• Proceedings of the Korean Information Science Society Conference
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• 2006.06a
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• pp.37-39
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• 2006

지지 벡터 기계(Support Vector Machine; SVM)는 기본적으로 이진분류를 위해 고안되었지만, 최근 다양한 분류기 생성전략과 결합전략이 고안되어 다중부류 분류에도 적용되고 있다. 본 논문에서는 OVR(One-Vs-Rest) 전략으로 생성된 SVM을 NB(Naive Bayes) 분류기를 이용하여 동적으로 구성함으로써, OVR SVM을 이용한 다중부류 분류 시스템에서 자주 발생하는 동점을 효과적으로 해결하는 방법은 제안한다. 이 방법을 유전발현 데이터를 이용한 다중부류 암 분류에 적용하였는데, 고차원의 데이터로부터 NB 분류기 구축에 유용한 유전자를 선택하기 위해 Pearson 상관계수를 사용하였다. 14개의 암 유형과 16,063개의 유전발현 수준을 가지는 대표적인 다중부류 암 분류 데이터인 GCM 암 데이터에 적용하여 제안하는 방법의 유용성을 확인하였다.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.8
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• pp.372-377
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• 2008

Multiclass cancer classification has been actively investigated based on gene expression profiles, where it determines the type of cancer by analyzing the large amount of gene expression data collected by the DNA microarray technology. Since gene expression data include many genes not related to a target cancer, it is required to select informative genes in order to obtain highly accurate classification. Conventional rank-based gene selection methods often use ideal marker genes basically devised for binary classification, so it is difficult to directly apply them to multiclass classification. In this paper, we propose a novel method for multiclass gene selection, which does not use ideal marker genes but directly analyzes the distribution of gene expression. It measures the class-discriminability by discretizing gene expression levels into several regions and analyzing the frequency of training samples for each region, and then classifies samples by using the naive Bayes classifier. We have demonstrated the usefulness of the proposed method for various representative benchmark datasets of multiclass cancer classification.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.612-615
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• 2006

본 논문에서는 Late 암으로부터 측정된 상관 값을 보정하여 상관함수의 비대칭을 완화시키고 다중경로 신호 오차를 제거하는 새로운 상관기 설계법을 제안하였다. 다중경로 오차에 의한 신호 추적 오차는 상관함수의 Early-Late 간 비대칭과 관련이 있으므로, 다중상관기 구조를 이용하여 상관함수의 Early-Late간 상관값 차를 측정하면 상관함수의 비대칭 정도를 추정할 수 있다. 상관값 차를 이용하여 추정한 상관함수 비대칭을 감소시키면 다중경로 신호에 의한 코드 추적 오차를 줄일 수 있다. 제안한 상관기는 4개의 암과 보정치 생성 블록으로 구성된다. 제안한 상관기의 다중경로 오차 제거 성능은 시뮬레이션을 이용하여 확인하였다. 여러 가지 지연시간 및 신호 진폭을 가지는 다중경로 신호에 대하여 일반 수신기와의 위상 추적 오차를 비교하여 성능을 평가하였다. 시뮬레이션 결과에서 제안한 상관기는 우수한 다중경로 오차 제거 성능을 가지며 일반상관기와 유사한 평균 신호 획득시간을 가짐을 알 수 있다.

• Journal of Chest Surgery
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• v.37 no.2
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• pp.184-187
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• 2004

The synchronous double cancer of the esophagus and lung is rare. Right lower lobectomy and Ivor Lewis procedure were performed simultaneously in a 75 year-old male patient who had synchronous double primary squamous cell carcinoma of the thoracic esophagus and right lower lobe of the lung, Left upper lobectomy was performed in a 69 year-old male patient who had squamous cell carcinoma of the left upper lobe of the lung, and four months later we performed Ivor Lewis procedure for the squamous cell carcinoma that occurred in the thoracic esophagus. The above two patients were doing well 10 months and 24 months after the operation respectively without recurrence. We treated the two cases of synchronous double cancer of the esophagus and lung with complete resection, and report this with review of literature.

• Korean Journal of Head & Neck Oncology
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• v.14 no.1
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• pp.3-14
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• 1998

Objectives: Many complicated problems exist in establishing head and neck cancer(HNCa) patient registry system. In this study, a newly devised and simplified approach named as 'Single Sheet Multiple Event System' was compared with a conventional approach named as 'Multiple Sheet System'. Material and Method: According to several kinds of registry sheets in the two systems, data were collected from 486 patients with HNCa diagnosed at Department of Otolaryngology, Seoul National University Hospital from 1979 through 1994. Results: The new system produced more simple and efficient data retrieval. Conclusion: It could make the implementation of HNCa patient registry system more simple and efficient.

• Journal of radiological science and technology
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• v.27 no.1
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• pp.37-42
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• 2004

2000년 후반부터 국내에 도입된 MDCT는 한번 숨을 참고 검사할 수 있는 volume coverage speed를 향상시킴으로 복부의 검사시간을 단축시켰고 보다 얇은 단면영상획득, isotropic resolution에 의한 reformation의 활용, 다중시기검사, 균일하게 조영된 3차원 혈관영상 획득이 가능해져 미세한 조기 복부암 진단에 주도적 역할을 수행하고 있다. 이에 CT의 기술적 발전과정과 MDCT를 이용한 복부암 진단에 대하여 소개하고자 한다.

• The Korean Journal of Applied Statistics
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• v.37 no.2
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• pp.225-237
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• 2024

In the analysis of competing risks data, some of covariates may not be fully observed for some subjects. In such cases, excluding subjects with missing covariate values from the analysis may result in biased estimates and loss of efficiency. In this paper, we studied multiple imputation and the augmented inverse probability weighting method for regression parameter estimation in the cause-specific proportional hazards model with missing covariates. The performance of estimators obtained from multiple imputation and the augmented inverse probability weighting method is evaluated by simulation studies, which show that those methods perform well. Multiple imputation and the augmented inverse probability weighting method were applied to investigate significant risk factors for the risk of death from breast cancer and from other causes for breast cancer data with missing values for tumor size obtained from the Prostate, Lung, Colorectal, and Ovarian Cancer Screen Trial Study. Under the cause-specific proportional hazards model, the methods show that race, marital status, stage, grade, and tumor size are significant risk factors for breast cancer mortality, and stage has the greatest effect on increasing the risk of breast cancer death. Age at diagnosis and tumor size have significant effects on increasing the risk of other-cause death.

• The Journal of Korean Society for Radiation Therapy
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• v.33
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• pp.9-14
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• 2021

This study examined dose change depending on the reposition error of the junction at the time of treatment with multi-isocenter volumetric modulated arc therapy. This study selected a random treatment region in the Arccheck Phantom and established the treatment plan for multi-isocenter volumetric modulated arc therapy. Then, after setting the error of the junction at 0 ~ 4 mm in the X (left), Y (upper), and Z (inner and outer) directions, the area was irradiated using a linear accelerator; the point doses and gamma indexes obtained through the Phantom were subsequently analyzed. It was found that when errors of 2 and 4 mm took place in the X and Y directions, the gamma pass rates (point doses) were 99.3% (2.085) and 98% (2.079 Gy) in the former direction and 98.5% (2.088) and 95.5% (2.093 Gy) in the latter direction, respectively. In addition, when errors of 1, 2, and 4 mm occurred in the inner and outer parts of the Z direction, the gamma pass rates (point doses) were found to be 94.8% (2.131), 82.6% (2.164), and 72.8% (2.22 Gy) in the former part and 93.4% (2.069), 90.6% (2.047), and 79.7% (1.962 Gy) in the latter part, respectively. In the X and Y directions, errors up to 4 mm were tolerable; however, in the Z direction, error values exceeding 1 mm were beyond the tolerance level. This suggests that for high and low dose areas, errors in the direction same as the progress direction in the treatment region have a more sensitive dose distribution. If the guidelines for set-up errors are established at the institutional level through continuous research in the future, it will be possible to provide good quality treatment using junctions.

• Investigative Magnetic Resonance Imaging
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• v.14 no.2
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• pp.121-125
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• 2010

Purpose : The purpose of this study was to evaluate the diagnostic accuracy of 3.0-T breast MRI for detecting additional breast cancer soon after the initial diagnosis of breast cancer. Materials and Methods : From March to June 2009, 101 patients recently diagnosed breast cancer underwent breast MRI and surgery. Parameters analyzed on MRI were total extent of tumor, suspicious findings of multifocal, multicentric, or contralateral cancer. The diagnosis of MRI-detected cancer was confirmed by means of biopsy or surgical specimen evaluation after the localization. Results : MRI showed 37 additional suspicious findings in 34 patients. Twenty nine findings were true-positive (29/37, 78.4%), including 16 cases of multifocality, 11 cases of multicentricity and 2 cases of contralateral cancer. Among these cancers, 13 (44.8%) were ductal carcinoma in situ (DCIS) and 16 (55.1%) were infiltrating cancer. Eight findings were false-positive (8/37, 21.6%) including 6 cases of benign disease and 2 cases of high-risk lesions. Conclusion : In women with recently diagnosed breast cancer, 3.0-T MR imaging showed additional suspicious findings in 33.7%. The sensitivity and specificity for detecting additional breast cancer was 100% and 89.3%, respectively.

• Radiation Oncology Journal
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• v.28 no.1
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• pp.39-49
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• 2010

Purpose: This aim of this study is to analyze the dosimetric difference between intensity-modulated radiation therapy (IMRT) using 3 or 5 beams and MSF in the radiotherapy of the left breast. Materials and Methods: We performed a comparative analysis of two radiotherapy modalities that can achieve improved dose homogeneity. First is the multistatic fields technique that simultaneously uses both major and minor irradiation fields. The other is IMRT, which employs 3 or 5 beams using a fixed multileaf collimator. We designed treatment plans for 16 early left breast cancer patients who had taken breast conservation surgery and radiotherapy, and analyzed them from a dosimetric standpoint. Results: For the mean values of $V_{95}$ and dose homogeneity index, no statistically significant difference was observed among the three therapies. Extreme hot spots receiving over 110% of the prescribed dose were not found in any of the three methods. A Tukey test performed on IMRT showed a significantly larger increase in exposure dose to the ipsilateral lung and heart than multistatic fields technique (MSF) in the low-dose area, but in the high-dose area, MSF showed a slight increase. Conclusion: In order to improve dose homogeneity, the application of MSF, which can be easily planned and applied more widely, is considered an optimal alternative to IMRT for radiotherapy of early left breast cancer.