• 한국의학물리학회지:의학물리
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• 제28권3호
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• pp.83-91
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• 2017

In this work, we investigated the recently proposed phase-contrast x-ray imaging (PCXI) technique, the so-called single grid-based PCXI, which has great simplicity and minimal requirements on the setup alignment. It allows for imaging of smaller features and variations in the examined sample than conventional attenuation-based x-ray imaging with lower x-ray dose. We performed a systematic simulation using a simulation platform developed by us to investigate the image characteristics. We also performed a preliminary PCXI experiment using an established a table-top setup to demonstrate the performance of the simulation platform. The system consists of an x-ray tube ($50kV_p$, 5 mAs), a focused-linear grid (200-lines/inch), and a flat-panel detector ($48-{\mu}m$ pixel size). According to our results, the simulated contrast of phase images was much enhanced, compared to that of the absorption images. The scattering length scale estimated for a given simulation condition was about 117 nm. It was very similar, at least qualitatively, to the experimental contrast, which demonstrates the performance of the simulation platform. We also found that the level of the phase gradient of oriented structures strongly depended on the orientation of the structure relative to that of linear grids.

• 한국항행학회논문지
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• 제11권2호
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• pp.163-169
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• 2007

본 논문에서는 x-ray 영상시스템의 영상을 획득하기 위하여 x-ray 발생기와 영상획득시스템 사이의 동기를 맞추어 주는 트리거 발생기를 연구분석 하였다. 무선 트리거 발생기는 디지털영상 획득시스템으로부터 영상획득의 시작을 지시할 수 있는 ACQ_START 신호와 영상획득의 끝을 알리는 ACC_END 신호를 발생시킬 수 있도록 설계하였다. 디지털 영상의 획득은 ACQ_START 신호와 ACQ_END 신호 사이의 시간동안에만 정확하게 이루어지며 무선 원격 x-ray 신호의 검출을 통하여 유선통신 프로토콜 없이 정확한 x-ray 영상의 획득이 가능하고 20 mAs 의 x-ray 레벨에서 3.5 line pair /mm 분해능을 나타냄을 확인하였다.

• 융합신호처리학회논문지
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• 제2권4호
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• pp.46-52
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• 2001

방사광을 이용한 형강 X선 CT 이미징의 고속화를 위한 촬상 시스템과 처리 알고리즘을 검토하였다. 본 논문에서 사용된 촬상시스템은 고계수율 영역에서 안정된 동작을 한 전자 시스템으로 불감시간이 약 6%로 감소되고 계측시간의 경우도 1 점 당 3초로 단축되었다. 또한 재구성 알고리즘의 효율화를 증명하였고, 메모리와 계산량을 약 1/100로 감소시켰다. 물리적 phantom으로 그 정량성을 확인하였고, 시험관내의 갑상선의 화상으로부터 요드 분포를 추정하였다. 이러한 결과는 생체내에서 형광 X선 CT 계측의 실현 가능성을 보여준 것이다.

• Journal of Magnetics
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• 제21권4호
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• pp.593-598
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• 2016

In order to reduce the amount of noise component in X-ray imaging system, various reduction techniques were frequently used in the field of diagnostic imaging. Although the previous techniques -such as median, Wiener filters and Anscombe noise reduction technique - were able to reduce the noise, the edge information was still damaged. In order to cope with this problem, total variation (TV) noise reduction technique has been developed and researched. The purpose of this study was to evaluate and compare the image quality using normalized noise power spectrum (NNPS) and contrast-to-noise ratio (CNR) through simulations and experiments with respect to the above-mentioned noise reduction techniques. As a result, not only lowest NNPS value but also highest CNR values were acquired using a TV noise reduction technique. In conclusion, the results demonstrated that TV noise reduction technique is proved as the most practical method to ensure accurate denoising in X-ray imaging system.

• 대한디지털의료영상학회논문지
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• 제13권1호
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• pp.27-32
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• 2011

The conventional types of X-ray generators were bulky in physical size and heavy in weight, and the control accuracies of the output voltages were not always satisfactory. The high frequency switching inverter and converter technology on power conversion and control systems have been greatly closed up introducing power semiconductor devices. To decreasing the volume and the weight of high voltage transformer, and to stabilize ripple. In this paper, the newly developed x-ray generator in a low cost using duty modulation PWM inverter. This system verify improved performance by stabilize ripple of X-ray tube voltage and compared the reproducibility, linearity and dose in single phase, three phase and PSU.

• 한국방사선학회논문지
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• 제1권1호
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• pp.11-16
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• 2007

본 연구에서는 a-Se 기반 디지털 X-선 영상장치의 저대조도 특성을 평가하기 위하여 contrast-detail 곡선 해석을 수행하였다. 본 실험에 사용된 X-선 영상장치는 픽셀크기가 $139mm{\times}139mm$이고 유효면적이 $46.7cm{\times}46.7cm$인 a-Si TFT 기판 위에 500mm 두께의 광전도체가 코팅된 구조를 갖고 있다. Contrast-detail 곡선을 측정하기 위하여 우선 주어진 촬영조건(즉, 40, 50, 60, 70, 80 kVp, and 16 mA.s)에서 상용 팬톰인 CDRAD 2.0을 사용하여 X-선 영상을 획득한 후, 그 영상으로부터 IQFinv 인자를 사용하여 그 특성을 최종 평가하였다. 평가된 IQFinv 값은 주어진 광 플루언스(즉, $1.8{\times}105$, $5.9{\times}105$, $11.3{\times}105$, $19.4{\times}105$, and $29.4{\times}105$ photons/$mm^2$)에서 각각 24.4, 35.3, 39.2, 41.5, 43.4으로 광 플루언스가 증가할수록 점진적으로 증가하였으며 이는 광 플루언스가 증가할수록 영상의 가독성이 향상됨을 나타낸다.

• 비파괴검사학회지
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• 제19권3호
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• pp.217-232
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• 1999

The ability to see the internal organs of the human body in a noninvasive way is a powerful diagnostic tool of modern medicine. Among these imaging modalities such as X-ray, MRI, and ultrasound. MRI and ultrasound are presenting much less risk of undesirable damage of both patient and examiner. In fact, no deleterious effects have been reported as a result of clinical examination by using MRI and ultrasound diagnostic equipment. As a result. their market volume has been rapidly increased. MRI has a good resolution. but there are a few disadvantages such as high price. non-real-time imaging capability. and expensive diagnostic cost. On the other hand, the ultrasound imaging system has inherently poor resolution as compared with X-ray and MRI. In spite of its poor resolution, the ultrasound diagnostic equipment is lower in price and has an ability of real-time imaging as compared with the others. As a result. the ultrasound imaging system has become general and essential modality for imaging the internal organs of human body. In this review various researches and developments to enhance the resolution of the ultrasound images are explained and future trends of the ultrasound imaging technology are described.

• Journal of Astronomy and Space Sciences
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• 제21권4호
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• pp.329-342
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• 2004

In this paper, we present preliminary feasibility studies on three types of solar observation payloads for future Korean Science and Technology Satellite (STSAT) programs. The three candidates are (1) an UV imaging telescope, (2) an UV spectrograph, and (3) an X-ray spectrometer. In the case of UV imaging telescope, the most important constraint seems to be the control stability of a satellite in order to obtain a reasonably good spatial resolution. Considering that the current pointing stability estimated from the data of the Far ultraviolet Imaging Spectrograph (FIMS) onboard the Korean STSAT-1, is around 1 arc minutes/sec, we think that it is hard to obtain a spatial resolution sufficient for scientific research by such an UV Imaging Telescope. For solar imaging missions, we realize that an image stabilization system, which is composed of a small guide telescope with limb sensor and a servo controller of secondary mirror, is quite essential for a very good pointing stability of about 0.1 arcsec. An UV spectrograph covering the solar full disk seems to be a good choice in that there is no risk due to poor pointing stability as well as that it can provide us with valuable UV spectral irradiance data valuable for studying their effects on the Earth's atmosphere and satellites. The heritage of the FIMS can be a great advantage of developing the UV spectrograph. Its main disadvantage is that two major missions are in operation or scheduled. Our preliminary investigations show that an X-ray spectrometer for the full disk Sun seems to be the best choice among the three candidates. The reasons are : (1) high temporal and spectral X-ray data are very essential for studying the acceleration process of energetic particles associated with solar flares, (2) we have a good heritage of X-ray detectors including a rocket-borne X-ray detector, (3) in the case of developing countries such as India and Czech, solar X-ray spectrometers were selected as their early stage satellite missions due to their poor pointing stabilities, and (4) there is no planned major mission after currently operating Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) mission. Finally, we present a preliminary design of a solar X-ray spectrometer covering soft X-ray (2 keV) to gamma ray (10 MeV).

• International Journal of Precision Engineering and Manufacturing
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• 제9권4호
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• pp.86-100
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• 2008

This article reviews the development of flat-panel detectors for digital radiography based on amorphous materials, Important design parameters and developments are described for the two main components of flat-panel detectors: the X-ray converter and the readout pixel array. This article also introduces the advanced development concepts of new detectors. In addition, the cascaded linear systems method is reviewed because it is a very powerful tool for improving the design and assessment of X-ray imaging detector systems.

• 치과방사선
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• 제29권2호
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• pp.387-396
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• 1999

In dentistry. RadioVisioGraphy was introduced as a first electronic dental x-ray imaging modality in 1989. Thereafter. many types of direct digital radiographic system have been produced in the last decade. They are based either on charge-coupled device(CCD) or on storage phosphor technology. In addition. new types of digital radiographic system using amorphous selenium. image intensifier etc. are under development. Advantages of digital radiographic system are elimination of chemical processing, reduction in radiation dose. image processing, computer storage. electronic transfer of images and so on. Image processing includes image enhancement. image reconstruction. digital subtraction, etc. Especially digital subtraction and reconstruction can be applied in many aspects of clinical practice and research. Electronic transfer of images enables filmless dental hospital and teleradiology/teledentistry system. Since the first image management and communications system(IMACS) for dentomaxillofacial radiology was reported in 1992. IMACS in dental hospital has been increasing. Meanwhile. researches about computer-assisted diagnosis, such as structural analysis of bone trabecular patterns of mandible. feature extraction, automated identification of normal landmarks on cephalometric radiograph and automated image analysis for caries or periodontitis. have been performed actively in the last decade. Further developments in digital radiographic imaging modalities. image transmission system. imaging processing and automated analysis software will change the traditional clinical dental practice in the 21st century.