• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2006년도 제33회 추계학술대회 발표논문집
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• pp.151-151
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• 2006

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2002년도 제7차 학술대회 초록집
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• pp.84-84
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• 2002

목적： 야간성 전두협 발작 (Nocturnal frontal lobe epilepsy NFLE)은 임상적으로 특징적인 야간성 운동성 발작으로 잘 알려져 있지만 일반적인 MR 영상에서는 대부분에서는 특이한 소견을 보이지 않아 확산 텐서 영상 (DTI)에서의 이상 소견 발현 유무를 알아보고자 한다. 대상 및 방법： 임상적 소견과, EEG 소견으로 진단된 NFLE 환자 6명을 대상으로 DTI 영상을 촬영하였다. 남자 2명, 여자 4명으로 평균연령은 32세 이었다. DTI영상은 single shot spin echo EPI 펄스 열을 사용하였고 사용한 영상 변수는 b value는 0, 1000 s/$\textrm{mm}^2$, TR 10000 msec, TE 71.8/72.3 msec, matrix 128$\times$128 (256 reconstruction), FOV 23cm, 5mm thickness, 2mm interstice gap, NEX 1. 19 slices, time은 4min 21sec (25방향) 이었다. 대조군으로 정상 성인 10명 (평균연령 31세)에서 동일한 방법으로 DTI 영상을 시행하여 분할 비등방도 (fractional anisotropy) 영상을 얻고 전두엽 백질에서 분할 비등방도 값을 측정하여 NFLE 환자군과 비교하였다.

• 대한의용생체공학회:의공학회지
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• 제27권5호
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• pp.203-209
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• 2006

The aim of this study is to investigate the feasibility of ex vivo MR diffusion tensor imaging technique in order to observe the diffusion-contrast characteristics of human gastric tissues. On normal and pathologic gastric tissues, which have been fixed in a polycarbonate plastic tube filled with 10% formalin solution, laboratory made 3D diffusion tensor Turbo FLASH pulse sequence was used to obtain high resolution MR images with voxel size of $0.5{\times}0.5{\times}0.5mm^3\;using\;64{\times}32{\times}32mm^3$ field of view in conjunction with an acquisition matrix of $128{\times}64{\times}64$. Diffusion weighted- gradient pulses were employed with b values of 0 and $600s/mm^2$ in 6 orientations. The sequence was implemented on a clinical 3.0-T MRI scanner(Siemens, Erlangen, Germany) with a home-made quadrature-typed birdcage Tx/Rx rf coil for small specimen. Diffusion tensor values in each pixel were calculated using linear algebra and singular value decomposition(SVD) algorithm. Apparent diffusion coefficient(ADC) and fractional anisotropy(FA) map were also obtained from diffusion tensor data to compare pixel intensities between normal and abnormal gastric tissues. The processing software was developed by authors using Visual C++(Microsoft, WA, U.S.A.) and mathematical/statistical library of GNUwin32(Free Software Foundation). This study shows that 3D diffusion tensor Turbo FLASH sequence is useful to resolve fine micro-structures of gastric tissue and both ADC and FA values in normal gastric tissue are higher than those in abnormal tissue. Authors expect that this study also represents another possibility of gastric carcinoma detection by visualizing diffusion characteristics of proton spins in the gastric tissues.

• 한국의학물리학회지:의학물리
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• 제18권4호
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• pp.214-220
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• 2007

Line propagation과 Brute force approach를 기반으로 한 확산텐서 트랙토그래피에서 신경다발추적을 위한 시작점을 선택하기 위한 조건으로 기존에 사용하는 Fractional anisotropy (FA)값 이외에 vector correlation function (VCF)를 제안하여 트랙토그래피를 구현하였다. 뇌전체의 트랙토그래피에 대하여, 본 연구에서 제안한 VCF를 사용할 경우 FA가 0.3 이상인 경우에 백질 외 영역에서 41% 적은 시작점을 사용하여 백질 외의 신경섬유가 아닌 부분들이 제거된 결과를 얻었다. 또한 관심영역에 대한 피질척수로의 영상에서는 백질 내에서는 50% 적은 시작점을 사용하였으나 기존기법과 매우 유사한 결과를 얻었다.

• Korean Chemical Engineering Research
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• 제46권4호
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• pp.756-763
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• 2008

본 연구에서는 잉크젯용 전도성 금속 나노 잉크 개발을 목표로 통계적인 실험과 분석을 진행하여 재현성 있는 고품질의 은 나노 입자를 합성할 수 있는 기술을 개발하고자 하였다. 은 나노 입자는 상용 수계분산제 Daxad19를 이용한 용액 환원침전법을 통해 0.3 M의 고농도로 합성되었다. 합성에 주요한 영향을 주는 6개의 인자를 선정한 후 실험 계획법(Design-of-experiment)을 통해 실험을 수행하였다. 합성된 은 입자는 SEM, TEM, UV-Visible 등의 분석법을 이용하여 입자크기 및 분포와 분산도 등을 측정하였으며 통계 프로그램인 Minitab으로 이를 최적화하였다. 통계적인 실험계획 및 분석은 2차 부분요인분석법(2k-fractional factorial design)과 반응표면분석법인 박스-벤켄법(Box-Behnken design)으로 진행하였다. 이를 통한 합성 최적화로 평균입경 $30nm{\pm}10%$를 가진 구형의 은 나노 입자를 합성하였다. 또한 본 연구에서는 실험 결과 해석을 통해 환원침전법에서의 입자크기 및 형상 제어의 방식도 실험적으로 밝혀냈다.

• Korean Journal of Radiology
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• 제19권6호
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• pp.1161-1171
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• 2018

Objective: The aim of this study was to investigate diffusion tensor (DT) imaging-derived properties of benign oligemia, true "at risk" penumbra (TP), and the infarct core (IC) during the first 3 hours of stroke onset. Materials and Methods: The study was approved by the local animal care and use committee. DT imaging data were obtained from 14 rats after permanent middle cerebral artery occlusion (pMCAO) using a 7T magnetic resonance scanner (Bruker) in room air. Relative cerebral blood flow and apparent diffusion coefficient (ADC) maps were generated to define oligemia, TP, IC, and normal tissue (NT) every 30 minutes up to 3 hours. Relative fractional anisotropy (rFA), pure anisotropy (rq), diffusion magnitude (rL), ADC (rADC), axial diffusivity (rAD), and radial diffusivity (rRD) values were derived by comparison with the contralateral normal brain. Results: The mean volume of oligemia was $24.7{\pm}14.1mm^3$, that of TP was $81.3{\pm}62.6mm^3$, and that of IC was $123.0{\pm}85.2mm^3$ at 30 minutes after pMCAO. rFA showed an initial paradoxical 10% increase in IC and TP, and declined afterward. The rq, rL, rADC, rAD, and rRD showed an initial discrepant decrease in IC (from -24% to -36%) as compared with TP (from -7% to -13%). Significant differences (p < 0.05) in metrics, except rFA, were found between tissue subtypes in the first 2.5 hours. The rq demonstrated the best overall performance in discriminating TP from IC (accuracy = 92.6%, area under curve = 0.93) and the optimal cutoff value was -33.90%. The metric values for oligemia and NT remained similar at all time points. Conclusion: Benign oligemia is small and remains microstructurally normal under pMCAO. TP and IC show a distinct evolution of DT-derived properties within the first 3 hours of stroke onset, and are thus potentially useful in predicting the fate of ischemic brain.

• Journal of Korean Neurosurgical Society
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• 제59권3호
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• pp.306-309
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• 2016

Using diffusion tensor tractography (DTT), we demonstrated injury of the arcuate fasciculus (AF) in the nondominant hemisphere in two patients who showed subfalcine herniation after intracerebral hemorrhage (ICH) in the dominant hemisphere. Two patients (patient 1 and patient 2) with ICH and six age-matched control patients who have ICH on the left corona radiata and basal ganglia without subfalcine herniation were recruited for this study. DTT was performed at one month after onset in patient 1 and patient 2. AFs of both hemispheres in both patients were disrupted between Wernicke's and Broca's areas. The fractional anisotropy value and tract numbers of the right AFs in both patients were found to be more than two standard deviations lower than those of control patients. In contrast, the apparent diffusion coefficient value was more than two standard deviations higher than those of control patients. Using the configuration and parameters of DTT, we confirmed injury of the AF in the nondominant hemisphere in two patients with subfalcine herniation following ICH in the dominant hemisphere. Therefore, DTT would be a useful tool for detection of underlying injury of the AF in the nondominant hemisphere in patients with subfalcine herniation.

• PNF and Movement
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• 제14권1호
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• pp.41-47
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• 2016

Purpose: In general, confabulation is defined as confusion of reality with past events without apparent prompting, in association with disruption of the capacity for retrieval and encoding of memory. We report on a patient who showed spontaneous confabulation associated with injury of the Papez circuit following middle cerebral artery (MCA) infarction. Methods: A 67-year-old female patient suffered cerebral infarct resulting from spontaneous MCA territory. After onset of the MCA infarct, she showed severe memory impairment and provoked confabulation. The Papez circuit was reconstructed for evaluation of part of it using diffusion tensor tractography (DTT). Fractional anisotropy (FA), mean diffusivity (MD), and tract volume were measured. Results: The right thalamocingulate tract showed a significant decrement of FA value and tract volume, and an increment of MD value by more than two standard deviations of that of normal control subjects. The tract volume in the left fornix and mammillothalamic tract decreased by more than two standard deviations of that of normal control subjects. Conclusion: Injuries of the Papez circuit were demonstrated in a patient who showed severe memory impairment and provoked confabulation following MCA infarct. We believe that analysis of the Papez circuit tract using DTT is useful in elucidating the cause of provoked confabulation in patients with MCA infarct.

• The Journal of Korean Physical Therapy
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• 제32권6호
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• pp.388-390
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• 2020

Objectives: The nigrostriatal tract (NST) connect from the substantia nigra pars compacta to the striatum. A few previous studies have reported on the NST in the Parkinson's disease using a proboblistic tractography method. However, no study has been conducted for identification of the NST using streamline DTT technique. In the current study, we used streamline DTI technique to investigate the reconstruction method and characteristics of the NST in normal subjects. Methods: Eleven healthy subjects were recruited in this study. The NST from the substantia nigra of the midbrain and the striatum of basal ganglia was reconstructed using DTI data. Fractional anisotropy, apparent diffusion coefficient (ADC) values and fiber numbers of the NST were measured. Results: In all subjects, the NST between the substantia nigra of the midbrain and the striatum. Mean values for FA, ADC, and tract volume were 0.460, 0.818, and 154.3 in the right NST, and 0.485, 0.818, and 176.3 in the left NST respectively. Conclusions: we reconstructed the NRT from the substantia nigra of the midbrain and the striatum of the basal ganglia using streamline tractography method. We believe that the findings and the proposed streamline reconstruction method of this study would be useful in future researches on the NST of the human brain.

• Geomechanics and Engineering
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• 제29권1호
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• pp.53-63
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• 2022

Simplified analytical solutions are developed for the dynamic analyses of an axially loaded pile foundation embedded in a transverse-isotropic, fluid-filled, poro-visco-elastic soil with rigid substratum. The pile is modeled as a viscoelastic Rayleigh-Love rod, while the surrounding soil is regarded as a transversely isotropic, liquid-saturated, viscoelastic, porous medium of which the mechanical behavior is represented by the Boer's poroelastic media model and the fractional derivative model. Upon the separation of variables, the frequency-domain responses for the impedance function of the pile top, and the vertical displacement and the axial force along the pile shaft are gained. Then by virtue of the convolution theorem and the inverse Fourier transform, the time-domain velocity response of the pile head is derived. The presented solutions are validated, compared to the existing solution, the finite element model (FEM) results, and the field test data. Parametric analyses are made to show the effect of the soil anisotropy and the excitation frequency on the pile-soil dynamic responses.