• Journal of radiological science and technology
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• v.26 no.3
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• pp.7-11
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• 2003

Currently, many hospitals are hastening to introduce digital radiography systems. This is a direct result of the intentions to improve medical services and to digitalize radiology information systems, and is also leading to the improvement of medical imaging technology. Throughout F/S system's long history, many people have researched the image quality and dosage concerning these systems, and as a result, huge improvements in the dosage of patients were possible. Similarly, I believe that DR systems need the same kind of effort. Of course, decreases in dosage that ignore image quality are unthinkable. The results of experiments conducted by five hospitals during a period of 3 months brought to us the conclusions listed below. 1. Based on the comparison and analysis of the exposure control of F/S systems and DR systems, DR systems generally showed higher exposure control for parts of the phantom that became thicker, and the exposure control improved rapidly as the thickness increased. 2. DR systems still proved to be somewhat deficient in resolution measurements compared to existing F/S systems. The image processing part of DR systems contributed much to these result. 3. Under conditions used clinically, the dosage measurements of DR systems were generally higher regardless of region. 4. According to the evaluation of image quality, DR systems showed a higher degree of satisfaction as the thickness of the region became thinner. As mentioned above and based on the mutual relationship experiments between the dosage and image quality of F/S systems and DR systems, research to increase the satisfaction of DR systems must be considered.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.1
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• pp.59-65
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• 2004

Root perforations that result in a communication of the root space with the periodontal tissues occasionally occur during endodontic procedures. They may be induced iatrogenically. Successful treatment depends mainly on immediate sealing of the perforation and prevention of infection. Several factors affect the achievement of these goals, most important of which are time of occurrence, size and location of the perforation. Identification of root perforations is possible by direct observation of bleeding, radiography and an apex locator. Perforation defects may be repaired by nonsurgical or surgical techniques. We report two cases of root perforation. One was treated by glass ionomer, other was treated by composite resin with calcium hydroxide.

• Imaging Science in Dentistry
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• v.34 no.4
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• pp.179-182
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• 2004

Purpose: The purpose of this study is to examine the effects of X-ray beam angulation on the fractal dimension of trabecular bone structure of human dry mandible using the tile counting method. Materials and Methods: We divided 5 human dry mandibles into an angle and a molar groups depending on the regions and deciding the region of interest (ROI). When contrasted with the ROI, the inferior cortex was appointed to be low and the lines perpendicular to the buccal cortex were appointed to be the standard angle. Direct digital intraoral radiographs were obtained from 9 different projection angles. We analyzed statistically the fractal dimension using the tile counting method. Results: There was a statistically significant difference in the fractal dimension of the regions and the mandibles, but there was no statistically significant difference in the fractal dimension according to the X-ray beam angulation. Conclusion : There is no statistically significant effect of the angle of the projection on the fractal dimension of trabecular bone structure of a human dry mandible according to the tile counting method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.395-398
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• 2002

Many research group started study to develope x-ray detector using thin film transistor from 1970. But realization of TFT based x-ray detector development was caused by progress of thin film transistor liquid crystal display(TFTLCD) device technology in 1990. The main current of TFT technology is display device. Research results expend TFT technology field from display device to sensor manufacture technology. These days many research group in the world realize various digital x-ray detector. In this study, We compare discharge erasing method to visible light erasing method in a-Se based digital x-ray detector. Visible light erasing method is known reset process in direct conversion x-ray detector. Digital x-ray detector using visible light erasing method is not adaptive for conventional x-ray device, because of its thickness. And it is not avaliable for real-time imaging for digital fluoroscopy, because of its long reset time. In this study we overcome these limitations and show new idea for real-time imaging method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.424-427
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• 2002

In this papaer, there is a basic research for the development of the Hybrid digital radiation detector with a new system, make up for existing digital radiation detector of direct/indirect method with a weak point. for enhance the efficiency characteristics of signal response from X-ray detector using the a-Se, We make sample with various kinds of layer, through the ratio of As(0.l%,0.3%,0.5%,1%,1.5%,5%,10%). We measure net charge with a leakage current and photo current for electric charateristics. Ratio of As in a-Se consist of 7 stage, It made of using the thermal deposition system, In the made of samples, we made multi layer using the EFIRON optical adhesives from phosphor layer consist of Oxybromide$(BrO_2)$. As a result of X-ray measurement, the best result is ; leakage current(0.30nA/cm2), net charge(610.13pC/cm2/mR) when the condition is voltage(9V/um), 0.3% ratio of As in multi layer(BrO2 + a-Se)

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.436-439
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• 2002

Recently, It has performed that the basic research of the photoconductive material and the development and application of the digital radiograph detector which is divided into the direct and indirect method. The objective of this study investigate the effect of the electric characteristic about changing the composition of Arsenic in hybrid detector system for compensating a defect of conventional. We fabricated samples using the amorphous Selenium and Arsenic alloy with various concentrations of the Arsenic{seven step 0.1%, 0.3%, 0.5%, 1%, 1.5%, 3%, 5%). And using EFIRON optical adhesives the formed multi-layer$(Gd_{2}O_{2}S(Eu^{2+}))$ composed phosphor layer. X-ray and light sensitivity was measured to study x-ray response characteritics. As results, highest value was measured as output net charge and SNR were $315.7pC/cm^2/mR$ and 99.4 at 0.3%As doping ratio.

• Journal of Dental Rehabilitation and Applied Science
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• v.32 no.3
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• pp.158-168
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• 2016

This article is to review various methods used to investigate internal and marginal adaptation of fixed dental prostheses, and to summarize a merit, worth, and limitation of each method, using some results of previous studies. The methods of measuring internal and marginal gap are divided into two categories in this study; in vivo and in vitro. In vivo methods are clinical evaluations, including exploration, radiography, and impression technique. In vitro methods are laboratory evaluations such as direct view, cross-sectioning, and silicone replica technique using microscope. Measuring by micro computed tomography (CT) or profilometer is also in vitro methods. In recent years, the development of scanning systems is able to analyze 3-dimensional internal and marginal space in detail. As measuring and analyzing technology become more advanced, the ability to thoroughly examine crown adaptation is becoming both simpler and more efficient.

• Transactions on Electrical and Electronic Materials
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• v.4 no.6
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• pp.9-12
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• 2003

The electrical properties of stabilized amorphous selenium typical of the material used in direct conversion x-ray imaging devices are reported. Carrier mobility was measured using time-of-flight (TOF) measurements to investigate the transport properties of holes and electrons in stabilized a-Se film. A laser beam with pulse duration of 5 ns and wavelength of 350nm was illuminated on the surface of a-Se with thickness of 400 $\mu\textrm{m}$. The photo induced signals of a-Se film as a function of time were measured. The measured transit times of hole and electron were about 8.73${\mu}\textrm{s}$ and 229.17${\mu}\textrm{s}$, respectively. The hole and electron drift mobilities decreases with increase of electric field up to 4V/$\mu\textrm{m}$. Above 4V/$\mu\textrm{m}$, the measured drift mobilities exhibited no observable dependence with respect to electric field. The experimental results showed that the hole and electron drifting mobility were 0.04584 $\textrm{cm}^2$ V$\^$-1/s$\^$-1/ sand 0.00174 $\textrm{cm}^2$V$\^$-1/s$\^$-1/ at 10 V/$\mu\textrm{m}$.

• Korean Journal of Applied Biomechanics
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• v.28 no.1
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• pp.55-60
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• 2018

Objective: This study aimed to analyze the effects of computer game exposure on pathological musculoskeletal symptoms in adolescents. Method: This study included 10 male junior high school students who used computers less than 3 times a week for 1 hr per day. The subjects were asked to play computer games for 4 hr. Magnetic resonance imaging of the hand and wrist, from the distal radius and ulnar head to the distal phalanges, and radiography of the cervical vertebrae were performed before and after playing computer games. For each dependent variable, a paired t-test was performed to identify significant changes before and after a 4-hr active computer game (p<.05). Results: The horizontal diameters of the flexor tendons in the index and middle fingers were significantly reduced after playing computer games. The horizontal diameters of the flexor tendons of other fingers did not show any significant differences, but there was a tendency toward a decrease after playing computer games. There was no significant change in the cervical lordosis angle before and after playing computer games. However, the cervical lordosis angle was relatively decreased. Conclusion: The results of this study showed that computer game exposure had direct and indirect effects on morphological changes of flexor tendons. In addition, playing computer games for long periods of time can have a negative effect on normal functioning of the musculoskeletal system, with the possible development of abnormalities. However, computer game exposure in adolescents cannot be decisively identified as a factor causing pathological symptoms, based on the results of this study alone. Thus, longterm longitudinal studies on the overall musculoskeletal system are necessary.

• Journal of Chest Surgery
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• v.30 no.6
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• pp.566-572
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• 1997

A major obstacles to evaluation of newly-developed treatment strategy for human lung cancer has been the lack of appropriate experimental animal models. We describe a new experimental model of orthotopically-developed non-small cell lung cancer in nude rat, involving inoculation of tumor cell suspension by thoracotomy. Over 40 direct implantation to the periphery of the lung has been performed to date, each requiring less than'1 hour for completion. This model has been used to perform a series of experiments to investigate whether the rat lung and surrounding structures trapped tumor cells with 2 different non-small cell lung cancer cell lines(NCI-H46O and NCI-H1299). Every animal showed development of tumor masses, which were loculated at the periphery of the lung karenchyma and identified also by radiography. After 3 weetu of the inoculation, tumor develop meat at the mediastinal strutures were identified. The life expectancies of the victims were different between the cell lines, but were approximately 5 weeks when NCI-H46O cell line was used. This new orthotopic lung cancer model may be facilitate future studies of the new therapeutics of localized non-small cell lung cancer .