• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2014.06a
• /
• pp.105-106
• /
• 2014

본 논문에서는 중요도 지도를 사용한 화소값 사이 척력 기반 영상 대조비 향상 기법을 제안한다. 공간상에서 인접한 화소들 사이에 자주 발생하는 화소값들의 차이를 크게 하면 효과적으로 영상의 디테일을 두드러지게 할 수 있다. 대조비 증가를 위해 화소값 사이 척력을 정의하고, 유효 화소값 사이 척력들의 합을 사용하여 대조비의 증가 정도를 조절한다. 중요도 지도는 영상의 화소마다 사람의 시선이 머무르는 정도를 상대적인 수치로 나타낸 것이다. 따라서 영상 화질을 개선할 때 중요도 지도를 사용하면 사람의 시선을 끄는 화소값들의 대조비를 선택적으로 높일 수 있다. 실험 결과를 통하여 제안 기법이 우수한 화질개선 영상을 생성함을 확인한다.

• Investigative Magnetic Resonance Imaging
• /
• v.3 no.1
• /
• pp.60-65
• /
• 1999

Purpose : The purpose of this study was to evaluate the image quality, contrast characteristics, and possible clinical utility of Medium Tau Inversion Recovery(MTIR) sequence with white matter suppression in patients with brain cortical lesion. Materials and methods : Two normal volunteers and twenty-one patients with cortical lesion were scanned with MTIR as well as other MR imaging sequences. Gray-white matter contrast was evaluated objectively using region-of-interest calculations, including percent contrast and contrast-to-noise ratio(CNR). MTIR sequence was visually compared with other sequences in 21 patients with cortical lesion including conspicuity and detection rate. Results : MTIR sequence had the highest present contrast and CNR between the gray matter and white matter. In twenty-one cases of cortical lesion including cortical dysplasia, MTIR sequence improved delineation and conspicuity of lesion, but MTIR sequence could not detect new lesions. Conclusion : The MTIR sequence well delineated the cortical lesions, particularly in including cortical dysplasia. It may be used as an adjunctive imaging sequence in case of poor gray and white matter differentiation with conventional T1-weighted sequences.

• Journal of Korea Multimedia Society
• /
• v.16 no.11
• /
• pp.1250-1260
• /
• 2013

The contrast enhancement techniques based on Laplacian pyramid image fusion have a benefit that they can faithfully describe the image information because they combine the multiple resource images by selecting the desired pixel in each image. However, they also have some problem that the output image may contain noise, because the methods evaluate the visual information on the basis of each pixel. In this paper, an improved contrast enhancement method, which effectively suppresses the noise, using image fusion is proposed. The proposed method combines the resource images by making Laplacian pyramids generated from weight maps, which are produced by measuring the difference between the block-based local well exposedness and local homogeneity for each resource image. We showed the proposed method could produce less noisy images compared to the conventional techniques in the test for various images.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2018.11a
• /
• pp.44-45
• /
• 2018

본 논문은 감마 보정 기반의 저조도 영상의 대조비 향상을 위한 최적의 계수 추정 기법을 제안한다. 제안하는 기법은 먼저 입력 영상의 휘도 정보를 로그 함수를 이용하여 정규화 한 후, 입력 영상을 밝은 부분과 어두운 부분으로 나눈다. 그런 다음 각각의 영역에서 통계적 특성을 고려한 비용 함수를 정의하고, 컨벡스 최적화 이론을 이용하여 최적의 감마보정 계수를 얻는다. 마지막으로 과포화 현상이 발생을 억제할 수 있는 색상 복원 기법을 적용한다. 컴퓨터 모의실험을 통해 제안하는 기법이 기존 기법에 비해서 낮은 계산 복잡도를 보이면서도 향상된 대조비를 보임을 확인한다.

• Korean Journal of Digital Imaging in Medicine
• /
• v.5 no.1
• /
• pp.98-101
• /
• 2002

대조도와 관용도사이의 손실 교환은 투사 방사선 촬영에 있어서 잘 알려져 있고 또한 오랫동안 지속되어온 영상의 질에 있어서의 제약이었다. 전자적인 영상획득의 도입으로 한 영상 내에 넓은 영역의 X-Tay 노출을 포획하는 것이 가능해 졌다. 그러나, 진단에 필요한 세부영역 들을 위해 적절한 대조도를 유지하는 반면, 일반적으로 기대되는 관용도 범위 이외의 정보가 시각화 되어지는 것과 같은 영상의 rendering과 displaying의 문제가 남아 있었다. 이 문서에 묘사되는 EVP(Enhanced Visualization Processing)는 이 문제를 중점적으로 다룬다. 방대한 진단용 CR 영상 데이터베이스로부터 선택된 14개의 검사유형 당 각각 5개의 영상들을 포함한, 총 70개의 영상들을 사용하여 임상 보고서가 제출되었다. 각 영상에 대해, control rendering은 현재 개발되어 있는 automatic tone scaling algorithm(자동 톤 스케일 알고리즘)에 의해 생성되었고, test rendering은 그 control of image에 EVP를 인가함에 의해 생성되었다. 10명의 radiologist들은 각자 개별적으로 140개의 이미지들(70개의 test renderings와 70개의 control renderings)을 9점의 진단 상의 품질 척도로 평가했다. EVP는 세부 대조도의 부당한 손실 없이 증가된 노출 관용도를 제공했다. 많은 영상에서 EVP는 과소 투과 영역에서의 정보의 손실을 줄여주고, 반면 과다 투과 영역의 밝게 빛나는 현상을 실제적으로 감소시켰다. 진단상의 품질 평가는 EVP image와 control image 모두 평균적으로 높았다. 그럼에도 EVP images의 평균 등위는 control image의 그것보다 1 단계 완전히 높은 범위에 있는 것으로 평가되었다. 쌍으로 그 영상들을 보면, EVP images의 76%가 일치하는 control images의 평가 단계보다 1 또는 그 이상 높은 범주인 것으로 평가되었고, 반면 control image의 6% 만이 일치하는 EVP 영상보다 우수한 것으로 평가되었다. 유사한 결과가 연구된 14개의 검사유형에 대해 획득되었다.

• Progress in Medical Physics
• /
• v.19 no.3
• /
• pp.150-156
• /
• 2008

An applied technique of contrast enhancement for X-ray image is proposed which is based on combined enhancement of scaling and wavelet coefficients in discrete wavelet transform space. Conventional contrast enhancement methods such as contrast limited adaptive histogram equalization (CLAHE), multi-scale image contrast amplification (MUSICA) and gamma correction were applied on scaling coefficients to enhance the contrast of an original. In order to enhance the detail as well as reduce the blurring caused by up scaling of contrast modified scale coefficients from lower resolution, the sigmoid manipulation function was used to manipulate wavelet coefficients. The contrast detail mammography (CDMAM) phantom was imaged and processed to measure the image line profile of results and contrast to noise ratio (CNR) comparatively. The proposed technique produced better results than direct application of various contrast enhancement methods on image itself. The proposed method can enhance contrast, and also suppress the amplification of noise components in a single process. It could be useful for various applications in medical, industrial and graphical images where contrast and detail are of importance.

• 대한방사선방어학회:학술대회논문집
• /
• 2009.04a
• /
• pp.238-239
• /
• 2009

• Journal of Biomedical Engineering Research
• /
• v.20 no.2
• /
• pp.165-172
• /
• 1999

An enhancement technique for phase dependent image contrast in MRI(Manetic Resonance Imaging) is proposed. Because the method can enhance inherent phase contrast it is suited for susceptibility imaging and flow imaging where intravoxel phase is a source of image contrast. In this paper, applying external phase in the voxel enhances phase contrast. The external phase is generated by a tailored RF pulse so that one can control the phase contrast and even produces phase only contrast. Signal intensity due to both inherent phase and external phase is analyzed and the proposed technique is applied to a susceptibility effect only imaging and a flow effect only imaging. To verify the proposed technique, computer simulations are performed and their results are given.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.52 no.11
• /
• pp.55-65
• /
• 2015

Contrast enhancement methods for a single image applied to videos may cause flickering artifacts because these methods do not consider continuity of videos. On the other hands, methods considering the continuity of videos can reduce flickering artifacts but it may cause unnecessary fade-in/out artifacts when the intensity of videos changes abruptly. In this paper, we propose a robust method of video contrast enhancement for sudden illumination changes. The proposed method enhances each frame by Fast Gray-Level Grouping(FGLG) and considers the continuity of videos by an exponential smoothing filter. The proposed method calculates the smoothing factor of an exponential smoothing filter using a sigmoid function and applies to each frame to reduce unnecessary fade-in/out effects. In the experiment, 6 measurements are used for the performance analysis of the proposed method and traditional methods. Through the experiment. it has been shown that the proposed method demonstrates the best quantitative performance of MSSIM and Flickering score and show the adaptive enhancement under sudden illumination change through the visual quality comparison.

• Progress in Medical Physics
• /
• v.26 no.4
• /
• pp.215-222
• /
• 2015

In this work, we performed a proof-of-concept experiment for phase-contrast x-ray imaging (PCXI) based on a single antiscatter grid and a polychromatic x-ray source. We established a table-top setup which consists of a focused-linear grid having a strip density of 200 lines/inch, a microfocus x-ray tube having a focal-spot size of about $5{\mu}m$, and a CMOS-type flat-panel detector having a pixel size of $48{\mu}m$. By using our prototype PCXI system and the Fourier demodulation technique, we successfully obtained attenuation, scattering, and differential phase-contrast images of improved visibility from the raw images of several selected samples at x-ray tube conditions of $90kV_p$ and 0.1 mAs. Further, fusion image (e.g., the attenuation+the scattering) may have an advantage in displaying details of the sample's structures that are not clearly visible in the conventional attenuation image. Our experimental results indicate that single-grid-based approach seems a useful method for PCXI with great simplicity and minimal requirements on the setup alignment.