• Investigative Magnetic Resonance Imaging
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• v.4 no.2
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• pp.113-119
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• 2000

Purpose : To know the possibility of clinical application of MRI using oxygen inhalation as a perfusion MRI Materials and methods : Two healthy volunteers and three patients of one moyamoya disease, one acute infarction and one meningioma were studied using a 1.5 Tesla MRI unit. Oxygen (15 liters/min) mixed with room air was given using face mask from 8 second to 35 second during the study. Images were acquired 25 times (scan time per study were 1.6 seconds) using susceptibility contrast EPI (echo planar image) sequence. Difference maps were acquired by early (study 12-18), and late (study 19-25) O2 inhalation image groups minus pre-O2 inhalation image group (study 3-9) with a Z-score of 0.7-1.0 using VB31C program of Magneton Vision. The resulting perfusion images were created by superimposition of difference maps on corresponding T1 weighted anatomic images. On moyamoya patient, similar perfusion images were acquired after Gd-DTPA injection, and compared with O2 inhalation perfusion images. Results ; The author can get the perfusion images of the brain by oxygen inhalation with susceptibility contrast EPI sequence at the volunteers, and the patient of moyomoya disease, acute infarction and meningioma. On moyamoya patient, perfusion images with O2 inhalation are similar with perfusion images by Gd-DTPA injection. Conclusion 1 This study has demonstrated that the susceptibility contrast EPI by oxygen inhalation can be used as the clinically useful perfusion MRI technique

• Investigative Magnetic Resonance Imaging
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• v.7 no.2
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• pp.108-115
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• 2003

Purpose : To evaluate the effect of the gradient switching noise on the ECD source localization with the EEG data recorded during the MRI scan. Materials and Methods : We have fabricated a spherical EEG phantom that emulates a human head on which multiple electrodes are attached. Inside the phantom, electric current dipole(ECD) sources are located to evaluate the source localization error. The EEG phantom was placed in the center of the whole-body 3.0 Tesla MRI magnet, and a sinusoidal current was fed to the ECD sources. With an MRI-compatible EEG measurement system, we recorded the multi channel electric potential signals during gradient echo single-shot EPI scans. To evaluate the effect of the gradient switching noise on the ECD source localization, we controlled the gradient noise level by changing the FOV of the EPI scan. With the measured potential signals, we have performed the ECD source localization. Results : The source localization error depends on the gradient switching noise level and the ECD source position. The gradient switching noise has much bigger negative effects on the source localization than the Gaussian noise. We have found that the ECD source localization works reasonably when the gradient switching noise power is smaller than $10\%$ of the EEG signal power. Conclusion : We think that the results of the present study can be used as a guideline to determine the degree of gradient switching noise suppression in EEG when the EEG data are to be used to enhance the performance of fMRI.

• Journal of the Korean Magnetics Society
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• v.11 no.3
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• pp.104-108
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• 2001

The effect of specular electron scattering on natural oxidation of free layer in NiO spin valves have been investigated. The magnetoresistance (MR) ratio and the exchange biasing field ( $H_{ex}$) of NiO(600 $\AA$)Ni$_{81}$$Fe_{19}$(50$\AA$)/Co(7 $\AA$)/Cu(20 $\AA$)/Co(7 $\AA$)Ni$_{81}$$Fe_{19}$(70 $\AA$) spin valves were increased from 4.9 % to 7.3 %, and 110 Oe to 170 Oe after natural oxidation in the atmosphere for 80 days, respectively. The sheet resistivity p decreased from 28$\mu$$\Omega$m to 17$\mu$$\Omega$m, but $\Delta$$\rho$ did not almost change after the oxidation. The spin valves enhanced by the specular electron scattering in the natural]y Co/NiFe/NiFe $O_{x}$ free layer were confirmed from the depth profiles using Auger electron spectroscopy.scopy..

• Journal of Broadcast Engineering
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• v.17 no.1
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• pp.73-80
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• 2012

Recently, medical equipments are developed and used for diagnosis or studies. In addition, demand of techniques which automatically deal with three dimensional medical images obtained from the medical equipments is growing. One of the techniques is automatic bone segmentation which is expected to enhance the diagnosis efficiency of osteoporosis, fracture, and other bone diseases. Although various researches have been proposed to solve it, they are unable to be used in practice since a size of the medical data is large and there are many low contrast boundaries with other tissues. In this paper, we present a fast and accurate automatic framework for bone segmentation based on multi-resolutions. On a low resolution step, a position of the bone is roughly detected using constrained branch and mincut which find the optimal template from the training set. Then, the segmentation and the registration are iteratively conducted on the multiple resolutions. To evaluate the performance of the proposed method, we make an experiment with femur and tibia from 50 test knee magnetic resonance images using 100 training set. The proposed method outperformed the constrained branch and mincut in aspect of segmentation accuracy and implementation time.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.271-271
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• 2015

The Ecuadorian coast has two different climate regions. One is humid region where the annual rainfall is above 2000 mm and rain falls in almost all months of the year, and the other is dry region where the annual rainfall can fall below 50 mm and rainfall can be very seasonal. The agriculture is frequently limited by the seasons during the year and the availability of rainfall amounts. The corn fields in Ecuador are cultivated during the rainy season, due to this reason. The weather conditions for optimum development of corn growth require a monthly average rainfall of 120 mm to 140 mm and a temperature range of $22^{\circ}C{\sim}32^{\circ}C$ for the dry region, and a monthly average rainfall of 200 mm to 400 mm and a temperature range of $25^{\circ}C{\sim}30^{\circ}C$ for the humid area. The objective of this study is to predict how the weather conditions are going to change in corn fields of the coastal region of Ecuador in the future decades. For this purpose, this study selected six General Circulation Models (GCM) including BCC-CSM1-1, IPSL-CM5A-MR, MIROC5, MIROC-ESM, MIROC-ESM-CHEM, MRIC-CGC3 with different climate scenarios of the RCP 4.5, RCP 6.0, and RCP 8.5, and applied for the period from 2011 to 2100. The climate variables information was obtained from the INAMHI (National Institute of Meteorology and Hydrology) in Ecuador for the a base line period from 1986 to 2012. The results indicates that two regions would experience significant changes in rainfall and temperature compared to the historical data. In the case of temperature, an increment of $1^{\circ}C{\sim}1.2^{\circ}C$ in 2025s, $1.6^{\circ}C{\sim}2.2^{\circ}C$ in 2055s, $2.1^{\circ}C{\sim}3.5^{\circ}C$ in 2085s were obtained from the dry region while less increment were shown from the humid region with having an increment of $1^{\circ}C$ in 2025s, $1.4^{\circ}C{\sim}1.8^{\circ}C$ in 2055s, $1.9^{\circ}C{\sim}3.2^{\circ}C$ in 2085s. Significant changes in rainfall are also projected. The rainfall projections showed an increment of 8%~11% in 2025s, 21%~33% in 2055s, and 34%~70% in 2085s for the dry region, and an increment of 2%~10%, 14%~30% and 23%~57% in 2025s, 2055s and 2085s decade respectively for humid region.

• Korean Journal of Construction Engineering and Management
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• v.22 no.1
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• pp.3-12
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• 2021

In the remodeling projects, clients without architectural expertise have limitations in presenting requirements accurately. In some cases, designers and contractors may not recognize their demands exactly, and deliver final products that are different from the clients' intentions. 3D modeling visualizing final products in previous has been regarded as a solution to enhance understanding and communication. However, this approach has the limitation that the final results are presented as a virtual outputs. In the remodeling project, an alternative, mixed-reality, is likely to reinforce the reality as it enables to present remain structure and the parts to be built together. This paper examines the mixed reality as a solution to support decision making of clients and practitioners in remodeling projects. The examinations is conducted in high-rise office remodeling projects by means of action-research. Clients and practitioners, overview product models presented in the format of 2D drawings, BIM and mixed reality asked to evaluate the effectiveness of each methods in 12 standards. The results have shown that mixed reality has improved the sense of reality, making it easier to predict results, but recognizing patterns is difficult in some areas such as the floor, and it caused dizziness.

• Journal of the Korean Society of Radiology
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• v.5 no.1
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• pp.37-49
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• 2011

To examine the possible changes in the SNRs, CNRs, and ADC values for lumbar spines with metastasis based on the DW images before and after contrast agent injection taken from metastatic spinal cancer patients using a 1.5 T MR machine. The quantitative analysis revealed that in case of spinal cancer subjects, both SNRs and CNRs at all of those assessed locations significantly increased on the DWI after contrast agent injection compared to before, while on the ADC map images, SNRs significantly decreased. On the other hand, significantly decreased ADC values at all the assessed locations were found on the ADC map images. With reference to the normal group, significantly increased SNRs were found at all of the assessed locations on the DWI image after injection compared to before, while significantly decreased SNRs were found on the ADC map images. Also, significantly decreased ADC values at all the assessed locations were found on the ADC map images. For the qualitative analysis, after contrast agent injection, significantly increased signal intensities were found at the locations with spinal cancer on the DWI. In contrast, significantly decreased signal intensities were found on the ADC map images. The implication from the results showing that SNR and CNR significantly increased while ADC value significantly decreased at, above, and below the location of metastatic spinal cancer on DWI after contrast agent injection is that DWI obtained after contrast agent injection can be made available for wider application to vertebral disorders.

• Journal of radiological science and technology
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• v.32 no.3
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• pp.313-323
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• 2009

Diffusion-weighted imaging (DWI) has been demonstrated to be a practical method for the diagnosis of various brain diseases such as acute infarction, brain tumor, and white matter disease. In this study, we used two techniques to examine the average signal intensity (SI) and apparent diffusion coefficient (ADC) of the brains of patients who ranged in age from 10 to 60 years. Our results indicated that the average SI was the highest in amygdala (as derived from DWI), whereas that in the cerebrospinal fluid was the lowest. The average ADC was the highest in the cerebrospinal fluid, whereas the lowest measurement was derived from the pons. The average SI and ADC were higher in $T_2^*$-DW-EPI than in FLAIR-DW-EPI. The higher the b-value, the smaller the average difference in both imaging techniques; the lower the b-value, the greater the average difference. Also, comparative analysis of the brains of patients who had experienced cerebral infarction showed no distinct lesion in the general MR image over time. However, there was a high SI in apparent weighted images. Analysis of other brain diseases (e.g., bleeding, acute, subacute, chronic infarction) indicated SI variance in accordance with characteristics of the two techniques. The higher the SI, the lower the ADC. Taken together, the value of SI and ADC in accordance with frequently occurring areas and various brain disease varies based on the b-value and imaging technique. Because they provide additional useful information in the diagnosis and treatment of patients with various brain diseases through signal recognition, the proper imaging technique and b-value are important for the detection and interpretation of subacute stroke and other brain diseases.

• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.1
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• pp.19-25
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• 2014

Purpose: Integrated PET/MRI has been developed recently has become a lot of help to the point oncologic, neological, cardiological nuclear medicine. By using this PET/MRI, a ${\mu}-map$ is created some special MRI sequence which may be divided parts of the body for attenuation correction. However, because an MRI contrast agent is necessary in order to obtain an more MRI information, we will evaluate to see an effect of SUV on PET image that corrected attenuation by MRI with contrast agent. Materials and Methods: As PET/MRI machine, Biograph mMR (Siemens, Germany) was used. For phantom test, 1mCi $^{18}F-FDG$ was injected in cylinderical uniformity phantom, and then acquire PET data about 10 minutes with VIBE-DIXON, UTE MRI sequence image for attenuation correction. T1 weighted contrast media, 4 cc DOTAREM (GUERBET, FRANCE) was injected in a same phatnom, and then PET data, MRI data were acquired by same methodes. Using this PET, non-contrast MRI and contrast MRI, it was reconstructed attenuation correction PET image, in which we evanuated the difference of SUVs. Additionally, for let a high desity of contrast media, 500 cc 2 plastic bottles were used. We injected $^{18}F-FDG$ with 5 cc DOTAREM in first bottle. At second bottle, only $^{18}F-FDG$ was injected. and then we evaluated a SUVs reconstructed by same methods. For clinical patient study, rectal caner-pancreas cancer patients were selected. we evaluated SUVs of PET image corrected attenuastion by contrast weighted MRI and non-contrast MRI. Results: For a phantom study, although VIBE DIXON MRI signal with contrast media is 433% higher than non-contrast media MRI, the signals intensity of ${\mu}-map$, attenuation corrected PET are same together. In case of high contrast media density, image distortion is appeared on ${\mu}-map$ and PET images. For clinical a patient study, VIBE DIXON MRI signal on lesion portion is increased in 495% by using DOTAREM. But there are no significant differences at ${\mu}-map$, non AC PET, AC-PET image whether using contrast media or not. In case of whole body PET/MRI study, %diff between contras and non contrast MRAC at lung, liver, renal cortex, femoral head, myocardium, bladder, muscle are -4.32%, -2.48%, -8.05%, -3.14%, 2.30%, 1.53%, 6.49% at each other. Conclusion: In integrated PET/MRI, a segmentation ${\mu}-map$ method is used for correcting attenuation of PET signal. although MRI signal for attenuation correciton change by using contrast media, ${\mu}-map$ will not change, and then MRAC PET signal will not change too. Therefore, MRI contrast media dose not affect for attenuation correction PET. As well, not only When we make a flow of PET/MRI protocol, order of PET and MRI sequence dose not matter, but It's possible to compare PET images before and after contrast agent injection.

• Radiation Oncology Journal
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• v.22 no.2
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• pp.155-163
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• 2004

Purpose : To confirm the reproducibility of in vivo transmission dosimetry system and the accuracy of the a1gorithms for the estimation of transmission dose in head and neck radiation therapy patients. Materials and Methods : From September 5 to 18, 2001, transmission dose measurements were peformed when radiotherapy was given to brain or head and neck cancer patients. The data of 35 patients who were treated more than three times and whose central axis of the beam was not blocked were analyzed in this study. To confirm the reproducibility of this system, transmission dose was measured before dally treatment and then repetitively every hour during the treatment time, with a field size of 10$\times$10 cm$^{2}$ and a delivery of 100 MU. The accuracy of the transmission dose calculation algorithms was confirmed by comparing estimated dose with measured dose. To accurately estimate transmission dose, tissue inhomogeneity correction was done. Results : The measurement variations during a day were within $\pm$0.5$\%$ and the dally variations in the checked period were within $\pm$ 1.0$\%$, which were acceptable for system reproducibility. The mean errors between estimated and measured doses were within $\pm$5.0$\%$ in Patients treated to the brain, $\pm$2.5$\%$ in head, and $\pm$ 5.0%$\%$in neck. Conclusion : The results of this study confirmed the reproducibility of our system and its usefulness and accuracy for dally treatment. We also found that tissue inhomogeneity correction was necessary for the accurate estimation of transmission dose in patients treated to the head and neck.