• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.3
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• pp.163-171
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• 2003

To evaluate the performance of the digital radiography(DR) system developed in our group, the modulation transfer function(MTF) was measured and compared with that of an analog X- ray detector, film/screen system. The DR system has an amorphous selenium(a-Se) layer vacuum-evaporated on a TFT flat panel detector. The speed class 400 film/screen (Fuji) system has been being used in the clinical field as analog X-ray detectors. Both the square wave and slit method were used to evaluate their MTF. The square method was applied to both film/screen and the DR system. The slit method, however, was applied to only DR system. The full-width half maximum resolution of film/screen was 357${\mu}{\textrm}{m}$(1.4 lp/mm at 50% spatial frequency), and the resolution of DR was limited to 200${\mu}{\textrm}{m}$(2.5 lp/mm at 30%). These results indicate the measured resolution limitations approximate to the pixel pitch, 139 ${\mu}{\textrm}{m}$ of TFT. The MTF of DR is higher than that of film/screen by the factor of 1.785. It is proved that our a-Se based DR system has potential usefulness in the clinical field.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.116.3-116
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• 2001

A diagnosis methodology for thickness quality in hot finishing mill is proposed based on multivariate statistical analysis. The thickness of hot strip is a key quality factor that is measured by x-ray thickness gauge. Currently, the thickness quality is guaranteed by upper and lower limit of thickness deviation from target thickness. But if any over-limit is occurred, there is no in-line method to identify the causes. In this paper, many parameters are extracted from the thickness deviation signal such as mean deviation(top, middle, tail), rms deviation(top, middle, tail) and peak deviation(top, middle, tail) as time domain parameters ...

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.179.1-179
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• 2001

Successive image contrast enhancement was used to direct digital radiography system. This system was accurately required acquisition signal in each pixel. But, applied high electric field in a-Se thin film for x-ray conversion layer was caused to acquisition signal distortion, then bring low image contrast. The purpose of this study was to reduce the signal distortion, carried out different electrode size.

• Progress in Medical Physics
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• v.27 no.1
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• pp.8-13
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• 2016

Dual energy cone-beam CT can distinguish two materials with different atomic compositions. The principle of dual energy cone-beam CT based on modulation layer is that higher energy spectrum can be acquired at blocked x-ray window. To evaluate the possibility of modulation layer based dual energy cone-beam CT, we analyzed x-ray spectrum for various thicknesses of modulation layers by Monte Carlo simulation. To compare with the results of simulation, the experiment was performed on prototype cone-beam CT for 50~100 kVp with CdTe XR-100T detector. As the result of comparing, the mean energy of energy spectrum for 80 kVp are well matched with that of simulation. The mean energy of energy spectrum for 80 and 120 kVp were increased as 1.67 and 1.52 times by 2.0 mm modulation layer, respectively. We realized that the virtual dual energy x-ray source can be generated by modulation layer.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.539-542
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• 2001

본 논문에서는 검출기의 반응 특성을 선형화 모델링 하여 정규화 할 수 있는 방법을 제안한다. 디지털 의료영상 시스템에서 X-선을 검출하는 검출기의 반응 특성이 모든 검출기마다 다르기 때문에 이 특성을 쉽고 빠르게 정규화 하는 방법이 필요하다. 본 논문에서는 균일한 피사체에 X-선 조사량의 비율을 다르게 하여 두 번 찍은 영상으로 검출기의 반응 특성을 정규화 한다. 실험 결과 일정한 두께의 납 평판에 조사량을 달리하여 촬영한 두 개의 결과 영상을 가지고 검출기의 반응 특성을 보정하면 매우 안정된 결과 영상을 얻을 수 있다.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1915_1916
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• 2009

스테레오 X-선 영상시스템 개발을 위하여 수치적 프로젝션을 획득하는 방법론 및 수치적 팬텀 영상을 고안하고 시험하였다. 오픈소스인 TAKE21을 사용하여 수치적 팬텀을 설계하고 그로부터 프로젝션 이미지를 획득하였다. 스테레오 영상을 위한 평행 원근 투영(Parallel-Perspective) 기하구조에 대한 스테레오 프로젝션 영상을 얻기 위해서 계측기의 계와 선원의 위치에 대해 동차 좌표계(Homogeneous coordinate)에서의 선형변환(Linear Transform)을 적용되는 방식을 이용하였다. 이러한 시뮬레이션은 스테레오 X-선 검색 장치의 설계 및 알고리즘 개발에 유용하게 사용될 수 있을 것이다.

• Journal of Radiation Protection and Research
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• v.36 no.2
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• pp.86-92
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• 2011

This study used the optically stimulated luminescence dosimeters (OSLDs), recently, received the revaluation of usefulness in vivo dosimetry, and the diode detecters to measure the skin dose of patient with the rectal cancer. The measurements of dose delivered were compared with the planned dose from the treatment planning system (TPS). We evaluated the clinical application of OSDs in radiotherapy. We measured the calibration factor of OSLDs and used the percent depth dose to verified, also, we created the three point of surface by ten patients of rectal cancer to measured. The calibration factors of OSLD was 1.17 for 6 MV X-ray and 1.28 for 10 MV X-ray, demonstrating the energy dependency of X-ray beams. Comparison of surface dose measurement using the OSLDs and diode detectors with the planned dose from the TPS, The skin dose of patient was increased 1.16 ~ 2.83% for diode detectors, 1.36 ~ 2.17% for OSLDs. Especially, the difference between planned dose and the delivery dose was increased in the perineum, a skin of intense flexure region, and the OSLDs as a result of close spacing of measuring a variate showed a steady dose verification than the diode detecters. Therefore, on behalf of the ionization chamber and diode detecters, OSLDs could be applied clinically in the verification of radiation dose error and in vivo dosimety. The research on the dose verification of the rectal cancer in the around perineal, a surface of intense flexure region, suggest continue to be.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.300-307
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• 2022

Time-resolved serial femtosecond crystallography (TR-SFX) is a powerful technique for determining temporal variations in the structural properties of biomacromolecules on ultra-short time scales without causing structure damage by employing femtosecond X-ray laser pulses generated by an X-ray free electron laser (XFEL). The mixing rate of reactants and biomolecule samples, as well as the hit rate between crystal samples and x-ray pulses, are critical factors determining TR-SFX performance, such as accurate image acquisition and efficient sample consumption. We here develop two distinct sample delivery systems that enable ultra-fast mixing and on-demand droplet injecting via pneumatic application with a square pulse signal. The first strategy relies on inertial mixing, which is caused by the high-speed collision and subsequent coalescence of droplets ejected through a double nozzle, while the second relies on on-demand pneumatic jetting embedded with a 3D-printed micromixer. First, the colliding behaviors of the droplets ejected through the double nozzle, as well as the inertial mixing within the coalesced droplets, are investigated experimentally and numerically. The mixing performance of the pneumatic jetting system with an integrated micromixer is then evaluated by using similar approaches. The sample delivery system devised in this work is very valuable for three-dimensional biomolecular structure analysis, which is critical for elucidating the mechanisms by which certain proteins cause disease, as well as searching for antibody drugs and new drug candidates.

• Journal of radiological science and technology
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• v.43 no.2
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• pp.65-70
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• 2020

PA(postero-anterior) and AP(antero-posterior) chest projections are the most sought-after types of all kinds of projections. But if a radiological technologist puts wrong information about the position in the computer, the orientation of left and right side of an image would be reversed. In order to solve this problem, we utilized CNN(convolutional neural network) which has recently utilized a lot for studies of medical imaging technology and rule-based system. 70% of 111,622 chest images were used for training, 20% of them were used for testing and 10% of them were used for validation set in the CNN experiment. The same amount of images which were used for testing in the CNN experiment were used in rule-based system. Python 3.7 version and Tensorflow r1.14 were utilized for data environment. As a result, rule-based system had 66% accuracy on evaluating whether the orientation reversal on chest x-ray image. But the CNN had 97.9% accuracy on that. Being overcome limitations by CNN which had been shown on rule-based system and shown the high accuracy can be considered as a meaningful result. If some problems which can occur for tasks of the radiological technologist can be separated by utilizing CNN, It can contribute a lot to optimize workflow.

• Journal of the Korean Society of Radiology
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• v.17 no.3
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• pp.459-464
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• 2023

Due to the development of advanced technology, a lot of digital radiographic equipment has been developed, which is very helpful for accurate diagnosis and treatment, and it is very important to train personnel who have acquired professional knowledge in order to use it safely and effectively. Students are exposed to the risk of radiation exposure in radiography training using diagnostic X-ray equipment, and some educational institutions do not use X-ray equipment due to management difficulties in accordance with the Nuclear Safety Act. As a solution to this, this study developed a medical radiation simulator for education that does not generate radiation by using a vision sensor and self-developed software. Through this, educational institutions can reduce the burden of administrative implementation according to the law, and students can obtain a high level of educational effects in a healthy practice environment without radiation exposure.