• Journal of the Korean Society of Radiology
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• 제10권2호
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• pp.109-115
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• 2016

Despite of increasing the use of the digital imaging device in the radiology area, the setting on the optimal irradiation conditions are insufficient. In this study, the exposure dose and image quality by exposure condition of digital radiography device were compared. The exposure doses were obtained by adjusting the exposure condition as 5 steps respectively based on the exposure conditions that are currently used of CR and DR radiography devices. The acquired image has been assessed by 20 medical image professors using the assessment method of the Japanese Society for Tuberculosis Prevent. As a result, in the case of the CR system, the better image quality was obtained in the condition of 120 kVp and 1.5 mAs~2.4 mAs (quality score 91~95.5 points) than standard exposure condition(110 kVp, 3.2 mAs, 86 points). And exposure dose was evaluated as low with $61.3{\sim}98.4{\mu}Gy$ than standard condition($105.11{\mu}Gy$). In DR system, however, the image quality score was higher as 97~98.6 points in the lower tube voltage range (112 kVp, 2.4~3.2 mAs) condition than the standard exposure condition (125 kVp, 3.2 mAs, 91 points). In addition, the exposure dose was $61.5-77.2{\mu}Gy$ lower than standard condition($93{\mu}Gy$). In addition, the exposure dose was low as $61.5-77.2{\mu}Gy$ than standard condition($93{\mu}Gy$). With the results of this study, we confirmed that it is possible to reduce the patient exposure dose with the same image quality by adjusting the optimal exposure condition of digital device.

• Journal of radiological science and technology
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• 제26권4호
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• pp.39-46
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• 2003

Digital radiographic systems based on solid-state detectors, commonly referred to as flat-panel detectors, are gaining popularity in clinical practice. Large area, flat panel solid state detectors are being investigated for digital radiography. The purpose of this work was to evaluate the active matrix flat panel digital x-ray detectors in terms of their modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). In this paper, development and evaluation of a selenium-based flat-panel digital x-ray detector are described. The prototype detector has a pixel pitch of $139\;{\mu}m$ and a total active imaging area of $14{\times}8.5\;inch^2$, giving a total 3.9 million pixels. This detector include a x-ray imaging layer of amorphous selenium as a photoconductor which is evaporated in vacuum state on a TFT flat panel, to make signals in proportion to incident x-ray. The film thickness was about $500\;{\mu}m$. To evaluate the imaging performance of the digital radiography(DR) system developed in our group, sensitivity, linearity, the modulation transfer function(MTF), noise power spectrum (NPS) and detective quantum efficiency(DQE) of detector was measured. The measured sensitivity was $4.16{\times}10^6\;ehp/pixel{\cdot}mR$ at the bias field of $10\;V/{\mu}m$ : The beam condition was 41.9\;KeV. Measured MTF at 2.5\;lp/mm was 52%, and the DQE at 1.5\;lp/mm was 75%. And the excellent linearity was showed where the coefficient of determination ($r^2$) is 0.9693.

• The Journal of the Korean dental association
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• 제55권8호
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• pp.516-526
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• 2017

Objective: To suggest diagnostic reference levels (DRLs) for dental panoramic radiography in adults and children through the nationwide survey in Korea. Materials and Methods: Two hundred twelve dental institutions on a national basis were visited. The radiographic examination protocols were surveyed and their patient doses at the clinical exposure setting for adult and children (5- and 10-year old) were measured at 244 panoramic radiographic equipment. The measured DAP were analyzed and compared according to age group, the size of hospital, the type of radiographic system, the installation duration of equipment. Results: The mean exposure parameters were 70.1 kV, 9.2 mA, 14.4 second for adult and 66.6 kV, 7.9 mA, 13.8 second for 10-year old child and 65.5 kV, 7.3 mA, 13.7 second for 5-year old child. The mean and third quartile patient DAPs were $138.3mGy\;cm^2$ and $151.0mGy\;cm^2$ for adult, $99.5mGy\;cm^2$ and $104.8mGy\;cm^2$ for 10-year old child and $89.5mGy\;cm^2$ and $95.5mGy\;cm^2$ for 5-year old child. The mean patient dose at the university dental hospital was lower than that at the dental clinic (p<0.05). The mean patient dose of direct digital radiography type was higher than that of film-based type. However, the difference did not show statistically significance. Conclusion: DRLs for dental panoramic radiography in adult, 10- and 5-year old child were suggested to be $151mGy\;cm^2$, $105mGy\;cm^2$, and $96mGy\;cm^2$ in Korea based on this nationwide survey.

• Journal of the Institute of Electronics Engineers of Korea SC
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• 제40권3호
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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.

• Progress in Medical Physics
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• 제19권4호
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• pp.201-208
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• 2008

Physical evaluations provide the basis for an objective and quantitative analysis of the image quality. Nonetheless, there are limitations in using physical evaluations to judge the utility of the image quality if the observer's subjectivity plays a key role despite its imprecise and variable nature. This study proposes a new method for objective and quantitative evaluation of image quality to compensate for the demerits of both physical and subjective image quality and combine the merits of them. The images of chest phantom were acquired from four digital radiography systems on clinic sites. The physical image quality was derived from an image analysis algorithm in terms of the contrast-to-noise ratio (CNR) of the low-contrast objects in three regions (lung, heart, and diaphragm) of a digital chest phantom radiograph. For image analysis, various image processing techniques were used such as segmentation, and registration, etc. The subjective image quality was assessed by the ability of the human observer to detect low-contrast objects. Fuzzy integral was used to integrate them. The findings of this study showed that the physical evaluation did not agree with the subjective evaluation. The system with the better performance in physical measurement showed the worse result in subjective evaluation compared to the other system. The proposed protocol is an integral evaluation method of image quality, which includes the properties of both physical and subjective measurement. It may be used as a useful tool in image evaluation of various modalities.

• Journal of radiological science and technology
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• 제39권1호
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• pp.13-17
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• 2016

In this study, standard model of medical radiation dosage quality control system will be suggested and the useful of this system in clinical field will be reviewed. Radiation dosage information of modalities are gathered from digital imaging and communications in medicine(DICOM) standard data(such as DICOM dose SR and DICOM header) and stored in database. One CT scan, two digital radiography modalities and two mammography modalities in one health promotion center in Seoul are used to derive clinical data for one month. After 1 months research with 703 CT scans, the study shows CT $357.9mGy{\cdot}cm$ in abdomen and pelvic CT, $572.4mGy{\cdot}cm$ in brain without CT, $55.9mGy{\cdot}cm$ in calcium score/heart CT, screening CT at $54mGy{\cdot}cm$ in chest screening CT(low dose screening CT scan), $284.99mGy{\cdot}cm$ in C-spine CT and $341.85mGy{\cdot}cm$ in L-spine CT as health promotion center reference level of each exam. And with 1955 digital radiography cases, it shows $274.0mGy{\cdot}cm2$ and for mammography 6.09 mGy is shown based on 536 cases. The use of medical radiation shall comply with the principles of justification and optimization. This quality management of medical radiation exposure must be performed in order to follow the principle. And the procedure to reduce the radiation exposure of patients and staff can be achieved through this. The results of this study can be applied as a useful tool to perform the quality control of medical radiation exposure.

• Korean Journal of Digital Imaging in Medicine
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• 제6권1호
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• pp.24-30
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• 2003

Flat-panel detector(FPD) is the driving force for realizing the next gene ration of x-ray system. In this study, we developed amorphous selenium(a-Se) based flat-panel digital X-ray detector(DXD) for radiography. The prototype detector consists of an amorphous selenium layer and a thin-film transistor(TFT) array. Comparing to other papers1)-4), optimization of amorphous selenium and progress of evaporation were similar. The pixel pitch of fabricated detector was $139{\mu}m$, fill factor was 86%, and the size was 14"${\times}$8.5". Hand and test bar pattern images were acquired. A high modulation transfer function(MTF) factor was obtained: 58% at 3.0 lp/mm.

• Journal of radiological science and technology
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• 제36권1호
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• pp.1-10
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• 2013

IEC publications have applied in many countries all over the world such as Europe or Japan and these also have been published as in dustrial standards (KS) and notifications of Korea Food and Drug Administration (KFDA) in Korea. As the general standard of IEC 60601 series for medical electric (ME) equipment was revised as $3^{rd}$ edition in 2005, additional and particular standards have been revised or established newly. Under these circumstances, it is importance for manufacturing and assembling companies or authorized testing companies to understand the trend for revisions of IEC publications. Therefore in this study, the latest version of 3 IEC standards related to medical X-ray equipment : IEC 60601-2-44 for X-ray equipment for computed tomography (CT), IEC 60601-2-45 for mammographic X-ray equipment and IEC 60601-2-54 for X-ray equipment for radiography or radioscopy were covered and analyzed for trends and features accompanied by revision based on IEC 60601-1 $3^{rd}$ Ed. As KFDA notifications in force have referred to the particular standards based on 2nd edition of IEC 60601-1, those revised version of 3 particular standards were compared to KFDA notifications in force. The features of the latest standards applying IEC 60601-1 $3^{rd}$ Ed were shown as following: 1) Requirements for mechanical hazards, especially (motorized) moving parts were emphasized. 2) Indication and recording of patient dose were required. 3) Risk management process was introduced and enabled to monitor potential risks systematically. 4) DR system (digital radiography system) as well as analogue system (film-screen system) was included in the scope. Presently, KFDA will revise the notifications applying the particular standards based on IEC 60601-1 $3^{rd}$ Ed in a few years. Therefore the features of particular standards applying IEC 60601-1 $3^{rd}$ Ed was expected to help manufacturers, assemblers or testing companies of medical electric equipment understand IEC publications or KFDA notifications slated to be published.

• Proceedings of the KIEE Conference
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(II)
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• pp.1313-1316
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• 1987

Bone and tissue, the major components of human body, can be separated by Dual Energy Method. We present a basic idea to this technique, and discuss the experimental procedure and result. The basic system is the Digital Radiography System which was developed in Dep. of Biomedical Eng. in Seoul National University Hospital.

• Journal of the Korean Society of Radiology
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• 제2권2호
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• pp.23-30
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• 2008

X-ray microscopy with synchrotron radiation(SR) might be a useful tool for novel x-ray imaging in the clinical and laboratory settings. Microscopically, it enables us to observe detailed structure of animal organs samples with a great magnification power and an excellent resolution. The phase contrast mechanisms in image by X-ray are described. The phase-contrast X-ray imaging with SR from in-vivo and in-vitro mouse tail, rat nerve and rat lung were obtained with an 8 KeV monochromatic beam. The visual image was magnified using 10x microscope objective lens and captured using an digital CCD camera. The results showed more structural details and high resolution images with SR imaging system than conventional X-ray radiography system. The SR imaging system may have a potential for imaging in biological researches, material applications and clinical radiography.