner (SFLC) using both the adaptive filter and FLC to remove effectively the motion artifacts as well as background noise in the real time without additional signal correlated with motion from a accelerometer. The proposed method would be useful to reduce the movement and background noise which are not synchronized with heart rate.

• Proceedings of the Korea Society for Simulation Conference
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• 2003.11a
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• pp.201-206
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• 2003

In clinical practice, CT Angiography is a powerful technique for the visualziation of blood flow in arterial vessels throughout the body. However CT Angiography images of blood vessels anywhere in the body may be fuzzy if the patient moves during the exam. In this paper, we propose a novel technique for removing global motion artifacts in the 3D space. The proposed methods are based on the two key ideas as follows. First, the method involves the extraction of a set of feature points by using a 3D edge detection technique based on image gradient of the mask volume where enhanced vessels cannot be expected to appear, Second, the corresponding set of feature points in the contrast volume are determined by correlation-based registration. The proposed method has been successfully applied to pre- and post-contrast CTA brain dataset. Since the registration for motion correction estimates correlation between feature points extracted from skull area in mask and contrast volume, it offers an accelerated technique to accurately visualize blood vessels of the brain.

• Progress in Medical Physics
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• v.20 no.4
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• pp.244-252
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• 2009

The purpose of this study is to compensate for susceptibility and a ferromagnetic body artifact using CFA and TGV on MR Imaging. A total of 30 patients (15 men and 15 women, mean age: 45 years) were performed on head and neck diseases. MR Unit used a 1.5T superconducting magnet (GE medical system, High Density). This study have investigated by changing with CFA and TGV (70, 90, 110, 130, 150) searching for compensation values about susceptibility and a ferromagnetic body artifact in 60 kg standards of body weight (p<0.05). As a quality results, Image qualities were obtained at different score from CFA and TGV (70, 90, 110, 130, $150=3.23{\pm}0.35$, $4.31{\pm}0.02$ $4.23{\pm}0.21$, $5.12{\pm}0.25$, $7.13{\pm}0.72$, $8.31{\pm}0.01$, $5.21{\pm}0.15$, $6.14{\pm}0.08$, $5.23{\pm}0.72$, $5.91{\pm}0.06$, p<0.05). Absolute CNRs (TG, CNRpre, CNRpost) were acquired with (70:$-1.44{\pm}0.11$, $-2.7{\pm}0.04$, 90:$-2.18{\pm}0.42$, $-4.41{\pm}0.43$, 110:$-2.89{\pm}0.43$, $-5.23{\pm}0.02$, 130:$-2.34{\pm}0.05$, $-5.26{\pm}0.01$, 150: $-2.09{\pm}0.08$, $-3.87{\pm}0.12$, p<0.05). In conclusions, this study could be compensated for metal and flow artifacts surrounding the tissues having artifact by changing CFA and TGV.

• The Korean Journal of Physiology
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• v.5 no.1
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• pp.59-69
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• 1971

Studies were undertaken on the changes in the renal blood flow by relating them with the alterations in the amplitudes in the rheogram of rabbits. The changing pattern of the electrical conductivity was recorded by means of the needle electrodes inserted into the kidney and the surrounding aluminium foil which was grounded. The Impedance Rheograph manufactured by the Narco Company was used. The small artifact which persisted after ligation of the renal vessels was subtracted from the value obtained in each pulsatile wave in the rheogram. The animals were nembutalized intravenously, 30 mg/kg. A plastic canule was inserted into the carotid artery and the arterial blood pressure was monitored continuously with the pressure transducer connected to the physiograph. Stepwise bleedings were performed on the animal. The first bleeding was between 13 to 18 ml in the amount, and it was folowed by consecutive hemorrhages, 5 or 10 ml each time. The total amount of bleeding was summed as much as 1.5-2% of the body weight. Two minutes fter each bleeding th arterial blood pressure, ECG and the rheogram were taken. That was the necessary time to obtain the stabilized picture of each parameter. After closing the bleeding process, the shed blood was retransfused into the animal and the response in the renal blood flow was observed as well as the arterial blood pressure. Particularly the presence or absence of the autoregulatory mechanism in the situation of the hemorrhage was also studied. The results obtained were as follows: 1. In 7 cases out of 22, that was about one third of the total number of experiments, the autoregulatory mechanism of the renal blood flow persisted even in acute hemorrhage, and the decreases in the renal blood flow were less than 10% of the control values even when the arterial blood pressure dropped to 66-87% of the original value obtained before the bleeding. 2. Because of the stepwise bleeding the exact blood pressure at which the renal blood flow reduced as much as one third of the control value could not be obtained. However, the results revealed that the approximate pressure, expressed as percentage of the control value, was 50-60% in 3 cases, 61-70% in 4 cases and 71-80% in 8 cases. In one case the decrease in the renal blood flow exceeded one third of the control value before the pressure dropped to 80% of the control. 3. In 19 cases the decreases in the renal blood flow exceeded one half of the control values by hemorrhage. Then the arterial blood pressure revealed less than 40% of the control value in 6-cases. In 2 cases the pressure was 51-60% of the control pressure. In 5 cases the range of bleed pressure was 61-70%, and in e remaining 6 cases the pressure ranged from 71 to 80% of e control value. 4. Out of 15 cases of retransfusion after definite decreases in the renal blood flow loller·ing the hemorrhage, 9 cases restored their renal blood flow. On the contrary 6 cases showed low values even when the shed blood was retransfused. 5. Theories concerning the mechanism of the autoregulation of the renal blood flow were reviewed for the purpose of explanation of the results obtained. However, there are much to be done before greater satisfaction

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.10
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• pp.1498-1507
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• 2003

A SMPS(scanning mobility particle sizer) system measures the number size distribution of particles using electrical mobility detection technique. An aerosol charge neutralizer, which is a component of the SMPS, is a bipolar charger using a radioactive source to apply an equilibrium charge distribution to aerosols of unknown charge distribution. However, the performance of aerosol charge neutralizers is not well known, especially for highly charged particles. In this study, the effect of the particle charging characteristics of two aerosol charge neutralizers on the measurement using a SMPS system was experimentally investigated for highly charged polydisperse particles. One has radioactive source of $^{85}$ Kr (beta source, 2 mCi) and the other has $^{210}$ Po (alpha source, 0.5 mCi). The air flow rate passing through each aerosol charge neutralizer was changed from 0.3 to 3.0 L/min. The results show that the non-equilibrium character in particle charge distribution appears as the air flow rate increases although the particle number concentration is relatively low in the range of 1.5∼2x10$^{6}$ particles/㎤. The low neutralizing efficiency of the $^{85}$ Kr aerosol charge neutralizer for highly charged particles can cause to bring an artifact in the measurement using a SMPS system. However, the performance of the $^{210}$ Po aerosol charge neutralizer is insensitive to the air flow rate.

• Journal of the Korean Society of Earth Science Education
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• v.10 no.2
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• pp.140-160
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• 2017

The purpose of this study was to develop computational thinking (CT) analysis tool that can be used to analyze CT practices; first, by defining what CT practices are, and then, by identifying which components of CT are reflected in STEAM classes. Exploring various kinds of CT practices, which can be identified while applying the proposed CT analysis tool for exemplary STEAM classes, is another goal of this study. Firstly, to answer the question of "What is CT in science education" and thereby to develop the proposed CT practice analysis tool, three types of published documents about CT definition as the main data in this study have been considered. In the first "analysis tool development" part of this study, the following five elements have been identified as the main components of CT analysis tool as follows; (1) connecting open problems with computing, (2) using tools or computers to develop computing artifact, (3) abstraction process, (4) analyzing and evaluating computing process and artifact, and (5) communicating and cooperating. Based on the understandings that there is a consistent flow among the five components due to their interactions, a flow chart of CT practice has also been developed. In the second part of this study, which is an implementation study, the proposed CT practice analysis tool has been applied in one exemplary STEAM program. To select the candidate STEAM program, four selection criteria have been identified. Then, the proposed CT practice analysis tool has been applied for the selected STEAM program to determine the degree of CT practice reflected in the program and furthermore, to suggest a way of improving the proposed CT analysis tool if it shows some weak points. Through the findings of this study, we suggest that the actual definition of computational thinking will be helpful to converge Technology and Engineering to STEAM education and a strong complement to reinforce STEAM education.

• Investigative Magnetic Resonance Imaging
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• v.4 no.1
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• pp.42-51
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• 2000

Purpose: Projection-type Fast Spin Echo (PFSE) imaging is robust to patient motion or flow related artifact compared to conventional Fast Spin Echo (FSE) imaging, however, it has difficulty in controlling $T_2$ contrast. In this paper, Tz contrast in the PFSE method is analyzed and compared with those of the FSE method with various effective echo times by computer simulation. The contrasts in the FSE and PFSE methods are also compared by experiments with volunteers. From the analysis and simulation, it is shown that ${T_2}-weighted$ images can well be obtained by the PFSE method proposed. Materials and methods: Pulse sequence for the PFSE method is implemented at a 1.0 Tesla whole body MRI system and $T_2$ contrasts in the PFSE and FSE methods are analyzed by computer simulation and experiment with volunteers. For the simulation, a mathematical phantom composed of various $T_2$ values is devised and $T_2$ contrast in the reconstructed image by the PFSE is compared to those by the FSE method with various effective echo times. Multi-slice ${T_2}-weighted$ head images of the volunteers obtained by the PFSE method are also shown in comparison with those by the FSE method at a 1.0 Tesla whole body MRI system. Results: From the analysis, $T_2$ contrast by the PFSE method appears similar to those by the FSE method with the effective echo time in a range of SO-lOOms. Using a mathematical phantom, contrast in the PFSE image appears close to that by the FSE method with the effective echo time of 96ms. From experiment with volunteers, multi-slice $T_2-weighted$ images are obtained by the PFSE method having contrast similar to that of the FSE method with the effective echo time of 96ms. Reconstructed images by the PFSE method show less motion related artifact compared to those by the FSE method. Conclusion: The projection-type FSE imaging acquires multiple radial lines with different angles in polar coordinate in k space using multiple spin echoes. The PFSE method is robust to patient motion or flow, however, it has difficulty in controlling $T_2$ contrast compared to the FSE method. In this paper, it is shown that the PFSE method provides good $T_2$ contrast (${T_2}-weighted$ images) similar to the FSE method by both computer simulation and experiments with volunteers.

• Analytical Science and Technology
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• v.5 no.3
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• pp.269-276
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• 1992

An ion-exchange/conductometric method is applied for the determination of total acidity in simulated atmospheric samples. Non-$H^+$ cations and strong acid anions are enriched by the preconcentrator columns in series and eluted through the corresponding parallel suppressor units. The conductivities from each channel correspond to the concentrations of the resulting ionized species in equivalents per unit volume. The difference is the measure of acidity due to strong acids. With 5-min sampling at a flow rate of 0.3 mL/min, the detection limits for ${NH_4}^+$ and ${SO_4}^{2-}$ are 0.3 and $0.1{\mu}equiv/L$, respectively. The acidity for samples composed of various ions can be determined without significant error, usually less than 5%. The proposed method discriminates against the artifact from the $CO_2$ dissolution. Principles of acidity measurements are also presented.

• Investigative Magnetic Resonance Imaging
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• v.22 no.2
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• pp.131-134
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• 2018

Susceptibility-weighted imaging (SWI) is well known for detecting the presence of hemorrhagic transformation, microbleeds and the susceptibility of vessel signs in acute ischemic stroke. But in some cases, it can provide the tissue perfusion state as well. We describe a case of a patient with hyperacute ischemic infarction that had a slightly hypodense, patchy lesion at the left thalamus on the initial SWI, with a left proximal posterior cerebral artery occlusion on a magnetic resonance (MR) angiography and delayed time-to-peak on an MR perfusion performed two hours after symptom onset. No obvious abnormal signals at any intensity were found on the initial diffusion-weighted imaging (DWI). On a follow-up MR image (MRI), an acute ischemic infarction was seen on DWI, which is the same location as the lesion on SWI. The hypointensity on the initial SWI reflects the susceptibility artifact caused by an increased deoxyhemoglobin in the affected tissue and vessels, which reflects the hypoperfusion state due to decreasing arterial flow. It precedes the signal change on DWI that reflects a cytotoxic edema. This case highlights that, in some hyperacute stages of ischemic stroke, hypointensity on an SWI may be a finding before the hyperintensity is seen on a DWI.

• Investigative Magnetic Resonance Imaging
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• v.11 no.1
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• pp.1-9
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• 2007

The obstacles for cardiac imaging are motion artifacts due to cardiac motion, respiration, and blood flow, and low signal due to small tissue volume of heart. To overcome these obstacles, fast imaging technique with ECG gating is utilized. Cardiac exam using MRI comprises of morphology, ventricular function, myocardial perfusion, metabolism, and coronary artery morphology. During cardiac morphology evaluation, double and triple inversion recovery techniques are used to depict myocardial fluidity and soft tissue structure such as fat tissue, respectively. By checking the first-pass enhancement of myocardium using contrast-enhanced fast gradient echo technique, myocardial blood flow can be evaluated. In addition, delayed imaging in 10 - 15 minutes can inform myocardial destruction such as chronic myocardial infarction. Ventricular function including regional and global wall motion can be checked by fast gradient echo cine imaging in quantitative way. MRI is acknowledged to be practical for integrated cardiac evaluation technique except coronary angiography. Especially delay imaging is the greatest merit of MRI in myocardial viability evaluation.