• Radiation Oncology Journal
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• v.17 no.3
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• pp.249-255
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• 1999

Purpose : The purpose of this study is to investigate fundamental aspects of the dose response of fluorescent screen-based electronic portal imaging devices (EPIDS). Materials and Methods : We acquired scanned signal across portal planes as we varied the radiation that entered the EPID by changing the thickness and anatomy of the phantom as well as the air gap between the phantom and the EPID. In addition, we simulated the relative contribution of the scintillation light signal in the EPID system. Results : We have shown that the dose profile across portal planes is a function of the air gap and phantom thickness. We have also found that depending on the density change within the phantom geometry, errors associated with dose response based on the EPID scan can be as high as $7\%$. We also found that scintillation light scattering within the EPID system is an important source of error. Conclusion : This study revealed and demonstrated fundamental characteristics of dose response of EPID, as relative to that of ion chambers. This study showed that EPID based on fluorescent screen cannot be an accurate dosimetry system.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.53-53
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• 2011

This paper describes results for surface and bulk characterization of the most promising thin film solar cell material for high performance devices, (Ag,Cu) (In,Ga) Se2 (ACIGS). This material in particular exhibits a range of exotic behaviors. The surface and general materials science of the material also has direct implications for the operation of solar cells based upon it. Some of the techniques and results described will include scanning probe (AFM, STM, KPFM) measurements of epitaxial films of different surface orientations, photoelectron spectroscopy and inverse photoemission, Auger electron spectroscopy, and more. Bulk measurements are included as support for the surface measurements such as cathodoluminescence imaging around grain boundaries and showing surface recombination effects, and transmission electron microscopy to verify the surface growth behaviors to be equilibrium rather than kinetic phenomena. The results show that the polar close packed surface of CIGS is the lowest energy surface by far. This surface is expected to be reconstructed to eliminate the surface charge. However, the AgInSe2 compound has yielded excellent atomic-resolution images of the surface with no evidence of surface reconstruction. Similar imaging of CuInSe2 has proven more difficult and no atomic resolution images have been obtained, although current imaging tunneling spectroscopy images show electronic structure variations on the atomic scale. A discussion of the reasons why this may be the case is given. The surface composition and grain boundary compositions match the bulk chemistry exactly in as-grow films. However, the deposition of the heterojunction forming the device alters this chemistry, leading to a strongly n-type surface. This also directly explains unpinning of the Fermi level and the operation of the resulting devices when heterojunctions are formed with the CIGS. These results are linked to device performance through simulation of the characteristic operating behaviors of the cells using models developed in my laboratory.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.944-945
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• 2016

Gamma-ray Detector for gamma-ray imaging device is composed of a shielding body for shielding gamma-rays incident from the radiation source. Distribution of the gamma ray can be represented by the distribution information on the direction in which the detecting section and the signal through the incident hole of collimator. The role of the shield is important because all signals should be treated as noise except for the signal from the incident hole.In this paper In this paper, we have produced a compact, lightweight and Collimator shield by changing the structure and physical properties with respect to the collimator and shielding of lead-based gamma-ray detectors. And we analyzed the shielding effectiveness relative to the incident gamma ray sphere measured signal value through the gamma irradiation test facility. The results confirmed that the production and Collimator shielding the imaging device Implementing more efficient to implement.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.4
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• pp.352-358
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• 2010

This paper presented compact CW sub-THz imaging system using the terahertz transmitter(Tx) that generating 0.34 THz electromagnetic wave on based electronic device. Using 0.34 THz electromagnetic wave generated by Tx, we transmitted to sample by point by point scan method and measured transmitting terahertz wave magnitude and phase information respectively with terahertz receiver(Rx) based on sub harmonic mixer. This paper measured and compared images of several samples to obtain better imaging results by changing time delay and step distance of scanning stage which affect image resolution. Also, through the imaging measurement of various samples, we were able to assure possibility of application of terahertz wave.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.1
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• pp.80-87
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• 2012

We have developed the ATE(Automatic Test Equipment) system for the performance test of pre-amplifier of thermal imaging devices. The device regenerates the electronic signals of photon detection module which is normally in weak energy, for the image signals processing. Previous ATE system was primarily and actively developed in the field of semiconductor devices quality parts inspection. Recently, it has been studied in the field of performance testing of equipment. In the field of thermal performance test equipment, however, it lacks the study of ATE compared to other areas, which causes the maintenance related to the core of military thermal imaging system maintenance to be limited. In this paper, a new study of ATE in the field of thermal imaging system is done. It is designed to be used universally for the ATE system with different types of circuit card of thermal imaging system by adopting matrix relays. Using the developed ATE measuring the pre-amplifier amplitude, an average amplified amplitude of 2.71Vpp was measured which confirms that it is within the range of theoretical analysis and also verifies the good performance of the developed ATE.

• Journal of Biosystems Engineering
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• v.39 no.3
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• pp.244-252
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• 2014

Purpose: The development of an efficient in vitro cell culture device to process various cells would represent a major milestone in biological science and engineering. However, the current conventional macro-scale in vitro cell culture platforms are limited in their capacity for detailed analysis and determination of cellular behavior in complex environments. This paper describes a microfluidic-based culture device that allows accurate control of parameters of physical cues such as pressure. Methods: A microfluidic device, as a model microbioreactor, was designed and fabricated to culture Saccharomyces cerevisiae and Chlamydomonas reinhardtii under various conditions of physical pressure stimulus. This device was compatible with live-cell imaging and allowed quantitative analysis of physical cue-induced behavior in yeast and microalgae. Results: A simple microfluidic-based in vitro cell culture device containing a cell culture channel and an air channel was developed to investigate physical pressure stress-induced behavior in yeasts and microalgae. The shapes of Saccharomyces cerevisiae and Chlamydomonas reinhardtii could be controlled under compressive stress. The lipid production by Chlamydomonas reinhardtii was significantly enhanced by compressive stress in the microfluidic device when compared to cells cultured without compressive stress. Conclusions: This microfluidic-based in vitro cell culture device can be used as a tool for quantitative analysis of cellular behavior under complex physical and chemical conditions.

• Journal of Radiation Protection and Research
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• v.39 no.3
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• pp.150-158
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• 2014

Radiation-related practitioners and radiation-treated patients at medical institutions are inevitably exposed to radiation for diagnosis and treatment. Although standards for maximum doses are recommended by the International Commission on Radiological Protection (ICPR) and the International Atomic Energy Agency (IAEA), more direct and available measurement and analytical methods are necessary for optimal exposure management for potential exposure subjects such as practitioners and patients. Thus, in this study we developed a system for real-time radiation monitoring at a distance that works with existing portable device. The monitoring system comprises three parts for detection, imaging, and transmission. For miniaturization of the detection part, a scintillation detector was designed based on a silicon photomultiplier (SiPM). The imaging part uses a wireless charge-coupled device (CCD) camera module along with the detection part to transmit a radiation image and measured data through the transmission part using a Bluetooth-enabled portable device. To evaluate the performance of the developed system, diagnostic X-ray generators and sources of $^{137}Cs$, $^{22}Na$, $^{60}Co$, $^{204}Tl$, and $^{90}Sr$ were used. We checked the results for reactivity to gamma, beta, and X-ray radiation and determined that the error range in the response linearity is less than 3% with regard to radiation strength and in the detection accuracy evaluation with regard to measured distance using MCNPX Code. We hope that the results of this study will contribute to cost savings for radiation detection system configuration and to individual exposure management.

• The Journal of the Korea Contents Association
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• v.16 no.11
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• pp.699-706
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• 2016

This study aimed to propose the necessity and system establishment of noise reduction facility via evaluating noise level exposed by the radiographer due to MRI scan. Noise measurements were carried out using at S general hospital in Daejeon using 1.5 Tesla MRI (7 exams) and 3.0 Tesla MRI (16 exams), while using SC-804 noise meter. The measurement distance was from the soundproof door of the MRI room to the radiographer which measured 100cm, and the measurement height, the height to the radiographer's ears when working, 100cm. The noise measured for each exam was an average of three measures per exam which observed the noise occurring in each sequence recorded every 20 seconds. As the results, the maximum of noise exposed by the radiographer is 73.3 dB(A), which is MRCP by the 3.0 Tesla device, and also the maximum of average noise is 66.9(3.1) dB(A), which is Myelogram by the 3.0 Tesla device. Average noise by each device is 61.9(4.1) dB(A) by the 3.0 Tesla device and 52.0(3.1) dB(A) by the 1.5 Tesla device, which comes to the result that the 3.0 Tesla MRI device is about 10 dB(A) degree higher(p <0.001). The noise level exposed by the radiographer does not affect auditory acuity, but the level is able to incur a non auditory effect. The reflect sound can be removed by installing curtains in the rear wall of MRI control room in order to reduce the noises, but, first of all, An institutional system is needed in order to prevent noise.

• The Journal of the Korea Contents Association
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• v.7 no.4
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• pp.184-191
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• 2007

Our objective was to develop and evaluate a non-invasive device for rigid immobilization and surface disease non-contact of the table in the lower extremity during CT angiography. The immobilization device consists of two components. The patient's lower limb device stabilizing elements made of polyethylene resin soft materials, and pelvis parts foam pad is used for non-contact surface. In a Prospective study the lower extremity device was used in patients who underwent a CT angiography of the lower limb. Immobilization with our device was well tolerated by all patients. The quality of the resulting images in the popliteal and infrapopliteal region was rated by five-point scale. The rigid immobilization resulted in a complete absence of motion artifacts. The new device is an effective, well tolerated and easily used immobilization that is suitable of use in 3D lower extremity CT angiography.

• Journal of the Korean Society of Visualization
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• v.16 no.1
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• pp.15-20
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• 2018

For the measurement of biophysical properties related with cardiovascular diseases (CVD), various microfluidic devices were proposed. However, many devices were monitored by optical equipment. Ultrasound measurement to quantify the biophysical properties can provide new insights to understand the cardiovascular diseases. This study aims to check feasibility of microfluidic device for ultrasound image analysis based on 3D printer. To facilitate acoustic transmission, agarose solution is poured around 3D mold connected with holes of the acrylic box. By applying speckle image velocimetry(SIV) technique, flow information in the bifurcated channel was estimated. Considering that ultrasound signal amplitude is determined by red blood cell (RBC) aggregation, RBC aggregation in the bifurcated channel can be estimated through the analysis of ultrasound signal. As examples of microfluidic device which mimic the CVD model, velocity fields in microfluidic devices with stenosis and aneurysm were introduced.