• Korean Journal of Radiology
• /
• v.22 no.5
• /
• pp.735-741
• /
• 2021

Objective: To evaluate circularity as a quantitative shape factor of small renal tumor on computed tomography (CT) in differentiating fat-poor angiomyolipoma (AML) from renal cell carcinoma (RCC). Materials and Methods: In 257 consecutive patients, 257 pathologically confirmed renal tumors (either AML or RCC less than 4 cm), which did not include visible fat on unenhanced CT, were retrospectively evaluated. A radiologist drew the tumor margin to measure the perimeter and area in all the contrast-enhanced axial CT images. In each image, a quantitative shape factor, circularity, was calculated using the following equation: 4 x π x (area ÷ perimeter²). The median circularity (circularity index) was adopted as a representative value in each tumor. The circularity index was compared between fat-poor AML and RCC, and the receiver operating characteristic (ROC) curve analysis was performed. Univariable and multivariable binary logistic regression analysis was performed to determine the independent predictor of fat-poor AML. Results: Of the 257 tumors, 26 were AMLs and 231 were RCCs (184 clear cell RCCs, 25 papillary RCCs, and 22 chromophobe RCCs). The mean circularity index of AML was significantly lower than that of RCC (0.86 ± 0.04 vs. 0.93 ± 0.02, p < 0.001). The mean circularity index was not different between the subtypes of RCCs (0.93 ± 0.02, 0.92 ± 0.02, and 0.92 ± 0.02 for clear cell, papillary, and chromophobe RCCs, respectively, p = 0.210). The area under the ROC curve of circularity index was 0.924 for differentiating fat-poor AML from RCC. The sensitivity and specificity were 88.5% and 90.9%, respectively (cut-off, 0.90). Lower circularity index (≤ 0.9) was an independent predictor (odds ratio, 41.0; p < 0.001) for predicting fat-poor AML on multivariable logistic regression analysis. Conclusion: Circularity is a useful quantitative shape factor of small renal tumor for differentiating fat-poor AML from RCC.

• Journal of Chest Surgery
• /
• v.57 no.1
• /
• pp.70-78
• /
• 2024

Background: This study investigated the outcomes of biventricular repair using right ventricle to pulmonary artery (RV-PA) conduit placement in patients aged <1 year. Methods: Patients aged <1 year who underwent biventricular repair using an RV-PA conduit between 2011 and 2020 were included in this study. The outcomes of interest were death from any cause, conduit reintervention, and conduit dysfunction (peak velocity of ≥3.5 m/sec or moderate or severe regurgitation). Results: In total, 141 patients were enrolled. The median age at initial conduit implantation was 6 months. The median conduit diameter z-score was 1.3. The overall 5-year survival rate was 89.6%. In the multivariable analysis, younger age (p=0.006) and longer cardiopulmonary bypass time (p=0.001) were risk factors for overall mortality. During follow-up, 61 patients required conduit reintervention, and conduit dysfunction occurred in 68 patients. The 5-year freedom from conduit reintervention and dysfunction rates were 52.9% and 45.9%, respectively. In the multivariable analysis, a smaller conduit z-score (p<0.001) was a shared risk factor for both conduit reintervention and dysfunction. Analysis of variance demonstrated a nonlinear relationship between the conduit z-score and conduit reintervention or dysfunction. The hazard ratio was lowest in patients with a conduit z-score of 1.3 for reintervention and a conduit z-score of 1.4 for dysfunction. Conclusion: RV-PA conduit placement can be safely performed in infants. A significant number of patients required conduit reintervention and had conduit dysfunction. A slightly oversized conduit with a z-score of 1.3 may reduce the risk of conduit reintervention or dysfunction.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.35 no.11
• /
• pp.511-518
• /
• 1986

An algorithm for block-decomposition of a linear, time-invariant, discrete large-scale systems is presented, based upon the matrix sign function on Z-plane. The block-decomposition is performed by defining a reference circle, a circular stripe and projection operators. Simulation study shows that the presented algorithm is very useful for multivariable control system's analysis and design.

• 제어로봇시스템학회:학술대회논문집
• /
• 1990.10a
• /
• pp.485-492
• /
• 1990

This paper propose a optimal design method for robust notion controllers of under-water vehicles using the combined technique between classical and modern theories. The proposed method is presented which utilizes classical control methods to obtain a good robustness and modern control methods to set optimal gains. LQ, SVD, multivariable frequency analysis and Bode-Root Locus (BRL) plot are used.

• 제어로봇시스템학회:학술대회논문집
• /
• 1998.10a
• /
• pp.157-160
• /
• 1998

We argue that the combination of optimal control synthesis and QFT tuning enables design of controllers with levels of performance that surpasses what can be achieved using only a single technique. Using a constructive example, we demonstrate how the strength of each technique is utilized to arrive at a particularly desired controller in terms of tradeoffs between performance and controller complexity.

• Korean Journal of Radiology
• /
• v.23 no.6
• /
• pp.615-624
• /
• 2022

Objective: To compare the therapeutic outcomes of laparoscopic hepatic resection (LHR) and laparoscopic radiofrequency ablation (LRFA) for single subcapsular hepatocellular carcinoma (HCC). Materials and Methods: We screened 244 consecutive patients who had received either LHR or LRFA between January 2014 and December 2016. The feasibility of LRFA in patients who underwent LHR was retrospectively assessed by two interventional radiologists. Finally, 60 LRFA-feasible patients who had received LHR and 29 patients who had received LRFA as the first treatment for a solitary subcapsular HCC between 1 cm and 3 cm were finally included. We compared the therapeutic outcomes, including local tumor progression (LTP), recurrence-free survival (RFS), and overall survival (OS) between the two groups before and after propensity score (PS) matching. Multivariable Cox proportional hazard regression was also used to evaluate the difference in OS and RFS between the two groups for all 89 patients. Results: PS matching yielded 23 patients in each group. The cumulative LTP and OS rates were not significantly different between the LHR and LRFA groups after PS matching (p = 0.900 and 0.003, respectively). The 5-year LTP rates were 4.6% and 4.4%, respectively, and OS rates were 100% and 90.7%, respectively. The RFS rate was higher in LHR group without statistical significance (p = 0.070), with 5-year rates of 78.3% and 45.3%, respectively. OS was not significantly different between the LHR (reference) and LRFA groups in multivariable analyses, with a hazard ratio (HR) of 1.33 (95% confidence interval, 0.12-1.54) (p = 0.818). RFS was higher in LHR (reference) than in LRFA without statistical significance in multivariable analysis, with an HR of 2.01 (0.87-4.66) (p = 0.102). Conclusion: There was no significant difference in therapeutic outcomes between LHR and LRFA for single subcapsular HCCs measuring 1-3 cm. The difference in RFS should be further evaluated in a larger study.

• Journal of Environmental Health Sciences
• /
• v.46 no.1
• /
• pp.96-102
• /
• 2020

Objectives: This study identified factors impacting radiation knowledge among aircrew, who are affected by cosmic radiation exposure due to their occupational environment. Methods: In September 2019 we conducted an online survey of aircrew through a Google link. We evaluated the level of radiation knowledge using a ten-item (10 points) questionnaire. The following exploratory variables were evaluated in relationship with the level of radiation knowledge using univariable linear regression models: sex, age, duration of employment, position level, company, marriage, education level, personal/family history of disease, and the number of times acquiring information on radiation through various channels (internet searching, watching television, reading newspaper, conversation about radiation with aircrew/non-aircrew, in-house training). With a p of 0.2 in univariable models, we built a multivariable linear regression model using a stepwise selection method. Results: The average radiation knowledge score of the 356 respondents was 7.22. Univariable linear regression analysis showed that radiation knowledge of the aircrew was associated with their company, position level, age, and number of conversations with other aircrew members. Our multivariable model showed that the radiation knowledge level of aircrew decreased as they had more conversations about radiation with other aircrew members and as their age increased. Conclusions: Korean air crew showed a lower level of radiation knowledge as their age and the number of conversations with colleagues increased. The study suggests that more education is needed in order for aircrew to gain accurate radiation knowledge.

• Nutrition Research and Practice
• /
• v.7 no.3
• /
• pp.233-241
• /
• 2013

There are limited data on healthy dietary patterns protective against metabolic syndrome (MetSyn) development. We identified dietary patterns among middle-aged and older adults and investigated the associations with the incidence of MetSyn. A population-based prospective cohort study included 5,251 male and female Koreans aged 40-69 years. At baseline, all individuals were free of MetSyn, other major metabolic diseases, and known cardiovascular disease or cancer. Cases of MetSyn were ascertained over a 6-year of follow-up. Dietary patterns and their factor scores were generated by factor analysis using the data of a food frequency questionnaire. We performed pooled logistic regression analysis to estimate multivariable-adjusted relative risk (RR) and 95% confidence interval (CI) for associations between factor scores and MetSyn risk. Two dietary patterns were identified; (1) a healthy dietary pattern, which included a variety of foods such as fish, seafood, vegetables, seaweed, protein foods, fruits, dairy products, and grains; and (2) an unhealthy dietary pattern, which included a limited number of food items. After controlling for confounding factors, factor scores for the healthy dietary pattern were inversely associated with MetSyn risk (P-value for trend < 0.05) while those for the unhealthy dietary pattern had no association. Individuals in the top quintile of the healthy diet scores showed a multivariable-adjusted RR [95% CI] of 0.76 [0.60-0.97] for MetSyn risk compared with those in the bottom quintile. The beneficial effects were derived from inverse associations with abdominal obesity, low HDL-cholesterol levels, and high fasting glucose levels. Our findings suggest that a variety of healthy food choices is recommended to prevent MetSyn.

• Journal of Trauma and Injury
• /
• v.25 no.3
• /
• pp.72-78
• /
• 2012

Purpose: Clinical observation and research findings show that acute traumatic coagulopathy (ATC) is a major factor that must be addressed in the early care of severe trauma patients. ATC is associated with increased transfusion requirements and poor clinical outcomes. This study aimed to correlate the early predictable factors of ATC with the outcomes in severe trauma patients. Methods: Retrospective data from the trauma registry on severe trauma patients (Injury Severity Score (ISS) ${\geq}16$) were used to identify variables independently associated with coagulopathy. Univariate associations were calculated, and a multivariable logistic regression analysis was used to determine variables independently associated with ATC. Results: Patients were mostly male, aged $51.9{\pm}17.8$ years, with an injury severity score of $24.1{\pm}12.4$. ATC, as diagnosed in the emergency department (ED), occurred in 17% of the severe trauma patients. Using a multivariable logistic regression analysis, early predictable variables independently associated with ATC were base deficit (odds ratio (OR): 13.03; 95% confidence interval (CI): 3.47-48.93), acute liver injury (OR: 4.24; 95% CI: 1.06-17.00), and transfer from another hospital (OR: 21.00; 95% CI: 3.23-136.60). Conclusion: ATC is associated with mortality in severe trauma patients, and some variables associated with trauma and shock are an independent predictors of ATC. These variables contribute to the early recognition and management of coagulopathy, which may improve the outcome from trauma resuscitation.

• Pediatric Gastroenterology, Hepatology & Nutrition
• /
• v.18 no.3
• /
• pp.168-174
• /
• 2015

Purpose: Recent studies have suggested that decreased serum potassium level may contribute to various metabolic disorders in adult patients including nonalcoholic fatty liver disease (NAFLD). We aimed to study the correlation between serum potassium levels and the histologic severity of NAFLD in children. Methods: Pediatric patients with biopsy-proven NAFLD were included in this study. Demographic, clinical, and histopathological data were obtained. Multivariable logistic regression analysis was used to assess whether potassium levels are associated with the presence of nonalcoholic steatohepatitis (NASH) or fibrosis after adjusting for possible confounders. A p-value <0.05 was considered statistically significant. Results: Among 125 biopsies, 49.6% (62) had evidence of NASH while 66.4% (83) had some degree of fibrosis (stage 1-3). Mean serum potassium was significantly lower in NASH group as compared to non-NASH group ($4.4{\pm}0.42mmoL/L$ vs. $4.8{\pm}0.21$, p<0.001). Higher potassium level had negative correlation with presence of steatosis, ballooning, lobular inflammation, fibrosis and NAFLD activity score (p<0.05). On multivariable analysis and after adjusting for the metabolic syndrome and insulin resistance, higher potassium level was significantly associated with lower likelihood of having a histological diagnosis of NASH on biopsy (odds ratio [OR], 0.12; 95% confidence interval [95% CI], 0.05-0.28; p<0.001). Similarly, the likelihood of having fibrosis decreases by 76% for every 0.5 mmoL/L increase in potassium (OR, 0.24; 95% CI, 0.11-0.54; p<0.001). Conclusion: Our study shows an inverse relationship between serum potassium levels and the presence of aggressive disease (NASH and fibrosis) in children with NAFLD.