• 정보과학회 논문지
• /
• 제44권9호
• /
• pp.992-1004
• /
• 2017

이미지 품질을 정확히 평가하기 위해 이미지 평가 도구는 인간 시각 시스템을 반영해야 한다. 즉, 이미지의 구조, 색, 명암 비 등 여러 가지 요소들을 고려하여 평가해야 한다. 또한 스마트 폰과 같은 모바일 임베디드 기기의 폭넓은 사용에 따라 빠른 수행 속도를 갖는 것이 중요하다. 본 논문에서는 인간 시각 만족과 빠른 계산속도 달성을 동시에 얻기 위하여 색 유사도, 변화율 유사도, 위상 유사도를 상승적으로 결합하였고 최적화된 이미지 풀링 및 양자화 기반으로 설계하였다. 제안하는 기법은 기존에 존재하는 13개의 기법과 비교하였고 네 가지 검증 도구를 사용하여 성능을 검증하였다. 실험 결과 세 검증 도구에서 가장 우수한 성능을 보였고 한 검증 도구에서 기존 최고 기법인 VSI에 이어 두 번째로 좋은 성능을 보였으며 실행 속도는 VSI에 대해 평균 약 20% 개선된 결과를 얻었다. 또한 기존의 기법들 보다 더 인간 시각 시스템과 제안 기법의 품질 평가 값의 연관성이 크게 존재함을 확인하였다.

• 대한방사선기술학회지:방사선기술과학
• /
• 제45권2호
• /
• pp.117-125
• /
• 2022

Although stationary inverse-geometry digital tomosynthesis (s-IGDT) is able to reduce motion artifacts, image acquisition time and radiation dose, the image quality of the s-IGDT is degraded due to the truncations arisen in projections. Therefore, the effects of geometric and image acquisition conditions in the s-IGDT should be analyzed for improving the image quality and clinical applicability of the s-IGDT system. In this study, the s-IGDT images were obtained with the various X-ray source arrangement types and the various number of projections. The resolution and noise characteristics of the obtained s-IGDT images were evaluated, and the characteristics were compared with those of the conventional DT images. The s-IGDT system using linear X-ray source arrangement and 40 projections maximized the image characteristics of resolution and noise, and the corresponding system was superior to the conventional DT system in terms of image resolution. In conclusion, we expect that the s-IGDT system can be used for providing medical images in diagnosis.

• Nuclear Engineering and Technology
• /
• 제51권3호
• /
• pp.719-722
• /
• 2019

Gamma-ray images generally suffer from a lot of noise because of low photon detection in the gamma camera system. The purpose of this study is to improve the image quality in gamma-ray images using a gamma camera system with a fast nonlocal means (FNLM) noise reduction algorithm with an acceleration function. The designed FNLM algorithm is based on local region considerations, including the Euclidean distance in the gamma-ray image and use of the encoded information. To evaluate the noise characteristics, the normalized noise power spectrum (NNPS), contrast-to-noise ratio (CNR), and coefficient of variation (COV) were used. According to the NNPS result, the lowest values can be obtained using the FNLM noise reduction algorithm. In addition, when the conventional methods and the FNLM noise reduction algorithm were compared, the average CNR and COV using the proposed algorithm were approximately 2.23 and 7.95 times better than those of the noisy image, respectively. In particular, the image-processing time of the FNLM noise reduction algorithm can achieve the fastest time compared with conventional noise reduction methods. The results of the image qualities related to noise characteristics demonstrated the superiority of the proposed FNLM noise reduction algorithm in a gamma camera system.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제9권6호
• /
• pp.2230-2250
• /
• 2015

Multiple projectors with partially overlapping regions can be used to project a seamless image on a large projection surface. With the advent of high-resolution photography, such systems are gaining popularity. Experts set up such projection systems by subjectively identifying the types of errors induced by the system in the projected images and rectifying them by optimizing (correcting) the parameters associated with the system. This requires substantial time and effort, thus making it difficult to set up such systems. Moreover, comparing the performance of different multi-projector display (MPD) systems becomes difficult because of the subjective nature of evaluation. In this work, we present a framework to quantitatively determine the quality of an MPD system and any image projected using such a system. We have divided the quality assessment into geometric and photometric qualities. For geometric quality assessment, we use Feature Similarity Index (FSIM) and distance-based Scale Invariant Feature Transform (SIFT). For photometric quality assessment, we propose to use a measure incorporating Spectral Angle Mapper (SAM), Intensity Magnitude Ratio (IMR) and Perceptual Color Difference (ΔE). We have tested the proposed framework and demonstrated that it provides an acceptable method for both quantitative evaluation of MPD systems and estimation of the perceptual quality of any image projected by them.

• 한국컴퓨터정보학회논문지
• /
• 제28권8호
• /
• pp.11-19
• /
• 2023

본 논문에서는 기존에 영상의 품질을 평가하는 데 사용되던 지표가 저조도 영상에 대해서도 적용될 수 있음을 확인한다. 저조도 영상의 특성상, 빛과 관련된 요인들이 다양한 잡음 패턴을 만들어내고 빛의 양이 적을수록 극심한 잡음을 가지고 있다. 그렇기 때문에, 잡음이 없는 깨끗한 영상을 구하기 힘든 상황에서 잡음이 제거된 저조도 영상의 품질을 사람의 눈으로 판단하는 경우가 많다. 본 논문에서는, ground truth를 구할 수 없는 저조도 영상의 잡음을 Noise2Noise를 이용해서 제거하고, MTF와 SNR 등의 지표로 공간 해상도와 방사 해상도를 ISO 12233 차트와 colorchecker를 대상으로 평가한다. 정성적 평가 위주로 평가되던 저조도 영상의 품질이 정량적으로도 평가될 수 있음을 보여줄 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제15권11호
• /
• pp.4043-4064
• /
• 2021

Night-time image quality evaluation is an urgent requirement in visual inspection. The lighting environment of night-time results in low brightness, low contrast, loss of detailed information, and colour dissonance of image, which remains a daunting task of delicately evaluating the image quality at night. A new blind quality assessment metric is presented for realistic night-time scenario through a comprehensive consideration of contrast, texture, and colour in this article. To be specific, image blocks' color-gray-difference (CGD) histogram that represents contrast features is computed at first. Next, texture features that are measured by the mean subtracted contrast normalized (MSCN)-weighted local binary pattern (LBP) histogram are calculated. Then statistical features in Lαβ colour space are detected. Finally, the quality prediction model is conducted by the support vector regression (SVR) based on extracted contrast, texture, and colour features. Experiments conducted on NNID, CCRIQ, LIVE-CH, and CID2013 databases indicate that the proposed metric is superior to the compared BIQA metrics.

• 대한방사선기술학회지:방사선기술과학
• /
• 제45권2호
• /
• pp.127-134
• /
• 2022

In order to overcome the image quality limitations of the conventional C-arm, a flat panel detector (FPD) is used to enhance spatial resolution, detective quantum efficiency, frame rate, and dynamic range. Three-dimensional (3D) visualized information can be obtained from C-arm computed tomography (CT) equipped with an FPD, which can reduce patient discomfort and provide various medical information to health care providers by conducting procedures in the interventional procedure room without moving the patient to the CT scan room. Unlike a conventional C-arm device, a C-arm CT requires different basic safety and essential performance evaluation criteria; therefore, in this study, basic safety and essential performance evaluation criteria to protect patients, medical staff, and radiologists were derived based on International Electrotechnical Commission (IEC) standards, the Ministry of Food and Drug Safety (MFDS) standards in Korea, and the rules on the installation and operation of special medical equipment in Korea. As a result of the study, six basic safety evaluation criteria related to electrical and mechanical radiation safety (leakage current, collision protection, emergency stopping device, overheating, recovery management, and ingress of water or particulate matter into medical electrical (ME) equipment and ME systems: footswitches) and 14 essential performance evaluation criteria (accuracy of tube voltage, accuracy of tube current, accuracy of loading time, accuracy of current time product, reproducibility of radiation output, linearity and consistency in radiography, half layer value in X-ray equipment, focal size and collimator, relationship between X-ray field and image reception area, consistency of light irradiation versus X-ray irradiation, performance of the mechanical device, focal spot to skin distance accuracy, image quality evaluation, and technical characteristic of cone-beam computed tomography) were selected for a total of 20 criteria.

• 농촌계획
• /
• 제17권2호
• /
• pp.33-41
• /
• 2011

To evaluate the value of a preserved tree as rural landscape resource, the growth environment and health condition was investigated, and the image evaluation was implemented on land~ape architectural major undergraduate students for zelkova trees in Yesan-gun. The image evaluation results of zelkova trees were as followings; 1) Typical image of preserved tree examined by Semantic Differential Scale were 'Old', 'Big', and 'Good'. 2) The 'big' image of zelkova tree and the height of tree, the width of tree crown, the breast girth of tree, the root girth of tree, the external formation of tree, and the health of tree bark is mutually related. Especially, the correlation between the 'big' and the external formation and the width of tree crown is high. 3) Typical image of preserved tree examined by Likert Scale were 'Natural', 'Green', 'Peaceful', and 'Rural'. 4) The preservation necessity for preserved tree was highly related with the state of ground, and the management necessity for preserved tree was highly related with contamination level and the state of ground. The appropriate management plan for preserved tree are proposed to improve the quality of rural landscape(basis of these results).

• 대한방사선기술학회지:방사선기술과학
• /
• 제26권3호
• /
• pp.7-11
• /
• 2003

방사선과에 도입된 새로운 디지털 의료 영상 시스템은 많은 변화를 요구하고 있다. 기존의 F/S 시스템에서 부족하거나, 예측하지 못하는 일부분을 대체로 만족하는 수준에 이르렀다. 하지만, 영상의 질과 환자의 피폭선량에서는 아직도 구체적인 자료가 제시되지 않고 있는 것이 현실이다. 이에 본 연구는 기존의 F/S 시스템의 의료 영상과 디지털 의료 영상을 비교하는데 있어서 환자의 피폭선량의 관점에서 실험을 하였으며, 실험결과 값을 이용하여 보다 우수한 환자 서비스 개선을 위한 DR 시스템의 영상의 질과 피폭선량의 측면에서 자료를 제시하고자 연구하였다.

• 대한방사선기술학회지:방사선기술과학
• /
• 제46권4호
• /
• pp.295-301
• /
• 2023

In addition to protocol adjustments during CT examinations, the height of the CT table can also affect image quality. Therefore, this study aimed to investigate the change in image quality depending on the height of the table in brain CT, which accounts for a large proportion of CT examinations, by measuring signal to contrast to noise ratio (CNR) and noise power spectrum (NPS) using the head phantom and evaluating them. The head phantom images were acquired using Philips Brilliance iCT 256. When the image was acquired, the table height was adjusted to 815, 865, 915, 965, 1015, and 1030 mm, respectively, and each scan was performed 3 times for each height. The CNR result showed the highest value at 965 mm, which is the height adjacent to the center of the head phantom. NPS showed the lowest NPS at 915 mm, the center of the head phantom in the low frequency region. From these results, it can be seen that the height of the table in CT examination is closely related to the image quality, and it can be seen the characteristics of image quality according to CT table through quantitative evaluation methods such as CNR and NPS.