• Title/Summary/Keyword: Low Contrast

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Image characteristics of cone beam computed tomography using a CT performance phantom (CT performance phantom을 이용한 cone beam형 전산화단층영상의 특성)

  • Han, Choong-Wan;Kim, Gyu-Tae;Choi, Yong-Suk;Hwang, Eui-Hwan
    • Imaging Science in Dentistry
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    • v.37 no.3
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    • pp.157-163
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    • 2007
  • Purpose: To evaluate the characteristics of (widely used) cone beam computed tomography (CBCT) images. Materials and Methods: Images were obtained with CT performance phantoms (The American Association of Physicists in Medicine; AAPM). CT phantom as the destination by using PSR $9000N^{TM}$ dental CT system (Asahi Roentgen Ind. Co., Ltd., Japan) and i-CAT CBCT (Imaging Science International Inc., USA) that have different kinds of detectors and field of view, and compared these images with the CT number for linear attenuation, contrast resolution, and spatial resolution. Results: CT number of both PSR $9000N^{TM}$ dental CT system and i-CAT CBCT did not conform to the base value of CT performance phantom. The contrast of i-CAT CBCT is higher than that of PSR $9000N^{TM}$ dental CT system. Both contrasts were increased according to thickness of cross section. Spatial resolution and shapes of reappearance was possible up to 0.6 mm in PSR $9000N^{TM}$ dental CT system and up to 1.0 mm in i-CAT CBCT. Low contrast resolution in region of low contrast sensitivity revealed low level at PSR $9000N^{TM}$ dental CT system and i-CAT CBCT. Conclusion: CBCT images revealed higher spatial resolution, however, contrast resolution in region of low contrast sensitivity was the inferiority of image characteristics.

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Image Contrast Enhancement Technique Using Clustering Algorithm (클러스터링 알고리듬을 이용한 영상 대비 향상 기법)

  • Kim, Nam-Jin;Kim, Yong-Soo
    • Journal of the Korean Institute of Intelligent Systems
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    • v.14 no.3
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    • pp.310-315
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    • 2004
  • Image taken in the night can be low-contrast images because of poor environment and image transmission. We propose an algorithm that improves the acquired low-contrast image. MPEG-2 separates chrominance and illuminance, and compresses respectively because human vision is more sensitive to luminance. We extracted illumination and used K-means algorithm to find a proper crossover point automatically. We used K-means algorithm in the viewpoint that the problem of crossover point selection can be considered as the two-category classification problem. We divided an image into two subimages using the crossover point, and applied the histogram equalization method respectively. We used the index of fuzziness to evaluate the degree of improvement. We compare the results of the proposed method with those of other methods.

Alternation of Topical Heat and Cold for Chronic Low Back Pain : A Randomized Controlled Pilot Trial

  • Choi, Young Doo;Jo, Su Jeong;Jung, Chan Yung;Kim, Kap Sung;Lee, Seung Deok
    • Journal of Acupuncture Research
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    • v.33 no.2
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    • pp.77-87
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    • 2016
  • Objectives : This is a pilot study for a large randomized controlled trial to investigate the efficacy and safety of a newly developed contrast therapy device-- alternating topical heat and cold -- for patients with chronic low back pain. The main objective of this study is to confirm the feasibility of the study design. Methods : The design was a randomized, 2-arm, parallel-group, single-blind, placebo controlled trial. Patients in each group received real or sham contrast therapy in an acupuncture point 10 times over four weeks. The primary outcome measure was pain intensity on a 100-mm visual analogue scale (VAS). The secondary outcomes were back-related dysfunction based on the Oswestry Disability Index (ODI), the Roland-Morris disability questionnaire (RMDQ), and range of motion of lumbar spine based on the modified Schober test (mSchober test), Finger-to-Floor distance (FTF distance), and Finger-to-Thigh distraction (FTT distraction). Results : A total of 30 subjects with chronic low back pain were randomly assigned to a contrast therapy group (n=15) or a sham group (n=15). A repeated-measures analysis of variance showed statistically significant group time interaction for VAS, RMDQ, mSchober test and FTF distance (p<0.05). The treatment group showed significant improvement in pain intensity and functional disability as compared to the sham group. Conclusion : Contrast therapy may be an effective and safe treatment for chronic low back pain.

The Effect of Spatial Attention in Hangul Word Recognition: Depending on Visual Factors (한글 단어 재인에서 시각적 요인에 따른 공간주의의 영향)

  • Ko Eun Lee;Hye-Won Lee
    • Korean Journal of Cognitive Science
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    • v.34 no.1
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    • pp.1-20
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    • 2023
  • In this study, we examined the effects of spatial attention in Hangul word recognition depending on visual factors. The visual complexity of words (Experiment 1) and contrast (Experiment 2) were manipulated to examine whether the effect of spatial attention differs depending on visual quality. Participants responded to words with and without codas in experiment 1 and words in high-contrast and low-contrast conditions in experiment 2. The effects of spatial attention were investigated by calculating the difference in performance between the condition where spatial cues were given at the target location (valid trial) and the condition where the spatial cues were not given at the target location (invalid trial) as the cuing effects. As a result, the cuing effects were similar depending on the complexity of the words. It indicates that the effects of spatial attention were not different across the visual complexity conditions. The cuing effects were greater in the low-contrast condition than in the high-contrast condition. The greater effect of spatial attention when the contrast is low was explained as a mechanism of signal enhancement.

Anaphylactic Shock Following Nonionic Contrast Medium during Caudal Epidural Injection

  • Lee, Sang Hyun;Park, Jae Woo;Hwang, Byeong Mun
    • The Korean Journal of Pain
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    • v.28 no.4
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    • pp.280-283
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    • 2015
  • Caudal epidural injection is a common intervention in patients with low back pain and sciatica. Even though the complications of fluoroscopically directed epidural injections are less frequent than in blind epidural injections, complications due to contrast media can occur. We report a case of anaphylactic shock immediately after injection of an intravenous nonionic contrast medium (iohexol) during the caudal epidural injection for low back pain and sciatica in a patient without a previous allergic history to ionic contrast media (ioxitalamate). Five minutes after the dye was injected, the patient began to experience dizziness, and the systolic blood pressure dropped to 60 mmHg. Subsequently, the patient exhibited a mild drowsy mental state. About 30 minutes after the subcutaneous injection of 0.2 mg epinephrine, the systolic blood pressure increased to 90 mmHg. The patient recovered without any sequela. Life-threatening complications after injection of intravenous contrast medium require immediate treatment.

Cognitive Contrast Enhancement of Image Using Adaptive Parameter Based on Non-Linear Masking (비선형 마스킹 기법 기반의 적응적 파라미터를 이용한 영상의 인지적 대비 향상)

  • Kim, Kyoung-Su;Kim, Jong-Sung;Lee, Cheol-Hee
    • Journal of Korea Multimedia Society
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    • v.14 no.11
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    • pp.1365-1372
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    • 2011
  • This paper proposes a cognitive contrast enhancement algorithm based on the non-linear masking to advance low cognitive contrast in dark regions of images. In order to improve brightness in dark regions of an image, we propose a new contrast enhancement algorithm based on the non-linear masking using regional adaptive parameters of an image. For performance evaluation of the proposed method, chromaticity and saturation comparison as a quantitative assessment and z-score comparison as a qualitative assessment were executed between test images and their simulated images by SSR, MSR, a conventional non-linear masking and the proposed method, respectively. As a result, the proposed method showed low chromaticity and saturation difference and improved cognitive contrast for the three methods.

Automatic Threshold Selection and Contrast Intensification Technique for Image Enhancement (영상 향상을 위한 자동 임계점 선택 및 대비 강화 기법)

  • Lee, Geum-Boon;Cho, Beom-Joon
    • Journal of Korea Multimedia Society
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    • v.11 no.4
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    • pp.462-470
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    • 2008
  • This study applies fuzzy functions to improve image quality under the assumption that uncertainty of image information due to low contrast is based on vagueness and ambiguity of the brightness pixel values. To solve the problem of low contrast images whose brightness distribution is inclined, we use the k-means algorithm as a parameter of the fuzzy function, through which automatic critical points can be found to differentiate objects from background and contrast between bright and dark points can be improved. The fuzzy function is presented at the three main stages presented to improve image quality: fuzzification, contrast enhancement and defuzzification. To measure improved image quality, we present the fuzzy index and entropy index and in comparison with those of histogram equalization technique, it shows outstanding performance.

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Breast Ultrasound Microvascular Imaging and Radiogenomics

  • Ah Young Park;Bo Kyoung Seo;Mi-Ryung Han
    • Korean Journal of Radiology
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    • v.22 no.5
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    • pp.677-687
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    • 2021
  • Microvascular ultrasound (US) techniques are advanced Doppler techniques that provide high sensitivity and spatial resolution for detailed visualization of low-flow vessels. Microvascular US imaging can be applied to breast lesion evaluation with or without US contrast agents. Microvascular US imaging without a contrast agent uses a sophisticated wall filtering system to selectively obtain low-flow Doppler signals from overlapped artifacts. Microvascular US imaging with second-generation contrast agents amplifies flow signals and makes them last longer, which facilitates hemodynamic evaluation of breast lesions. In this review article, we will introduce various microvascular US techniques, explain their clinical applications in breast cancer diagnosis and radiologic-histopathologic correlation, and provide a summary of a recent radiogenomic study using microvascular US.

Automatic Extraction of Size for Low Contrast Defects of LCD Polarizing Film (Low Contrast 특성을 갖는 LCD 편광필름 결함의 크기 자동 검출)

  • Park, Duck-Chun;Joo, Hyo-Nam;Rew, Keun-Ho
    • Journal of Institute of Control, Robotics and Systems
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    • v.14 no.5
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    • pp.438-443
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    • 2008
  • In this paper, segmenting and classifying low contrast defects on flat panel display is one of the key problems for automatic inspection system in practice. Problems become more complicated when the quality of acquired image is degraded by the illumination irregularity. Many algorithms are developed and implemented successfully for the defects segmentation. However, vision algorithms are inherently prone to be dependent on parameters to be set manually. In this paper, one morphological segmentation algorithm is chosen and a technique using frequency domain analysis of input images is developed for automatically selection the morphological parameter. An extensive statistical performance analysis is performed to compare the developed algorithms.

Study on Extraction of the Center Point of Steam Generator Tubes (증기발생기 세관의 중심좌표추출에 대한 연구)

  • 조재완;김창회;서용칠;최영수;김승호
    • Proceedings of the IEEK Conference
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    • 2002.06d
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    • pp.263-266
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    • 2002
  • This paper describes extraction procedure for the center coordinates of steam generator tubes of Youngkwang NPP #6, which are arrayed in triangular patterns. Steam generator tube images taken with wide field-of-view lens and low-light lamp mounted on a ccd camera tend to have low contrast, because steam generator is sealed and poorly illuminated. The extraction procedures consists of two steps. The first step is to process the region with superior contrast in entire image of steam generator tubes and to extract the center points. Using the extracted coordinates in the first step and the geometrical array characteristics of tubes lined up in regular triangle forms, the central points of the rest region with low contrast are estimated. The straight lines from center point of a tube to neighbour points in horizontal and 60, 120$^{\circ}$ degree directions are derived. The intersections of straight line In horizontal direction and slant line in regular triangle direction are selected as the center coordinates of steam generator tubes. The Chi-square interpolation method is used to determine the line's coefficients in horizontal and regular triangle direction.

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