• Imaging Science in Dentistry
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• v.40 no.4
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• pp.155-158
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• 2010

Digital radiographic systems allow the implementation of a fully digital picture archiving and communication system (PACS), and provide the greater dynamic range of digital detectors with possible reduction of X-ray exposure to the patient. This article reviewed the basic physical principles of digital radiographic imaging system in dental clinics generally. Digital radiography can be divided into computed radiography (CR) and direct radiography (DR). CR systems acquire digital images using phosphor storage plates (PSP) with a separate image readout process. On the other hand, DR systems convert X-rays into electrical charges by means of a direct readout process. DR systems can be further divided into direct and indirect conversion systems depending on the type of X-ray conversion. While a direct conversion requires a photoconductor that converts X-ray photons into electrical charges directly, in an indirect conversion, lightsensitive sensors such as CCD or a flat-panel detector convert visible light, proportional to the incident X-ray energy by a scintillator, into electrical charges. Indirect conversion sensors using CCD or CMOS without lens-coupling are used in intraoral radiography. CR system using PSP is mainly used in extraoral radiographic system and a linear array CCD or CR sensors, in panoramic system. Currently, the digital radiographic system is an important subject in the dental field. Most studies reported that no significant difference in diagnostic performance was found between the digital and conventional systems. To accept advances in technology and utilize benefits provided by the systems, the continuous feedback between doctors and manufacturers is essential.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.12
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• pp.247-253
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• 2013

The purpose is a comparative evaluation in the DR System according to the dosimetry and image quality of the quantitative and objective via Direct digital radiography, Indirect digital radiography, Image intensifier (Charge Coupled Device type) digital radiography. The experimental method used rando phantom and measured the entrance surface dose. And through using the measured entrance surface dose and then using the PCXMC program were evaluated risk due to irradiation and the effective dose. SNR and NPS and CNR were measured and analyzed by using 21cm acryl phantom. Significance of measured value was evaluated by statistics method. Entrance surface dose, major organ dose, effective dose all of them were measured the lowest rated in direct DR when it is on the basis of direct DR dose, high-dose ratio were measured in I.I DR approximately 1.3 times, indirect DR approximately 2.4 times. Risk in accordance with radiation also was measured same as dose ratio. On the conclusion that SNR measurement result based on direct DR SNR measurements, low-SNR ratio were measured in I.I DR approximately 7.25 times, indirect DR approximately 1.48 times. On the conclusion that CNR measurement result based on direct DR CNR measurements, high-dose ratio were measured in I.I type DR approximately 1.16 tims and low-dose ratio were measured in indirect DR approximately 0.87 times. Therefore Direct DR system using a-selenium sensing element to detect x-ray photon is thought effectively at the examination such as infant to sensitive irradiation and the genital gland. Because quality image is built by low dose. Also when it is necessary that image test requiring many diagnosis information, indirect DR system is thought effectively.

• Journal of the Korean Society of Radiology
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• v.4 no.1
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• pp.25-30
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• 2010

The objective of this study was to compare the resolution and density appropriate to diagnosis in chest PA radiography. In comparing the resolution, we radiographed with conventional radiography, computed radiography(CR) and digital radiography(DR) using the linear resolution phantom(Nuclear Associates-Carle Place. N.Y.). 2 radiologists and 3 radiological technologists read the resolution value by the blind test. DR, conventional radiography and CR measured 3.95, 3.58, 3.48 resolution value respectively. In analysing the density, we chose the fifty normal chest CR and DR and conventional film. We estimated the density using by densitometer(X-rite company-Model 301) in seven regions(lung field, lung field margine, mediastinum I, mediastinum II, heart shadow I, heart shadow II, diaphragm) of chest film. We adapted to analysis the Japanese chest X-ray evaluating method and table. It was scored 0(farthest density value) to 2(nearest density value). DR scored 2 at mediastinum I, mediastinum II, heart shadow I, heart shadow II and diaphragm. On the contrary with, CR scored 2 at lung field and lung field margine. Consequently, DR superior than CR and conventional radiography film compairing density and resolution. It was due to small pixel size and post processing algorithm with digital radiography.

• Journal of Advanced Navigation Technology
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• v.15 no.5
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• pp.833-838
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• 2011

X-ray device used in the diagnosis has made possible to have more effective and accurate diagnosis, powered by the development of various devices. Based on this, X-ray device has become the most basic and essential diagnostic equipment in clinical medicine. At present, in the image acquisition field using X-ray, the use of Digital radiography which is useful in the acquisition time reduction and transfer of images and is possible to have the dose reduction has expanded. With the structure using one detector, this DR device has disadvantages in that it needs structural changes unlike existing X-ray and the detector should be moved to the desired position depending on the shooting location. Therefore, in this study, using BLDC(Brushless direct current) motor and PID(Proportional integral differential) control method, the automatic control system of 3-axis which is upward and downward, left and right and rotation of detector where having the most movement in DR was designed and produced and its performance was evaluated.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.69-69
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• 2003

Flat panel based digital radiography (DR) systems have recently become useful and important in the field of diagnostic radiology. For DRs with amorphous silicon photosensors, CsI(TI) is normally used as the scintillator, which produces visible light corresponding to the absorbed energy. The visible light photons are converted into an electric signal in the amorphous silicon photodiode. In order to produce good quality images, we need to understand the detailed behavior of DR detectors in radiation. We, therefore, investigated the relationship between DR outputs and X -ray in terms of absorbed energy, using the SPEC-78, X-ray energy spectrum model. We calculated the total filtration of X-ray equipment measuring air exposure and this value was used in the calculation of absorbed energy. The relationship between DR output and the absorbed energy of the X-ray was obtained by matching the absorbed energy with pixel values of real images under various conditions. It was found that the relationship between these two values was almost linear. The results were verified using phantoms made of water and aluminium. The pixel value of the phantom image was estimated and compared with previous results under various conditions. The estimated pixel value coincided with the results, although the effect of scattered photons introduced some errors.

• Journal of the Korean Society of Radiology
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• v.10 no.2
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• pp.117-124
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• 2016

The purpose of this study was tried to evaluate the filling sodium states inside the fuel rod of sodium-cooled fast reactor by digital medical X-ray. We used the diagnostic X-ray generators in digital radiography (DR). This study have found the optimal conditions by changing the effective focal spot size of X-ray tube and post-processing of the DR method with a tungsten edge plate in order to ensure excellent sharpness At this time, the sharpness and resolution were evaluated using the MTF (modulation transfer function). As a result, this study obtained a spatial resolution of 3.871 lp/mm (0.1 MTF), 3.290 lp/mm (0.5 MTF) when implemented the contrast strengthen post-processing in small focal spot. In this research, the result is able to evaluate the level of sodium inside the fuel rod by using the diagnostic X-ray generators in medical digital radiographic images.

• Journal of the Korean Society of Radiology
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• v.1 no.1
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• pp.31-37
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• 2007

The purpose of this research was to compare and analyze image quality for each Detector of CR(Computed Radiography) and DR(Digital Radiography). The results showed that CR(AGFA MD 4.0 General plate, JAPAN) was superior to DR(HOLOGIC nDirect Ray, USA) based on the quantitative values and comparison of MTF(Modulation Transfer Function), NPS(Noise Power Spectrum), Photon fluence and DQE(Detective Quantum Efficiency) which have been widely accepted for the estimation of CR and DR. Quantitative evaluations of CR and DR system were obtained and they may be very helpful for QA and QC of general X-ray systems.

• Journal of radiological science and technology
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• v.35 no.4
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• pp.309-314
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• 2012

Nowadays, digital Radiography (DR) systems are widely used in clinical sites and substitute the analog-film x-ray imaging systems. The resolution of DR images depends on several factors such as characteristic contrast and motion of the object, the focal spot size and the quality of x-ray beam, x-ray scattering, the performance of the DR detector (x-ray conversion efficiency, the intrinsic resolution). The DR detector is composed of an x-ray capturing element, a coupling element and a collecting element, which systematically affect the system resolution. Generally speaking, the resolution of a medical imaging system is the discrimination ability of anatomical structures. Modulation transfer function (MTF) is widely used for the quantification of the resolution performance for an imaging system. MTF is defined as the frequency response of the imaging system to the input of a point spread function and can be obtained by doing Fourier transform of a line spread function, which is extracted from a test image. In clinic, radiologic technologists, who are in charge of system maintenance and quality control, have to evaluate or make routine check on their imaging system. However, it is not an easy task for the radiologic technologists to measure MTF accurately due to lack of their engineering and mathematical backgrounds. The objective of this study is to develop and provide for radiologic technologists a medical system imaging evaluation tool, so that they can measure and quantify system performance easily.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.389-392
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• 2002

Digital radiography (DR) is being developed for numerous applications in medical imaging. For understanding DR image, it is necessary to comprehend DR responses to X-ray in terms of absorbed energy. This study reports on the relationship of absorbed energy in the scintillator vs. pixel value of detector. Pixel value and exposure were measured from 50 kVp to 120 kVp until the detector was saturated. For representing radiation produced at the X-ray tube, we used program Srs-78 and compared experimental exposure with calculated exposure. Absorbed energy was acquired using spectrum and we got the relation between the two values.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.12
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• pp.120-127
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• 2016

In order to acquire digital x-ray images, developing radiography detectors have been recently conducted based on the DR (digital radiography) technology. The noise property of the radiography detector can be observed from measuring the NNPS (normalized noise power spectrum) using uniform exposure images. Here, the image difference of two images is used to remove the fixed pattern noise in measuring the detector NNPS. In this paper, two average images are first calculated using several images and then their difference is used to calculate an NNPS value. Here, the obtained NNPS value is usually lower than the true detector NNPS due to the average. Hence, a compensation constant, which is a function of the number of used images, is also proposed to compensate the NNPS value to obtain the true detector NNPS. Furthermore, another measurement method, in which the ratio of the average images is used, is proposed. Through NNPS measuring experiments using real x-ray images, it is observed that the proposed method can provide further accurate NNPS measurements.