• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2006년도 춘계종합학술대회
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• pp.239-242
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• 2006

골다공증은 해면골의 골소주 두께 감소 및 파단에 기인한 전체적인 골질이 저하되는 질병이다. 골다공증을 예방과 조기진단을 하기 위해서는 골밀도를 측정하여야 한다. 보다 나은 이미지를 얻기 위해 Digital X-Ray로 골밀도를 측정하여 영상 처리하기 위한 방법을 제시한다. 먼저 디지털 센서에서 증감지와 렌즈간 거리가 가까워서 증감지의 중심과 주변부의 광 경로차이가 발생하므로 왜곡이 발생하는데 이를 균일화하여야 한다. 그리고 X-Ray장비의 조건에 따라 영상에 많은 차이를 보이므로 영상의 밝기를 보정하는 과정이 필수적이다.

• 한국의학물리학회지:의학물리
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• 제32권1호
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• pp.1-17
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• 2021

The evolution of X-ray computed tomography (CT) has been based on the discovery of X-rays, the inception of the Radon transform, and the development of X-ray digital data acquisition systems and computer technology. Unlike conventional X-ray imaging (general radiography), CT reconstructs cross-sectional anatomical images of the internal structures according to X-ray attenuation coefficients (approximate tissue density) for almost every region in the body. This article reviews the essential physical principles and technical aspects of the CT scanner, including several notable evolutions in CT technology that resulted in the emergence of helical, multidetector, cone beam, portable, dual-energy, and phase-contrast CT, in integrated imaging modalities, such as positron-emission-tomography-CT and single-photon-emission-computed-tomography-CT, and in clinical applications, including image acquisition parameters, CT angiography, image adjustment, versatile image visualizations, volumetric/surface rendering on a computer workstation, radiation treatment planning, and target localization in radiotherapy. The understanding of CT characteristics will provide more effective and accurate patient care in the fields of diagnostics and radiotherapy, and can lead to the improvement of image quality and the optimization of exposure doses.

• Current Applied Physics
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• 제18권11호
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• pp.1212-1217
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• 2018

The electric field-induced modifications of magnetic anisotropy in CoFeB/MgO systems are studied using X-ray resonant magnetic scattering and magneto-optical Kerr effect. Voltage dependent changes of the magnetic anisotropy of -12.7 fJ/Vm and -8.32 fJ/Vm are observed for Ta/CoFeB/MgO and Hf/CoFeB/MgO systems, respectively. This implies that the interfacial perpendicular magnetic anisotropy is reduced (enhanced) when electron density is increased (decreased). X-ray resonant magnetic scattering measurements reveal that the small in-plane magnetic component of the remanent state of CoFeB/MgO systems with weak magnetic anisotropy changes depending on the applied voltage leading to modification of the magnetic anisotropy at the CoFeB/MgO interface.

• 한국전문물리치료학회지
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• 제8권1호
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• pp.51-58
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• 2001

In children with cerebral palsy, bone density is decreased by disturbance of bone remodelling due to lack of normal weight bearing and muscle contraction through physical activity. Loss of bone density cause fracture, delays treatment with immobilization, and leads to functional limitation. The purpose of this study was to investigate bone mineral density of lumbar spine in children with spastic quadriplegia and diplegia. Six spastic quadriplegia and 14 spastic diplegia were evaluated in this study. QDR 4500 X-ray densitometer was used to measure bone density at lumbar spine (L1~L4). Children with cerebral palsy showed lower bone density than that of normal children. Bone density in children with spastic quadriplegia and diplegia was $-1.812{\pm}.962$, $-1.519{\pm}.935$, respectively. However, there was no significant differences in bone density between children with spastic quadriplegia and diplegia. There was no significant difference in bone density relation to motor development level, height, and weight. Further study is needed to find the appropriate interventions for preventing loss of bone density in children with cerebral palsy.

• 한국환경보건학회지
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• 제34권2호
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• pp.131-136
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• 2008

The variation of the particle size distribution and density as well as the chemical composition of aerosols is important to evaluate the particles. This study measured and analyzed airborne particles using a scanning mobility particle sizer (SMPS) system and an aerodynamic particle sizer (APS) at the University of Seoul during every season. The highest particle number concentration of airborne particles less than $0.9\;{\mu}m$, occurred in winter, while the highest particle number concentration of airborne particles more than $0.9\;{\mu}m$, occurred in spring. Mass concentration appeared highest at spring. Also, when we compared $\beta$-ray's mass concentration with calculated mass concentration by using the SMPS-APS system during each season, density of the winter is $1.92\;g/cm^3$, spring density is $1.64\;g/cm^3$, fall density is $1.57\;g/cm^3$. We found out that PM10 density was differ every season. However, while the calculated density is whole density for PM10 the density of each diameter was different. In this study the density estimation equation of the QCM cascade impactor measured mass concentration of each diameter.

• Imaging Science in Dentistry
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• 제30권1호
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• pp.16-22
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• 2000

Purpose : To evaluate the bone densities measured on copper-equivalent image of cross sectional view of mandibular edentulous premolar area obtained by multifuctional panoramic x-ray machine, PM 2002 CC with transversal slicing system. Materials and Methods: Panoramic cross sectional views with 8 mm focal layer of aluminum step and blocks, of hydroxyapatite (RA) step, 6 HA blocks and copper step wedge having 0.03 mm thickness of each step, and of 3 bone blocks cutted by 8 mm thickness mesiodistally and a dry mandible with copper step wedge were taken by using transversal slicing system in PM 2002 Cc. All reference-equivalent images were made and analyzed by NIH image program. Results: The average copper-equivalent value of cancellous bone of bone blocks on the panoramic cross sectional view was 0.026 ± 0.020 mm Cu. The calculated average bone density was 0.38g/cm². There was no significant difference (P>0.1) between the bone densities on intraoral digital view and on the panoramic digital cross sectional view. Conclusion: The copper-equivalent image of panoramic digital cross sectional view obtained by PM 2002 CC with very thin copper step wedge was supposed to be useful to measure the bone density of cancellous bone of mandible at the premolar edentulous area.

• 한국결정성장학회지
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• 제4권4호
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• pp.388-394
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• 1994

단결정 Hg(1-x)Cd(x)Te (MCT,X=0,21)가 특수 제작된 고압로에서 Traveling Heater Method(THM)으로 성장되었다.X-선 회절 실험으로 MCT는 입방ZnS 구조임을 확인하였다. 측정된 격자상수는 $6.464 {\AA}$이엇으며, J.C.Wooley가 측정한 값과 비교하여 얻은 MCT의 성분비는 0.21이었다.MCT의 결정 구조를 분석하기 위하여 X-선 회절 강도로 부터 전자 밀도를 계산하였다.전자 분포 밀도도로 부터 MCT는 주로 공유 결합을 하고 있으며, 인접 원자들 상에는 사면체 구조를 이루고 있음을 알 수 있다. 격자 상수가 Vegard line으로 부터 편이 되는 원인은 성분비x가 증가될 때 원자간 거리 변화의 비선형적 증가로 판단되며, 이것은 결합 에너지와 관련될 것으로 추축된다.

• 대한방사선기술학회지:방사선기술과학
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• 제10권1호
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• pp.49-53
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• 1987

This thesis compared and analyzed the characteristics, centered on a characteristic curve, about X-ray computerized tomographic film generally used in Korea recently. The results were as follows: 1. Maximum gradient (gamma) was film A-2.19, film B-2.00, film C-1.92. 2. Latitude was confined within the limits of density 0.6-2.0 in all. 3. When we changed window center from 0 to 40, the difference of density, which was in 1.0, was film A-0.12, film B-0.16, fil m C-0.14. 4. When we changed window width from 0 to 500, the difference of density, which was in 1.0, was film A-0.06, film B-0.08, film C-0.05. 5. In the case of window width 50 and window center 20, latitude was 0.5-2.0, 0.5-2.2, 0.5-1.9 and gamma value was 1.74, 1.82, 1.72 respectively, 6. In the case of window width 80 and window center 30, latitude was 0.6-2.2, 0.6-2.3, 0.8-2.2 and gamma value was 2.0, 2.13, 1.95 respectively.

• 대한방사선기술학회지:방사선기술과학
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• 제8권2호
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• pp.11-14
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• 1985

The author came to analize and get the following problems after researched radiographic quality in order to find out the necessary factors to improve in radiographs of frontal projection of the chest selected at random of the adult patients (1545 male, 1520 female) who had been examined in 4 departments of radiology of the general hospitals in Seoul and Kyungki area. 1. Problems of x-ray film or of radiographic cassette appeared in 2.97% radiographs on account of selection of the film size (except costophrenic sinus) (1.79%), poor screen-film contact (0.85%), light leakage of cassette (0,33%). 2. Problems of patients' positioning or breathing appeared in 16.57% radiographs of all because of overlapping of lung apex and clavicle (6.98%), overlapping of scapula and lung field (5.87%), asymmetrical projection of clavicles (1.76%), errors in positioning and breathing of the patient (1.96%). 3. Problems of x-ray exposure factors or film processing appeared in 22.25% radiographs because of over-density (2.64%), under-density (3.95%), fog (0.59%), demonstration density under clavicles or lung marking unsharply (3.82%), not clear of lung marking from breast region (0.94%), not clear the lung marking from the part overlapped of heart and lungs (3.92%), not clear the lung marking from the part overlapped of liver and lung (6.49%).

• 대한방사선기술학회지:방사선기술과학
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• 제43권3호
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• pp.187-194
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• 2020

Bone mineral density is a examination to measure the amount of bone in patients with metabolic bone disease. It is a low dose, but may cause unnecessary exposure to the gonads and other organs located in the periphery when examining the lumbar and proximal femurs. Therefore, the purpose of this study was to evaluated the exposure dose for each organ exposed during the bone mineral density through simulation, and analyzed the applicability of the subject to radiation shielding devices using 3D printing materials. As a result, the highest dose was shown at 11.47 uSv in the breast during lumbar examination and 8.98 uSv in the testis during proximal femur examination. Also, the farther away from the examination site, the lower the effect of the scattering-ray. The shielding effect of using 3D printing shielding device showed high results in proportion to the effective atomic number and specific gravity of the printing material. Among the printing materials, ABS + W showed an effect of at least 78.72 to 96.3 9% compared to the existing lead material.