• International Journal of Contents
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• 제2권3호
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• pp.27-32
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• 2006

We present an effective algorithm for automatic tracing of retinal vessel structure and vascular landmark extraction of bifurcations and ending points. In this paper we deal with vascular patterns from RGB images for personal identification. Vessel tracing algorithms are of interest in a variety of biometric and medical application such as personal identification, biometrics, and ophthalmic disorders like vessel change detection. However eye surface vasculature tracing in RGB images has many problems which are subject to improper illumination, glare, fade-out, shadow and artifacts arising from reflection, refraction, and dispersion. The proposed algorithm on vascular tracing employs multi-stage processing of ten-layers as followings: Image Acquisition, Image Enhancement by gray scale retinal image enhancement, reducing background artifact and illuminations and removing interlacing minute characteristics of vessels, Vascular Structure Extraction by connecting broken vessels, extracting vascular structure using eight directional information, and extracting retinal vascular structure, and Vascular Landmark Extraction by extracting bifurcations and ending points. The results of automatic retinal vessel extraction using jive different thresholds applied 34 eye images are presented. The results of vasculature tracing algorithm shows that the suggested algorithm can obtain not only robust and accurate vessel tracing but also vascular landmarks according to thresholds.

• 대한원격탐사학회지
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• 제19권2호
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• pp.99-106
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• 2003

부산 해운대 백사장에 설치된 원격무인 자동 영상 관측시스템에서 관측한 비데오 영상을 이용하여 해안선 변화를 관측하고 분석하였다. 1999년 10월 태풍 바트 기간 중 촬영된 비데오 경사 영상들에 평균영상처리 및 기하 보정 기법을 적용함으로서 파랑과 조석에 의하여 변화되는 해안선의 변화에 대한 정량적인 분석을 시도하였다. 연구 결과 카메라 관측 시스템은 파랑과 조석 등에 의하여 계속적으로 변화하는 해안선을 저비용 고효율로 장기간 관측할 수 있을 것으로 보인다.

• 한국멀티미디어학회논문지
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• 제6권6호
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• pp.991-999
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• 2003

본 논문에서는 호흡에 의하여 변화하는 기도 내부 영역의 형태학적인 정보를 반영할 수 있는 EBCT를 이용한 영상 획득 기법과 이 기법을 이용하여 획득한 단층 영상으로부터 기도 내벽의 윤곽선을 자동적으로 검출하는 방법을 제안하였다. 기도의 각 준위에 대한 영상데이터들을 적용한 컴퓨터 시뮬레이션 결과들을 통하여 제안한 방법이 효과적으로 기도의 윤곽선을 검출함을 확인하였으며 시간적 변화에 따른 기도 내벽의 단면적인 변화를 볼 수 있었다. 따라서, 제안한 방법이 임상에서의 정량적 평가에 활용할 수 있을 것으로 판단된다.

• International Journal of Contents
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• 제9권2호
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• pp.66-69
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• 2013

In the U.S., performance assessment on the Automatic Exposure Control system (AEC) is managed according to the Mammography Quality Standards Act (MQSA). However, The AEC is not available in the performance assessment conducted in Korea. Also, there is no study made on the performance of the automatic exposure control system for mammography in Korea. For this reason, this study examined the performance of the automatic exposure control system for mammography that was clinically used in the Incheon area. Result showed that the difference of the mean optical density was 0.79 ~ 2.81. This implies that some devices caused unnecessary x-ray exposure to patients. Furthermore, only 61.5% of the entire experimental device was shown to be satisfactory in terms of change in mean optical density. Moreover, in terms of the subject's thickness, change in radiographic density was shown to be severe among lower X-ray tube voltage while there was severe density change in X-ray image depending on X-ray tube voltage among the subjects with more thickness. Therefore, it is suggested to provide performance management on the AEC for mammography.

• 대한방사선기술학회지:방사선기술과학
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• 제44권1호
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• pp.39-46
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• 2021

This study confirmed the usefulness of the copper filter according to the mode change by comparing and analyzing the energy change according to the application of the copper filter and the change in effective dose and image quality according to the distance to the subject in the DR(Digital Radiography) system. The average energy increased when the copper filter was applied and the reduction rate by 50% of mAs was increased as the thickness of the copper filter increased according to the application of the 10 kVp rule in AEC mode. The effective dose decreased as the thickness increased when the copper filter was applied in AEC(Automatic Exposure Control) mode and manual mode according to the application of the 10 kVp rule, and the decrease rate decreased with increasing 10 kVp increments. As a result of analyzing the dicom images for AEC mode and manual mode with Image J. the PSNR(Peak Signal to Noise Ratio) values were approximate values of less than 30 dB for each mode and for each copper filter thickness. When the copper filter was applied, the average energy increased, so when the 10 kVp rule was applied, the mAs for each mode could be reduced, and the effective dose could also be reduced. However, as the distance and tube voltage increased, the reduction rate of mAs decreased, and the quality of the image was found to decrease when the copper filter was applied, but there was no difference in quality of the image when the copper filter thickness increased.

• 한국통신학회논문지
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• 제21권3호
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• pp.553-563
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• 1996

Detecting edges is one of issues with essentialimprotance in the area of image analysis. An edge in an image is a boundary or contour at which a significant change occurs in image intensity. Edge detection has been studied in many addlications such as imagesegmentation, robot vision, and image compression. In this paper, we propose an automatic threshold selection scheme for edge detection and show its application to noise elimination. The scheme suggested here applied statistical properties of the noise estimated from a noisy image to threshold selection. Since a selected threshold value in the scheme depends on not the characgreistic of an orginal image but the statistical feature of added noise, we can remove ad-hoc manners used for selecting the threshold value as well as decide the value theoretically. Furthermore, that shceme can reduce the number of edge pixels either generated or lost by noise. an application of the scheme to noise elimination is shown here. Noise in the input image can be eliminated with considering the direction of each edge pixedl on the edge map obtained by applying the threshold selection scheme proposed in this paper. Achieving significantly improved results in terms of SNR as well as subjective quality, we can claim that the suggested method works well.

• 대한방사선치료학회지
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• 제21권2호
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• pp.83-88
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• 2009

목 적: 온 보드영상(OBI)장치를 이용한 콘빔CT는 환자 치료 중 실시간으로 전산화모의치료 영상과 비교하여 환자의 자세 및 표적용적의 움직임과 셋업오차를 확인 할 수 있다. IMRT 시 콘빔CT를 이용해 환자의 자세 및 표적용적의 변화와 움직임을 확인하여 치료계획과의 오차정도를 산출하고, Automatic Match System을 이용하여 위치 보정을 한 후 전자포털영상 장치를 통하여 위치보정의 정확성을 검증하고, IMRT에서 콘빔CT의 유용성과 Automatic Match System의 정확성에 대하여 알아보고 자 한다. 대상 및 방법: 본원에서 치료받은 IMRT 환자 중 두 경부 치료환자 3명, 골반부 치료환자 1명을 대상으로 치료 자세의 변동과 그에 따른 조사용적의 위치변동을 알아보기 위해 선형가속기에 장착된 온 보드 영상 장치를 이용해 콘빔 CT를 촬영하였다. IMRT 전 매 치료 시 마다 콘빔CT를 촬영하여 전산화단층모의치료 영상과 비교하여 좌표별로 치료계획과의 오차값을 확인하고 3D/3D Match의 Automatic Match System을 통하여 치료계획과 일치하도록 이동 보정한 후 전자포털영상 장치를 이용하여 검증, 평가하였다. 결 과: 치료 전 콘빔 CT와 전산화단층모의치료 영상 비교 시 두 경부에서 좌표별 평균오차는 Vertical 0.99 mm, Longitudinal 1.14 mm, Lateral 0.84 mm, Rotation $0.49^o$이고, 골반부의 평균오차는 Vertical 2.78 mm, Longitudinal 2.04 mm, Lateral 4.91 mm, Rotation $1.07^o$로 부위별로 다소 근소한 차이를 보였다. 보정 후 검증에서는 전자포털영상 장치에 의한 영상과 DRR 영상 비교 결과 0.5 mm 이내의 오차로 정확한 보정이 이루어졌음을 알 수 있었다. 결 론: 치료 전 콘빔CT 영상은 환자의 셋업오차와 장기 및 표적의 위치변화를 2차원적 영상의 비교와 달리 하나의 체적으로 재구성된 3차원적 영상으로 비교함으로써 보다 정확하게 위치변화와 표적용적의 변동 등을 측정, 보정하여 정확한 치료를 할 수 있으며, 그 오차 값을 산출하여 비교할 수 있다. 이상의 연구로 보아 콘빔CT는 치료계획과 일치하는 정확한 치료전달과 반복적인 치료재현성에 유용하였으며, 만족스러운 결과를 얻을 수 있었다. 콘빔CT에 의해 향상된 정확도는 복잡한 모양의 표적용적과 급격한 선량분포의 변화가 나타나는 IMRT에서 더욱 필요하며 각 치료 부위별, 치료 목적별로 Match focus에 대한 기준을 연구해야 될 것으로 사료된다.

• 대한원격탐사학회지
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• 제20권3호
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• pp.189-196
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• 2004

This paper describes what an operational change detection tool requires and the software which was designed and developed according to the requirements. The top requirement for the application of the software to operational change detection was identified: minimization of false detections, missing detections and operational cost. In order to meet such a requirement, the software was designed with the concept that the ultimate decision and isolation of changes must be performed manually by visual interpretation and all automatic algorithms and/or visualization techniques must be defined as support functions. In addition, the modular structure of the proposed software enables the addition of a new support function with the minimum development cost and minimum change of the operational environment.

• 대한원격탐사학회지
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• 제26권3호
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• pp.325-333
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• 2010

Image registration involves overlapping images of an identical region and assigning the data into one coordinate system. Image registration has proved important in remote sensing, enabling registered satellite imagery to be used in various applications such as image fusion, change detection and the generation of digital maps. The image descriptor, which extracts matching points from each image, is necessary for automatic registration of remotely sensed data. Using contrast enhancement algorithms such as histogram equalization and image stretching, the normalized data are applied to the image descriptor. Drawing on the different spectral characteristics of high resolution satellite imagery based on sensor type and acquisition date, the applied normalization method can be used to change the results of matching interest point descriptors. In this paper, the matching points by scale invariant feature transformation (SIFT) are extracted using various contrast enhancement algorithms and injection of Gaussian noise. The results of the extracted matching points are compared with the number of correct matching points and matching rates for each point.

• 지구물리와물리탐사
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• 제2권3호
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• pp.154-158
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• 1999

본 논문에서는 부분 윤곽선 추출기법을 이용하여 다중 시차 영상을 위한 자동 변화 추적 시스템의 속도를 증가시키고자 한다. 기존의 변화 추적 시스템에서는 전체 영상에서 윤곽선을 추출하여 사용하였으나, 본 연구에서는 윤곽선 추출이 필요한 부분을 미리 선택하여 이 부분에서만 윤곽선을 추출하게 함으로써 처리 속도를 향상시킬 수 있었다. 따라서 본 시스템은 특히 위성 영상 자료나 물리 탐사 자료 등의 방대한 영상 자료에서의 변화 탐지와 추적, 정량적인 분석 등을 위해 효과적으로 활용될 수 있을 것으로 기대된다.