• 한국광학회지
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• 제34권6호
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• pp.225-234
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• 2023

모드 잠금 레이저는 주기성을 가지고 짧은 시간 동안 레이저 출력이 펄스로 동작한다. 그러나 시간-주파수 영역에서 모드 잠금된 펄스 레이저의 펄스 반복률의 주기성은 푸리에 변환으로 일정한 주파수 간격을 가진 광 주파수 빗과 같이 이해된다. 이때 광 주파수 빗의 각 주파수 성분은 연속적으로 발진하는 수십만 개의 단일 주파수 성분을 가진 continuous-wave 레이저들과 같다. 광 주파수 빗은 약 20년 전에 개발되어 세계에서 가장 정밀한 원자 시계의 개발을 가능케 하고 안정된 광 주파수를 정밀하게 전송하는 데에 사용되었으며, 다양한 응용연구로도 발전했다. 본 논문에서는 광 주파수 빗의 단일 주파수 구성 요소를 선택적으로 추출하고, 광 빗의 주파수 구성 요소를 제어하는 연구를 소개한다. 또한 광 주파수 빗의 개념과 원리를 해설함으로써 시간-주파수 도메인에서 빛의 특성을 이해하고, 광 주파수 빗을 활용한 다양한 응용 연구를 개발하는 데 도움을 주고자 한다.

• Korean Journal of Radiology
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• 제22권6호
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• pp.912-921
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• 2021

Objective: To compare the performance of the deep learning-based lesion detection algorithm (DLLD) in detecting liver metastasis with that of radiologists. Materials and Methods: This clinical retrospective study used 4386-slice computed tomography (CT) images and labels from a training cohort (502 patients with colorectal cancer [CRC] from November 2005 to December 2010) to train the DLLD for detecting liver metastasis, and used CT images of a validation cohort (40 patients with 99 liver metastatic lesions and 45 patients without liver metastasis from January 2011 to December 2011) for comparing the performance of the DLLD with that of readers (three abdominal radiologists and three radiology residents). For per-lesion binary classification, the sensitivity and false positives per patient were measured. Results: A total of 85 patients with CRC were included in the validation cohort. In the comparison based on per-lesion binary classification, the sensitivity of DLLD (81.82%, [81/99]) was comparable to that of abdominal radiologists (80.81%, p = 0.80) and radiology residents (79.46%, p = 0.57). However, the false positives per patient with DLLD (1.330) was higher than that of abdominal radiologists (0.357, p < 0.001) and radiology residents (0.667, p < 0.001). Conclusion: DLLD showed a sensitivity comparable to that of radiologists when detecting liver metastasis in patients initially diagnosed with CRC. However, the false positives of DLLD were higher than those of radiologists. Therefore, DLLD could serve as an assistant tool for detecting liver metastasis instead of a standalone diagnostic tool.

• Korean Journal of Radiology
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• 제22권1호
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• pp.63-71
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• 2021

Objective: To identify the CT findings associated with treatment failure after antibiotic therapy for acute appendicitis. Materials and Methods: Altogether, 198 patients who received antibiotic therapy for appendicitis were identified by searching the hospital's surgery database. Selection criteria for antibiotic therapy were uncomplicated appendicitis with an appendiceal diameter equal to or less than 11 mm. The 86 patients included in the study were divided into a treatment success group and a treatment failure group. Treatment failure was defined as a resistance to antibiotic therapy or recurrent appendicitis during a 1-year follow-up period. Two radiologists independently evaluated the following CT findings: appendix-location, involved extent, maximal diameter, thickness, wall enhancement, focal wall defect, periappendiceal fat infiltration, and so on. For the quantitative analysis, two readers independently measured the CT values at the least attenuated wall of the appendix by drawing a round region of interest on the enhanced CT (HU_post) and non-enhanced CT (HU_pre). The degree of appendiceal wall enhancement (HU_sub) was calculated as the subtracted value between HU_post and HU_pre. A logistic regression analysis was used to identify the CT findings associated with treatment failure. Results: Sixty-four of 86 (74.4%) patients were successfully treated with antibiotic therapy, with treatment failure occurring in the remaining 22 (25.5%). The treatment failure group showed a higher frequency of hypoenhancement of the appendiceal wall than the success group (31.8% vs. 7.8%; p = 0.005). Upon quantitative analysis, both HU_post (46.7 ± 21.3 HU vs. 58.9 ± 22.0 HU; p = 0.027) and HU_sub (26.9 ± 17.3 HU vs. 35.4 ± 16.6 HU; p = 0.042) values were significantly lower in the treatment failure group than in the success group. Conclusion: Hypoenhancement of the appendiceal wall was significantly associated with treatment failure after antibiotic therapy for acute appendicitis.

• Korean Journal of Radiology
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• 제22권2호
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• pp.225-232
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• 2021

Objective: To determine whether changes in the transiting nerve rootlet or its surroundings, as seen on MRI performed after lumbar hemilaminectomy, are associated with persistent postoperative pain (PPP), commonly known as the failed back surgery syndrome. Materials and Methods: Seventy-three patients (mean age, 61 years; 43 males and 30 females) who underwent single-level partial hemilaminectomy of the lumbar spine without postoperative complications or other level spinal abnormalities between January 2010 and December 2018 were enrolled. Two musculoskeletal radiologists evaluated transiting nerve rootlet abnormalities (thickening, signal alteration, distinction, and displacement), epidural fibrosis, and intrathecal arachnoiditis on MRI obtained one year after the operations. A spine surgeon blinded to the radiologic findings evaluated each patient for PPP. Univariable and multivariable analyses were used to evaluate the association between the MRI findings and PPP. Results: The presence of transiting nerve rootlet thickening, signal alteration, and ill-distinction was significantly different between the patients with PPP and those without, for both readers (p ≤ 0.020). Conversely, the presence of transiting nerve rootlet displacement, epidural fibrosis, and intrathecal arachnoiditis was not significantly different between the two groups (p ≥ 0.128). Among the above radiologic findings, transiting nerve rootlet thickening and signal alteration were the most significant findings in the multivariable analyses (p ≤ 0.009). Conclusion: On MRI, PPP was associated with transiting nerve rootlet abnormalities, including thickening, signal alterations, and ill-distinction, but was not associated with epidural fibrosis or intrathecal arachnoiditis. The most relevant findings were the nerve rootlet thickening and signal alteration.

• 경영정보학연구
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• 제22권1호
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• pp.91-111
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• 2020

최근 디지털 콘텐츠 시장의 패러다임이 소유에서 소비라는 관점으로 바뀌는 가운데, 전자책 시장에서는 무제한 정액 구독 서비스가 빠르게 보급되고 있다. 본 연구는 무제한 정액제가 새로이 도입되는 상황에서 소비자들의 가격제 선택 행태와 더불어, 구독 후 실제로 어떠한 전자책 구매 패턴을 보이는지에 대해 실증적으로 검증하였다. 분석 결과, 소비자들은 합리적 의사결정을 바탕으로 정액제에 지불한 금액 이상의 도서를 다운로드 받으며 경제적 실리를 취하고 있었다. 헤비유저일수록 정액제를 선호하였으며, 과거 구독을 통해 실제로 경제적 효용을 경험한 유저일수록 정액제 이용을 갱신하는 경향이 나타났다. 한 편, 구독 기간과 관련해서는 1일 혹은 1달 단위의 정액제 구독 보다 1주일 정액제 이용 시에 경제적 효용이 가장 큰 것으로 나타나, 기간이 너무 짧거나 길지 않을 때 미래 수요를 가장 합리적으로 판단할 수 있음을 시사하였다. 마지막으로 인앱결제 기능 유무에 따라 iOS와 안드로이드 유저 간에 정액제 선호와 전자책 구매패턴이 다르게 나타남을 발견하였다.

• 대한영상의학회지
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• 제83권4호
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• pp.759-770
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• 2022

인공지능의 연구 개발 및 활용에서 윤리의 중요성이 의료분야뿐 아니라 전 사회적으로 점차 널리 인식되고 있다. 이 종설은 영상의학 영상데이터를 인공지능 연구에 활용할 때 개인정보의 보호 및 데이터에 대한 권리 측면에서 윤리적으로 고려할 사항들에 대해서 국내 독자들에게 실용적인 정보를 제공하고자 한다. 따라서 이 글에 담긴 내용은 많은 부분이 관련된 국내 법과 정부 제도에 바탕을 두고 있다. 인공지능의 연구 개발 및 활용에서 개인정보 보호는 매우 중요한 윤리적 원칙이며 연구 데이터의 적절한 가명처리는 개인정보 보호를 위한 핵심 방법이다. 아울러 인공지능 연구 개발에 의료 데이터를 상업적 이해관계를 최소화하며 윤리적으로 공유할 필요성도 부각되고 있다. 연구 데이터 공유는 개인정보 유출의 위험을 증가시키므로 개인정보 보호에 더욱 주의가 필요하다.

• 대한한의학회지
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• 제45권1호
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• pp.165-181
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• 2024

Objectives: This study was aimed to review the global status of adverse event (AE) reports and the characteristics of the reported AEs of plants managed as herbal medicines (HMs) with toxic precautions in Korea. Methods: This is a cross-sectional quantitative study that analyzed information available through VigiAccess, a website that provides summarized statistical information from the WHO's global AE database to the public. VigiAccess was searched in 8 Jan, 2024. Information on the total number of reports, number of reports by year and continent, and the age and gender of patients were obtained, and the types of frequently reported AEs were also reviewed. Results: Data on the status of report submissions were obtained for a total of 9 HMs including Aconitum ciliare, Aconitum carmichaeli, Arisaema japonicum, Pinellia ternata, Euphorbiae Lathyridis, Croton tiglium, Strychni Ignatii, Strychnons nux-vomica, and Linum usitatissimum. The number of reports per HM was from 1 to 137. The most commonly reported type of AEs were gastrointestinal disorders in most of the HMs, followed by neurological disorders. Serious adverse events were reported only in Strychni Ignatii, Strychnons nux-vomica, and Linum usitatissimum, including one case of death. Conclusions: This study shows the status of reported AEs of botanicals considered as HMs with toxic precautions in Korea based on real world data. However, when interpreting the findings of this study, readers should consider the significant limitations of this study mainly because of the characteristics of the data source.

• Korean Journal of Radiology
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• 제20권6호
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• pp.985-996
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• 2019

Objective: To determine the correlation between cerebral blood flow (CBF) on arterial spin labeling (ASL) MRI and the degree of postoperative revascularization assessed on digital subtraction angiography in children with moyamoya disease (MMD). Materials and Methods: Twenty-one children (9 boys and 12 girls; mean age, 8.4 ± 3.6 years; age range, 3-16 years) with MMD who underwent both pseudocontinuous ASL MRI at 1.5T and catheter angiography before and after superficial temporal artery encephaloduroarteriosynangiosis were included in this retrospective study. The degree of revascularization in the middle cerebral artery (MCA) territory was evaluated on external carotid angiography and was graded on a 3-point scale. On ASL CBF maps, regions of interest were manually drawn over the MCA territory of the operated side at the level of the centrum semi-ovale and over the cerebellum. The normalized CBF (nCBF) was calculated by dividing the CBF of the MCA territory by the CBF of the cerebellum. Changes in nCBFs were calculated by subtracting the preoperative nCBF values from the postoperative nCBF values. The correlation between nCBF changes measured with ASL and the revascularization grade from direct angiography was evaluated. Results: The nCBF value on the operated side increased after the operation (p = 0.001). The higher the degree of revascularization, the greater the nCBF change was: poor revascularization (grade 1), -0.043 ± 0.212; fair revascularization (grade 2), 0.345 ± 0.176; good revascularization (grade 3), 0.453 ± 0.182 (p = 0.005, Jockheere-Terpstra test). The interobserver agreement was excellent for the measured CBF values of the three readers (0.91-0.97). Conclusion: The nCBF values of the MCA territory obtained from ASL MRI increased after the revascularization procedure in children with MMD, and the degree of nCBF change showed a significant correlation with the degree of collateral formation evaluated via catheter angiography.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권5호
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• pp.1273-1300
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• 2024

In the complex virtual environment of cyberspace, comprised of digital and communication networks, ensuring the security of information is being recognized as an ongoing challenge. The importance of 'Cyber Situation Awareness (CSA)' is being emphasized in response to this. CSA is understood as a vital capability to identify, understand, and respond to various cyber threats and is positioned at the heart of cyber security strategies from a defensive perspective. Critical industries such as finance, healthcare, manufacturing, telecommunications, transportation, and energy can be subjected to not just economic and societal losses from cyber threats but, in severe cases, national losses. Consequently, the importance of CSA is being accentuated and research activities are being vigorously undertaken. A systematic five-step approach to CSA is introduced against this backdrop, and a deep analysis of recent research trends, techniques, challenges, and future directions since 2019 is provided. The approach encompasses current situation and identification awareness, the impact of attacks and vulnerability assessment, the evolution of situations and tracking of actor behaviors, root cause and forensic analysis, and future scenarios and threat predictions. Through this survey, readers will be deepened in their understanding of the fundamental importance and practical applications of CSA, and their insights into research and applications in this field will be enhanced. This survey is expected to serve as a useful guide and reference for researchers and experts particularly interested in CSA research and applications.

• Korean Journal of Radiology
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• 제21권6호
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• pp.684-694
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• 2020

Objective: The purpose was to review the diagnostic performance of the length of tumor capsular contact (LCC) on magnetic resonance imaging (MRI) for detecting prostate cancer extraprostatic extension (EPE). Materials and Methods: PubMed and EMBASE databases were searched up to March 24, 2019. We included diagnostic accuracy studies that evaluated LCC on MRI for EPE detection using radical prostatectomy specimen histopathology as the reference standard. Quality of studies was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. Sensitivity and specificity were pooled and graphically presented using hierarchical summary receiver operating characteristic (HSROC) plots. Meta-regression and subgroup analyses were conducted to explore heterogeneity. Results: Thirteen articles with 2136 patients were included. Study quality was generally good. Summary sensitivity and specificity were 0.79 (95% confidence interval [CI] 0.73-0.83) and 0.67 (95% CI 0.60-0.74), respectively. Area under the HSROC was 0.81 (95% CI 0.77-0.84). Substantial heterogeneity was present among the included studies according to Cochran's Q-test (p < 0.01) and Higgins I² (62% and 86% for sensitivity and specificity, respectively). In terms of heterogeneity, measurement method (curvilinear vs. linear), prevalence of Gleason score ≥ 7, MRI readers' experience, and endorectal coils were significant factors (p ≤ 0.01), whereas method to determine the LCC threshold, cutoff value, magnet strength, and publication year were not (p = 0.14-0.93). Diagnostic test accuracy estimates were comparable across all assessed MRI sequences. Conclusion: Greater LCC on MRI is associated with a higher probability of prostate cancer EPE. Due to heterogeneity among the studies, further investigation is needed to establish the optimal cutoff value for each clinical setting.