• The Journal of Korean Society for Radiation Therapy
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• v.25 no.2
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• pp.175-180
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• 2013

Purpose: Modern radiation therapy technique such as IGRT has become a routine clinical practice on LINAC for decrease patient's set-up error. CBCT can be used to adjust patient set-up error and treat patient more accurately. The Purpose of this study is to evaluate field size of CBCT for improving Image quality and suggest reference date of CBCT field size. Materials and Methods: Image date were acquired using KV CBCT and Catphan phantom (Half fan and full fan mode were scanned from 2 ~16 cm, at intervals of 2 cm). Field size were categorized by Small field size (2 cm, 4 cm), Medium field size (8 cm, 10 cm), Large field size (more than 14 cm) and evaluate. To estimated the CTDi using CTDi phantom and Ion chamber. Results: CT number linearity of Small and Large field size are greater than Medium field size. Spatial resolution are not significantly different without Small field size. But half fan mode is more different than full fan mode. In full fan, except Medium field size, all field size exceed recommendation for HU uniformity. But half pan has stability for all field except Small field size. CTDi makes radical sign function graph in Medium field size. Conclusion: The worst result was given by Small field size for Image quality and practically. Medium field size can be useful to prevent patient from radiation exposure and give better Image quality. So this study recommends that Medium field size (8~10 cm) is more suitable for CBCT.

• Journal of Korean Institute of Industrial Engineers
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• v.23 no.3
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• pp.533-544
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• 1997

Among numerous factors that have an effect on visual field, the effects of background condition on the size of the visual field were investigated to obtain more practical visual field that can be readily applicable to industrial settings. A visual experiment was conducted, in which the subject was instructed to search a target with distinct orientations. Size contrast, meridian, nontarget density, and subject's gender showed a significant effect on the size of the visual field at $\alpha=0.01$. The size of the visual field was linearly proportional to size contrast, and inversely proportional to density. Female's visual fields were found to be significantly larger than male subjects', The size of the visual field on horizontal axis was larger than that on vertical axis, and the size of the head & eye field on right meridian was also larger than that on left meridian. The shape was found to be horizontally oriented oval and statistically asymmetric with respect to horizontal and vertical axes. The regression equations to predict the visual fields on the given background condition were suggested. The visual fields suggested in this study would be valuable to the design of visual displays and the panel layout of various displays and controls.

• Journal of the Ergonomics Society of Korea
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• v.14 no.1
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• pp.59-67
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• 1995

Depending upon the eye and head movement, the visual field is often classified into three categories ; stationary field, eye field and head and eye field. To investigate the effect of background condition on the size of the visual field, an experiment was conducted, in which the subject was instructed to search a target with distinct orientations. In each trial, a single target was presented on the perimeter modified to cover the range of 330 .deg. around the fixation point, with the visual angle subtended 1.4 .deg. vertically and horizontally. Nontarget density, meridian, size contrast and subject showed a significant effect on the visual field at .alpha. =0.01, where density was inversely proportional to the size of the visual field, and size contrast linearly proportional to the size of the visual field. The size of the visual field on horizontal axis was larger than that on vertical axis, and that on right and upper meridian was also larger than on left and lower meridian. The shape was found to be horizontally oriented oval and statistically asymmetric with respect to horizontal and vertical axes. In addition, the regression equations to predict the visual field on the given background condition were suggested. These results were expected to be used as a design guideline when arranging displays and controls on panels such as automobile display panels, cockpits, etc.

• Journal of radiological science and technology
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• v.44 no.3
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• pp.183-187
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• 2021

The field size of the lumbar spine X-ray examination, which belongs to the most frequent examination in general radiography, is 5 times wider than the width of the lumbar spine. Exposure index (EI) as per International Electrotechnical Commission has a proportional relationship with the dose incident on the image receptor for clinical protocols in addition to RQA5, which is a calibration beam quality. In this study, the effectiveness of the set field size was evaluated through the change of EI according to the size of field during lumbar spine X-ray examinations. Lumbar anterior-posterior and lateral examinations was performed using a whole-body phantom, and the national average exposure conditions of Korea investigated in 2017 were introduced for the X-ray exposure. As a result of comparing the EI displayed on the console of digital radiography system for the three field size in ① 18 × 36 cm2 ② 25 × 36 cm2 ③ 36 × 36 cm2, the EI values showed a tendency to increase as the field size increased. Since the patient dose, such as organ dose around the lumbar spine, increases as the field size becomes larger, thus, if the EI obtained from the field size at a level that does not interfere with diagnosis is set as a reference, the effectiveness of the field size can be evaluated through the EI displayed on the console when the lumbar spine X-ray examination is conducted.

• Journal of radiological science and technology
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• v.8 no.2
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• pp.71-72
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• 1985

This study was performed on the dose distribution of various field size and the effect of penumbra shield in the telecobalt unit. The results obtained are as follows. 1. Errors of the light and ${\gamma}-ray$ field size was below the regulation as 0.52 percentage. 2. The coefficient of field area was increased with the larger field area, and this coefficient was showed the more difference in larger SSD. 3. The rectangular field areas, which were described by level of the same percentage depth does, were decreased with the more elongation factor. At the same elongation factor, the compensating factor was decreased with the larger field size. 4. The lead block or extension collimator was able to shield r-ray exposure of outside field size from 50 to 80 percentage. 5. On the matching adjacent fields, while the gap between beam edges are contacted, that overlapped beam edges indicated up to 140 percentage, and while the gap was 1 cm, it could be reduced to 90 Percentage. The lead-libocking on the overlapped area was more effective to lower dose, as 80 percentage in this case. 6. Percentage depth dose of various trimming field sizes were increased linearlly according to area 1 perimeter size, but the center split field size did not maintain linearlly.

• Interaction and multiscale mechanics
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• v.2 no.1
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• pp.15-30
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• 2009

The theoretical framework of the interaction fields for multiple scales based on field theory is applied to one-dimensional problem mimicking dislocation substructure sensitive intra-granular inhomogeneity evolution under fatigue of Cu-added steels. Three distinct scale levels corresponding respectively to the orders of (A)dislocation substructures, (B)grain size and (C)grain aggregates are set-up based on FE-RKPM (reproducing kernel particle method) based interpolated strain distribution to obtain the incompatibility term in the interaction field. Comparisons between analytical conditions with and without the interaction, and that among different cell size in the scale A are simulated. The effect of interaction field on the B-scale field evolution is extensively examined. Finer and larger fluctuation is demonstrated to be obtained by taking account of the field interactions. Finer cell size exhibits larger field fluctuation whereas the coarse cell size yields negligible interaction effects.

• Journal of radiological science and technology
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• v.41 no.1
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• pp.1-6
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• 2018

The purpose of this study is to provide baseline data on lung field size measured radiological method by chest PA image in normal Korean. The subject of this study is 496 normal persons who performed chest PA examination using x-ray digital radiography system. The measurement method is from the apex of right and left lung to the costophrenic angle of both lung, from the top of the image to the lowest costophrenic angle of both lung and transverse line of the largest lung area. As a result of this study, the following conclusions were obtained. A lung field size of male is larger than the female(p<0.05). The younger the age, the longer both lung length and total lung height statistically significant. As a increase height and length, A lung field size was increased(p<0.05). But, BMI is not associated with a lung field size. This study will be data of reference data when radiological technologists perform chest PA examination.

• Radiation Oncology Journal
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• v.5 no.2
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• pp.157-163
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• 1987

It is known that fixed source to skin distance (SSD) cannot be used when the treatment field is sloped or larger than the size of second collimator in electron beam irradiation and inverse square law using effective ssd should be adopted. Effective SSDs were measured in different field sizes in each 6, 9, 12, 15 and 18MeV electron energy by suing NELAC 1018D linear accelerator of Kosin Medical Center. We found important parmeters of effective SSD. 1. Minimum effective SSD was 58.8cm in small field size of $6\pm6cm$ and maximum effective SSD was 94.9cm in large field size of $25\pm25cm$, with 6MeV energy. It's difference was 36.1cm. The dose rate at measuring point was quite different even with a small difference of SSD in small field $(6\times6cm)$ and low energy (6 MeV). 2. Effective SSD increased with field size in same electron energy. 3. Effective SSDs gradually increased with the electron energies and reached maximum at 12 or 15 MeV electron energy and decreased again at 18MeV electron energy in each identical field size. And so the effective SSD should be measured in each energy and field size for practical radiotherapy.

• Journal of the Korean Statistical Society
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• v.36 no.4
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• pp.479-488
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• 2007

The elliptic random field is an extension to the Gaussian random field. We proved a theorem which characterizes the elliptic random field. We proposed a heuristic approach to derive an approximation to the distribution of the size of one connected component of its excursion set above a high threshold. We used this approximation to approximate the distribution of the largest cluster size. We used simulation to compare the approximation with the exact distribution.

• Radiation Oncology Journal
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• v.14 no.3
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• pp.237-244
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• 1996

Purpose : The accurate dosimetry of independent collimator equipped for 6MV and 15MV X-ray beam was investigated to search for the optimal correction factor. Materials and Methods : The field size factors, beam quality and dose distribution were measured by using 6MV, 15MV X-ray Field size factors were measured from $3{\times}3cm^2$ to $35{\times}35cm^2$ by using 0.6cc ion chamber (NE 2571) at Dmax. Beam qualities were measured at different field sizes, off-axis distances and depths. Isodose distributions at different off-axis distance using $10\times10cm^2$ field were also investigated and compared with symmetric field. Result: 1) Relative field size factors was different along lateral distance with maximum changes in $3.1\%$ for 6MV and $5\%$ for 15MV. But the field size factors of asymmetric fields were identical to the modified central-axis values in symmetric field, which corrected by off-axis ratio at Dmax. 2) The HVL and PDD was decreased by increasing off-axis distance. PDD was also decreased by increasing depth For field size more than $5{\times}cm^2$ and depth less than 15cm, PDD of asymmetric field differs from that of symmetric one ($0.5\~2\%$ for 6MV and $0.4\~1.4\%$ for 15MV). 3) The measured isodose curves demonstrate divergence effects and reduced doses adjacent to the edge close to the flattening filter center was also observed. Conclusion . When asymmetric collimator is used, calculation of MU must be corrected with off-axis and PDD with a caution of underdose in central axis.