• Biomedical Engineering Letters
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• 제8권4호
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• pp.355-364
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• 2018

When focusing using an ultrasonic transducer array, a main lobe is formed in the focal region of an ultrasound field, but side lobes also arise around the focal region due to the leakage. Since the side lobes cannot be completely eliminated in the focusing process, they are responsible for subsequent ultrasound image quality degradation. To improve ultrasound image quality, a signal processing strategy to reduce side lobes is definitely in demand. To this end, quantitative determination of main and side lobes is necessary. We propose a theoretically and actually error-free method of exactly discriminating and separately computing the main lobe and side lobe parts in ultrasound image by computer simulation. We refer to images constructed using the main and side lobe signals as the main and side lobe images, respectively. Since the main and side lobe images exactly represent their main and side lobe components, respectively, they can be used to evaluate ultrasound image quality. Defining the average brightness of the main and side lobe images, the conventional to side lobe image ratio, and the main to side lobe image ratio as image quality metrics, we can evaluate image characteristics in speckle images. The proposed method is also applied in assessing the performance of side lobe suppression filtering. We show that the proposed method may greatly aid in the evaluation of medical ultrasonic images using computer simulations, albeit lacking the use of actual experimental data.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.322-323
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• 2002

Partial volume averaging effect of PET data influences on the accuracy of quantitative measurements of regional brain metabolism because spatial resolution of PET is limited. The purpose of this study was to evaluate the accuracy of partial volume correction carried out on $^{18}$ F-PET images using Hoffman brain phantom. $^{18}$ F-PET Hoffman phantom images were co-registered to MR slices of the same phantom. All the MR slices of the phantom were then segmented to be binary images. Each of these binary images was convolved in 2 dimensions with the spatial resolution of the PET. The original PET images were then divided by the smoothed binary images in slice-by-slice, voxel-by-voxel basis resulting in larger PET image volume in size. This enlarged partial volume corrected PET image volume was multiplied by original binary image volume to exclude extracortical region. The evaluation of partial volume corrected PET image volume was performed by region of interests (ROI) analysis applying ROIs, which were drawn on cortical regions of the original MR image slices, to corrected and original PET image volume. From the ROI analysis, range of regional mean values increases of partial volume corrected PET images was 4 to 14%, and average increase for all the ROIs was about 10% in this phantom study. Hoffman brain phantom study was useful for the objective evaluation of the partial volume correction method. This MR-based correction method would be applicable to patients in the. quantitative analysis of FDG-PET studies.

• Nuclear Engineering and Technology
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• 제55권1호
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• pp.222-228
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• 2023

This study aimed to analyze the applicability of the improved median filter in positron emission tomography (PET)/magnetic resonance (MR) fusion images based on parallel imaging using generalized autocalibrating partially parallel acquisition (GRAPPA). In this study, a PET/MR fusion imaging system based on a 3.0T magnetic field and ¹⁸F radioisotope were used. An improved median filter that can set a mask of the median value more efficiently than before was modeled and applied to the acquired image. As quantitative evaluation parameters of the noise level, the contrast to noise ratio (CNR) and coefficient of variation (COV) were calculated. Additionally, no-reference-based evaluation parameters were used to analyze the overall image quality. We confirmed that the CNR and COV values of the PET/MR fusion images to which the improved median filter was applied improved by approximately 3.32 and 2.19 times on average, respectively, compared to the noisy image. In addition, the no-reference-based evaluation results showed a similar trend for the noise-level results. In conclusion, we demonstrated that it can be supplemented by using an improved median filter, which suggests the problem of image quality degradation of PET/MR fusion images that shortens scan time using GRAPPA.

• 한국컴퓨터그래픽스학회논문지
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• 제28권2호
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• pp.11-19
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• 2022

최근 의료영상의 발전에 따라 의료 영상 생성에 대한 다양한 연구가 제안되고 있는데, 이와 관련하여 생성된 의료 영상의 품질과 다양성을 정확하게 평가하는 것이 중요해지고 있다. 생성된 의료 영상을 평가하는 방법으로는 전문가의 시각적 튜링 테스트(visual turing test), 특징 분포 시각화, IS, FID를 통한 정량적 평가를 통해 평가하고 있으나 의료 영상을 품질(fidelity)과 다양성(diversity) 측면에서 정량적으로 평가 하는 방법은 거의 이루어지고 있지 않다. 본 논문에서는 DCGAN과 PGGAN 생성 모델을 통해 비소세포폐암 환자의 흉부 CT 데이터 셋을 학습하여 영상을 생성하고, 이를 품질(fidelity)과 다양성(diversity) 측면에서 두 생성 모델의 성능을 평가한다. 1차원 점수 기반 평가방법인 IS, FID와 2차원 점수 기반 평가방법인 Precision 및 Recall, 개선된 Precision 및 Recall을 통해 성능을 정량적으로 평가하고, 의료영상에서의 각 평가방법들의 특징과 한계점에 대해서도 분석한다.

• 대한건축학회논문집:구조계
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• 제34권10호
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• pp.11-18
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• 2018

In this study, the cross-sectional image has been acquired to evaluate the aggregate distribution affecting quality of lightweight aggregate concrete, and through the binarization method, the study is to calculate the aggregate area of upper and lower sections to develop the method to assess the aggregate distribution of concrete. The acquisition of cross-section image of concrete for the above was available from the cross-sectional photography of cleavage tension of a normal test specimen, and an easily accessible and convenient image analysis software was used for image analysis. As a result, through such image analyses, the proportion of aggregate distribution of upper and lower sections of the test specien could be calculated, and the proportion of aggregate area U/L value of the upper and lower regions of concrete cross-section was calculated, revealing that it could be used as the comprehensive index of aggregate distribution. Moreover, through such method, relatively easy image acquisition methods and analytic methods have been proposed, and this indicated that the development of modeling to assess aggregate distribution quantitatively is available. Based on these methods, it is expected that the extraction of fundamental data to reconsider the connectivity with processes in concrete will be available through quality assessment of quantitative concrete.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.100-102
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• 2003

This system is capable of obtaining quantitative information from images using natural features on the ortho-image maps that correspond with those from topographical maps. However, the qualitative information can also be obtained because because of the excellent visibility of ortho-image maps. There are plenty of promise for the use of ortho-image maps in the next generation topographic technology because of its wider applicability within the field. In keeping with the cutting edge, we produced ortho-image maps by scanning a specified area in narrow sections using the PKNU 2: a multispectral digital aerial photographing system made by ourselves. We evaluated the precision of the ortho-image maps, and performed an evaluation of the PKNU 2 system's capacity to improve the equipment of the PKNU 2. Ortho-image maps were made using Ground Control Points (GCPs) which were obtained from digital maps and aerial photographs of the PKNU 2. Thus, we demonstrated that it was possible to produce the ortho-image maps, which has a good constant level rate of less than 1m. The PKNU 2 system needs to be improving in the sensitivity of level maintenance equipment in the evaluation in terms of performance. It is thus required to survey the GCPs precisely for an accurate study.

• 대한의용생체공학회:의공학회지
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• 제32권3호
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• pp.257-263
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• 2011

Sparse-view CT imaging is considered to be a solution to reduce x-ray dose of CT. Sparse-view CT imaging may have severe streak artifacts that could compromise the image qualities. We have compared quality of sparseview images reconstructed with two representative iterative reconstruction techniques, SIRT and TV-minimization, in terms of image error and edge preservation. In the comparison study, we have used the Shepp-Logan phantom image and real CT images obtained with a micro-CT. In both phantom image and real CT image tests, TV-minimization technique shows the best performance in error reduction and preserving edges. However, the excessive computation time of TV-minimization is a technical challenge for the practical use.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권8호
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• pp.517-520
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• 2005

Cleft lip is a congenital deformity condition with separation of the two sides of the lip and results in nose deformity Evaluation of surgical corrections and outcome assessments in nose deformity resulting from the cleft lip depend mainly on doctor's objective judgment. Development of an objective assessment tool in evaluation of the condition and surgical outcome of cleft lip nose deformity patients will help in advancement and evaluation of surgical techniques of cleft lip. Hence, our study aimed at quantitative assessment of a cleft lip nose deformity condition by comparing following parameters gathered from a photographic image of a cleft lip patient: (1) angle difference between two nostril axis, (2) center of the nostril and distance between two centers, (3) overlapped area of two nostrils and (4) the overlapped area ratio of two nostrils. Assessment results of the nose deformity were determined by statistical analysis of evaluation results from three experienced plastic surgeons. In addition, regression model was developed using correlation relationship and factor analysis of parameters from results of the image analysis

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.45-47
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• 2005

Cleft lip is a congenital deformity condition with separation of the two sides of the lip and results in nose deformity. Evaluation of surgical corrections and outcome assessments in nose deformity resulting from the cleft lip depend mainly on doctor's objective judgment. Development of an objective assessment tool in evaluation of the condition and surgical outcome of cleft lip nose deformity patients will help in advancement and evaluation of surgical techniques of cleft lip. Hence, our study aimed on quantitative assessment of a cleft lip nose deformity condition by comparing following parameters gathered from a photographic image of a cleft lip patient: (1) angle difference between two nostril axis, (2) center of the nostril and distance between two centers, (3) overlapped area of two nostrils and (4) the overlapped area ratio of two nostrils. Assessment results of the nose deformity were determined by statistical analysis of evaluation results from three greatly experienced plastic surgeons. In addition, regression model was developed using correlation relationship and factor analysis of parameters from results of the image analysis.

• 한국환경생태학회지
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• 제7권2호
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• pp.231-240
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• 1994

덕유산 국립공원의 삼림경관, 삼림 시설물 경관, 집단시설지구 경관, 사찰경관을 대강으로 물리적 환경이 지닌 환경적 질을 계량적 접근방법으로 분석하여 합리적인 이용개발 및 보전관리에 필요한 기초자료를 제시하는 것을 목적으로 심리량 분석을 취해 S. D. Scale 을 측정하고 인자분석 $\ulcorner$알고니즘$\lrcorner$을 통하여 물리적 환경의 공간 이미지 구조를 밝혔으며, 시각적 선호도를 측정하여 결정 인자를 추출하였으며 각 인자 상호간의 중요성을 규명하였다. 덕유산 국립공원의 공간 $\ulcorner$이미지$\lrcorner$를 함축하는 변인은 종합평가적 차원, 호감성 차원, 공간적 차원, 자연성 차원 및 품격 차원 등 5개 인자군으로 분석되었으며 종합평가적 차원, 공간적 차원 및 호감성 차원의 인자가 공간 이미지를 대표하는 인자군으로 나타났다. 시각적 선호도를 결정짓는 주요 설명 변수는 계곡물의 깨끗함과 상쾌함, 지형지세의 특이성, 등산로 설치의 자연스러움 및 사찰건물 외관과 주변 인공식생과의 어울림 등이 시각적 선호도 결정의 주요변수로 작용하고 있었다.