• Annual Conference on Human and Language Technology
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• 1998.10c
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• pp.186-190
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• 1998

정상 피험자에 있어서 수행 성적의 차이를 보이는 음소적 단어 생성과 의미적 단어생성에 관련한 대뇌 피질의 활동양상의 차이를 밝히기 위해 피험자에게 단어 생성의 과제를 주면서 기능적 자기공명 영상술(functional magnetic resonance imaging, fMRI)을 시행하였다. 모두 7명의 정상인에서 음소 단서에 의한 단어생성은 의미 범주 단어에 의한 단어생성보다 광범위한 피질 영역의 활성화를 보였는데, 특히 bilateral posteroinferior temporal cortices, left premotor cortex, right cerebellum, bilateral superior parietal lobules에서 더 높은 활성화를 보였다. 이에 반하여 의미적 단어생성은 주로 bilateral posterior cingulate gyri에서 더 높은 활성화를 보였다. 이런 결과는 음소적 생성은 가능한 자모를 조합하여 어휘를 생성한 후 작업기억에 일시 저장시켜 놓고 verbal rehearsal 과정을 사용하여 단어 여부를 판별하는 것을 시사하며, 의미적 생성은 mental imagery를 통하여 시각적 인출 단서를 찾은 후, 의미 기억으로부터 단어를 직접 인출하는 것으로 보인다.

• Proceedings of the Korea Society for Simulation Conference
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• 2004.05a
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• pp.118-122
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• 2004

본 논문에서는 인체의 머리 부분을 촬영한 의료 영상에서 뇌 영역만을 분할하는 방법에 대해 제시하고자 한다. 뇌의 해부학적 구조 및 기능적 이상 부위를 파악할 경우에 영상 내에 함께 보여지는 두개골과 뇌척수액 등을 제외한 대뇌피질 영역을 분할하면 보다 효과적인 정보 분석 및 진단이 가능하게 된다. 본 시스템에서는 3단계 알고리즘을 제시한다. 첫 번째 단계에서는 영상 내에 존재하는 잡음을 제거하기 위한 필터링이고, 두 번째 단계에서는 필터링된 결과에 대한 영상분할을 수행하는 것이다 이 때 정확한 결과 도출을 위하여 사용자의 인터렉션이 들어가게 된다. 세번째 단계에서는 형태학적 방법을 이용하여 분할 결과를 보완한다. 본 연구를 위한 실험에는 자기 공명 촬영 영상(MRI: Magnetic Resonance Imaging), 단일 광전자 방출 단층 촬영영상(SPECT: Single Photon Emission Computed Tomography), 양전자 방출 단층 촬영영상(PET: Positron Emission Tomography) 등을 사용하였다. 본 시스템에서는 다양한 모달리티의 뇌 영상에서 대뇌피질 부분을 정확하게 영상 분할함으로써 뇌의 구조적 이상을 판단하기 위한 해부학적 정보 분석을 가능케 하고 있다. 뿐만 아니라 뇌 질환에 대한 정확한 진단 시뮬레이션도 가능하게 하고자 한다.

• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.71-71
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• 2003

For fast MRI, the number of phase encoding steps has to be reduced. However, the reconstructed image is aliased if the phase encoding steps don't satisfy Nyquist sampling theory. SENSE is used in order to eliminate the aliasing effect as well as to reduce imaging time. SENSE is a linear algebraic technique applied to the multiple receiver data. In this study, we implement a tool to reconstruct the original image (SENSE image) with Sensitivity Encoding (SENSE)

• Journal of Biomedical Engineering Research
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• v.40 no.3
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• pp.105-115
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• 2019

Brain tumor surgery may be difficult, but it is also incredibly important. The technological improvements for traditional brain tumor surgeries have always been a focus to improve the precision of surgery and release the potential of the technology in this important area of the body. The need for precision during brain tumor surgery has led to an increase in Robotic-assisted surgeries (RAS). One of the challenges to the widespread acceptance of RAS in the neurosurgery is to recognize invisible tumor accurately. Therefore, it is important to detect brain tumor size and location because surgeon tries to remove as much tumor as possible. In this paper, we proposed brain tumor detection procedures for MRI (Magnetic Resonance Imaging) system. A method of automatic brain tumor detection is needed to accurately target the location of the lesion during brain tumor surgery and to report the location and size of the lesion. In the qualitative assessment, the proposed method showed better results than those obtained with other brain tumor detection methods. Comparisons among all assessment criteria indicated that the proposed method was significantly superior to the threshold method with respect to all assessment criteria. The proposed method was effective for detecting brain tumor.

• Journal of Korean Neurosurgical Society
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• v.52 no.4
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• pp.377-383
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• 2012

Objective : Detection of focal non-hemorrhagic lesion (NHL) has become more efficient in diffuse axonal injury (DAI) patients using an MRI. The aims of this study are to find out the radiological distribution, progress of NHL and its clinical significance. Methods : Between September 2005 and October 2011, 32 individuals with NHLs on brain MRI were enrolled. NHLs were classified by brain location into 4 major districts and 13 detailed locations including cortical and subcortical, corpus callosum, deep nuclei and adjacent area, and brainstem. The severity of NHL was scored from grades 1 to 4, according to the number of districts involved. Fourteen patients with NHL were available for MRI follow-up and an investigation of the changes was conducted. Results : Thirty-two patients had 59 NHLs. The most common district of NHL was cortical and subcortical area; 15 patients had 20 NHSs. However the most common specific location was the splenium of the corpus callosum; 14 patients had 14 lesions. The more lesions patients had, the lower the GCS, however, this was not a statistically meaningful difference. On follow-up MRI in 14 patients, out of 24 lesions, 13 NHLs resolved, 5 showed cystic change, and 6 showed atrophic changes. Conclusion : NHLs were located most commonly in the splenium and occur frequently in the thalamus and the mesial temporal lobe. Because most NHS occur concomitantly with hemorrhagic lesions, it was difficult to determine their effects on prognosis. Since most NHLs resolve completely, they are probably less significant to prognosis than hemorrhagic lesions.

• Journal of Korean Neurosurgical Society
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• v.54 no.6
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• pp.453-460
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• 2013

Objective : There is a rich literature confirming the default mode network found compatible with task-induced deactivation regions in normal subjects, but few investigations of alterations of the motor deactivation in patients with intracranial lesions. Therefore, we hypothesized that an intracranial lesion results in abnormal changes in a task-induced deactivation region compared with default mode network, and these changes are associated with specific attributes of allocated regions. Methods : Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) during a motor task were obtained from 27 intracranial lesion patients (mean age, 57.3 years; range 15-78 years) who had various kinds of brain tumors. The BOLD fMRI data for each patient were evaluated to obtain activation or deactivation regions. The distinctive deactivation regions from intracranial lesion patients were evaluated by comparing to the literature reports. Results : There were additive deactivated regions according to intracranial lesions : fusiform gyrus in cavernous hemangioma; lateral occipital gyrus in meningioma; crus cerebri in hemangiopericytoma; globus pallidus, lateral occipital gyrus, caudate nucleus, fusiform gyrus, lingual gyrus, claustrum, substantia nigra, subthalamic nucleus in GBM; fusiform gyrus in metastatic brain tumors. Conclusion : There is increasing interest in human brain function using fMRI. The authors report the brain function migrations and changes that occur in patients with intracranial lesions.

• Investigative Magnetic Resonance Imaging
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• v.3 no.2
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• pp.173-178
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• 1999

Purpose : To evaluate the usefulness of functional MRI (fMRI) of visual cortex in patients with ischemic infarction in the occipital lobe. Materials and Methods : Four patients with the symptoms and signs of visual cortical ischemia were included. Functional MRI was performed by 2D-FLASH technique with the parameter of 90/56msec TR/TE, $40^{\circ}$ flip angle, $240{\times}240{\;}FOV,{\;}64{\times}128$ matrix number, 8.32 seconds acquisition time, 8mm slice thickness. An axial slice including both visual cortices was selected and alternative activation and resting of the visual cortex was performed using red color photostimulator. all patients undertook visual field test, and vascular abnormality was examined by MRA (n=4) and DSA (n=2). fMRI results were compared with the results of a visual field test, conventional MRI and cerebral angiography. Results : On fMRI, decreased activity of the visual cortex was found in the occipital lobe corresponding to stenosis of the posterior cerebral artery or its branch noted on angiogram. However, 2 of 4 patients showed no abnormal findings on conventional MRI. Visual field defect was noted in 3 patients, one and of whom showed no abnormality on conventional MRI and diffusion-weighted image, but revealed decreased activity in the corresponding visual cortex on fMRI. Conclusion : fMRI may be a sensitive method for detection of the status of decreased blood flow or vascular reserve which other methods can not.

• Korean Journal of Radiology
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• v.23 no.10
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• pp.986-997
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• 2022

Objective: Whether metabolic redistribution occurs in patients with white matter hyperintensities (WMHs) on magnetic resonance imaging (MRI) is unknown. This study aimed 1) to propose a measure of the brain metabolic network for an individual patient and preliminarily apply it to identify impaired metabolic networks in patients with WMHs, and 2) to explore the clinical and imaging features of metabolic redistribution in patients with WMHs. Materials and Methods: This study included 50 patients with WMHs and 70 healthy controls (HCs) who underwent ¹⁸F-fluorodeoxyglucose-positron emission tomography/MRI. Various global property parameters according to graph theory and an individual parameter of brain metabolic network called "individual contribution index" were obtained. Parameter values were compared between the WMH and HC groups. The performance of the parameters in discriminating between the two groups was assessed using the area under the receiver operating characteristic curve (AUC). The correlation between the individual contribution index and Fazekas score was assessed, and the interaction between age and individual contribution index was determined. A generalized linear model was fitted with the individual contribution index as the dependent variable and the mean standardized uptake value (SUV_mean) of nodes in the whole-brain network or seven classic functional networks as independent variables to determine their association. Results: The means ± standard deviations of the individual contribution index were (0.697 ± 10.9) × 10^-3 and (0.0967 ± 0.0545) × 10^-3 in the WMH and HC groups, respectively (p < 0.001). The AUC of the individual contribution index was 0.864 (95% confidence interval, 0.785-0.943). A positive correlation was identified between the individual contribution index and the Fazekas scores in patients with WMHs (r = 0.57, p < 0.001). Age and individual contribution index demonstrated a significant interaction effect on the Fazekas score. A significant direct association was observed between the individual contribution index and the SUV_mean of the limbic network (p < 0.001). Conclusion: The individual contribution index may demonstrate the redistribution of the brain metabolic network in patients with WMHs.

• Journal of the Korean Society of Radiology
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• v.82 no.1
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• pp.255-260
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• 2021

Primary central nervous system T-cell lymphoma (PCNSTL) is an extremely rare type of brain tumor. There are only few reports on the imaging findings of patients with PCNSTL. Herein, we report the imaging findings of a patient with peripheral T-cell lymphoma-not otherwise specified that presented with numerous small nodular and patchy strongly enhancing lesions on MRI.

• Proceedings of the KSMRM Conference
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• 2002.11a
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• pp.112-112
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• 2002

Purpose： The Purpose of this study was to evaluate the quantitative variation of brain activity evoked by visual sexual stimulation before and after testosterone supplementation in hypogonadal patients by using BOLD functional MR imaging.