• 순환기질환의공학회:학술대회논문집
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• 순환기질환의공학회 2006년도 춘계학술강연회
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• pp.28-36
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• 2006

The x-ray PIV method was improved for measuring quantitative velocity fields of real blood flows using a coherent synchrotron x-ray source. Without using any contrast media or seeding particles, this method can visualize flow pattern of blood by enhancing the phase-contrast and interference characteristics of blood cells based on a synchrotron x-ray imaging mechanism. The enhanced x-ray images were achieved by optimizing the sample-to-scintillator distance, the sample thickness, and hematocrit. The quantitative velocity fields of blood flows inside opaque tubes were obtained by applying a 2-frame PIV algorithm to the x-ray images of the blood flows. The measured velocity field data show typical features of blood flows such as the yield stress effect. The non-Newtonian flow characteristics of blood flows were analyzed using the x-ray PIV method and the experimental results were compared with hemodynamic models.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 한국방송공학회 1999년도 학술대회
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• pp.3-8
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• 1999

In this paper, we propose a new connected operator using morphological grayscale reconstruction for region-based coding. First, an effective method of reference-image creation is proposed, which is based on the size as well as the contrast. The conventional connected operators are good for removing small regions, but have a serious drawback for low-contrast regions that are larger than the structuring element. That is, when the conventional connected operators are applied to these regions. the simplification becomes less effective or several meaningful regions are merged to one region. To avoid this, the conventional geodesic dilation is modified to propose an adaptive operator. To reduce the effect of inappropriate propagation, pixels reconstructed to the original values are excluded in the dilation operation. Experimental results have shown that the proposed algorithm achieves better performance in terms of the reconstruction of flat zones. The picture quality has also been improved by about 7dB, compared to the conventional methods.

• International Journal of Vascular Biomedical Engineering
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• 제4권1호
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• pp.1-8
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• 2006

The x-ray PIV method was improved for measuring quantitative velocity fields of real blood flows using a coherent synchrotron x-ray source. Without using any contrast media or seeding particles, this method can visualize flow pattern of blood by enhancing the phase-contrast and interference characteristics of blood cells based on a synchrotron x-ray imaging mechanism. The enhanced x-ray images were achieved by optimizing the sample-to-scintillator distance, the sample thickness, and hematocrit. The quantitative velocity fields of blood flows inside opaque tubes were obtained by applying a 2-frame PIV algorithm to the x-ray images of the blood flows. The measured velocity field data show typical features of blood flows such as the yield stress effect. The non-Newtonian flow characteristics of blood flows were analyzed using the x-ray PIV method and the experimental results were compared with hemodynamic models.

• Journal of Integrative Natural Science
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• 제8권2호
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• pp.141-144
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• 2015

As the visual quality of X-ray images is a critical reference for the accuracy of the clinical diagnosis, the methods to improve the quality of X-ray images have been investigated. Among many existing methods, using frequency domain filter is a very powerful method to improve the visual quality of images. In this paper, the inherent noises of the input images are suppressed by adding the Laplacian image to the subjected image. The medical X-ray images using the optimal high pass filter has shown improved edges. Further, the optimal high frequency emphasis filter has shown the improved contrast of flat areas by using the result image from the optimal high pass filter. Also the resulting images of the global contrast have improved by the histogram equalization. As a result, the proposed methods have shown enhanced contrast and edges of the images with noise canceling effect.

• Fashion & Textile Research Journal
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• 제12권1호
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• pp.1-9
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• 2010

A purpose of this study was to find out how the casual and formal style clothes of stripe pattern giving variety by pattern direction, pattern width, and contrast coloration have an effect on image of wearers. 432 stimuli were made and 2,800 testee evaluated them using semantic differential scale. As a result, five image dimensions were drawn as a factor of attractiveness, activeness, gracefulness, visibility, and tenderness. In consequence of analysing the image difference by stripe pattern and clothing style, the stripe pattern and clothing style affect image presentation as a significant clue. And besides, as a result of positioning stimuli by image, pattern direction, coloration, and tone combination were important clues that decide image. Consequently, clothing style, stripe pattern, and contrast coloration were made clear as an efficient parameter in image presentation of clothing wearers.

• Korean Journal of Optics and Photonics
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• 제11권2호
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• pp.130-134
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• 2000

In this paper, the configuration of a reflectIve bistable tWIsted nematic (BTN) liquid crystal cell is optmnzed for high contrast and high brightness operation. We searched for the optimum opncal parameters of a reflective BTN cell by calculating its optical performances at 3 wavelengths; red, green, and blue. By studying the effect of each optical parameter on the optical performances, we found that the angle of !he polmlzer IS more important than any other opnea! parmlleters iu the deSIgn of a reflective BTN cell. We fablicated a reflective BTN cell with a wide-band retardation Him, whose measmed contrast ratio is 10.6: 1. .6: 1.

• Current Optics and Photonics
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• 제6권3호
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• pp.304-312
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• 2022

Digital images of cultural relics captured using line scan cameras present limitations due to uneven intensity and low contrast. To address this issue, this report proposes a colour linear array image enhancement method that can maintain a constant colour. First, the colour linear array image is converted from the red-green-blue (RGB) colour space into the hue-saturation-intensity colour space, and the three components of hue, saturation, and intensity are separated. Subsequently, the hue and saturation components are held constant while the intensity component is processed using the established intensity compensation model to eliminate the uneven intensity of the image. On this basis, the contrast of the intensity component is enhanced using an improved local contrast enhancement method. Finally, the processed image is converted into the RGB colour space. The experimental results indicate that the proposed method can significantly improve the visual effect of colour linear array images. Moreover, the objective quality evaluation parameters are improved compared to those determined using existing methods.

• Journal of Korean Ophthalmic Optics Society
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• 제19권2호
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• pp.261-270
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• 2014

Purpose: To study the effect of an artificially induced dioptric blur on acuity and contrast sensitivity using the $Optec^{(R)}$ 6500. Methods: Healthy 31 subjects aged $22.90{\pm}1.92$ (male 16, female 15) who were recruited from university students with 6/6 (20/20) or better corrected visual acuity and normal binocularity. They were measured objective and subjective refraction for full correction and dioptric blur using 0.00 ~ +3.00 D (+0.50 D steps) trial lenses and trial frame. They were measured binocularly visual acuity and contrast sensitivity with the $Optec^{(R)}$ 6500 (Stereo Optical Co., Inc., Chicago, Illinois, USA) under day conditions (photopic condition, $85cd/m^2$). Results: The higher dioptric blur, the less distance visual acuity and decrease rate of visual acuity. The higher dioptric blur, the less contrast sensitivity at all frequencies, and the peak of contrast sensitivity was shifted from middle frequency (6 cpd) to low frequency (1.5 cpd). When the visual acuity was best visual acuity to 0.77, there was the peak point at 6 cpd which was normal contrast sensitivity peak point. Conclusions: If the low refractive error is uncorrected or the refractive error is inappropriate, the contrast sensitivity is decreased and the peak point of contrast sensitivity frequency is shifted abnormally though small uncorrected refractive error. So it will be considered that regular eye test and decision of refractive error correction is important.

• Journal of Digital Convergence
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• 제13권9호
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• pp.431-437
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• 2015

This convergence study analyzed the effectiveness of contrast agent reduction by normal saline solution dilution in the computed tomography of arteries of lower limb. 48 patients of 125 cc contrast agent and 30 patients of the same amount divided at a ratio of 7:3 for the contrast agent and normal saline solution were studied. The average attenuation coefficient(HU) and signal to noise ratio(SNR) of abdominal aorta, femoral artery, popliteal artery and posterior tibial artery at each image were evaluated quantitatively and the four criteria in the five point scale was conducted qualitatively by two radiologists and four radiological technologists. In the quantitative evaluation, both HU and SNR had high average score before dilation but there were no statistical significance by independent t-test(p>0.05). In the qualitative evaluation, there were a little differences in the average scores between 4.86~4.77 of original contrast agent and 4.83~4.67 of dilated contrast agent but there were no statistical significance(p>0.05). In the computed tomography of arteries of lower limb, the dilated contrast agent doesn't influence image quality and reduces overall contrast agent and lowers iodine content per unit of molecular therefore will contribute to decrease side effect of contrast agent.

• Journal of the Korean Society of Radiology
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• 제12권5호
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• pp.693-698
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• 2018

Currently, shields for shielding medical radiation during medical examinations in the medical environment are lead robe and lead glass. Lead, the main component of this shielding, has limitations in lead poisoning and light weight, and high price. Iodine, which is used as contrast medium instead of lead shield, is expected to be effective as a shield because it has radiation absorbing properties. The purpose of this study was to evaluate the effectiveness of shielding by using acrylic plate filled with CT contrast agent for clinical use instead of conventional lead glass. As a result, it was found that the acrylic plate filled with the CT contrast agent showed a shielding effect of 7 times or more when the scattering ray dose was not shielded. Therefore, CT contrast agent composed of iodine is expected to be used as a shield instead of conventional lead glass.