• 한국건설순환자원학회논문집
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• 제8권4호
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• pp.498-505
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• 2020

골재는 콘크리트 체적의 약 70~85%를 차지하며, 콘크리트의 건조수축을 저감시켜주는 필수요소이다. 하지만 고층건축물 건설시 천연골재의 높은 하중으로 인해 문제점으로 작용한다. 고층 건물 건설시 하중이 커지게 되면 크리프가 발생하고 지반이 침식될 우려가 있으므로 기초를 크게 설계하고 암반층까지 깊게 내린 지정이나 파일등을 설치해야 하므로 공사비 및 재료비가 늘어 경제적 문제점이 있다. 콘크리트의 하중을 줄이기 위해 골재의 경량화를 진행하고 있다. 하지만 인공경량골재는 천연 골재에 비해 높은 흡수율과 낮은 부착강도로 인해 골재와 페이스트 사이의 계면에 영향을 주고 콘크리트 전체 강도에 영향을 미친다. 따라서 본 연구에서는 천연골재와 경량골재 종류별 계면을 파악하기 위해 비파괴 실험인 EIS측정 장비를 활용하여 전기저항을 측정하는 방식을 채택하였고, 경량골재 겉면을 고로슬래그 코팅을 통해 계면상태의 변화를 실험하였다. 실험결과, 골재 종류별 및 코팅유무에 따른 압축강도의 차이를 보였고, 경량골재 종류별 임피던스 값과 위상각의 차이를 보였다.

• Pediatric Infection and Vaccine
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• 제29권2호
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• pp.77-83
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• 2022

소아청소년에서 코로나바이러스 감염증(coronavirus disease 2019, COVID-19)은 성인에 비해 증상이 심하지 않은 것으로 알려져 있다. 본 연구는 2021년 8월부터 11월 사이에 COVID-19으로 진단받은 후 고열과 호흡곤란이 동반되어 입원치료를 받았던 18세 미만의 소아청소년 환자 중 산소 공급에도 불구하고 지속적인 호흡곤란과 저산소증으로 항바이러스제인 remdesivir와 스테로이드(dexamethasone) 병합 치료를 시행한 환자를 대상으로 심한 폐렴의 위험인자를 알아보고자 후향적으로 의무 기록을 검토하였다. 소아청소년 8명이 심한 폐렴으로 산소치료, remdesivir와 스테로이드를 투여하였고, 남자 5명, 여자 3명이었다. 중간 나이는 16세(범위: 9-17세)였으며, 8명 중 6명의 체질량지수가 중간값이 30.5 kg/m² (범위: 29.4-38.5 kg/m²)였다. 모든 환자가 고열과 저산소증을 동반한 호흡곤란이 있었다. 흉부 단순 X-ray 검사에서 다양한 폐렴의 양상을 보였다. 7명은 remdesivir와 스테로이드 투여 후 1-2일 이내에 증상 호전되었다. 본 증례 연구에서는 심한 폐렴을 동반한 COVID-19 환자 8명 중 6명에서 비만이 있었다.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.1061-1070
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• 2023

Over the last few years, lead-free inorganic metal perovskites have gained impressive ground in empowering satellites in space exploration owing to their material stability and performance evolution under extreme space environments. The present work has examined the versatility of eight such perovskites as space radiation shielding materials by computing their photon, charged particles and neutron interaction parameters. Photon interaction parameters were calculated for a wide energy range using PAGEX software. The ranges of heavy charged particles (H, He, C, N, O, Ne, Mg, Si and Fe ions) in these perovskites were estimated using SRIM software in the energy range 1 keV-10 GeV, and that of electrons was computed using ESTAR NIST software in the energy range 0.01 MeV-1 GeV. Further, the macroscopic fast neutron removal cross-sections were also calculated to estimate the neutron shielding efficiencies. The examined shielding parameters of the perovskites varied depending on the radiation type and energy. Among the selected perovskites, Cs₂TiI₆ and Ba₂AgIO₆ displayed superior photon attenuation properties. A 3.5 cm thick Ba₂AgIO₆-based shield could reduce the incident radiation intensity to half its initial value, a thickness even lesser than that of Pb-glass. Besides, CsSnBr₃ and La_0.8Ca_0.2Ni_0.5Ti_0.5O₃ displayed the highest and lowest range values, respectively, for all heavy charged particles. Ba₂AgIO₆ showed electron stopping power (on par with Kovar) better than that of other examined materials. Interestingly, La_0.8Ca_0.2Ni_0.5Ti_0.5O₃ demonstrated neutron removal cross-section values greater than that of standard neutron shielding materials - aluminium and polyethylene. On the whole, the present study not only demonstrates the employment prospects of eco-friendly perovskites for shielding space radiations but also suggests future prospects for research in this direction.

• Korean Journal of Radiology
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• 제22권4호
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• pp.652-662
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• 2021

Objective: To investigate the association between CT imaging features and survival outcomes in patients with primary invasive mucinous adenocarcinoma (IMA). Materials and Methods: Preoperative CT image findings were consecutively evaluated in 317 patients with resected IMA from January 2011 to December 2015. The association between CT features and long-term survival were assessed by univariate analysis. The independent prognostic factors were identified by the multivariate Cox regression analyses. The survival comparison of IMA patients was investigated using the Kaplan-Meier method and propensity scores. Furthermore, the prognostic impact of CT features was assessed based on different imaging subtypes, and the results were adjusted using the Bonferroni method. Results: The median follow-up time was 52.8 months; the 5-year disease-free survival (DFS) and overall survival rates of resected IMAs were 68.5% and 77.6%, respectively. The univariate analyses of all IMA patients demonstrated that 15 CT imaging features, in addition to the clinicopathologic characteristics, significantly correlated with the recurrence or death of IMA patients. The multivariable analysis revealed that five of them, including imaging subtype (p = 0.002), spiculation (p < 0.001), tumor density (p = 0.008), air bronchogram (p < 0.001), emphysema (p < 0.001), and location (p = 0.029) were independent prognostic factors. The subgroup analysis demonstrated that pneumonic-type IMA had a significantly worse prognosis than solitary-type IMA. Moreover, for solitary-type IMAs, the most independent CT imaging biomarkers were air bronchogram and emphysema with an adjusted p value less than 0.05; for pneumonic-type IMA, the tumors with mixed consolidation and ground-glass opacity were associated with a longer DFS (adjusted p = 0.012). Conclusion: CT imaging features characteristic of IMA may provide prognostic information and individual risk assessment in addition to the recognized clinical predictors.

• Korean Journal of Radiology
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• 제22권2호
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• pp.281-290
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• 2021

Objective: To assess the performance of content-based image retrieval (CBIR) of chest CT for diffuse interstitial lung disease (DILD). Materials and Methods: The database was comprised by 246 pairs of chest CTs (initial and follow-up CTs within two years) from 246 patients with usual interstitial pneumonia (UIP, n = 100), nonspecific interstitial pneumonia (NSIP, n = 101), and cryptogenic organic pneumonia (COP, n = 45). Sixty cases (30-UIP, 20-NSIP, and 10-COP) were selected as the queries. The CBIR retrieved five similar CTs as a query from the database by comparing six image patterns (honeycombing, reticular opacity, emphysema, ground-glass opacity, consolidation and normal lung) of DILD, which were automatically quantified and classified by a convolutional neural network. We assessed the rates of retrieving the same pairs of query CTs, and the number of CTs with the same disease class as query CTs in top 1-5 retrievals. Chest radiologists evaluated the similarity between retrieved CTs and queries using a 5-scale grading system (5-almost identical; 4-same disease; 3-likelihood of same disease is half; 2-likely different; and 1-different disease). Results: The rate of retrieving the same pairs of query CTs in top 1 retrieval was 61.7% (37/60) and in top 1-5 retrievals was 81.7% (49/60). The CBIR retrieved the same pairs of query CTs more in UIP compared to NSIP and COP (p = 0.008 and 0.002). On average, it retrieved 4.17 of five similar CTs from the same disease class. Radiologists rated 71.3% to 73.0% of the retrieved CTs with a similarity score of 4 or 5. Conclusion: The proposed CBIR system showed good performance for retrieving chest CTs showing similar patterns for DILD.

• 대한영상의학회지
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• 제81권3호
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• pp.591-603
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• 2020

목적 본 연구는 Coronavirus disease 2019 (이하 COVID-19) 폐렴 환자의 임상 양상과 흉부 전산화단층촬영(이하 CT) 소견을 분석하고자 하였다. 대상과 방법 IRB의 승인을 받은 연구로, 51명의 COVID-19 확진 환자들을 후향적으로 분석하였다. 환자들을 임상 양상에 따라 경증과 중증으로 나누어 두 그룹 간에 임상 양상과 흉부 CT 소견을 비교하였다. 결과 총 51명의 환자(남자 22명, 여자 29명, 평균 56.5 ± 16세, 범위 22~88세) 중 37명(72.5%)은 경증, 14명(27.5%)은 중증이었다. 중증 환자들의 평균 연령(68.7 ± 12.5세)은 경증 환자들(51.8 ± 14.9세)보다 많았다(p < 0.001). 중증 환자가 기저질환을 가지고 있는 경우가 많았으며(71% vs. 41%, p = 0.049), 혈액검사에서 림프구 백분율 감소를 보이는 경우가 많았다(86% vs. 32%, p = 0.001). 흉부 CT 소견은 대부분의 환자들에서 간유리음영과 폐경화가 혼합된 양상이거나(76%) 간유리음영으로(22%) 나타났고, 양측 폐 하부, 후방, 변연부에 나타나는 경우가 많았다. 중증 환자에서 병변이 더 많은 수의 폐엽을 침범했고, CT 위중도 점수도 높았다. 결론 COVID-19 폐렴 확진 환자의 특징적인 흉부 CT 소견을 숙지하는 것이 빠른 진단과 적절한 치료에 도움이 될 것이다.

• 대한영상의학회지
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• 제82권6호
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• pp.1581-1588
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• 2021

세계적으로 전자담배 사용의 급속한 증가와 함께 미국을 중심으로 전자담배와 관련된 사망보고들이 발생함에 따라 전자담배 관련 급성 폐 손상은 중요한 사회적 문제로 대두되었다. 이 증례 보고는 급성 호흡기 증상과 전자담배 흡연력이 있는 24세 남자 환자에서 전자담배 관련 급성 폐 손상을 진단한 국내 첫 사례이다. 흉부 CT에서 흉막하부 보존을 보이는 미만성간유리음영과 폐경화 및 중심소엽성 미세결절의 소견을 보여 전자담배 관련 폐 손상의 특징적 형태인 기질화폐렴과 미만성폐포손상에 해당하는 증례로 생각되었고, 검사실 소견에서 감염이 배제되고, 환자의 질병을 설명할 다른 원인이 없었다. 따라서, 임상 소견 및 부합하는 영상 소견으로 진단 기준을 충족하여, 다학제 진료를 통해 전자담배 관련 급성 폐 손상을 진단하였다. 이를 통해 영상의학과 의사들이 전자담배 관련 급성 폐 손상의 진단에 중요한 역할을 할 수 있을 것으로 생각된다.

• Korean Journal of Radiology
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• 제24권4호
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• pp.362-370
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• 2023

Objective: To report the clinical and radiological characteristics of patients with underlying B-cell lymphoma and coronavirus disease 2019 (COVID-19) showing migratory airspace opacities on serial chest computed tomography (CT) with persistent COVID-19 symptoms. Materials and Methods: From January 2020 to June 2022, of the 56 patients with underlying hematologic malignancy who had undergone chest CT more than once at our hospital after acquiring COVID-19, seven adult patients (5 female; age range, 37-71 years; median age, 45 years) who showed migratory airspace opacities on chest CT were selected for the analysis of clinical and CT features. Results: All patients had been diagnosed with B-cell lymphoma (three diffuse large B-cell lymphoma and four follicular lymphoma) and had received B-cell depleting chemotherapy, including rituximab, within three months prior to COVID-19 diagnosis. The patients underwent a median of 3 CT scans during the follow-up period (median 124 days). All patients showed multifocal patchy peripheral ground glass opacities (GGOs) with basal predominance in the baseline CTs. In all patients, follow-up CTs demonstrated clearing of previous airspace opacities with the development of new peripheral and peribronchial GGO and consolidation in different locations. Throughout the follow-up period, all patients demonstrated prolonged COVID-19 symptoms accompanied by positive polymerase chain reaction results from nasopharyngeal swabs, with cycle threshold values of less than 25. Conclusion: COVID-19 patients with B-cell lymphoma who had received B-cell depleting therapy and are experiencing prolonged SARS-CoV-2 infection and persistent symptoms may demonstrate migratory airspace opacities on serial CT, which could be interpreted as ongoing COVID-19 pneumonia.

• Korean Journal of Radiology
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• 제23권1호
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• pp.112-123
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• 2022

Objective: To investigate the relationship between ¹⁸F-FDG PET/CT semi-quantitative parameters and the International Association for the Study of Lung Cancer, American Thoracic Society/European Respiratory Society (IASLC/ATS/ERS) histopathologic classification, including histological subtypes, proliferation activity, and somatic mutations. Materials and Methods: This retrospective study included 419 patients (150 males, 269 females; median age, 59.0 years; age range, 23.0-84.0 years) who had undergone surgical removal of stage IA-IIIA lung adenocarcinoma and had preoperative PET/CT data of lung tumors. The maximum standardized uptake values (SUVmax), background-subtracted volume (BSV), and background-subtracted lesion activity (BSL) derived from PET/CT were measured. The IASLC/ATS/ERS subtypes, Ki67 score, and epidermal growth factor/anaplastic lymphoma kinase (EGFR/ALK) mutation status were evaluated. The PET/CT semi-quantitative parameters were compared between the tumor subtypes using the Mann-Whitney U test or the Kruskal-Wallis test. The optimum cutoff values of the PET/CT semi-quantitative parameters for distinguishing the IASLC/ATS/ERS subtypes were calculated using receiver operating characteristic curve analysis. The correlation between the PET/CT semi-quantitative parameters and pathological parameters was analyzed using Spearman's correlation. Statistical significance was set at p < 0.05. Results: SUVmax, BSV, and BSL values were significantly higher in invasive adenocarcinoma (IA) than in minimally IA (MIA), and the values were higher in MIA than in adenocarcinoma in situ (AIS) (all p < 0.05). Remarkably, an SUVmax of 0.90 and a BSL of 3.62 were shown to be the optimal cutoff values for differentiating MIA from AIS, manifesting as pure ground-glass nodules with 100% sensitivity and specificity. Metabolic-volumetric parameters (BSV and BSL) were better potential independent factors than metabolic parameters (SUVmax) in differentiating growth patterns. SUVmax and BSL, rather than BSV, were strongly or moderately correlated with Ki67 in most subtypes, except for the micropapillary and solid predominant groups. PET/CT parameters were not correlated with EGFR/ALK mutation status. Conclusion: As noninvasive surrogates, preoperative PET/CT semi-quantitative parameters could imply IASLC/ATS/ERS subtypes and Ki67 index and thus may contribute to improved management of precise surgery and postoperative adjuvant therapy.

• Korean Journal of Radiology
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• 제21권6호
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• pp.736-745
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• 2020

Objective: To identify the initial chest computed tomography (CT) findings and clinical characteristics associated with the course of coronavirus disease 2019 (COVID-19) pneumonia. Materials and Methods: Baseline CT scans and clinical and laboratory data of 72 patients admitted with COVID-19 pneumonia (39 men, 46.2 ± 15.9 years) were retrospectively analyzed. Baseline CT findings including lobar distribution, presence of ground glass opacities, consolidation, linear opacities, and lung severity score were evaluated. The outcome event was recovery with hospital discharge. The time from symptom onset to discharge or the end of follow-up (for those remained hospitalized) was recorded. Data were censored in events such as death or discharge without recovery. Multivariable Cox proportional hazard regression was used to explore the association between initial CT, clinical or laboratory findings, and discharge with recovery, whereby hazard ratio (HR) values < 1 indicated a lower rate of discharge at four weeks and longer time until discharge. Results: Thirty-two patients recovered and were discharged during the study period with a median length of admission of 16 days (range, 9 to 25 days), while the rest remained hospitalized at the end of this study (median, 17.5 days; range, 4 to 27 days). None died during the study period. After controlling for age, onset time, lesion characteristics, number of lung lobes affected, and bilateral involvement, the lung severity score on baseline CT (> 4 vs. ≤ 4 [reference]: adjusted HR = 0.41 [95% confidence interval, CI = 0.18-0.92], p = 0.031) and initial lymphocyte count (reduced vs. normal or elevated [reference]: adjusted HR = 0.14 [95% CI = 0.03-0.60], p = 0.008) were two significant independent factors that influenced recovery and discharge. Conclusion: Lung severity score > 4 and reduced lymphocyte count at initial evaluation were independently associated with a significantly lower rate of recovery and discharge and extended hospitalization in patients admitted for COVID-19 pneumonia.