뇌 구조 분석을 위한 연속적인 퍼지 분할법과 구획화 방법의 개선

윤의철,황진우,김재석,김재진,김인영,권준수,김선일 대한의용생체공학회 2001 의공학회지 Vol.22 No.5

일반적으로 정신질환인 경우 뇌의 미세한 이상이 있는 것으로 알려져 있어 자기공명영상의 시각적 분석에서 뇌의 구조적 이상을 밝히는 데 한계가 있다. 따라서 특정 부위의 용적이나 모양의 이상을 통하여 정신질환의 뇌 구조적 이상을 연구하는 것이 일반적이다 이러한 경우 뇌 자기공명영상은 조직간의 경계가 불분명하여 뇌 구조 분석의 신뢰도는 조직별 분할의 정확성이 좌우한다 본 논문에서는 뇌 자기공명영상의 특성에 적합한 퍼지 분할법을 반복적으로 적용함으로써 분할 영상의 질을 개선하여 뇌 구조 분석의 신뢰도를 높이고, 사용자 편의성을 고려한 소프트웨어를 이용한 좌우 뇌섬엽 용적 측정을 통해 뇌 구조적 이상에 대한 보다 나은 분석 방법을 제시한다. Generally. there have been limitations to investigate structural brain abnormalities with MR images for psychiatric patients. such as schizophrenia. depression and autism, since the brain abnormalities of psychiatric Patients are too small to be detected easily. It has been suggested to exploit the result of size-comparison or analysis of specified Part in various brain tissues. Results of brain analysis highly depend on accuracy of the brain segmentation because it is hard to segment image that the boundary between tissues in the brain MRI is inherently value. In this Paper. we improve the quality of brain segmentation so that we increase the credit of brain analysis. In addition, we Provide the improved images for studying brain abnormalities through left-right insular volume measure using handy software tool .

부분용적효과를 고려한 확산텐서영상에 대한 관심영역 분석 연구

최우혁,윤의철,Choi, Woohyuk,Yoon, Uicheul 대한의용생체공학회 2016 의공학회지 Vol.37 No.2

In this study, we proposed ameliorated method for region of interest (ROI) study to improve its accuracy using partial volume effect (PVE). PVE which arose in volumetric images when more than one tissue type occur in a voxel, could be used to reduce an amount of gray matter and cerebrospinal fluid within ROI of diffusion tensor image (DTI). In order to define ROIs, individual b0 image was spatially aligned to the JHU DTI-based atlas using linear and non-linear registration (http://cmrm.med.jhmi.edu/). Fractional anisotropy (FA) and mean diffusivity (MD) maps were estimated by fitting diffusion tensor model to each image voxel, and their mean values were computed within each ROI with PVE threshold. Participants of this study consisted of 20 healthy controls, 27 Alzheimer's disease and 27 normal-pressure hydrocephalus patients. The result showed that the mean FA and MD of each ROI were increased and decreased respectively, but standard deviation was significantly decreased when PVE was applied. In conclusion, the proposed method suggested that PVE was indispensable to improve an accuracy of DTI ROI study.

Effect of Illiteracy on Cognition and Cerebral Morphology in Later Life

권오대,윤의철,Duk L. Na 대한치매학회 2015 Dementia and Neurocognitive Disorders Vol.14 No.4

Background and Purpose A better developmental environment has positive effects on brain development. The acquisition of literacyduring childhood may affect brain functional organization. The present study aimed to evaluate the effects of illiteracy on neuropsychologicaltest results and cerebral morphology in later life. Methods We recruited 7 illiterate elderly farmers who had never attended school and had no reading or writing knowledge. These subjectswere compared with 9 literate subjects in terms of neuropsychological performance and brain volume. All subjects were over 65-years-oldand had the same regional and occupational background. Results Neuropsychological tests indicated that the performance of the illiterate subjects was worse than that of literate subjects in all cognitivedomains except forward digit span, tool-use and tool-free gestures, verbal word recognition, and verbal generation of animals and groceryitems. The illiterate group also showed significantly decreased cortical volume and surface area in both parietal lobes. However, the illiterategroup showed increased cortical thickness in the left cuneus. Conclusions Literacy acquired in childhood may increase the volume of the parietal lobe and improve neuropsychological performancethrough the process of brain plasticity. The effects can be lifelong.

경도인지장애와 알츠하이머병 환자의 ¹⁸F-fludeoxyglucose PET 표준 섭취계수율에 대한 체적 및 피질 표면 기반 관심영역 분석

김선직,윤의철,Kim, Seonjik,Yoon, Uicheul 대한의용생체공학회 2018 의공학회지 Vol.39 No.6

$^{18}F$-fludeoxyglucose PET (FDG-PET) can help finding an abnormal metabolic activity in brain. In this study, we evaluated an efficiency of volume- and cortical surface-based analysis which were used to determine whether standardized uptake value ratio (SUVR) of FDG-PET was different among Alzheimer's disease (AD), mild cognitive impairment (MCI), and healthy control (HC). Each PET image was rigidly co-registered to the corresponding magnetic resonance imaging (MRI) using mutual information. All voxels of the co-registered PET images were divided by the mean FDG uptake of the cerebellum cortex which was thresholded by partial volume effect (>0.9). Also, the SUVR value of each vertex was linearly interpolated from volumetric SUVR image which was thresholded by gray matter partial volume effect (>0.1). Lobar mean values were calculated from both volume- and cortical surface-based SUVRs. Statistical analysis was conducted to compare two measures for AD, MCI and HC groups. Even though the results of volume (SUVR_vol) and cortical surface-based SUVR (SUVR_surf) analysis were not significantly different from each other, the latter would be better for detecting group differences in SUVR of PET.

3차원 MR 영상으로부터의 한국인 뇌조직확률지도 개발

김정현,이종민,윤의철,김현필,구방본,김인영,이동수,권준수,김선일 대한의용생체공학회 2004 의공학회지 Vol.25 No.5

The development of group-specific tissue probability maps (TPM) provides a priori knowledge for better result of cerebral tissue classification with regard to the inter-ethnic differences of inter-subject variability. We present sequential procedures of group-specific TPM and evaluate the age effects in the structural differences of TPM. We investigated 100 healthy volunteers with high resolution MRI scanning. The subjects were classified into young (60, 25.92±4.58) and old groups (40, 58.83±8.10) according to the age. To avoid any bias from random selected single subject and improve registration robustness, average atlas as target for TPM was constructed from skull-stripped whole data using linear and nonlinear registration of AIR. Each subject was segmented into binary images of gray matter, white matter, and cerebrospinal fluid using fuzzy clustering and normalized into the space of average atlas. The probability images were the means of these binary images, and contained values in the range of zero to one. A TPM of a given tissue is a spatial probability distribution representing a certain subject population. In the spatial distribution of tissue probability according to the threshold of probability, the old group exhibited enlarged ventricles and overall GM atrophy as age-specific changes, compared to the young group. Our results are generally consistent with the few published studies on age differences in the brain morphology. The more similar the morphology of the subject is to the average of the population represented by the TPM, the better the entire classification procedure should work. Therefore, we suggest that group-specific TPM should be used as a priori information for the cerebral tissue classification. 대뇌 조직 구분을 위한 선험적인 정보를 제공하기 위한 뇌 조직 확률 지도를 개발하는 경우 개인마다 구조적으로 다양한 형태를 가진 뇌의 특성과 특히 인종간의 두드러진 차이를 반드시 고려해야 한다. 본 연구에서는 특정 그룹에 대한 뇌 조직 확률 지도를 제작하는 데 필요한 절차를 알아보고 나이에 따른 그룹 간의 뇌 조직 확률 지도의 구조적인 차이를 살펴보고자 한다. 피험자 그룹은 100명의 건강한 한국인이며 나이에 따라 두 그룹으로 분류하였다. 뇌 확률 지도의 기준 좌표계를 설정하기 위해 전체 그룹 내의 모든 피험자의 뇌 영상에 대한 평균 영상을 구하고, 각 뇌 영상을 기준 좌표계로 정규화 시킨다. 정규화 과정에서 얻어진 변환 매개 변수를 미리 각 뇌 조직(회질, 백질, 뇌척수액)으로 분할된 피험자의 영상에 적용하고 각 그룹 내에서 변환된 뇌 조직 영상을 평균함으로써 뇌 조직 확률 지도를 완성하였다. 나이에 따른 구조적인 차이를 살펴보기 위해 그룹 간 확률 값의 차이 영상을 구하였다. 이전 연구결과에서와 마찬가지로 나이가 증가함에 따라 뇌실이 확대되고 회질의 위축이 전체적인 뇌 영역에서 일어났다. 그러므로 우리는 대뇌 조직 분할을 위해 선험적인 정보들을 사용하고자 할 때는 특정 그룹에 대한 뇌 확률 지도를 사용할 것을 제안한다.

특발정상압수두증에서 해마 및 외측 뇌실의 부피와 뇌척수액배액검사

강경훈,한재환,윤의철 대한의용생체공학회 2019 의공학회지 Vol.40 No.5

We investigated differences in ventricular and hippocampal volumes between CSF tap test (CSFTT) responders and non-responders in idiopathic normal-pressure hydrocephalus (INPH) patients and compared these parameters in INPH patients with that of age- and gender-matched healthy controls. We also evaluated relationships between ventricular and hippocampal volumes and clinical profiles in INPH patients. We enrolled 48 patients with INPH and 29 healthy controls. Ventricular and hippocampal volumes were measured on MRI, including 3-dimensional volumetric images. INPH patients, when compared to healthy controls, had significantly larger ventricular and smaller hippocampal volumes. No difference in ventricular and hippocampal volumes was found between CSFTT responders and non-responders in INPH patients. And hippocampal volumes showed significant negative correlations with Clinical Dementia Rating Scale scores, INPH grading scale cognitive scores, Timed Up and Go Test scores, and Unified Parkinson’s Disease Rating Scale motor scores in INPH patients. Volumetric assessment of ventricular and hippocampal regions may have no predictive value in differentiating between CSFTT responders and non-responders in INPH patients. Our findings may help us understand the potential pathophysiology of unique symptoms associated with INPH.

연령별 대뇌 피질 두께의 성별 차이에 대한 형태학적 분석

서해석,김수현,윤의철 대한의용생체공학회 2023 의공학회지 Vol.44 No.1

There have been many studies from the genetic system to physical activity and emotional expression such that there are gender differences. The purpose of this study was to determine how the structural characteristics of cortical thickness differ between males and females. This study used data from the Human Connectome Project (HCP). To analyze age-specific sexual dimorphisms of cortical thickness, selected 8-80 year old subjects were divided into five detailed age range groups according to each criterion. A total of 1,700 individual brain MRI T1 data were registered in stereotaxic space for analysis and classified into white matter (WM), gray matter (GM), and cerebro- spinal fluid (CSF). For surface-based analysis, the WM/GM surface was reconstructed from a spherical polygon model with 40962 vertices per hemisphere, and each vertex was extended to the GM/CSF boundary. Cortical thickness was then measured between each vertex using the t-link method. In the statistical analysis, intracranial volume was used as a covariate to exclude the effect of the difference in brain size of each individual, and the result of using age as a covariate was added to confirm the age effect within each group. Gender differences in cortical thickness had sig- nificant results by group. This may be an index to explain diseases with sexual dimorphism in prevalence or become a basis for explaining the characteristics of each sex that appear in behavior, personality, and aging. Therefore, the results of our study could be a criterion for age classification in future studies and for understanding ‘normal’ sexual dimorphism.

특발정상압수두증 환자의 보행 패턴과 대뇌피질의 구조적인 특징의 상관관계 분석

윤은경,강경훈,윤의철,Yun, EunKyeong,Kang, Kyunghun,Yoon, Uicheul 대한의용생체공학회 2021 의공학회지 Vol.42 No.6

Idiopathic normal-pressure hydrocephalus (INPH) is considered a potentially treatable neurological disorder by shunt surgery and characterized by a triad of symptoms including gait disturbance, cognitive impairment and urinary dysfunction. Although disorders of white matter are generally viewed as the principal pathological features of INPH, analysis of cortical features are important since the destruction of neural tracts could be associated with cortical structural changing. The aim of the study was to determine whether there was any relationship between gait parameter and structural features of cerebral cortex in INPH patients. Gait parameters were measured as follows: step width, toe in/out angle, coefficient of variation (CV) value of stride length, CV value of stride time. After obtaining individual brain MRI of patients with INPH and hemispheric cortical surfaces were automatically extracted from each MR volume, which reconstructed the inner and outer cortical surface. Then, cortical thickness, surface area, and volume were calculated from the cortical surface. As a result, step width was positively correlated with bilateral postcentral gyrus and left precentral gyrus, and toe in/out was positively correlated with left posterior parietal cortex and left insula. Also, the CV value of stride length showed positive correlation in the right superior frontal sulcus, left insula, and the CV value of stride time showed positive correlation in the right superior frontal sulcus. Unique parameter of cerebral cortical changes, as measured using MRI, might underline impairments in distinct gait parameters in patients with INPH.

대뇌피질 표면의 특징을 이용한 나이 및 성별 예측을 위한 그래프 기반 딥러닝 기법의 비교연구

김도환(Dohwan Kim),윤의철(Uicheul Yoon),강경훈(Kyunghoon Kang),김재일(Jaeil Kim) 한국정보과학회 2021 한국정보과학회 학술발표논문집 Vol.2021 No.6