• Physical Therapy Rehabilitation Science
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• 제6권4호
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• pp.176-181
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• 2017

Objective: The timed up and go (TUG) test is method used to determine the functional mobility of persons with stroke. Its reliability, validity, reaction rate, fall prediction, and psychological characteristics concerning ambulation ability have been validated. However, the relationship between TUG performance and community ambulation ability is unclear. The purpose of this study was to investigate whether the TUG performance time could indicate community ambulation levels (CAL) differentially in persons with chronic stroke. Design: Cross-sectional study. Methods: Eighty-seven stroke patients had participated in this study. Based on the self-reporting survey results on the difficulties experienced when walking outdoors, the subjects were divided into the independent community ambulation (ICA) group (n=35) and the dependent community ambulation group (n=52). Based on the area under the curve (AUC), the discrimination validity of the TUG performance time was calculated for classifying CAL. The Binomial Logistic Regression Model was utilized to produce the likelihood ratio of selected TUG cut-off values for the distinguishing of community ambulation ability. Results: The selected TUG cut-off values and the area under the curve were <14.87 seconds (AUC=0.871, 95% confidence interval=0.797-0.945), representing a mid-level accuracy. Concerning the likelihood ratio of the selected TUG cut-off value, it was found that the group with TUG performance times shorter than 14.87 seconds showed a 2.889 times higher probability of ICA than those with a TUG score of 14.87 seconds or longer (p<0.05). Conclusions: The TUG can be viewed as an assessment tool that is capable of classifying CAL.

• Journal of Trauma and Injury
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• 제35권3호
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• pp.181-188
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• 2022

Purpose: Inferior vena cava (IVC) collapse is related to hypovolemia. Sonography has been used to measure the IVC diameter, but there is variation depending on the skill of the operator and it is difficult to obtain accurate measurements in patients who have a large amount of intestinal gas or are obese. As a modality to obtain accurate measurements, we measured the diameters of the IVC and aorta on trauma computed tomography scans and investigated the correlation between the IVC to aorta ratio and the shock index in blunt trauma patients. Methods: We retrospectively analyzed the medical records of 588 trauma patients who were transferred to the regional trauma center (level 1) of Wonkang University Hospital from March 2020 to February 2021. We included trauma patients 18 years or older who met the trauma activation criteria and underwent trauma computed tomography scans with intravenous contrast within 40 minutes of admission. The shock index was calculated from vital signs before trauma computed tomography scan, and measurements of the anteroposterior diameter of the IVC (AP), the transverse diameter of the IVC (T), and aorta were made 10 mm above the right renal vein in the venous phase. Results: Overall, 271 patients were included in this study, of whom 150 had a shock index ≤0.7 and 121 had a shock index >0.7. The T to AP ratio and AP to aorta ratio were significantly different between groups. Cutoffs were identified for the T to AP ratio and AP to aorta ratio (2.37 and 0.62, respectively) that produced clinically useful sensitivity and specificity for predicting a shock index >0.7, demonstrating moderate accuracy (T to AP ratio: area under the curve, 0.71; sensitivity, 59%; specificity, 87% and AP to aorta ratio: area under the curve, 0.70; sensitivity, 55%; specificity, 91%). Conclusions: The T to AP ratio and AP to aorta ratio are useful for predicting hemorrhagic shock in trauma patients.

• 전자공학회논문지
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• 제53권2호
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• pp.47-52
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• 2016

스마트 기기와 소형 디스플레이에 사용되는 디지털 영상은 다운스케일링 (Downscaling)된 영상이 사용된다. 본 논문에서는 영상 픽셀값의 경사도에 따른 특징벡터를 이용한 다운스케일링 포저리 (Forgery) 영상 검출 알고리즘을 제안한다. 제안된 알고리즘에서, 원영상의 픽셀값 경사도로부터 자기회귀 (AR: Autoregressive) 계수를 계산한다. 이는 다운스케일링 포저리 영상 검출기의 SVM (Support Vector Machine) 분류를 위한 학습에 사용된다. 제안된 다운스케일링 검출 알고리즘은 동일 10-Dim. 특징벡터의 MFR (Median Filter Residual) 스킴과 686-Dim.의 SPAM (Subtractive Pixel Adjacency Matrix) 스킴과 비교하여 다운스케일링 90% 영상 포저리에서 성능이 우수하며, 평균필터링 ($3{\times}3$) 영상과 미디언필터링 ($3{\times}3$) 영상에서 높은 검출율을 보여 주었다. 특히, 평균필터링과 미디언필터링 영상에서는 성능평가 전체 항목에서 민감도 (Sensitivity; TP: True Positive rate)와 1-특이도 (1-Specificity; FP: False Positive rate)의 AUC (Area Under Curve)가 모두 1에 수렴하여 'Excellent (A)' 등급임을 확인하였다.

• 한국음향학회지
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• 제41권2호
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• pp.199-209
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• 2022

일반적인 비정상 탐지 알고리즘은 사전 데이터를 이용하여 학습된다. 따라서 시간에 따른 정상 데이터의 특징이 변화되는 경우에 기존의 배치 학습 기반 알고리즘의 성능 저하가 불가피하다. 본 논문에서는 정상 데이터의 점진적 특징 변화를 고려할 수 있는 온라인 비정상 탐지 알고리즘을 제안한다. 제안하는 알고리즘은 단일 클래스 분류 모델에 기반하며 오프라인 및 온라인 단계의 학습 과정을 포함한다. 제안된 알고리즘의 오프라인 학습 단계에서는 사전 데이터가 잠재 공간의 중심에 근접하도록 학습하고, 이후 온라인 학습단계에서는 신규 데이터에 의한 점진적 잠재 공간의 중심을 갱신하고, 갱신된 중심을 기준으로 계속 학습을 진행한다. 공개된 수중 음향 데이터를 이용한 실험결과 제안된 온라인 비정상 탐지 알고리즘은 점진적 중심 갱신 및 학습을 위해 단지 2 % 정도의 추가 학습시간이 소요되는 것으로 확인되었다. 반면에 시변 정상데이터가 수신되는 경우에 오프라인 학습 모델과 비교하여 19.10 % 개선된 Area Under the receiver operating characteristic Curve(AUC) 성능을 보였다.

• Korean Journal of Radiology
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• 제22권3호
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• pp.297-307
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• 2021

Objective: To compare the performance of simulated abbreviated breast MRI (AB-MRI) and full diagnostic (FD)-MRI in distinguishing between benign and malignant lesions detected by MRI and investigate the features of discrepant lesions of the two protocols. Materials and Methods: An AB-MRI set with single first postcontrast images was retrospectively obtained from an FD-MRI cohort of 111 lesions (34 malignant, 77 benign) detected by contralateral breast MRI in 111 women (mean age, 49.8. ± 9.8; range, 28-75 years) with recently diagnosed breast cancer. Five blinded readers independently classified the likelihood of malignancy using Breast Imaging Reporting and Data System assessments. McNemar tests and area under the receiver operating characteristic curve (AUC) analyses were performed. The imaging and pathologic features of the discrepant lesions of the two protocols were analyzed. Results: The sensitivity of AB-MRI for lesion characterization tended to be lower than that of FD-MRI for all readers (58.8-82.4% vs. 79.4-100%), although the findings of only two readers were significantly different (p < 0.05). The specificity of AB-MRI for lesion characterization was higher than that of FD-MRI for 80% of readers (39.0-74.0% vs. 19.5-45.5%, p ≤ 0.001). The AUC of AB-MRI was comparable to that of FD-MRI for all readers (p > 0.05). Fifteen percent (5/34) of the cancers were false-negatives on AB-MRI. More suspicious margins or internal enhancement on the delayed phase images were related to the discrepancies. Conclusion: The overall performance of AB-MRI was similar to that of FD-MRI in distinguishing between benign and malignant lesions. AB-MRI showed lower sensitivity and higher specificity than FD-MRI, as 15% of the cancers were misclassified compared to FD-MRI.

• 문화기술의 융합
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• 제5권4호
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• pp.413-420
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• 2019

본 연구의 목적은 기존의 body fat mass 변수와 고콜레스테롤혈증의 연관성연구를 벗어나, 머신러닝기법을 기반으로 body fat mass 변수들의 조합을 이용하여 고콜레스테롤혈증 예측 모델을 개발하는 것이다. 이러한 연구를 위하여 국민건강영양조사 데이터를 기반으로 두 가지 variable selection 메소드와 머신러닝 알고리즘을 이용하여 총 6개의 모델을 생성하였고 질병 예측력을 비교분석하였다. 여러 body fat mass 관련 변수들 중에서 몸통지방량 변수가 고콜레스테롤혈증 예측력이 가장 우수한 변수인 것을 밝혀내었고, 머신러닝 기반 예측모델들 중에서 correlation-based feature subset selection 기반 naive Bayes 알고리즘을 이용한 모델이 0.739의 the area under the receiver operating characteristic curve 값과 0.36의 Matthews correlation coefficient 값을 얻었다. 이러한 연구의 결과는 향후 국내외 대규모 스크리닝 및 대중보건 연구에서 질병예측분야의 중요정보로 활용될 것으로 예상한다.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제26권4호
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• pp.193-200
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• 2023

Purpose: Crohn's disease (CD) is a chronic, idiopathic bowel disorder that can progress to partial or complete bowel obstruction. At present, there are no reliable diagnostic tests that can readily distinguish between acute inflammatory, purely fibrotic and mixed inflammatory and fibrotic. Our aim is to study the utility of contrast enhanced ultrasound (CEUS) in combination with shear wave elastography (SWE) to differentiate fibrotic from inflammatory strictures in children with obstructive CD of the terminal ileum. Methods: Twenty-five (19 male) children between 2016-2021 with CD of the terminal ileum were recruited into the study. Among these patients, 22 had CEUS kinetic measurements of tissue perfusion, including wash-in slope (dB/sec), peak intensity (dB), time to peak intensity (sec), area under the curve (AUC) (dB sec), and SWE. In total, 11 patients required surgery due to bowel obstruction. Histopathologic analysis was performed by a pathologist who was blinded to the CEUS and SWE test results. Results: Patients that underwent surgical resection had significantly higher mean area under the curve on CEUS compared to patients responsive to medical therapy (p=0.03). The AUC also correlated with the degree of hypertrophy and the percent fibrosis of the muscularis propria, as determined by histopathologic grading (p<0.01). There was no difference in the mean elastography measurements between these two patient groups. Conclusion: CEUS is a useful radiological technique that can help identify pediatric patients with medically refractory obstructive fibrotic strictures of the terminal ileum that should be considered for early surgical resection.

• 한국정보통신학회논문지
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• 제20권1호
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• pp.22-29
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• 2016

수중환경 하에서 표적을 탐지하고 식별하는 문제는 군사적인 목적은 물론 비군사적 목적으로도 많은 연구가 수행되어 왔다. 수중환경에서의 수중음향 신호가 시간 공간적으로 특성이 변화하며 천해 다중경로 환경을 반영하는 복잡한 특성을 보이는 점으로 인해 능동 표적인식 기술은 매우 어려운 기술로 여겨져 왔다. 본 논문에서는 Fractional 푸리에 변환의 기본 개념과 최적 변환 차수에 대해 설명하고, 이를 이용하여 LFM 신호의 시간-주파수 특성과 스펙트럼 사이의 관계를 분석한다. 그리고 이러한 분석결과를 바탕으로 능동소나 표적 탐지 기법을 제안한다. 제안된 방법의 성능을 검증하기 위해, 기존의 FFT를 이용한 정합필터와 성능을 비교하였다. AUC(Area Under the ROC Curve)의 측면에서 볼 때 제안된 방식이 기존의 방법보다 성능이 우수한 실험결과를 보였다.

• 대한한방내과학회지
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• 제35권1호
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• pp.50-58
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• 2014

Objectives : The aim of this study was to analyze relationship between post-stroke depression (PSD) and cold, heat, deficiency and excess patterns. Methods : Twenty-eight PSD patients were recruited from STROKE center and measured with questionnaires for cold, heat, deficiency and excess patternvalues and saliva for cortisol awakening response (CAR). Saliva samples were collected immediately, 15, 30 and 45 min after awakening. In addition, Beck Depression Inventory (BDI) and Hamilton Depression Rating Scale (HDRS) were conducted for PSD severity. We conducted correlation analysis to find the relationship between cold, heat, deficiency and excess patterns and CAR or BDI and HDRS. Results : Deficiency and excess patterns werepositively correlated with area under the curve with respect to the increase (AUCi), but not with area under the curve with respect to the global (AUCg), in CAR. Furthermore, it was negatively correlated with BDI and HDRS, while cold and heat patterns were not correlated with CAR, BDI and HDRS. Conclusions : In terms of deficiency and excess patterns, the higher the PSD severity, the higher the deficiency and the lower the PSD severity, the higher the excess. However, there was not a significant relationship between PSD and cold and heat patterns.

• 한국산학기술학회논문지
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• 제21권6호
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• pp.374-382
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• 2020

본 연구에서 저장탄약 신뢰성평가(ASRP: Ammunition Stockpile Reliability Program)의 데이터 특성을 고려하여 입력변수를 줄이는 정규화기법을 제안함으로써 분류성능의 저하 없이 저장탄약 신뢰성분류 인경신경망모델의 학습 속도향상을 목표로 하였다. 탄약의 성능에 대한 기준은 국방규격(KDS: Korea Defense Specification)과 저장탄약 시험절차서(ASTP: Ammunition Stockpile reliability Test Procedure)에 규정되어 있으며, 평가결과 데이터는 이산형과 연속형 데이터가 복합적으로 구성되어 있다. 이러한 저장탄약 신뢰성평가의 데이터 특성을 고려하여 입력변수는 로트 추정 불량률(estimated lot percent nonconforming) 또는 고장률로 정규화 하였다. 또한 입력변수의 unitary hypercube를 유지하기 위하여 최소-최대 정규화를 2차로 수행하는 2단계 정규화 기법을 제안하였다. 제안된 2단계 정규화 기법은 저장탄약 신뢰성평가 데이터를 이용하여 비교한 결과 최소-최대 정규화와 유사하게 AUC(Area Under the ROC Curve)는 0.95 이상이었으며 학습속도는 학습 데이터 수와 은닉 계층의 노드 수에 따라 1.74 ~ 1.99 배 향상되었다.