• Journal of the Korean Society of Radiology
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• v.83 no.3
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• pp.750-750
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• 2022

• Investigative Magnetic Resonance Imaging
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• v.8 no.1
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• pp.42-49
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• 2004

Purpose : The quantization noise in magnetic resonance imaging (MRI) systems is analyzed. The signal-to-quantization noise ratio (SQNR) in the reconstructed image is derived from the level of quantization in the signal in spatial frequency domain. Based on the derived formula, the SQNRs in various main magnetic fields with different receiver systems are evaluated. From the evaluation, the quantization noise could be a major noise source determining overall system signal-to-noise ratio (SNR) in high field MRI system. A few methods to reduce the quantization noise are suggested. Materials and methods : In Fourier imaging methods, spin density distribution is encoded by phase and frequency encoding gradients in such a way that it becomes a distribution in the spatial frequency domain. Thus the quantization noise in the spatial frequency domain is expressed in terms of the SQNR in the reconstructed image. The validity of the derived formula is confirmed by experiments and computer simulation. Results : Using the derived formula, the SQNRs in various main magnetic fields with various receiver systems are evaluated. Since the quantization noise is proportional to the signal amplitude, yet it cannot be reduced by simple signal averaging, it could be a serious problem in high field imaging. In many receiver systems employing analog-to-digital converters (ADC) of 16 bits/sample, the quantization noise could be a major noise source limiting overall system SNR, especially in a high field imaging. Conclusion : The field strength of MRI system keeps going higher for functional imaging and spectroscopy. In high field MRI system, signal amplitude becomes larger with more susceptibility effect and wider spectral separation. Since the quantization noise is proportional to the signal amplitude, if the conversion bits of the ADCs in the receiver system are not large enough, the increase of signal amplitude may not be fully utilized for the SNR enhancement due to the increase of the quantization noise. Evaluation of the SQNR for various systems using the formula shows that the quantization noise could be a major noise source limiting overall system SNR, especially in three dimensional imaging in a high field imaging. Oversampling and off-center sampling would be an alternative solution to reduce the quantization noise without replacement of the receiver system.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.5
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• pp.52-62
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• 2008

In this paper, we develop a method that changes the resolutions of images in an arbitrary block transform domain by using a filter that suits to the characteristics of the underlying images. To accomplish this, we represent each procedure resizing images in an arbitrary transform domain as matrix multiplications and we derive the matrix that scales the image resolutions from the matrix multiplications. The resolution scaling matrix is also designed to be able to select the up/down-sampling filter that suits the characteristics of the image. Experiments show that the proposed method produces the reliable performances when it is applied to various transforms and to images that are mixed with predicted and non-predicted blocks which are generated during video coding.

• Korean Journal of Remote Sensing
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• v.14 no.2
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• pp.137-148
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• 1998

An algorithm developed for the precision correction of high resolution satellite images is introduced in this paper. In general, the polynomial warping algorithm which derives polynomial equations between GCPs extracted from an image and a base map requires many GCPs well-distributed over the image. The precision correction algorithm described in this paper is based on a sensor-orbit-Earth geometry, and therefore, it is capable of correcting a raw image using only 2-3 GCPs. This algorithm estimates the errors on the orbit determination and the attitude of the satellite by using a Kalman filter. This algorithm was implemented, tested and integrated into the KITSAT-3 image preprocessing software.

• Journal of the Korean Society of Radiology
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• v.81 no.4
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• pp.852-862
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• 2020

Interventional radiology (IR) embolization requires image guidance to steer catheters to the site of bleeding, where embolic agents such as Gelfoam or coils are administered to stem blood flow. In addition to treating iatrogenic trauma, embolization is suitable for injuries precluding surgery such as blush-bleeding of the liver or kidney and for locating and treating intimal blood vessel tears. However, during hospital off-hours (such as nights and holidays), experienced IR personnel are not always available. In such situations, there is a dire need to build a coordinated IR team to treat seriously injured patients rapidly and reliably. This article reviews the current principles and techniques used in IR such as virtual fluoroscopy and their usefulness, and makes a convincing case for emergency IR.

• The Journal of the Korea Contents Association
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• v.8 no.9
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• pp.115-123
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• 2008

The purpose of this research is how to build the film industry cluster compare with the policies of metropolitan areas and local film industry. This research select four areas including Seoul and Kyunggi areas and Busan, Jeonju. And through the compare with the film industry infra & policies which results in as follows. This research suggest that film industry cluster devided into the two types. The one is the Film Industry Cluster Type and the other is Film Connected Tourism Business Cluster Type. Film Industry Cluster Type is devided into international competitive cities and domestic film industry cities. We suggest that Seoul, Kyunggi and Busan areas are designated to international competitive cities and Jeonju and Daejeon areas are designated to domestical cities. And the kwangwon, Chungcheng, Cheju Areas designated to Film Connected Tourism Business Cluster for location and open set business to improve the local development.

• The Korean Journal of Nuclear Medicine
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• v.33 no.6
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• pp.527-536
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• 1999

Purpose: Radiotracers that bind to the central benzodiazepine receptor are useful for the investigation of various neurological and psychiatric diseases. [C-11]Flumazenil, a benzodiazepine antagonist, is the most widely used radioligand for central benzodiazepine receptor imaging by PET. We synthesized 3-(2-[F-18]fluoro)flumazenil, a new fluorine-18 ($t_{1/2}$= 110 min) labeled analogue of benzodiazepine receptor imaging agent, and evaluated in vivo for biodistribution in mice. Materials and Methods: Flumazenil (Ro 15-1788) was synthesized by a modification of the reported method. Precursor of 3-(2-[F-18]fluoro)flumazenil, the tosylated flumazenil derivative was prepared by the tosylation of the ethyl ester by ditosylethane. [F-18] labeling of tosyl substitued flumazenil precursor was performed by adding F-18 ion at $85^{\circ}C$ in the hot ceil for 20 min. The reaction mixture was trapped by C18 cartridge, washed with 10% ethanol, and eluted by 40% ethanol. Bidistribution in mice was determined after intravenous injection. Results: The total chemical yield of tosylated flumazenil derivative was ${\sim}40%$. The efficiency of labeling 3-(2-[F-18]fluoro)flumazenil was 66% with a total synthesis time of 50 min. Brain uptakes of 3-(2-[F-18]fluoro)flumazenil at 10, 30, 60 min after injection, were $2.5{\pm}0.37,\;2.2{\pm}0.26,\;2.1{\pm}0.11$ and blood activities were $3.7{\pm}0.43,\;3.3{\pm}0.07,\;3.3{\pm}0.09%ID/g$, respectively. Conclusion: We synthesized a tosylated flumazenil derivative which was successfully labeled with no-carrier-added F-18 by nucleophilic substitution.

• The Journal of Korean Society for Radiation Therapy
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• v.24 no.2
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• pp.175-181
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• 2012

Purpose: This study aimed to analyze the influence of aquaplastic mask which is used for the radiotherapy for patients with head and neck cancer on patient positioning by analyzing the results of 2D/2D matching with the use of Exactrac 6D couch system. Materials and Methods: 2D/2D matching-based Image guidance was performed with the use of Exactrac 6D couch system on a total of 14 patients with head and neck cancer who received radiotherapy at this hospital in a period from June 2010 to June 2011. The adjusted 6D values obtained after the image guidance were classified into values related with patients and values not related with patients as to the correlation between the results. Results: In the analysis of the relation of each adjusted value to patients, the coefficient of determination ($R^2$) of longitudinal and pitch direction was 0.76, of longitudinal and yaw direction was 0.48, and of pitch and yaw direction was 0.42 although the coefficient of determination for above factors was 0.03 or less when the dependency of patients was excluded. Conclusion: It was demonstrated that intrinsic factors of aquaplastic mask had influence on the immobilization of patients by aquaplastic mask although various factors related with patients had influence on the immobilization of patients. It is believed that if these factors are adjusted, the treatment of patients with head and neck cancer can be more accurate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2C
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• pp.229-237
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• 2004

In this paper. we propose a new autocalibration algorithm. 3D-based image synthesis is roughly divided into two methods. One is using autocalibration method, and the other is using real 3D data like pattern information. The former is more progressive method. because there is no constraint or information about the scenes. Therefore autocalibration method has very difficult progress dealing with complicate non-lineal equations. Nowadays, constraints of camera intrinsic parameters are used in many researches. Therefore we solve the linear equations instead of complicate non-lineal equations. For example, to fix principal point of camera is a representative method.

• The Journal of the Korea Contents Association
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• v.17 no.9
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• pp.173-183
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• 2017

In this research, analysis based on VR journalism outlet the New York Times' was carried out. The image analysis of was done through the frames of angle, shot (size, length, movement), and limited user-directed interaction (point, sound). The result of this is as follows. Firstly, the direction was done using a basis of normal and low angles. Secondly, it was able to be confirmed that the shooting was done in order by medium, full, and long shot. Thirdly, with regard to the length of the shot, most direction was done through long takes. Fourthly, most images came to consist of fixed shots. Lastly, this is limited user-directed interaction. This may be separated into 2 aspects: sound, and movement of the independent free agent. Through these, interaction was guided through free point of view concerning realistic situations to point of view guidance and users. This research may be referred to as foundational research for the further advancement of in-depth discussion pertaining to VR journalism.