• Journal of Korea Multimedia Society
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• v.15 no.9
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• pp.1075-1085
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• 2012

In clinical research using medical images, the image segmentation is one of the most important processes. Especially, the hippocampal atrophy is helpful for the clinical Alzheimer diagnosis as a specific marker of the progress of Alzheimer. In order to measure hippocampus volume exactly, segmentation of the hippocampus is essential. However, the hippocampus has some features like relatively low contrast, low signal-to-noise ratio, discreted boundary in MRI images, and these features make it difficult to segment hippocampus. To solve this problem, firstly, We selected region of interest from an experiment image, subtracted a original image from the negative image of the original image, enhanced contrast, and applied anisotropic diffusion filtering and gaussian filtering as preprocessing. Finally, We performed an image segmentation using two level set methods. Through a variety of approaches for the validation of proposed hippocampus segmentation method, We confirmed that our proposed method improved the rate and accuracy of the segmentation. Consequently, the proposed method is suitable for segmentation of the area which has similar features with the hippocampus. We believe that our method has great potential if successfully combined with other research findings.

• Proceedings of the Korea Multimedia Society Conference
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• 2004.05a
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• pp.688-691
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• 2004

본 논문에서는 메쉬, 복셀, 골격 데이터를 포함하는 복합적인 옥트리 기반의 형상 표현을 이용하여 해마의 형상을 분석하기 위한 효과적인 방법을 제공한다. 먼저, 자기공명영상으로부터 분할된 해마 영역에 마칭큐브 알고리즘을 적용하여 다단계 메쉬 데이터를 생성한다. 이렇게 생성된 메쉬 모델을 하드웨어 깊이맵을 이용한 복셀화 과정을 통하여, 중간 단계의 이진 복셀 표현으로 변환한다. 마지막으로 광선 추적 방법에 의해 추출된 샘플 메쉬들에 대하여 L2 Norm을 계산함으로써 형상 특징을 생성한다. 본 연구에서 제시한 방법은 사용자 피킹 인터페이스를 이용하여 국부적 부위에서의 계층적 형상 분석을 가능하게 한다. 또한 계층적 Level-of-Detail 접근방법은 정확도를 유지하며 형상분석의 소요 시간을 절약하도록 한다.

• Proceedings of the Korea Multimedia Society Conference
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• 2012.05a
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• pp.268-268
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• 2012

• The KIPS Transactions:PartA
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• v.11A no.7 s.91
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• pp.555-562
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• 2004

Both global volume reduction and local shape changes of hippocampus within the brain indicate their abnormal neurological states. Hippocampal shape analysis consists of two main steps. First, construct a hippocampal shape representation model ; second, compute a shape similarity from this representation. This paper proposes a novel method for the analysis of hippocampal shape using integrated Octree-based representation, containing meshes, voxels, and skeletons. First of all, we create multi-level meshes by applying the Marching Cube algorithm to the hippocampal region segmented from MR images. This model is converted to intermediate binary voxel representation. And we extract the 3D skeleton from these voxels using the slice-based skeletonization method. Then, in order to acquire multiresolutional shape representation, we store hierarchically the meshes, voxels, skeletons comprised in nodes of the Octree, and we extract the sample meshes using the ray-tracing based mesh sampling technique. Finally, as a similarity measure between the shapes, we compute $L_2$ Norm and Hausdorff distance for each sam-pled mesh pair by shooting the rays fired from the extracted skeleton. As we use a mouse picking interface for analyzing a local shape inter-actively, we provide an interaction and multiresolution based analysis for the local shape changes. In this paper, our experiment shows that our approach is robust to the rotation and the scale, especially effective to discriminate the changes between local shapes of hippocampus and more-over to increase the speed of analysis without degrading accuracy by using a hierarchical level-of-detail approach.

• The Korean Journal of Nuclear Medicine
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• v.38 no.1
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• pp.30-40
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• 2004

Purpose: The aims of this study were to find brain regions in which gray matter volume was reduced and to show the capability of voxel-based morphometry (VBM) analysis for lateralizing epileptogenic zones in medial temporal lobe epilepsy (mTLE). The findings were compared with fluorodeoxyglucose positron omission tomography (FDG PET). Materials and Methods: MR T1-weighted images of 12 left mTLE and 11 right mTLE patients were compared with those of 37 normal controls. Images were transformed to standard MNI space and averaged in order to create study-specific brain template. Each image was normalized to this local template and brain tissues were segmented. Modulation VBM analysis was performed in order to observe gray matter volume change. Gray matter was smoothed with a Gaussian kernel. After these preprocessing, statistical analysis was peformed using statistical parametric mapping software (SPM99). FDG PET images were compared with those of 22 normal controls using SPM. Results: Gray matter volume was significantly reduced in the left amygdala and hippocampus in left mTLE. In addition, volume of cerebellum, anterior cingulate, and fusiform gyrus in both sides and left insula was reduced. In right mTLE, volume was reduced significantly in right hippocampus. In contrast, FDG uptake was decreased in broad areas of left or right temporal lobes in left TLE and right TLE, respectively. Conclusions: Gray matter loss was found in the ipsilateral hippocampus by modulation VBM analysis in medial temporal lobe epilepsy. This VBM analysis might be useful in lateralizing the epileptogenic zones in medial temporal lobe epilepsy, while SPM analysis of FDG PET disclosed hypometabolic epileptogenic zones.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.160-164
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• 1995

정보통신 시스템의 고속/고밀도화 요구에 따라 개발되고 있는 ATM(Asynchronous Transfer Mode) 교환기 시스템은 팬을 이용한 강제대류냉각 방식의 채택과 시스템이 설치되는 장소에 따른 여러 환경조건에 의한 진동 문제가 발생될 수 있다. 시스템의 진동으로 인한 피해중 커넥터 접촉부에서 전기적 특성의 변화는 고속으로 전송되는 신호의 왜곡을 유발시킬 수 있어 시스템 개발시 이에 대한 충분한 연구 및 시험이 요구되고 있다. 진동환경에서 커넥터 접촉부는 접촉면의 상대운동으로 인한 접촉저항의 증가와 순간적인 신호전달 중단을 가져오게 되며, 특히 PCB/Connector Assembly에서 커넥터 접촉부는 PCB(Printed Circuit Board)의 장착 조건 및 동적 거동에 따라 전기적 특성이 변할 수 있다. 시스템에서 커넥터의 동적 거동을 이해하기 위해서는 PCB를 포함하는 시스템내 여러 요소의 동적 특성 이해와 복잡한 해석과정이 요구되며, 시스템 개발자는 진동 환경에서 이것의 시험 결과에 따라 커넥터의 사용을 결정해야 할 것이다. 커넥터의 전기적 특성 시험법은 IEC, EIA드 여러 국제 규격에 제시되어 있으며, 본 연구의 대상이 된 ATM교환기 시스템에서 PCB/Connector Assembly의 진동환경에서 접촉저항 측정과 관련된 접촉저항 임계치 및 측정법은 IEEE 규격 및 Bellcore 규격에 규정되어 있다. Bellcore에는 주어진 진동시험주기 전후에 IEC 규격의 LLCR(Low Level Contact Resistance) 측정회로를 이용한 측정법이 규정되어 있고, 냉각팬 및 주위 환경진동이 가해지는 동안의 영향에 대한 시험법은 규정되어 있지 않다. 본 연구에서는 한국통신의 전자장비 운용환경시험 조건의 진동에서 ATM 교환기 시스템에 사용되는 PCB/Connector Assembly 커넥터 접촉부의 접촉저항 변화와 PCB 진동에 의한 영향을 시험하였다.proach)등이 제시되었고 평면파 영역에 한하여 해서되어져 왔다. 본 논문에서는 분할 접근 방법(Segmentation Approach)을 이용하여 다공 요소로 이루어진 소음기를 해석하는데 적용하였다.로 성능 및 안정도에 영향을 미치므로 주의 깊게 선정해야 한다. 방법의 실질적인 적용에는 어려움이 있다. 본 연구에서는 기존의 방법들의 단점을 극복할 수 있는 새로운 회귀적 모우드 변수 규명 방법을 개발하였다. 이는 Fassois와 Lee가 ARMAX모델의 계수를 효율적으로 추정하기 위하여 개발한 뱉치방법인 Suboptimum Maximum Likelihood 방법[5]를 기초로 하여 개발하였다. 개발된 방법의 장점은 응답 신호에 유색잡음이 존재하여도 모우드 변수들을 항상 정확하게 구할 수 있으며, 또한 알고리즘의 안정성이 보장된 것이다.. 여기서는 실험실 수준의 평 판모델을 제작하고 실제 현장에서 이루어질 수 있는 진동제어 구조물에 대 한 동적실험 및 FRS를 수행하는 과정과 동일하게 따름으로써 실제 발생할 수 있는 오차나 error를 실험실내의 차원에서 파악하여 진동원을 있는 구조 물에 대한 진동제어기술을 보유하고자 한다. 이용한 해마의 부피측정은 해마경화증 환자의 진단에 있어 육안적인 MR 진단이 어려운 제한된 경우에만 실제적 도움을 줄 수 있는 보조적인 방법으로 생각된다.ofile whereas relaxivity at high field is not affected by τS. On the other hand, the change in τV does not affect low field profile but strongly in fluences on both inflection fie이 and the maximum relaxivity value. The results shows a fluences on both inflection field and the maximum relaxivity v

• Progress in Medical Physics
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• v.27 no.1
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• pp.14-24
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• 2016

Since the head and neck region is densely located with organs at risk (OAR), OAR-sparing is an important issue in the treatment of head and neck cancers. This study-in which different treatment plans were performed varying the head tilt angle on brain tumor patients-investigates the optimal head elevation angle for sparing normal organs (e.g. the hippocampus) and further compares the dosimetric characteristics of different types of radiation equipment. we performed 3D conformal radiation therapy (3D-CRT), intensity-modulated radiation therapy (IMRT), and tomotherapy on 10 patients with brain tumors in the frontal lobe while varying the head tilt angle of patients to analyze the dosimetric characteristics of different therapy methods. In each treatment plan, 95% of the tumor volume was irradiated with a dose of 40 Gy in 10 fractions. The step and shoot technique with nine beams was used for IMRT, and the same prescription dose was delivered to the tumor volume for the 3D-CRT and tomotherapy plans. The homogeneity index, conformity index, and normal tissue complication probability (NTCP) were calculated. At a head elevation angle of $30^{\circ}$, conformity of the isodose curve to the target increased on average by 53%, 8%, and 5.4%. In 3D-CRT, the maximum dose received by the brain stem decreased at $15^{\circ}$, $30^{\circ}$, and $40^{\circ}$, compared to that observed at $0^{\circ}$. The NTCP value of the hippocampus observed in each modality was the highest at a head and neck angle of $0^{\circ}$ and the lowest at $30^{\circ}$. This study demonstrates that the elevation of the patients' head tilt angle in radiation therapy improves the target region's homogeneity of dose distribution by increasing the tumor control rate and conformity of the isodose curve to the target. Moreover, the study shows that the elevation of the head tilt angle lowers the NTCP by separating the tumor volume from the normal tissues, which helps spare OARs and reduce the delivered dose to the hippocampus.