• Journal of the Korean Society of Radiology
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• v.83 no.5
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• pp.1153-1159
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• 2022

Dolichoectasia is an uncommon disorder characterized by the presence of a dilated, elongated, and tortuous cerebral artery. Its main pathologic mechanism is the disruption of the internal elastic lamina. Risk factors for dolichoectasia are advanced age, chronic hypertension, and metabolic disease. It mainly involves the vertebrobasilar vasculature (or "posterior circulation"), but dolichoectasia can also be seen in the anterior circulation, particularly the anterior cerebral artery. There are no reported cases of dolichoectasia involving both anterior and posterior circulation in South Korea. Here we report an unusual case of dolichoectasia involving both anterior and posterior circulation in a young female without any underlying disease on the basis of prominent imaging findings.

• Journal of the Korean Society of Radiology
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• v.83 no.1
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• pp.184-188
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• 2022

Persistent trigeminal artery (PTA) represent an unusual remnant of the fetal carotid-basilar anastomosis. Persistent trigeminal artery variant (PTAV) is a rare anastomosis between the internal carotid artery and cerebellar artery, without an interposing basilar artery segment. We report the case of 49-year-old female with an incidentally discovered, rare variation of PTA that directly terminated in the ipsilateral superior cerebellar artery. The variation was observed on CT angiography, digital subtraction angiography, and MR angiography. Additionally, we reviewed the embryogenesis of PTA and PTAV and discussed the clinical implications of this variation.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.3
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• pp.55-62
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• 2017

Non-negative matrix factorization (NMF) is one of the typical parts-based representation in which images are expressed as a linear combination of basis vectors that show the lcoal features or objects in the images. In this paper, we represent face images using various NMF methods and recognize their face identities based on extracted features using a learning vector quantization. We analyzed the various NMF methods by comparing extracted basis vectors. Also we confirmed the availability of NMF to the face recognition by verification of recognition rate of the various NMF methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.9B
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• pp.1277-1282
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• 2001

스테레오스코픽 비디오 영상은 좌측영상과 우측영상으로 이루어진 한 쌍의 영상으로 구성되며, 이들 좌우 영상들 사이에는 높은 상관관계를 가진다. 스테레오 영상의 압축을 위한 부호화는 이들 좌우 영상의 높은 상관관계와 각 시각 내에서의 이웃 픽쳐와의 시간적 상관 관계를 모두 고려하여 이루어진다. 이 때, 왼쪽 영상의 정보는 기저층에서 처리하고 오른쪽 영상 정보는 상위 층에서 처리하는 것이 일반적이다. 본 논문은 MPEG-2 다시점 프로파일을 이용하여 입체영상 부호화 코덱을 구현할 때, 상위 층의 픽쳐 처리순서에 따라 부호화 효율이 어떻게 달라지는지를 분석하여, 실제 시스템 운용을 위한 코덱 구조를 제안하였으며, DTV 및 HDTV급 스테레오 시퀀스를 사용한 실험을 통하여 검증하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.471-473
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• 2011

3D 콘텐츠들은 과거 입체영화 '아바타' 이후로 꾸준히 증가하고 있다. 그리고 인터넷 등을 포함한 사이버 공간의 모든 환경이 제공자 위주에서 사용자 중으로 급격하게 변화하고 있는 상황이다. 이에 사용자들은 원하는 높은 현실감을 바탕으로 디지털 콘텐츠의 입체영상 서비스를 제공받기를 원한다. 그렇기에 3D 콘텐츠의 증가에 따른 Stereoscopic 기술의 필요성이 증대 되었다. 따라서 본 논문은 3차원 입체영상 기술의 기저 기술 중에 하나인 Anaglyph 영상을 연구하기로 하였다. 최종적으로 일반 영상 및 입체 사진을 이용한 스테레오 영상 변환 연구를 진행한다. 세부적으로는 입체 사진(Anaglyph)을 이용한 스테레오 영상 분할, 일반 영상을 이용한 스테레오 영상 편집 연구로 나누어 진행 하였다.

• The Korean Journal of Nuclear Medicine
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• v.39 no.6
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• pp.481-488
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• 2005

Purpose: Functional imaging of dopamine transporter (DAT) defines integrity of the dopaminergic system, and DAT is the target site of drugs of abuse such as cocaine and methamphetamine. Functional imaging the DAT may be a sensitive and selective indicator of neurotoxic change by the drug. The aim of the present study is to evaluate the clinical implications of qualitative/quantitative analyses of dopamine transporter imaging in methamphetamine abusers. Materials and Methods: Six detoxified methamphetamine abusers (abuser group) and 4 volunteers (control group) were enrolled in this study. Brain MRI was performed in all of abuser group. Abuser group underwent psychiatric and depression assessment using brief psychiatric rating scale (BPRS) and Hamilton depression rating scale (HAMD), respectively. All of the subjects underwent I-123 IPT SPECT (IPT SPECT). IPT SPECT image was analysed with visual qualitative method and quantitative method using basal ganglia dopamine transporter (DAT) specific/non-specific binding ratio (SBR). Comparison of DAT SBR between abuser and control groups was performed. We also performed correlation tests between psychiatric and depression assessment results and DAT SBR in abuser group. Results: All of abuser group showed normal MRI finding, but had residual psychiatric and depressive symptoms, and psychiatric and depressive symptom scores were exactly correlated (r=1.0, p=0.005) each other. Five of them showed abnormal finding on qualitative visual I-123 IPT SPECT Abuser group had lower basal ganglia DAT SBR than that of control ($2.38{\pm}0.20\;vs\;3.04{\pm}0.27$, p=0.000). Psychiatric and depressive symptoms were negatively well correlated with basal ganglia DAT SBR (r=-0.908, p=0.012, r=-0.924, p=0.009). Conclusion: These results suggest that dopamine transporter imaging using I-123 IPT SPECT may be used to evaluate dopaminergic system of the basal ganglia and the clinical status in methamphetamine abusers.

• The korean journal of orthodontics
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• v.41 no.4
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• pp.224-236
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• 2011

Objective: The purpose of this study was to analyze the dental and basal arch forms in patients with normal occlusion using the computed tomography (CT) imaging method. Methods: CT images were taken from 27 normal occlusion subjects (male, 15; female, 12) and these images were reconstructed into three-dimensional models. A 3D-coordinate system was formed by setting the middle of the facial axis (FA) point of the maxillary central incisors as the origin. The morphology of the maxilla and mandibular dental and basal arches were analyzed by sectioning parallel to the maxillary occlusal plane. Results: There was no significant difference between A point and B point and between the maxillary 1st molars in both sides of the maxillary and mandibular basal bone. The dental arch was located more labially than the basal arch in the anterior portion. The bucco-lingual crossover of the dental arch and basal arch was formed at the molar region in the maxilla, and at the premolar region in the mandible. Conclusions: This study will help provide three-dimensional diagnostic information about the relationship between basal and dental arches in patients who have severe dental compensation and inappropriate jaw relationships.

• Journal of Korea Multimedia Society
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• v.6 no.5
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• pp.861-869
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• 2003

The rapid growth of multimedia network systems has caused overflowing illegal copies of digital contents. Among digital contents, watermarking technique can be used to protect ownership about the image. Copyright protection involves the authentication of image ownership and the identification of illegal copies of image. In this paper, a new digital watermarking technique using HVS and adaptive scale factor based on the wavelet transform is proposed to use the binary image watermark. The original image is decomposed by 3-level wavelet transform. It is embedded to baseband and high frequency band. The embedding in the baseband is considered robustness, the embedding in the high frequency band is concerned about HVS and invisibility. The watermarking of a visually recognizable binary image used the HVS and random permutation to protect the copyright. From the experimental results, we confirm that the proposed technique is strong to various attacks such as joint photographic experts ground(JPEG) compression, cropping, collusion, and inversion of lines.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.4
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• pp.34-41
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• 2009

In this paper we propose a new image encryption method which utilizes Complemented MLCA(Complemented Maximum Length Cellular Automata) based on IBCA(Intermediate Boundary CA) and 2D CAT(Cellular Automata Transform). The encryption method is processed in the following order. First, Complemented MLCA is used to create a PN (pseudo noise) sequence, which matches the size of the original image. And, the original image goes through a XOR operation with the created sequence to convert the image into Complemented MLCA image. Then, the gateway value is set to produce a 2D CAT basis function. The produced basis function is multiplied by the encrypted MLCA image that has been converted to process the encipherment. Lastly, the stability analysis and PSNR(Peak Signal to Noise Ratio) verifies that the proposed method holds a high encryption quality status.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.12
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• pp.2313-2327
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• 1994

As the communication environment evolves, there is an increasing need for multiresolution image coding. To meet this need, the entrophy constratined vector quantizer(ECVQ) for coding of image pyramids by spline wavelet transform is introduced in this paper. This paper proposes a new scheme for image compression taking into account psychovisual feature both in the space and frequency domains : this proposed method involves two steps. First we use spline wavelet transform in order to obtain a set of biorthogonal subclasses of images ; the original image is decomposed at different scale using a pyramidal algorithm architecture. The decomposition is along the vertical and horizontal directions and maintains constant the number of pixels required the image. Second, according to Shannon's rate distortion theory, the wavelet coefficients are vectored quantized using a multi-resolution ECVQ(entropy-constrained vector quantizer) codebook. The simulation results showed that the proposed method could achieve higher quality LENA image improved by about 2.0 dB than that of the ECVQ using other wavelet at 0.5 bpp and, by about 0.5 dB at 1.0 bpp, and reduce the block effect and the edge degradation.