• 대한디지털의료영상학회논문지
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• 제9권2호
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• pp.11-16
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• 2007

We have evaluated and compared of gradient echo and spin echo EPI for compensating about deeply distortion aspect in case of post-operation patients in magnetic resonance image. A total of 100 patients were performed on 3.0 T(GE Signa Excite E2, USA) with 8ch head coil. As a result of analysis, The SNRs of whiter and gray matter areas were 36.74 $\pm$ 06 and 39.96 $\pm$ 09 in the gradient echo EPI, the SNRs which white and gray matter areas were slightly higher than gradient echo EPI(P<0.005, paired student t-test). It was 46.24 $\pm$ 11 and 51.38 $\pm$ 13 in gradient and spin echo EPI, respectively. The signal intensity in the whiter and gray matter areas also were 87.33 $\pm$ 15.24 and 140.66 $\pm$ 13.45 in the gradient echo EPI techniques, The signal intensity of gradient echo EPI showed higher values compared to spin echo EPI. Otherwise, gradient echo EPI technique is distortion enough to operation wound and edge of the image, while spin echo EPI technique did not appear almost. In this point, the spin echo EPI technique, after surgical operation according to patient state beside gradient echo EPI techniques that signalbeside gradient echo EPI techniques that signal intensity is high and patient's case which image distortion is serious by metal etc, will be provide the useful information in adults and pediatric patients.

• 대한디지털의료영상학회논문지
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• 제9권2호
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• pp.31-38
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• 2007

To evaluate the accuracy and extent in the localization of cerebral motor coutex activation using a gradient- echo echo planar imaging(GE-EPI) compared to spin-echo echo planar iimaging(SE-EPI) on 3T MR imaging. Functional MR imaging of cerebral motor cortex activation was examined in GE-EPI and SE-EPI in five healthy male volunteers. A right finger movement was accomplished with a paradigm of 6 task and rest, periods and the cross-correlation was used for a statistical mapping algorithm. We evaluated any sorts of differenced of the time seried and the signal intensity changes between the rest and task periods obtained with two technoques. The qualitative analysis was distributed with activation sites of large veins and small veins by using two techniques and was found that both the techniques were clinically uesful for delineating large veins and small veins in fMRL Signal intensity charge of the rest and activation periods provided simmilar activations in both methods(GE-EPI : 0.93$\pm$0.11, SE-EPI : 0.80$\pm$.015) but the signal intensity in GE-EPI(133.95$\pm$15.76) was larger than in SE-EPI(74.5$\pm$18.90). The average SNRs of EPI raw data were higher at SMA in SE-EPI(48.54$\pm$12.37) than GE-EPI(41.4$\pm$12.54) and at M1 in SE-EPI(43.24$\pm$11.77) than GE-EPI(38.27$\pm$6.53). The localization of activation voxels of the GE-EPI showed a larger vein but the SE-EPI generally showed small vein. Then the analysis results of the two techniques were used for a statistacal paired student t-test. SE-EPI was found clinically useful for localizing the cerebral moter cortex cativation on 3.0T, but showed a little different activation patterns comparad to GE-EPI. In conclusion, SE-EPI may be feasible and can detect true cortical activation from capillaries and GE-EPI can obtain the large veins in the motor cortex activation on 3T MR imaging.

• Investigative Magnetic Resonance Imaging
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• 제3권2호
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• pp.167-172
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• 1999

목적 : Echo planar image (EPn와 다론 MR 영상기법에서 2시간 이내의 초급성 출혈의 발견율의 차이를 비교해 보고자 한다. 대상 및 방법 : 인위적으로 뇌출혈을 유발시킨 백서 10마리를 대상으로 EP1, 급속 스핀에코 (FSE) T2 강조영상, Fluid attenuated inversion recovery (FLAIR) 영상, 스펀에코 (SE) Tl 강조영상과 Tl 강조 Gradient echo (GE) 영상을 이용하여, 뇌출혈을 일으킨 2시간 후에 MR 촬영을 하였다. 추가적으로 3마리는 출혈 30분 후에, 6마리는 1시간 후에 각각 EPI와 FSE T2 강조영상을 얻었다. 얻어진 영상에 대한 주관적인 시각적 평가를 하기위하여 세명의 방사선과 의사가 출혈 병변이 어느 MR 영상 기법에서 제일 잘 보이는지를 평가하였다. 정량적인 평가 로는 병변-정상 뇌설질의 대조잡음비(contrast-to-noise ratio, CNR)를 측정하였다. 통계처리는 Wilcoxon-Ranks test를 이용하였다. 결과 : 시각적 평가에서 출혈 병변이 높은 신호강도로 나타난 EP1, FLAIR, FSE T2 영상 중 EPI 영상이 특히 높은 신호강도로 나타나 제일 쉽게 병변이 구별되었다. 정량적인 평가에서 출혈 병 변-정상 뇌설질의 CNR은 EPI와 FLAIR 영상에서 다른 세 영상기법에 비해 통계적으로 유의하게 우월하였다 (p<0.01). 그러나 EPI와 FLAIR 영상간의 CNR은 동계적으로 유의한 차이가 없었다 (p>0.10). 추가적으로 출혈 30분과 1l시간 후 촬영한 모두에서 EPI영상과 FSE T2 강조 영상은 정상에 비해 높은 신호강도를 보여 병변의 구별이 가능하였다. 결론 : 백서에서 유발시킨 초급성기 뇌출혈의 여러 기법의 MR 영상 중 EPI 영상이 영상획득 시간이 가장 빠르면서 시각적 평가와 정량적 평가에서 출혈의 발견율이 가장 높아 출혈의 선속한 진단에 유용할 것으로 생각된다.

• Applied Biological Chemistry
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• 제33권2호
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• pp.174-176
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• 1990

Oxidation of artemisinic acid was attempted with chromium trioxide-pyridine complex. Epi-Deoxyarteannuin B was formed almost quantitatively, while expected keto artemisinic acid was not the major product. The physical and spectral data of the product are presented(Received March 9, 1990, Accepted May 25, 1990)

• 대한전자공학회논문지
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• 제13권3호
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• pp.22-27
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• 1976

집적회로(I.C)의 설계에 있어서는 평수구조의 변형만이 가능하므로 여러가지 다른 트랜지스터 (Transistor)가 결합하여 하나의 특정한 기능을 발휘하게 되는 선형회로에는 회로의 설계와 동시에 사용될 적층(EPI)의 비저항 및 두께와 적층(EPI)과 기판 사이에 삽입되는 이침층(Buried Layer)의 구조 등을 정확히 알아야 한다. 본 연구에서는 집적회로의 동작전압과 적층 두께및 비저항과의 관계를 실측치와 비교분석 하였고 이 결과를 선형 집적회로 설계에 이용 가능하도록 도시하였다. For linear IC design, one has to know the epi thickness, resistivity, and structure of buried island inserted between epi and substrate because the mask structure can only be changed for linear IC consisted of various type of transistors to be made for desired specific function. The interrelation of IC operational and saturation voltages with epi resistivity, theckness and divice structure are studied and presented in graphic forms so that IC design engineers can utilize them.

• 한국방사선학회논문지
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• 제14권7호
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• pp.957-964
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• 2020

본 연구는 현재 사용되고 있는 가장 빠른 Pulse Sequence 중 하나인 EPI기법과 T2 FLAIR 기법 두 가지를 함께 적용하여 사용하는 EPI-FLAIR기법을 급성 허혈성 뇌경색 환자에게 적용하여, EPI-FLAIR 기법의 진단적 유용성에 대하여 평가하였다. 연구 결과 정성적, 정량적 분석 결과 EPI-FLAIR 기법이 T2 FLAIR 기법과 비교 시 통계적으로 유의한 차이가 있음을 알 수 있었으며, 결론적으로 EPI-FLAIR 기법은 화질의 저하 없이 영상획득시간을 줄일 수 있어 허혈성 급성 뇌경색 및 뇌출혈, 신경학적 결핍, 경색 시기 진단이 필요한 환자의 여러 가지 뇌 병변 평가와 함께 비협조적인 환자들에게 발생하는 Motion Artifact를 줄일 수 있는 장점 있어 T2 FLAIR와 비교하여 충분한 진단적 가치가 있다고 사료된다.

• Journal of Korean Neurosurgical Society
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• 제59권4호
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• pp.346-351
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• 2016

Objective : Early progressive infarction (EPI) is frequently observed and related to poor functional outcome in patients with middle cerebral artery (MCA) infarction caused by MCA occlusion. We evaluated the perfusion parameters of magnetic resonance imaging (MRI) as a predictor of EPI. Methods : We retrospectively analyzed patients with acute MCA territory infarction caused by MCA occlusion. EPI was defined as a National Institutes of Health Stroke Scale increment ${\geq}2$ points during 24 hours despite receiving standard treatment. Regional parameter ratios, such as cerebral blood flow and volume (rCBV) ratio (ipsilateral value/contralateral value) on perfusion MRI were analyzed to investigate the association with EPI. Results : Sixty-four patients were enrolled in total. EPI was present in 18 (28%) subjects and all EPI occurred within 3 days after hospitalization. Diabetes mellitus, rCBV ratio and regional time to peak (rTTP) ratio showed statically significant differences in both groups. Multi-variate analysis indicated that history of diabetes mellitus [odds ratio (OR), 6.13; 95% confidence interval (CI), 1.55-24.24] and a low rCBV ratio (rCBV, <0.85; OR, 6.57; 95% CI, 1.4-30.27) was significantly correlated with EPI. Conclusion : The incidence of EPI is considerable in patients with acute MCA territory infarction caused by MCA occlusion. We suggest that rCBV ratio is a useful neuro-imaging parameter to predict EPI.

• 한국방사선학회논문지
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• 제7권4호
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• pp.265-269
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• 2013

뇌척수액을 생산하고 있는 choroid plexuse를 확산강조영상 검사기법에 따라 신호강도를 분석하여 임상적인 유용성을 알아보고자 하였다. $T2^*$-DW-EPI 기법을 적용하여 choroid plexus가 고 신호 강도를 보이는 대상자를 추가적으로 FLAIR-DW-EPI 기법을 적용하여 영상을 얻었다. 두 기법으로 얻은 확산강조영상을 가지고 choroid plexus의 신호강도와 확산계수를 구하여 비교하였다. 그 결과 FLAIR-DW-EPI 기법에서는 choroid plexus의 신호가 뇌 실질과 같거나 저 신호로 나타나 두 기법간의 신호강도의 차이가 있음을 확인하였다. 이는 $T2^*$-DW-EPI 확산강조영상에서 choroid plexus가 고 신호를 보인 환자의 경우 FLAIR-DW-EPI 기법을 추가로 검사하여 정보를 제공함으로서 choroid plexus의 질병 유무를 진단하는데 도움이 될 것으로 생각한다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.249-251
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• 2003

This paper discribes the analysis of the breakdown voltage characteristics of SOI LIGBT with dual epi-layer. In case of SOI LIGBT with dual epi-layer, if we used high doping concentration in epi-layer, we obtained higher breakdown voltage compared with typical device because of charge compensation effect, and we obtained low on-state resistivity characteristic in the same breakdown voltage. In this paper, we analyzed on-state and off-state characteristics of SOI LIGBT with dual epi-layer. Breakdown voltage of proposed LIGBT was shown 125V when $T_1=T_2=2.5{\mu}m$, $N_1=7{\times}10^{15}/cm^3$ and $N_2=3{\times}10^{15}/cm^3$, respectively Although we used high doping concentration and thin epi-layer thickness, breakdown voltage was increased compared with conventional devices.

• Molecules and Cells
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• 제41권6호
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• pp.515-522
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• 2018

Patients with head and neck cancer are treated with therapeutic irradiation, which can result in irreversible salivary gland dysfunction. Because there is no complete cure for such patients, stem cell therapy is an emerging alternative for functional restoration of salivary glands. In this study, we investigated in vitro characteristics of primarily isolated epithelial cells from human salivary gland (Epi-SGs) and in vivo formation of acini-like structures by Epi-SGs. Primarily isolated Epi-SGs showed typical epithelial cell-like morphology and expressed E-cadherin but not N-cadherin. Epi-SGs expressed epithelial stem cell (EpiSC) and embryonic stem cell (ESC) markers. During long-term culture, the expression of EpiSC and ESC markers was highly detected and maintained within the core population with small size and low cytoplasmic complexity. The core population expressed cytokeratin 7 and cytokeratin 14, known as duct markers indicating that Epi-SGs might be originated from the duct. When Epi-SGs were transplanted in vivo with Matrigel, acini-like structures were readily formed at 4 days after transplantation and they were maintained at 7 days after transplantation. Taken together, our data suggested that Epi-SGs might contain stem cells which were positive for EpiSC and ESC markers, and Epi-SGs might contribute to the regeneration of acini-like structures in vivo. We expect that Epi-SGs will be useful source for the functional restoration of damaged salivary gland.