• The Journal of the Korea Contents Association
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• v.3 no.3
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• pp.11-18
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• 2003

Error diffusion is a procedure for generating high quality bilevel images from continuous-tone images but blurs the edge information. To solve this problem, we propose the improved method appling edge enhanced weights based on local characteristic of the original images. We consider edge information as local characteristic. First, we produce edges by appling 3$\times$3 sobel operator to the original image. The edge is normalized from 0 to 1. Edge information weights are computed by using sinusoidal function and the normalized edge information. The edge enhanced weights are computed by using edge information weights multiplied input pixels. The proposed method is compared with conventional methods by measuring the edge correlation and quality of the recovered images from the halftoned images. The proposed method provides better quality than the conventional method due to the enhanced edge and represents efficiently the detail edge. Also, the proposed method is improved in edge representation than the conventional method.

• The Journal of the Korea Contents Association
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• v.5 no.2
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• pp.221-228
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• 2005

The paper proposes the improved error diffusion halftoning system to enhance the edges using the spatial perceptual characteristics of the human visual system. The proposed method computes a spatial variation(SV), which is the difference between a pixel luminance and the average of its $3{\times}3$ neighborhood pixels' luminances weighted according to the spatial positioning. Information of edge enhancement(IEE) Is computed using the SV and the local average luminance. The IEE is added to the quantizer's input pixel and feeds into the halftoning quantizer. The quantizer produces the halftone image having the enhanced edge. The performance of the proposed method is compared with conventional methods by measuring the edge correlation. The halftone images by using the proposed method show better quality due to the enhanced edge. And the detailed edge is preserved in the halftone images by using the proposed method.

• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.683-690
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• 2009

The purpose of this study is to evaluate the usefulness of high-b-values diffusion weighted magnetic resonance imaging for the preoperative detection of focal rectum cancers. 60patients with diffusion weighted imaging were evaluated for the presence of rectal cancers. Forty were male and twenty were female, and their ages ranged from 38 to 71 (mean, 56) years. Used equipment was 1.5Tesla MRI((GE, General Electric Medical System, Excite HD). Examination protocols were used the fast spin echo T2, T1 weighted imaging. All examination protocols were performed by the same location with diffusion weighted imaging for accuracy detection. The b-values used in DWI were 250, 500, 750, 1000. 1500, 2000$(s/mm^2)$. The rectum, bladder to tumor contrast-to-noise ratio (CNR) of MR images were quantitativlely analyzed using GE software Functool tool, four experienced radiologists and three radiotechnologists qualitatively evaluated image quality in terms of image artifacts, lesion conspicuity and rectal wall. These data were analysed by using ANOVA and Freedman test with each b-value(p<0.05). Contrast to noise ratio of rectum, bladder and tumor in b-value 1000 were 27.21, 24.44, respectively(p<0.05) and aADC value was $0.73\times10^{-3}$. As a qualitative analysis, the conspicuity and discrimination from the rectal wall of lesions were high results as $4.0\pm0.14$, $4.4\pm0.16$ on b-value 1000(p<0.05), image artifacts were high results as $4.8\pm0.25$ on b-value 2000(p<0.05). In conclusion, DWI was provided useful information with depicting the pre-operative detection of rectal cancers, High-b-value 1000 image was the most excellent DWI value.

• Journal of the Korean Society of Radiology
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• v.81 no.1
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• pp.81-100
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• 2020

Magnetic resonance neurography (MRN) has been increasingly used in recent years for the assessment of peripheral neuropathies. Fat suppression T2-weighted imaging (T2WI) and diffusion-weighted imaging (DWI) have typically been used to provide high contrast MRN. Isotropic 3-dimensional (3D) sequences with fast spin echo, post-processing imaging techniques, and fast imaging methods, among others, allow good visualization of peripheral nerves that have a small diameter, complex anatomy, and oblique course within a reasonable scan time. However, there are still several issues when performing high contrast and high resolution MRN including standard sequence; fat saturation techniques; balance between resolution, field of view, and slice thickness; post-processing techniques; 2D vs. 3D image acquisition; different T2 contrasts between proximal and distal nerves; high T2 signal intensity of adjacent veins or joint fluid; geometric distortion; and appropriate p-values on DWI. The proper understanding of these issues will help novice radiologists evaluate peripheral neuropathies using MRN.

• Journal of Digital Convergence
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• v.11 no.1
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• pp.361-368
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• 2013

The purpose of this study is to know the clinical usefulness of optimal b-values by quantitative, qualitative evaluation of DW-MRI for lesions of benignity and malignity of female pelvis. The b-values used in DWI were 600, 800, 1000, 1200, 1400($s/mm^2$). Mean SNR and CNR of myoma in b-value 800 were the highest result as $84.6{\pm}4.57$(p=0.024) and $50.13{\pm}5.47$(p=0.028), Mean SNR and CNR of cervical cancer were the highest result as $12.0{\pm}2.04$(p=0.047) and $10.6{\pm}1.24$(p=0.001), Mean ADC value in myoma and cervical cancer in b-value 800 were $1.19{\times}10^{-3}mm^2/s$(p=0.008), $0.96{\times}10^{-3}mm^2/s$(p=0.027). As a qualitative analysis, the delineation and conspicuity were the highest result as $4.02{\pm}0.18$(p=0.028), $4.39{\pm}0.25$(p=0.015) on b-value 800. DW-MRI is an important method, and the optimal b values is 800 $s/mm^2$ for differentiation between benign and malignant lesions of female pelvis.

• Proceedings of the KSMRM Conference
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• 2001.11a
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• pp.166-166
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• 2001

목적： 척수의 질환에 대한 확산강조영상 소견에 대하여 알아본다. 대상 및 방법： 임상적으로 진단된 척수질환 환자 8명을 (acute transverse myelitis (n=3), spinal dural AV fistula (n=2), multiple sclerosis (n=1), spinal cord tumor (n=2)) 대상으로 하였다. 영상은 Philips Intera 1.5 T system을 이용하였고, multishot spin echo EPI 펄스열 및 EKG gating을 이용하여 영상을 얻었다. 3R-R 간격으로 영상을 얻었으며 TE=72msec, FOV=25cm, 256 matrix, 5mm thickness, b value=400으로 영상매개변수를 정하였다. 척수 중심으로 3개의 절편을 얻었으며 T2 강조 영상과 겉보기확산계수 영상을 같이 구하였다.

• Journal of radiological science and technology
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• v.34 no.3
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• pp.239-244
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• 2011

In this study, we evaluated diffusion weighted imaging (DWI) to investigate whether the DWI parameters can predict characteristic parameters on pathologic specimens of tumor or not. CFPAC-1 was injected subcutaneously on the back flank of athymic nude mice (n=13) then two tumors were initiated on each mouse (2${\times}$13=26 tumors). The mice were sacrificed to make specimen immediately after initial MR imaging then were compared with the MR image. A dedicated high-field (7T) small-animal MR scanner was used for image acquisitions. A T1 and T2 weighted axial image using RARE technique was acquired to measure the T2 values and tumor size. DWI MR was performed for calculating ADC values. To evaluate tumor cellularity and determine the levels of MVD, tumor cells were excised and processed for H-E staining and immunostaining using CD31. T2 values and ADC values were computed and analyzed for each half of the tumors and compared to the correlated specimens slide. Median ADC within each half of mass was compared to the cellularity and MVD in the correlated area of pathologic slide. The mean of ADC value is $0.7327{\times}10^{-3}$ $mm^2/s$ and standard deviation is $0.1075{\times}10^{-3}$ $mm^2/s$. There is a linear relationship between ADC value and tumor necrosis (R2=0.697, p< 0.001). DW image parameters including the ADC values can be utilized as surrogate markers to assess intratumoral neoangiogenesis and change of the internal structure of tumor cells.

• Journal of the Korean Society of Radiology
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• v.83 no.5
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• pp.1046-1058
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• 2022

The hippocampus is one of the most metabolically active regions of the brain; therefore, it may be affected by various acute disorders. This study aimed to introduce and categorize various acute conditions that can involve the hippocampus and explain the findings of MRI, especially diffusion-weighted imaging (DWI). Acute hippocampal disorders are divided into six categories: infection, inflammation, metabolic, ischemic, traumatic, and miscellaneous. In this study, patients were retrospectively reviewed based on clinical findings and MRI, especially DWI. All diseases had been confirmed clinically or pathologically. Many acute hippocampal disorders overlap with the clinical manifestations. Thus, it is necessary to categorize acute hippocampal lesions and understand their specific imaging findings for differential diagnosis.

• Journal of the Korean Society of Radiology
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• v.10 no.7
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• pp.545-550
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• 2016

The purpose of this study is to improve the mapping between functional image and conventional image by using rectangular FOV technique. Diffusion weighted imaging which is widely used for stroke was acquired by reducing the FOV and compared each Apparent Diffusion Coefficient(ADC). As a result, there is no significant difference of each ADC value in one-way-anova analysis and post-hoc analysis. Thus, Mismatching problem may be improved by matching the FOV with rectangular FOV technique because there is no difference in ADC values.

• Proceedings of the KSMRM Conference
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• 2002.11a
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• pp.83-83
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• 2002

목적： 현재 임상적으로 사용되고 있는 확산경사자장의 세기 이상( > 1200)의 강한 확산 경사자장이 가해진 경우 뇌구조물들의 확산계수값을 조사하고 고자장(Bo = 3T)에서 이러한 강한 확산 경사자장을 이용하는 경우 1.5T에서 시행하는 경우와의 차이점을 비교 연구해보고자 하였다. 대상 및 방법： 정상 성인 3명을 대상으로 b-value를 0부터 3500까지 변화시키며 확산강조영상을 최대경사자장 40 mT/m, slew rate 150 T/m/s의 경사자장계가 장착된 3T MR scanner (General Electric, USA)에서 획득하였다. 사용한 펄스열은 Stejskal-Tanner type의 확산강조 경사자장이 포함된 single-shot SE EPI를 사용하였으며 영상획득시 사용한 파라미터는 다음과 같다. TR/TE= 10000/95.1, Thickness/space=512mm, FOV=24$\times$21cm, Matrix=128$\times$128, NEX=1 뇌구조물들에 관심 영역을 설정하고 b-value에 따른 신호감소를 측정하였다. 측정된 데이터를 hi-exponential decay 모델을 이용하여 분석하였다.