• Korean Journal of Radiology
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• 제22권6호
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• pp.951-958
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• 2021

Objective: To evaluate the usefulness of virtual monochromatic images (VMIs) obtained using dual-layer dual-energy CT (DL-DECT) for evaluating brain tumors. Materials and Methods: This retrospective study included 32 patients with brain tumors who had undergone non-contrast head CT using DL-DECT. Among them, 15 had glioblastoma (GBM), 7 had malignant lymphoma, 5 had high-grade glioma other than GBM, 3 had low-grade glioma, and 2 had metastatic tumors. Conventional polychromatic images and VMIs (40-200 keV at 10 keV intervals) were generated. We compared CT attenuation, image noise, contrast, and contrast-to-noise ratio (CNR) between tumor and white matter (WM) or grey matter (GM) between VMIs showing the highest CNR (optimized VMI) and conventional CT images using the paired t test. Two radiologists subjectively assessed the contrast, margin, noise, artifact, and diagnostic confidence of optimized VMIs and conventional images on a 4-point scale. Results: The image noise of VMIs at all energy levels tested was significantly lower than that of conventional CT images (p < 0.05). The 40-keV VMIs yielded the best CNR. Furthermore, both contrast and CNR between the tumor and WM were significantly higher in the 40 keV images than in the conventional CT images (p < 0.001); however, the contrast and CNR between tumor and GM were not significantly different (p = 0.47 and p = 0.31, respectively). The subjective scores assigned to contrast, margin, and diagnostic confidence were significantly higher for 40 keV images than for conventional CT images (p < 0.01). Conclusion: In head CT for patients with brain tumors, compared with conventional CT images, 40 keV VMIs from DL-DECT yielded superior tumor contrast and diagnostic confidence, especially for brain tumors located in the WM.

• Restorative Dentistry and Endodontics
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• 제12권1호
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• pp.65-76
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• 1986

Carious dentin can be classified, on the basis of their clinical characteristics, into three groups; sound, sclerotic and active carious dentin. Active carious dentin differs from sclerotic dentin by its abscence of variable bacteria within tubles and amount of chemical content. But the apatite molecules of active carious dentin are not fully studied. The purpose of this study was to observed the physico-chemical characteristics of deep carious dentin. The samples of sound, sclerotic and active carious dentin were obtained respectively from 300 freshly extracted carious teeth. Bacterial-rich zone of superficial soft dentin layer was removed with hand instruments from all samples in advance. The samples were powdered and sieved (200 mesh) before analyses. Identification and estimation of the crystallinity of the samples were carried with X-ray diffraction and infrared absorption analyses. Measurements were made on a Rigaku Denki (Rigaku, geiger flex III, Japan) X-ray diffractometer with Cu-target at 30 Kv, 30 mA and are traced on a monochromatic tracer. Infrared absorption analysis was made on FT-IR spectrophometer (Nicolet Instrument Co.) using KBr pellets containing the samples and was recorded on data process (Model IR-80. Nicolet Instrument, Co). The following conclusions were as follows; 1. The nature of the main inorganic structure of sound, sclerotic and active carious dentin proved to be hydroxyapatite. 2. It was difficult to determine the identification due to their crystallinity of sound, sclerotic and active carious dentin. But sound dentin was the highest in crystallinity among them. 3. The magnesium whitlockite was to be found in active carious dentin, but not in sound and sclerotic dentin. 4. The carbonate content was highest in sound dentin, but the lowest was in active carious dentin.

• Bulletin of the Korean Chemical Society
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• 제25권7호
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• pp.983-985
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• 2004

PMMA-coated CdS nanorod was prepared by encapsulation of CdS nanorod through the polymerization process of PMMA on the surface of CdS nanorod. PMMA organic nanotube was then obtained from the elimination of the CdS nanorod by the photocorrosion. For the photocorrosion reaction of the CdS nanorod, monochromatic light was irradiated to the oxygen-saturated aqueous methyl viologen solution with PMMAcoated CdS nanorod. Photocorrosion reactions of PMMA-coated CdS nanorod were investigated and characterized by utilizing UV-Vis absorption, X-ray diffraction (XRD) and scanning electron microscopic (SEM) and transmission electron microscopic (TEM) images.

• 자원환경지질
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• 제42권5호
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• pp.509-512
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• 2009

제올라이트 메소라이트($Na_{5.33}Ca_{5.33}Al_{16}Si_{24}O_{80}{\cdot}21.33H_2O$)에 대한 고압에서의 회절자료가 200 마이크론 크기로 단색화 된 방사광가속기 X-선원과 다이아몬드 앤빌셀을 사용하여 5 GPa까지 측정되었다. 물과 알코올을 사용한 수압 하에서 메소라이트의 초기 탄성 특성은 0.5 GPa에서 1.5 GPa 사이에서 일어나는 ab-평면의 연속적인 팽창과 c-축 상의 수축에 기인한 전체적인 격자부피의 팽창으로 관찰된다. 이후의 압력에서는 회절패턴의 변화로부터 질서-무질서 전이의 증거가 보여진다. 메소라이트의 c-축에 평행한 채널에는 양이온으로서 소디움과 칼슘이 b-축 방향으로 1:2 비율의 질서 있는 배열을 보이고 있는데 이로 인해 1.5 GPa까지 에서는 이러한 배열의 증거인 $3b_{natrolite}$ 격자패턴이 관찰된다. 격자부피의 확장 이후 1.5 GPa 이상에서 2.5 GPa 까지 에서는 격자부피 변화의 정도가 약해지며, 양이온의 무질서적인 배열에 의한 $b_{natrolite}$ 격자패턴이 관찰된다. 이후 압력의 계속된 증가는 점진적인 격자부피의 감소를 유발시키며 새로운 형태의 질서 있는 배열상을 지시하는 $3c_{natrolite}$ 격자패턴으로의 변화를 보여준다. 이로부터 압력에 의한 초수화 상태의 메소라이트는 질서-무질서-질서 형태의 채널 내부 혹은 채널간의 양이온 배열패턴 변화를 겪는 것으로 추정할 수 있다.

• 자원환경지질
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• 제49권1호
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• pp.23-30
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• 2016

자연산 로소나이트(Ca-Lawsonite, $CaAl_2Si_2O_7(OH)_2{\cdot}H_2O$) 분말의 압력증가에 따른 변화와 구조적 특성을 소형 압력 발생장치인 다이아몬드 앤빌셀과 실시간 싱크로트론 X-선 회절실험을 통하여 확인하였다. 본 연구에서 시료에 적용한 압력은 1 기압에서 8 GPa 까지였으며 메탄올, 에탄올, 물의 혼합 용액을 압력 매개체로 하여 상온조건에서 실험하였고, 특이한 상전이나 압력하 부피변화의 이상현상은 발견되지 않은 가역적 압축특성을 관찰하였다. 최고압력까지 로소나이트는 결정성을 잃지 않는 것으로 확인되었고 압력증가에 따른 체적감소를 통해 체적탄성률($B_0$)을 계산해 본 결과 146(6) GPa로 도출되었다. 체적탄성률과 함께 계산된 선형압축률은 a-, b-, c-축에서 각각 0.0022, 0.0024, $0.0020GPa^{-1}$로 압력에 의한 부피감소는 대체적으로 3축이 같은 비율로 감소하는 것을 확인하였다.