• Journal of Biomedical Engineering Research
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• v.3 no.1
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• pp.49-50
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• 1982

In this paper, the information capacity, the intergrate performance measure of digital radiography system has been quantitatively analyzed. The effect of various factors affecting the information capacity of the digital radiography system in multi-stage detection processes has been considered and analyzed in detail. The results show that the more information capacity can be obtained with the smaller detector cell area, despite of the reduced signal to noise ratio due to the reduced number of X-ray photons per detector cell. Considering the limit of human visual acuity. however, the sufficient resolution will be obtained when the detector cell size in 0.2${\times}$0.2mm with 8 bit quantizaion. And also the results indicates that the information capacity may be severely reduced by the mixture of electric noise in final read-out stage.

• Journal of radiological science and technology
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• v.13 no.2
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• pp.15-20
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• 1990

In clinical fields, single screen-film system will be generalized according to high speed and high image qualify of intensifying screen film system in future. In single screen-film system, for imaging the best image, we must choice good film according to speed and gredient. Double screen-film system will be replaced single screen film system in general radiography. Author has thought that single screen film system will be developed new diagnosis area according to X-Ray films.

• Journal of Korean society of Dental Hygiene
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• v.12 no.5
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• pp.987-997
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• 2012

Objectives : This study was carried out in order to obtain basic data for students' efficient acquirement and instruction of radiography technology in the future by surveying dental hygiene students' recognition of periapical radiography. Methods : This study carried out a questionnaire survey targeting dental hygiene students from December 2009 to December 2010, and obtained the following results. Results : 1. As a result of examining recognition on periapical radiography, the bisecting angle technique was indicated to be averagely $3.84{\pm}0.566$ points. The paralleling technique was indicated to be $2.66{\pm}0.701$ points. 2. As a result of examining about problems given the bisecting angle technique, what had been most difficult given the bisecting angle technique was indicated to be the highest in cone positioning with 34.2%. The most difficulty given deciding on the X-ray vertical-angel irradiation direction was indicated to be the highest with 66.9% in adjusting the cone direction on the virtual bisector. 3. As a result of examining about problems given the paralleling technique, what had been most difficult in the process of the paralleling technique was indicated to be the highest with 56.7% in fixing the film immobilization device inside the mouth. Conclusions : Examining the above results, it is considered that there is a need of understanding morphological and anatomical structure inside the mouth in order to reduce the mistake rate given the periapical radiography, and that it is important to increase skill level by repetitively shooting several times with having enough time.

• Journal of radiological science and technology
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• v.42 no.6
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• pp.477-482
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• 2019

Recently, due to the increased use of medical radiation, the radiation exposure of radiation workers should be considered as well as medical exposure of patients. And it is recommended to close the door during radiography. however, In this study, when the door was inevitably opened for radiography, the proposed method was to install the shield as a method of reducing the exposure dose. And its efficiency was analyzed. In simple chest radiography, the measurement point was changed according to the measurement location. Dose rate were measured 10 times for each condition using a dosimeter. And the average value was derived. Using this, the change of dose according to the opening and closing of the door and the installation of the shield was analyzed. Using this, we compared and analyzed the dose change according to the door opening and closing and the installation of the shield, and significance was verified through the SPSS ver. 24. Depending on whether the door was opened or closed, 11,215.35%, 159.0%, 101.9% increased in front of the door in the consol room, behind the wall and behind the lead glass. Depending on the installing of the shield, the 49.2%, 29.6%, 19.9%, 30.6% decrease in front of the door in the examination and consol room, behind the wall and lead glass. In addition, statistical analysis was showed that there were significant differences in both the results according to whether the door was opened or closed and shielding(p<.05). Close the door during radiography. However, when the door should be opened, it was confirmed that the dose rate were reduced by installing the shield. Therefore, to optimize radiation protection, it is recommended to install shields when opening the door.

• Journal of radiological science and technology
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• v.33 no.1
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• pp.1-10
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• 2010

Dental panoramic radiography is an imaging technique which shows the information of teeth, jaws and superficial structures on a single image. In this study, we propose the clinical dose reference for dental panoramic radiography. Dental panoramic radiography is an application which can increase the radiation does of oral cavity. It is very important to study the real condition of management for these panoramic X-ray equipments. Since there was no researches on dental panoramic equipments in domestic and foreign study groups, we measured and analyzed the dose such as effective dose, DAP and DWP of panoramic radiography.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.28 no.1
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• pp.7-16
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• 1998

The Scanora/sup (R)/ X-ray unit uses the principles of narrow beam radiography and spiral tomography. Starting with a panoramic overview as a scout image. multiple tomographic projections could be selected. This study evaluated the accuracy of spiral tomography in comparison to routine panoramic radiography for dental implant treatment planning. An experimental study was performed on a cadaver mandible to assess the accuracy of panoramic radiography and spiral tomography film images for measurement of metallic spheres. After radiographic images of the metallic spheres on the surgical stent were measured and corrected for a fixed magnification of radiographic images. following results were obtained. 1. In the optimal position of the mandible. the minimal horizontal and vertical distortion was evident in the panoramic radiography images. The mean horizontal and vertical magnification error in anterior sites was 5.25％ and 0.75％. respectively. The mean horizontal and vertical magnification error in posterior sites was 0.50％ and 1.50％. respectively. 2. In the displaced forward or in an eccentric position of the mandible. the magnification error of the panoramic radiography images increased significantly over the optimal position. Overall, the mean horizontal magnification error of the anterior site in the different positions changed dramatically within a range of -17.25％ to 39.00％, compared to the posterior range of -5.25％ to 8.50％. However, the mean vertical magnification error stayed with the range of 0.5％ to 3.75％ for all the mandibular positions. 3. The magnification effects in the tomographic scans were nearly identical for the anterior and posterior with a range of 2.00％ to 5.75％ in the horizontal and 4.50％ to 5.50％ in the vertical dimension, respectively. 4. A statistically significant difference between the anterior and posterior measurements was found in the horizontal measurements of the panoramic radiography images of the displaced forward and backward position of the mandible(P<0.05). Also a significant difference between the optimal panoramic and tomographic projections was found only in the vertical measurement(P<0.05).

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.201-203
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• 2000

In this study, effect of welding parameters on the defect density in the weldments produced by high frequency electric resistance welding process. The defect density measured by X-ray radiography showed a W-type curve as a function of heat input rate. The mechanisms of the such behavior were discussed based on the chemical compositions of the oxides formed at the weldments.

• 보존과학연구
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• s.15
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• pp.1-20
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• 1994

A typology was established for 15 pottery artefacts at Chejuisland. Conjectured methods of manufacture were confirmed by radiography X-ray diffraction. Scanning electron microscopy etc. The compositions and mineralogy of $500^{\circ}C$ to $1200^{\circ}C$ was measured and compared with those of microstructure. The mechanism of sintering was impurity-initiated, liquid-phase sintering. The making, firing, and sometimes exploding of the figurines may have been the prime function of the pottery at this site rather than being manufactured as permanent, portable object.

• Journal of the Korean Society of Radiology
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• v.15 no.2
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• pp.173-179
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• 2021

Scattered x-ray generated by digital radiography systems also have the advantage of increasing signals, but ultimately detectability is reduced by decreasing resolution and increasing noise of x-ray images transmitted objects. An indirect method of measuring scattered x-ray in a modulation-transfer function (MTF) for evaluating resolution in a spatial-frequency domain can be considered as a drop in the MTF value corresponding to zero-frequency. In this study, polymethyl methacrylate (PMMA) was used as a patient tissue equivalent, and MTFs were obtained for various thicknesses to quantify the effect of scattered x-ray on resolution. X-ray image signals were observed to decrease by 35 ~ 83% with PMMA thickness increasing, which is determined by the absorption or scattering of x-rays in PMMA, resulting in reduced MTF and increased scatter fraction. The method to compensate for MTF degradation by PMMA resulted in the MTF inflation without considering the optical spreading generated by the indirect-conversion type detector. Data fitting or zero-padding are needed to compensate for MTF more reasonably on edge-spread function or line-spread function.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.4
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• pp.1-11
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• 2011

In order to obtain more clear x-ray images, an antiscatter grid, which can absorb the scattered rays, is employed. The artifacts due to the grid pattern are, however, visible, and thus should be removed by employing digital filters. For over exposed x-ray images, the strength of the grid artifacts are too big to be removed if fixed-bandwidth filters are employed. In this paper, for an efficient grid artifact reduction, we analyze the characteristics of the image formation and image saturation as the x-ray exposure increases. We can notice that, as the saturation begins to occur, the maximum of the artifact component decreases contrary to increasing exposure amount. We propose then an adaptive filtering algorithm for reduction of the grid artifacts, where the significant-signal bandwidth of the artifact component is used to choose appropriate filter bandwidths. The proposed algorithm is tested for real x-ray digital images, and can efficiently remove the grid artifacts.