• Imaging Science in Dentistry
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• 제48권3호
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• pp.167-176
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• 2018

Purpose: In the age of X-ray computed tomography (CT) and digital volume tomography (DVT), with their outstanding post-processing capabilities, indications for planar radiography for the study of the dentition of ancient Egyptian mummies may easily be overlooked. In this article, the advantages and limitations of different approaches and projections are discussed for planar oral and maxillofacial radiography using portable digital X-ray equipment during archaeological excavations. Furthermore, recommendations are provided regarding projections and sample positioning in this context. Materials and Methods: A total of 55 specimens, including 19 skeletonized mandibles, 14 skeletonized skulls, 18 separate mummified heads, and 4 partially preserved mummies were imaged using portable digital X-ray equipment in the course of archaeological excavations led by the University of Basel in the Valley of the Kings between 2009 and 2012. Images were evaluated by 2 authors with regard to the visibility of diagnostically relevant dental structures using a 4-point grading system(Likert scale). Results: Overall, the visibility of diagnostically relevant dental structures was rated highest by both authors on X-ray images acquired using a dental detector. The tube-shift technique in the lateral projections of mandibular dentition achieved the second-best rating, and lateral projections achieved the third-best rating. Conclusion: Conventional planar digital X-ray imaging, due to its ubiquity, remains an excellent method-and often the only practicable one-for examining the skulls and teeth of ancient Egyptian mummies under field conditions. Radiographic images of excellent diagnostic quality can be obtained, if an appropriate methodology regarding the selected projections and sample placement is followed.

• 한국의학물리학회지:의학물리
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• 제32권1호
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• pp.1-17
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• 2021

The evolution of X-ray computed tomography (CT) has been based on the discovery of X-rays, the inception of the Radon transform, and the development of X-ray digital data acquisition systems and computer technology. Unlike conventional X-ray imaging (general radiography), CT reconstructs cross-sectional anatomical images of the internal structures according to X-ray attenuation coefficients (approximate tissue density) for almost every region in the body. This article reviews the essential physical principles and technical aspects of the CT scanner, including several notable evolutions in CT technology that resulted in the emergence of helical, multidetector, cone beam, portable, dual-energy, and phase-contrast CT, in integrated imaging modalities, such as positron-emission-tomography-CT and single-photon-emission-computed-tomography-CT, and in clinical applications, including image acquisition parameters, CT angiography, image adjustment, versatile image visualizations, volumetric/surface rendering on a computer workstation, radiation treatment planning, and target localization in radiotherapy. The understanding of CT characteristics will provide more effective and accurate patient care in the fields of diagnostics and radiotherapy, and can lead to the improvement of image quality and the optimization of exposure doses.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.328-328
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• 2007

Large area matrix-addressed image detectors are a recent technology for x-ray imaging with medical diagnostic and other applications. The imaging properties of x-ray pixel detectors depend on the quantum efficiency of x-rays, the generated signal of each x-ray photon and the distribution of the generated signal between pixels. In a phosphor coated detector the light signal is generated by electrons captured in the phosphor screen. In our study we simulated the lateral spread distributions for phosphor coupled detector by Monte Carlo simulations. Most simulations of such detectors simplify the setup by only taking the conversion layer into account neglecting behind. The Monte Carlo code MCNPX has been used to simulate the complete interaction and subsequent charge transport of x-ray radiation. This has allowed the analysis of charge sharing between pixel elements as an important limited factor of digital x-ray imaging system. The parameters are determined by lateral distribution of x-ray photons and x-ray induced electrons. The primary purpose of this study was to develop a design tool for the evaluation of geometry factor in the phosphor coupled optical imaging detector. In order to evaluate the spatial resolution for different phosphor material, phosphor geometry we have developed a simulation code. The developed code calculates the energy absorption and spatial distribution based on both the signal from the scintillating layer and the signal from direct detection of x-ray in the detector. We show that internal scattering contributes to the so-called spatial resolution drop of the image detector. Results from the simulation of spatial distribution in a phosphor pixel detector are presented. The spatial resolution can be increased by optimizing pixel size and phosphor thickness.

• 대한방사선기술학회지:방사선기술과학
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• 제42권5호
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• pp.365-371
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• 2019

We have developed and applied a diagnostic Multi-Leaf Collimator (MLC) to optimized the X-ray field in medical imaging and the usefulness evaluated through the fusion of infrared image and X-ray image acquired by infrared camera. The hand and skull radiography with multi-leaf collimator(MLC) showed significant area dose reductions of 22.9% and 31.3% compared to ARC and leakage dose was compliant with KS A 4732. Also scattering doses of 50 cm and 100 cm showed a significant decrease to confirm the usefulness of MLC. It was confirmed that the fusion of infrared images with an adjustable degree of transparency was possible in the X-ray images. Therefore, fusion of anatomical information with physiological convergence is expected to contribute and improvement of diagnostic ability. In addition, the feasibility of convergence X-ray imaging and DITI devices and the possibility of driving MLC with infrared images were confirmed.

• 대한의용생체공학회:의공학회지
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• 제25권4호
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• pp.253-259
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• 2004

본 연구에서는 디지털 X-선 영상시스템의 최적화 설계를 위하여 몬테카를로 방법을 이용한 영상모의실험용 코드를 visual $C^{++}$ 프로그래밍 언어를 사용하여 개발하였다. 디지털 X-선 영상시스템으로 Gd$_2$O$_2$S(Tb) 섬광체 및 광센서 어레이를 고려하였으며, 일반적인 실험 환경을 모사하기 위해 2차원 평행 그리드를 포함시켰다. X-선과 피사체, 그리드 및 섬광체와의 반응, 그리고 섬광체에서 발생된 빛의 거동 및 광센서 어레이에서의 수집을 몬테카를로 방법을 이용하여 모사하였다. Gd$_2$O$_2$S(Tb) 섬광체의 두께는 66$\mu\textrm{m}$로 설정하였으며, 광센서 어레이의 픽셀 피치는 48$\mu\textrm{m}$ 그리고 픽셀의 포맷은 256${\times}$256으로 가정하였다. 다양한 모의실험조건에서 X-선 영상을 획득한 후 객관적인 영상시스템의 성능평가 지표인 SNR(signal-to-noise ratio), MTF(modulation transfer function), NPS(noise power spectrum), DQE(detective quantum efficiency) 등을 계산하였으며, 이를 통해 화질을 평가하였다. 본 연구에서 개발된 영상모의실험 코드는 다양한 디지털 X-선 영상시스템에 대해 여러 설계변수들에 대한 성능을 예측함으로써 영상시스템 최적설계에 활용될 수 있다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.94-95
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• 1998

We developed a digital x-ray medical imaging system using commercially available amorphous silicon image sensor plate. The image readout could be accomplished within 3.5 sec after radiation exposure and be displayed on a monitor through computer interface. This system needs not the conventional x-ray films and film processors, and also provides digital radiographic images. This system is the fastest digital radiography system developed so far, and expected to replace many of the conventional x-ray film systems or digital radiography systems.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2006년도 제33회 추계학술대회 발표논문집
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• pp.47-47
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• 2006

• 대한디지털의료영상학회논문지
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• 제12권1호
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• pp.19-25
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• 2010

This study is mainly for the reduction of exposure dose by using a heavy elements filter(Gd) in the digital radiology. They contained heavy elements filter of Gd and X-ray beam hardening filters such as Al and Cu. According to the results of experimental evaluation, X-ray property was not changed with variety of kVp in the case of the Gd filter. The surface dose and absorption dose were increased in order of Cu and Al. The contrast of image showed the higher value in order of Cu, Al and Gd. While the use of Gd has increased the numerical value of the CR image, and grayscale has decreased noise value of the DR image.

• 대한의용생체공학회:의공학회지
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• 제17권2호
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• pp.165-172
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• 1996

A scanning slot digital mammography system Luing a plastic scintillating fiber screen (SFS) is currently being developed To improve the x-ray interaction efficiency and absorption efficiency of an SFS, high Z elements can be added into the scintillating fiber core. In this paper, we investigated theoretically the zero spatial frequency detective quantum efficiency, DQE(0), and modulation transfer function, MTF(f), of three 2 cm thick SFSs made of polystyrene, polystyrene loaded with 5% by weight of lead, and polystyrene Loaded with 10% by weight of tin scintillating fibers. X-ray interaction efficiency, scintillating light intensity distributions and line spread functions were generated using Monte Carlo simulation. DQE(0) and MTF(f) were computed for x-ray energies ranging from 15 to 50 keV. Loading high Z elements into the SFS markedly increased the DQE(0). For x-ray energies used for mammovaphy, DQE(0) values of both high Z element loaded SFSs are about a factor of three higher than the DQE(0) of an Min-R screen. At mammographic x-ray energies, MTF(f) values of all three SFSs are Venter than 50% at 25 Ip/mm spatial frequency, and were found to be dominated by the 20 um individual scintillating fiber diameter used The results show that both hiP DQE(0) and spatial resolution can be achieved with the high Z element loaded SFSs, which make these SFSs attractive for use in a scanning slot detector for digital mammography.

• 한국방사선학회논문지
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• 제2권4호
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• pp.33-40
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• 2008

의료영상 시스템을 통해 볼 수 있는 모든 X-선 영상은 피사체 본래의 특성만이 표현된 영상이 아닌 그 영상시스템 고유의 특성이 반영된 영상이라 할 수 있다. 영상화질에서 시스템에 의한 열화는 시스템응답함수인 변조전달 함수(modulation transfer function; MTF)로 설명되며 잡음력 스펙트럼(noise power spectrum; NPS)으로 설명할 수 있다. 이 때, 열화된 영상은 영상시스템의 MTF와 NPS를 정확하게 측정함으로써 그 시스템의 특성에 따라 설계된 필터에 의해 원영상에 가깝게 복원(restoration)될 수 있다. 본 논문에서는, 영상복원 시뮬레이션을 통해 기존의 직접 역필터링(direct-inverse filtering), 제한된 역필터링(limited-inverse filtering), 위너 필터링(Wiener filtering) 기법을 바탕으로 열화된 영상을 원 영상에 가깝도록 복원하고 복원영상의 화질을 정량적으로 평가하였다.