• Korean Journal of Radiology
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• 제25권4호
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• pp.351-362
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• 2024

Objective: To measure inter-reader agreement and identify associated factors in interpreting complete response (CR) on magnetic resonance imaging (MRI) following chemoradiotherapy (CRT) for rectal cancer. Materials and Methods: This retrospective study involved 10 readers from seven hospitals with experience of 80-10210 cases, and 149 patients who underwent surgery after CRT for rectal cancer. Using MRI-based tumor regression grading (mrTRG) and methods employed in daily practice, the readers independently assessed mrTRG, CR on T2-weighted images (T2WI) denoted as mrCR_T2W, and CR on all images including diffusion-weighted images (DWI) denoted as mrCR_overall. The readers described their interpretation patterns and how they utilized DWI. Inter-reader agreement was measured using multi-rater kappa, and associated factors were analyzed using multivariable regression. Correlation between sensitivity and specificity of each reader was analyzed using Spearman coefficient. Results: The mrCR_T2W and mrCR_overall rates varied widely among the readers, ranging 18.8%-40.3% and 18.1%-34.9%, respectively. Nine readers used DWI as a supplement sequence, which modified interpretations on T2WI in 2.7% of cases (36/1341 [149 patients × 9 readers]) and mostly (33/36) changed mrCR_T2W to non-mrCR_overall. The kappa values for mrTRG, mrCR_T2W, and mrCR_overall were 0.56 (95% confidence interval: 0.49, 0.62), 0.55 (0.52, 0.57), and 0.54 (0.51, 0.57), respectively. No use of rectal gel, larger initial tumor size, and higher initial cT stage exhibited significant association with a higher interreader agreement for assessing mrCR_overall (P ≤ 0.042). Strong negative correlations were observed between the sensitivity and specificity of individual readers (coefficient, -0.718 to -0.963; P ≤ 0.019). Conclusion: Inter-reader agreement was moderate for assessing CR on post-CRT MRI. Readers' varying standards on MRI interpretation (i.e., threshold effect), along with the use of rectal gel, initial tumor size, and initial cT stage, were significant factors associated with inter-reader agreement.

• 대한영상의학회지
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• 제82권5호
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• pp.1218-1230
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• 2021

목적 고위험 환자에서 초기 간암 선별 검사로써 단축 자기공명영상 검사의 환자별 진단능을 기존의 고식적 간 자기공명영상검사와 비교하고자 한다. 대상과 방법 간암 고위험군에서 간 자기공명영상 검사를 시행 받은 총 201명의 환자에 대해 연구를 시행하였다. 단축 자기공명영상 검사 군의 프로토콜은 T2 강조영상, 담도기 T1 강조영상, 확산강조영상 등으로 구성되며, 두 명의 영상의학과 의사가 각각의 환자에 대해 후향적으로 단축 자기공명영상검사 군 및 고식적 자기공명영상검사 군, 두 군의 영상을 독립적으로 평가하였다. 두 연구자 간 일관성은 Cohen's kappa 값을 이용하여 비교하였다. 복합적인 참조표준을 이용하여 두 군에서 각각 진단능을 평가하여 비교하였다. 결과 79 명의 환자에서 총 93개의 간암이 발견되었다. 두 연구자 간 일관성은 두 군에서 모두 매우 양호하였다(κ = 0.839, 0.948). 단축 자기공명영상검사 군에서 민감도 및 음성예측도는 각각 94.9% 및 96.4%였으며, 이는 고식적 자기공명영상검사 군과 큰 차이를 보이지 않았다(96.2%, 97.5%). 결론 단축 자기공명영상검사는 고식적 자기공명영상검사에 비교하여 임상적으로 허용 가능한 민감도와 음성예측도를 갖는다. 따라서 간암 고위험군 환자에서 간암 선별검사로써 새로운 대안이 될 수 있을 것이다.

• Korean Journal of Radiology
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• 제24권3호
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• pp.235-246
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• 2023

Objective: It is difficult to predict the treatment response of tissue after stereotactic radiosurgery (SRS) because radiation necrosis (RN) and tumor recurrence can coexist. Our study aimed to predict tumor recurrence, including the recurrence site, after SRS of brain metastasis by performing a longitudinal tumor habitat analysis. Materials and Methods: Two consecutive multiparametric MRI examinations were performed for 83 adults (mean age, 59.0 years; range, 27-82 years; 44 male and 39 female) with 103 SRS-treated brain metastases. Tumor habitats based on contrast-enhanced T1- and T2-weighted images (structural habitats) and those based on the apparent diffusion coefficient (ADC) and cerebral blood volume (CBV) images (physiological habitats) were defined using k-means voxel-wise clustering. The reference standard was based on the pathology or Response Assessment in Neuro-Oncologycriteria for brain metastases (RANO-BM). The association between parameters of single-time or longitudinal tumor habitat and the time to recurrence and the site of recurrence were evaluated using the Cox proportional hazards regression analysis and Dice similarity coefficient, respectively. Results: The mean interval between the two MRI examinations was 99 days. The longitudinal analysis showed that an increase in the hypovascular cellular habitat (low ADC and low CBV) was associated with the risk of recurrence (hazard ratio [HR], 2.68; 95% confidence interval [CI], 1.46-4.91; P = 0.001). During the single-time analysis, a solid low-enhancing habitat (low T2 and low contrast-enhanced T1 signal) was associated with the risk of recurrence (HR, 1.54; 95% CI, 1.01-2.35; P = 0.045). A hypovascular cellular habitat was indicative of the future recurrence site (Dice similarity coefficient = 0.423). Conclusion: After SRS of brain metastases, an increased hypovascular cellular habitat observed using a longitudinal MRI analysis was associated with the risk of recurrence (i.e., treatment resistance) and was indicative of recurrence site. A tumor habitat analysis may help guide future treatments for patients with brain metastases.

• Korean Journal of Radiology
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• 제24권2호
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• pp.133-144
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• 2023

Objective: Cyclin-dependent kinase inhibitor (CDKN)2A/B homozygous deletion is a key molecular marker of isocitrate dehydrogenase (IDH)-mutant astrocytomas in the 2021 World Health Organization. We aimed to investigate whether qualitative and quantitative MRI parameters can predict CDKN2A/B homozygous deletion status in IDH-mutant astrocytomas. Materials and Methods: Preoperative MRI data of 88 patients (mean age ± standard deviation, 42.0 ± 11.9 years; 40 females and 48 males) with IDH-mutant astrocytomas (76 without and 12 with CDKN2A/B homozygous deletion) from two institutions were included. A qualitative imaging assessment was performed. Mean apparent diffusion coefficient (ADC), 5th percentile of ADC, mean normalized cerebral blood volume (nCBV), and 95th percentile of nCBV were assessed via automatic tumor segmentation. Logistic regression was performed to determine the factors associated with CDKN2A/B homozygous deletion in all 88 patients and a subgroup of 47 patients with histological grades 3 and 4. The discrimination performance of the logistic regression models was evaluated using the area under the receiver operating characteristic curve (AUC). Results: In multivariable analysis of all patients, infiltrative pattern (odds ratio [OR] = 4.25, p = 0.034), maximal diameter (OR = 1.07, p = 0.013), and 95th percentile of nCBV (OR = 1.34, p = 0.049) were independent predictors of CDKN2A/B homozygous deletion. The AUC, accuracy, sensitivity, and specificity of the corresponding model were 0.83 (95% confidence interval [CI], 0.72-0.91), 90.4%, 83.3%, and 75.0%, respectively. On multivariable analysis of the subgroup with histological grades 3 and 4, infiltrative pattern (OR = 10.39, p = 0.012) and 95th percentile of nCBV (OR = 1.24, p = 0.047) were independent predictors of CDKN2A/B homozygous deletion, with an AUC accuracy, sensitivity, and specificity of the corresponding model of 0.76 (95% CI, 0.60-0.88), 87.8%, 80.0%, and 58.1%, respectively. Conclusion: The presence of an infiltrative pattern, larger maximal diameter, and higher 95th percentile of the nCBV may be useful MRI biomarkers for CDKN2A/B homozygous deletion in IDH-mutant astrocytomas.

• 한국미생물·생명공학회지
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• 제51권4호
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• pp.500-506
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• 2023

Carbapenem 내성 Klebsiella pneumoniae (Carbapenem-resistant K. pneumonia, CRKP)는 전 세계적인 공중 보건 문제로 대두되고 있다. 최근 Klebsiella pneumoniae carbapenemase-2 (KPC-2) 생성 sequence type (ST)307은 CRKP의 주요 클론으로 확인되었으며, 국내에서 ST307의 확산이 보고되었다. 본 연구에서는 2020년 3월부터 2021년 12월까지 대전지역의 3차 병원에서 분리된 CRKP 50균주를 대상으로, 분자 특성과 항균제 내성 양상을 조사하였다. 역학적 관계는 multilocus sequence typing (MLST)를 통해 분석하였고, 항균제 감수성 검사는 디스크 확산법을 통해 확인하였다. PCR과 DNA 염기서열분석은 carbapenemase 유전자 확인을 위해 수행하였다. CRKP감염은 남성과 60세 이상의 환자에서 훨씬 더 빈번하게 확인되었다. CRKP 50균주 중 46균주(92.0%)는 다제내성(MDR)을 보였고, 44균주(88.0%)는 carbapenemase-producing K. pneumoniae (CPKP)로 확인되었다. 주요 carbapenemase 유형은 KPC-2 (36균주, 72.0%)였으며, New Delhi metallo-enzyme-1 (NDM-1)과 NDM-5는 각각 7균주(14.0%)와 1균주(2.0%)에서 확인되었다. 특히, KPC-2 생성 K. pneumoniae의 88.9% (32/36)가 ST307에 속한 반면, NDM-1,-5 생성 K. pneumoniae의 87.5% (7/8)가 non-ST307에 속한 것을 확인하였다. 이러한 결과는 ST307의 확산 뿐만 아니라 non-ST307의 발달을 예방하기 위한 적절한 감염관리와 효과적인 감시체계가 필요하다고 사료된다.

• Korean Journal of Radiology
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• 제21권7호
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• pp.812-828
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• 2020

Objective: To provide an evidence-based guide for the MRI interpretation of complete tumor response after neoadjuvant chemoradiation therapy (CRT) for rectal cancer using visual assessment on T2-weighted imaging (T2) and diffusion-weighted imaging (DWI). Materials and Methods: PubMed MEDLINE, EMBASE, and Cochrane Library were searched on November 28, 2019 to identify articles on the following issues: 1) sensitivity and specificity of T2 or DWI for diagnosing pathologic complete response (pCR) and the criteria for MRI diagnosis; 2) MRI alone vs. MRI combined with other test(s) in sensitivity and specificity for pCR; and 3) tests to select patients for the watch-and-wait management. Eligible articles were selected according to meticulous criteria and were synthesized. Results: Of 1615 article candidates, 55 eligible articles (for all three issues combined) were identified. Combined T2 and DWI performed better than T2 alone, with a meta-analytic summary sensitivity of 0.62 (95% confidence interval [CI], 0.43-0.77; I² = 80.60) and summary specificity of 0.89 (95% CI, 0.80-0.94; I² = 92.61) for diagnosing pCR. The criteria for the complete response on T2 in most studies had the commonality of remarkable tumor decrease to the absence of mass-like or nodular intermediate signal, although somewhat varied, as follows: (near) normalization of the wall; regular, thin, hypointense scar in the luminal side with (near) normal-appearance or homogeneous intermediate signal in the underlying wall; and hypointense thickening of the wall. The criteria on DWI were the absence of a hyperintense signal at high b-value (≥ 800 sec/mm²) in most studies. The specific algorithm to combine T2 and DWI was obscure in half of the studies. MRI combined with endoscopy was the most utilized means to select patients for the watch-and-wait management despite a lack of strong evidence to guide and support a multi-test approach. Conclusion: This systematic review and meta-analysis provide an evidence-based practical guide for MRI assessment of complete tumor response after CRT for rectal cancer.

• 접착 및 계면
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• 제25권2호
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• pp.69-74
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• 2024

소프트 액추에이터는 구성 재료 자체가 가지는 유연성과 부드러운 움직임으로 인해 의료 산업과 제조업 등 다양한 분야에서의 응용이 기대되고 있다. 자극감응성 하이드로젤은 유연하며 다양한 주위 자극에 의해 큰 부피 변화를 보일 수 있는 물질로서 소프트 액추에이터 재료로서 적합하다. 하지만, 자극감응성 하이드로젤의 부피 변화는 온도 변화의 속도 및 용매의 확산 속도에 기인하여 대부분의 작동 조건에서 느린 속도로 진행되며 이는 액추에이터의 반응속도를 제한한다. 본 연구에서는 온도감응성 하이드로젤인 polydiethylacrylamide에 광열효과를 가지는 공액고분자를 도입하여 빛에 의해 구동되는 소프트 액추에이터를 구현하였고, 공액고분자의 광열효과에 의한 반응속도의 개선효과를 조사하였다. 공액고분자의 도입에 의해 반응시간이 41% 개선됨을 확인하였고 이는 열전달 효율의 개선에 의한 것으로 짐작할 수 있다. 최종적으로 이러한 개선된 반응속도의 하이드로젤이 적용된 소프트 그리퍼를 제작하였고 반응속도를 조사하였다.

• 방사선산업학회지
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• 제17권4호
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• pp.397-403
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• 2023

The purpose of this study is to obtain brain MRI images through Heavenly T₂ FLAIR and DWI techniques to find out strengths and weaknesses of each image. Data were analyzed on 13 normal people and 17 brain tumor patients. Philips Ingenia 3.0TCX was used as the equipment used for the inspection, and 32 Channel Head Coil was used to acquire data. Using Image J and Infinity PACS Data, 3mm² of gray matter, white matter, cerebellum, basal ganglia, and tumor areas were set and measured. Quantitative analysis measured SNR and CNR as an analysis method, and qualitative analysis evaluated overall image quality, lesion conspicuity, image distortion, susceptibility artifact and ghost artifact on a 5-point scale. The statistical significance of data analysis was that Wilcox-on Signed Rank Test and Paired t-test were executed, and the statistical program used was SPSS ver.22.0 and the p value was less than 0.05. In quantitative analysis, the SNR of gray matter, white matter, cerebellum, basal ganglia, and tumor of Heavily T₂ FLAIR is 41.45±0.13, 40.52±0.45, 41.44±0.51, 40.96±0.09, 35.28±0.46 and the CNR is 15.24±0.13, 16.75±0.23, 16.28±0.41, 15.83±0.17, 16.63±0.51. In DWI, SNR is 32.58±0.22, 36.75±0.17, 30.21±0.19, 35.83±0.11, 43.29±0.08, and CNR is 13.14±0.63, 14.21±0.31, 12.95±0.32, 11.73±0.09, 17.56±0.52. In normal tissues, Heavenly T₂ FLAIR obtained high results, but in disease evaluation, high results were obtained at DWI, b=1000 (p<0.05). In addition, in the qualitative analysis, overall image quality, lesion conspicuity, image distortion, susceptibility artifact and ghost artifact aspects of the Heavily T₂ FLAIR were evaluated, and 3.75±0.28, 2.29±0.24, 3.86±0.23, 4.08±0.21, 3.79±0.22 values were found, respectively, and 2.53±0.39, 4.13±0.29, 1.90±0.20, 1.81±0.21, 1.52±0.45 in DWI. As a result of qualitative analysis, overall image quality, image distortion, susceptibility artifact and ghost artifact were rated higher than DWI. However, DWI was evaluated higher in lesion conspicuity (p<0.05). In normal tissues, the level of Heavenly T₂ FLAIR was higher, but the DWI technique was higher in the evaluation of the disease (tumor). The two results were necessary techniques depending on the normal site and the location of the disease. In conclusion, statistically significant results were obtained from the two techniques. In quantitative and qualitative analysis, the two techniques had advantages and disadvantages, and in normal and disease evaluation, the two techniques produced useful results. These results are believed to be educational data for clinical basic evaluation and MRI in the future.

• 인터넷정보학회논문지
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• 제16권6호
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• pp.123-131
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• 2015

최근 정보통신기술의 발전으로 스마트한 기술들이 확산되면서 이전과 다른 방법으로 소통하고 콘텐츠를 활용할 수 있게 되었다. 이러한 변화는 보다 다양한 학습방법을 가능하게 함으로써 교육산업에 큰 변화를 가져오고 있다. 한국은 e-러닝에 이어 스마트러닝 선도국으로 도약하기 위해 2011년 스마트교육 추진 정책 수립을 시작으로 공교육에 스마트러닝 도입을 적극 추진해왔다. 그러나 아직까지 스마트러닝의 추진 성과는 미미한 것으로 판단된다. 따라서 현 시점에서 공교육의 스마트러닝 추진 문제점을 파악하고 개선안을 마련할 필요가 있다. 본 연구는 스마트러닝이 공교육에 정착하기 위한 성공전략을 제안하는 것을 목적으로 한다. 이를 위하여 공교육과 스마트러닝 환경을 종합적으로 검토하고, SWOT 분석과 AHP 기법을 통해 전략 요인과 우선순위를 도출하였다. 분석 결과, 국내 공교육 환경에 스마트러닝을 성공적으로 정착시키기 위해서는 약점을 보완하여 위협을 극복하는 WT전략에 초점을 맞춰야 하는 것으로 나타났다. 세부 요인으로는 미흡한 스마트러닝 관련 교사 연수 제도(W2), 제도차원 교육환경기반 및 추진역량(S4), 스마트러닝 추진에 대한 제한적 정부지원(T4) 순으로 나타났다. 특히 정부의 제도적 기반이 우선적으로 검토되어야 한다는 시사점이 도출되었다. 이 연구는 향후 스마트러닝 추진을 위한 정책과 지원제도 수립 과정에 전략적 가이드라인을 제공할 수 있을 것으로 기대된다.

• Asia pacific journal of information systems
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• 제17권2호
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• pp.97-122
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• 2007

Conventional networking and telecommunications infrastructure characterized by wires, fixed location, and inflexibility is giving way to mobile technologies. Numerous research reports point to the ultimate domination of wireless communication. With the increasing prevalence of advanced cell-phones, various mobile data services (hereafter MDS) are gaining popularity. Although cellular networks were originally introduced for voice communications, statistics indicate that data services are replacing the matured voice service as the growth engine for telecom service providers. For example, SK Telecom, the Korea's largest mobile service provider, reported that 25.6% of revenue and 28.5% of profit came from MDS in 2006 and the share is growing. Statistics also indicate that, in 2006, the average revenue per user (ARPU) for voice didn't change but MDS grew seven percents from the previous year, further highlighting its growth potential. MDS is defined "as an assortment of digital data services that can be accessed using a mobile device over a wide geographic area." A variety of MDS have been deployed, with a few reaching the status of killer applications. Many of them need to access the Internet through the cellular-phone infrastructure. In the past, when the cellular network didn't have acceptable bandwidth for data services, SMS (short messaging service) dominated MDS. Now, Internet-ready, next-generation cell-phones are driving rich digital data services into the fabric of everyday life, These include news on various topics, Internet search, mapping and location-based information, mobile banking and gaming, downloading (i.e., screen savers), multimedia streaming, and various communication services (i.e., email, short messaging, messenger, and chaffing). The huge economic stake MDS has on its stakeholders warrants focused research to understand associated dynamics behind its adoption. Lyytinen and Yoo(2002) pointed out the limitation of traditional adoption models in explaining the rapid diffusion of innovations such as P2P or mobile services. Also, despite the increasing popularity of MDS, unexpected drop in its usage is observed among some people. Intrigued by these observations, an exploratory study was conducted to examine decision factors of MDS usage. Data analysis revealed that the increase and decrease of MDS use was influenced by different forces. The findings of the exploratory study triggered our confirmatory research effort to validate the uni-directionality of studied factors in affecting MDS usage. This differs from extant studies of IS/IT adoption that are largely grounded on the assumption of bi-directionality of explanatory variables in determining the level of dependent variables (i.e., user satisfaction, service usage). The research goal is, therefore, to examine if increase and decrease in the usage of MDS are explained by two separate groups of variables pertaining to information quality and system quality. For this, we investigate following research questions: (1) Does the information quality of MDS increase service usage?; (2) Does the system quality of MDS decrease service usage?; and (3) Does user motivation for subscribing MDS moderate the effect information and system quality have on service usage? The research questions and subsequent analysis are grounded on the two factor theory pioneered by Hertzberg et al(1959). To answer the research questions, in the first, an exploratory study based on 378 survey responses was conducted to learn about important decision factors of MDS usage. It revealed discrepancy between the influencing forces of usage increase and those of usage decrease. Based on the findings from the exploratory study and the two-factor theory, we postulated information quality as the motivator and system quality as the de-motivator (or hygiene) of MDS. Then, a confirmative study was undertaken on their respective role in encouraging and discouraging the usage of mobile data service.