• Journal of the Korean Society for Precision Engineering
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• v.18 no.5
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• pp.105-111
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• 2001

The creep crack growth properties in 3.3NiCrMoV steel were investigated at 55$0^{\circ}C$ by using CT specimen under constant load and constant Ct condition that was held during crack growth of Imm distance. Ct lelied on load line displacement rate, C＊usually increased with crack length though load is reduced in order to maintain constant Ct value as crack growth and appeared scatter band. At constant load and Ct region, crack growth slope was 0.900 and 0.844 each, on the other hand C＊ slope was 0.480. Fully coalesced area(FCA) ahead of crack tip increased as Ct increase to the critical value, and after that value FCA decreased. For the tertiary creep stage of crack growth test, the most of displacement was due to the steady state creep, except only small part due to the primary creep and other effects. Therefore, tests were mainly interrupted in the tertiary stage to obtain high value of Ct.

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.1
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• pp.77-84
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• 2017

Purpose: To evaluate the image quality improvement and dosimetric effects on virtual monochromatic images of a Dual Source-Dual Energy CT(DS-DECT) for radiotherapy planning. Materials and Methods: Dual energy(80/Sn 140 kVp) and single energy(120 kVp) scans were obtained with dual source CT scanner. Virtual monochromatic images were reconstructed at 40-140 keV for the catphan phantom study. The solid water-equivalent phantom for dosimetry performs an analytical calculation, which is implemented in TPS, of a 10 MV, $10{\times}10cm^2$ photon beam incident into the solid phantom with the existence of stainless steel. The dose profiles along the central axis at depths were discussed. The dosimetric consequences in computed treatment plans were evaluated based on polychromatic images at 120 kVp. Results: The magnitude of differences was large at lower monochromatic energy levels. The measurements at over 70 keV shows stable HU for polystyrene, acrylic. For CT to ED conversion curve, the shape of the curve at 120 kVp was close to that at 80 keV. 105 keV virtual monochromatic images were more successful than other energies at reducing streak artifacts, which some residual artifacts remained in the corrected image. The dose-calculation variations in radiotherapy treatment planning do not exceed ${\pm}0.7%$. Conclusion: Radiation doses with dual energy CT imaging can be lower than those with single energy CT imaging. The virtual monochromatic images were useful for the revision of CT number, which can be improved for target coverage and electron densities distribution.

• Journal of Haehwa Medicine
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• v.12 no.1
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• pp.11-26
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• 2003

Alzheimer's disease (AD) is characterized by amyloid deposition and associated loss of neunons in brain regions involved in learning and memory processes. Several causes of evidence support that the congnitive disturbance is closed associated with the deficit of cerebral acetylcholine neurotransmission, and the effect of carboxyl terminal 105 amino acid fragment (CT105) of the amyloid precursor protein (APP) on the gene expression of proinflammatory cytokines. We tested it on the scopolamine-induced amnesia model of the ICR mouse using the Morris water maze with repeated orally administration of 1st Green-Tea extract (200 mg/kg) and 2nd Green-Tea extract (200 mg/kg). The Green-Tea prevents impairment of learning and memory and neuronal loss in mouse models of cognitive disturbance and it demonstrated selectivity for inhibition of acetylcholinesterase (AChE). Furthermore, the repeated administration of Green-Tea, CT105-induced alzheimer's mouse model showed central cholinergic activity by ameliorates learning and memory impairment, and isolation of CD14 microglia showed significantly decreases intracellular release of the proinflammatory cytokines tumor necrosis factor-${\alpha}$, interleukin-$1{\beta}$ and reactive oxygen species (ROS). Because of its composite profile, oral therapeutic index and a prophylactic, Green-Tea is considered the better therapeutic candidate for the treatment of Alzheimer's disease.

• Journal of The Korean Association of Information Education
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• v.21 no.1
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• pp.105-114
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• 2017

Because the concepts and components of computational thinking included in the Information Education Curriculum and the Software Education Guidelines are different, it has been difficult to establish computational thinking-based software education in schools. Therefore, this study, which is based on the Delphi survey results from 39 experts, we defined computational thinking as 'computing thinking' and separated the components of computational thinking into five main categories: (1) problem definition, (2) data analysis, (3) abstraction, (4) automation, and (5) generalization. In addition, we selected software areas that are strongly related to computational thinking in the KAIE's information Curriculum Standard Model and surveyed experts to decide which computing thinking components are related to the achievement criteria of the software areas.

• Progress in Medical Physics
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• v.27 no.3
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• pp.105-110
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• 2016

Sparse angular sampling has been studied recently owing to its potential to decrease the radiation exposure from computed tomography (CT). In this study, we investigated the analytic reconstruction algorithm in sparse angular sampling using the sinogram interpolation method for improving image quality and computation speed. A prototype of the spectral CT system, which has a 64-pixel Cadmium Zinc Telluride (CZT)-based photon-counting detector, was used. The source-to-detector distance and the source-to-center of rotation distance were 1,200 and 1,015 mm, respectively. Two energy bins (23~33 keV and 34~44 keV) were set to obtain two reconstruction images. We used a PMMA phantom with height and radius of 50.0 mm and 17.5 mm, respectively. The phantom contained iodine, gadolinium, calcification, and lipid. The Feld-kamp-Davis-Kress (FDK) with the sinogram interpolation method and Maximum Likelihood Expectation Maximization (MLEM) algorithm were used to reconstruct the images. We evaluated the signal-to-noise ratio (SNR) of the materials. The SNRs of iodine, calcification, and liquid lipid were increased by 167.03%, 157.93%, and 41.77%, respectively, with the 23~33 keV energy bin using the sinogram interpolation method. The SNRs of iodine, calcification, and liquid state lipid were also increased by 107.01%, 13.58%, and 27.39%, respectively, with the 34~44 keV energy bin using the sinogram interpolation method. Although the FDK algorithm with the sinogram interpolation did not produce better results than the MLEM algorithm, it did result in comparable image quality to that of the MLEM algorithm. We believe that the sinogram interpolation method can be applied in various reconstruction studies using the analytic reconstruction algorithm. Therefore, the sinogram interpolation method can improve the image quality in sparse-angular sampling and be applied to CT applications.

• Journal of Radiation Protection and Research
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• v.46 no.3
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• pp.98-105
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• 2021

Background: In recent events of the coronavirus disease 2019 (COVID-19) pandemic, computed tomography (CT) scans are being globally used as a complement to the reverse-transcription polymerase chain reaction (RT-PCR) tests. It will be important to be aware of major organ dose levels, which are more relevant quantity to derive potential long-term adverse effect, for Korean pediatric and adult patients undergoing CT for COVID-19. Materials and Methods: We calculated organ dose conversion coefficients for Korean pediatric and adult CT patients directly from Korean pediatric and adult computational phantoms combined with Monte Carlo radiation transport techniques. We then estimated major organ doses delivered to the Korean child and adult patients undergoing CT for COVID-19 combining the dose conversion coefficients and the international survey data. We also compared our Korean dose conversion coefficients with those from Caucasian reference pediatric and adult phantoms. Results and Discussion: Based on the dose conversion coefficients we established in this study and the international survey data of COVID-19-related CT scans, we found that Korean 7-year-old child and adult males may receive about 4-32 mGy and 3-21 mGy of lung dose, respectively. We learned that the lung dose conversion coefficient for the Korean child phantom was up to 1.5-fold greater than that for the Korean adult phantom. We also found no substantial difference in dose conversion coefficients between Korean and Caucasian phantoms. Conclusion: We estimated radiation dose delivered to the Korean child and adult phantoms undergoing COVID-19-related CT examinations. The dose conversion coefficients derived for different CT scan types can be also used universally for other dosimetry studies concerning Korean CT scans. We also confirmed that the Caucasian-based CT organ dose calculation tools may be used for the Korean population with reasonable accuracy.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1999.04a
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• pp.105-107
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• 1999

본 연구의 목적은 CT장비로부터 얻어지는 단면 영상을 이용하여 재구성한 3차원 Voxel 정보를 기반으로 의료 시술 중 위험도가 높으며 장기간의 수술 훈련이 필요한 수술인 척추경나사 삽입술에 대한 모의 시술기를 개발하는 것이다. 모의 시술기의 입력은 환자의 환부에 대한 CT와 모의 시술을 해보고자 하는 의사 (사용자)의 입력 (경나사의 진입 위치와 각도)이 되며 출력은 의사들이 시술장에서 받을 수 있는 유일한 방법인 Voxel데이터로부터 재생성된 X-Ray이미지, 혹은 C-Arm의 동영상이며, 최종 결과 출력은 나사못이 삽입된 재구성 CT 이미지들과 3차원 정보를 볼 수 있는 Image Based Rendering의 Image data set이 된다. 본 연구에서는 각 시각화 부분의 특성을 고려하여 direct volume projection, surface modeling, 그리고 최근 많은 관심을 받고 있는 Image Based Rendering 기법을 intergrate하여 사용하였으며 각 시각화 모듈의 초고속 정보 통신망에서의 정보 교환에 대한 방법론에 대해 다루고 있다.

• Journal of Biomedical Engineering Research
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• v.33 no.3
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• pp.105-113
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• 2012

Biopsy is a type of histopathological examinations, in which a physician samples cells or tissues from a patient's suspicious lesion. Such a lesion frequently resides deep inside human body, and then a percutaneous biopsy is therefore performed using a thick needle with the assistance of medical imaging such as computed tomography(CT) and magnetic resonance imaging(MRI). Recently modern robotic technology is being introduced to percutaneous biopsy in order to reduce any possible human error and hazard on physicians caused by medical imaging. After medical imaging locates the exact location of lesion, an optimization algorithm plans the path for a biopsy needle. Subsequently, a robot system moves the biopsy needle to the lesion in accurate and safe way with the control of a practitioner or automatically. In this article, we try to look into the state-of-art of percutaneous biopsy using such robotic technology. We classified percutaneous biopsy robots by mechanical characteristics and by imaging technology. Then, advantage and disadvantage of each class type are described as well as the basic description, and a few representative designs for each type are introduced. Current research issues of robotized percutaneous biopsy are subjectively selected for the readers' convenience. We emphasize the basic technology of actuator and sensors compatible with imaging technology to conclude this review.

• Journal of Korean Neurosurgical Society
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• v.54 no.2
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• pp.100-106
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• 2013

Objective : To investigate the cases of intracranial abnormal brain MRI findings even in the negative brain CT scan after mild head injury. Methods : During a 2-year period (January 2009-December 2010), we prospectively evaluated both brain CT and brain MRI of 180 patients with mild head injury. Patients were classified into two groups according to presence or absence of abnormal brain MRI finding even in the negative brain CT scan after mild head injury. Two neurosurgeons and one neuroradiologist validated the images from both brain CT scan and brain MRI double blindly. Results : Intracranial injury with negative brain CT scan after mild head injury occurred in 18 patients (10.0%). Headache (51.7%) without neurologic signs was the most common symptom. Locations of intracranial lesions showing abnormal brain MRI were as follows; temporal base (n=8), frontal pole (n=5), falx cerebri (n=2), basal ganglia (n=1), tentorium (n=1), and sylvian fissure (n=1). Intracranial injury was common in patients with a loss of consciousness, symptom duration >2 weeks, or in cases of patients with linear skull fracture (p=0.00013), and also more frequent in multiple associated injury than simple one (35.7%>8.6%) (p=0.105). Conclusion : Our investigation showed that patients with mild head injury even in the negative brain CT scan had a few cases of intracranial injury. These findings indicate that even though the brain CT does not show abnormal findings, they should be thoroughly watched in further study including brain MRI in cases of multiple injuries and when their complaints are sustained.

• Journal of radiological science and technology
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• v.45 no.3
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• pp.213-223
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• 2022

Although the number of computed tomography(CT) is increasing every year, it is insufficient to establish appropriate workload calculation standards of radiologic technologist to provide optimal medical services to patients, such as patient safety management and infection management. The purpose of this study is to present guidelines for calculating the appropriate workload of radiologic technologist by analyzing the work flow of CT procedures and the time required for CT examination in major hospitals. As for the study subjects and methods, the appropriate process for each step of CT examination was investigated to systematically present the process and time required for the actual examination, and the CT procedure time of 104,105 adult patients and 465 pediatric patients under the age of 6 were analyzed. For the time required, data according to the use of contrast medium, procedure type, and adult/child were collected and compared. The test time of CT examination using contrast medium took about 13 minutes when one radiologic technologist worked and about 9 minutes when two radiologic technologists worked. The time required for the procedures were statistically significant depending on the presence or absence of contrast medium, multi-phase procedure, and patient age (considering pediatric patients). As a result, in order to thoroughly perform patient safety and infection management, the appropriate workload increased by about 40% when there were two radiologic technologists. The limit workload was an average of 32 people per day with one radiologic technologist per 15 minutes, and 48 people per day with two radiologic technologist per 10 minutes. This is a marginal workload, and in the case of procedures that require more time to acquire radiographic images, the interval between reservations should be widened.