• The Journal of Korean Society for Radiation Therapy
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• v.28 no.1
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• pp.47-55
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• 2016

To evaluate the position accuracy of the MLC. This study analyzed the variations of the dosimetric leaf gap(DLG) and MLC transmission factor to reflect the location of the MLC leaves according to the dose rate variation for dynamic IMRT. We used the 6 MV and 10 MV X-ray beams from linear accelerator with a Millennium 120 MLC system. We measured the variation of DLG and MLC transmission factor at depth of 10 cm for the water phantom by varying the dose rate to 200, 300, 400, 500 and 600 MU/min using the CC13 and FC-65G chambers. For 6 MV X-ray beam, a result of measuring based on a dose rate 400 MU/min by varying the dose rate to 200, 300, 400, 500 and 600 MU/min of the difference rate was respectively -2.59, -1.89, 0.00, -0.58, -2.89%. For 10 MV X-ray beam, the difference rate was respectively ?2.52, -1.69, 0.00, +1.28, -1.98%. The difference rate of MLC transmission factor was in the range of about ${\pm}1%$ of the measured values at the two types of energy and all of the dose rates. This study evaluated the variation of DLG and MLC transmission factor for the dose rate variation for dynamic IMRT. The difference of the MLC transmission factor according to the dose rate variation is negligible, but, the difference of the DLG was found to be large. Therefore, when randomly changing the dose rate dynamic IMRT, it may significantly affect the dose delivered to the tumor. Unless you change the dose rate during dynamic IMRT, it is thought that is to be the more accurate radiation therapy.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.3
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• pp.373-384
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• 2003

The purpose of this study was to evaluate the eruption pattern of a cyst-associated mandibular premolar after marsupialization of a dentigerous cyst in children. The result from the twenty two pairs of normalized panoramic radiographs of twenty two patients who underwent neither extraction nor orthodontic traction of the cyst-associated mandibular after marsupialization were as follows. 1. The eruption speed of a cyst-associated premolar was 3.5 times faster than that of the normal contra-lateral premolar(p<0.05). The angulation change of test group was an average of $2.7^{\circ}$ per month. 2. In the change of the level of root formation, the group which had a little root maturity tended to be faster in the eruption speed(p>0.05) and the R1/4 group had a great change in the angulation change(p>0.05). 3. In the change to be with the cusp position index, the eruption speeds were increased to the 30% deviation groups. But, the eruption speed was decreased above that(p>0.05). 4. Group with cyst diminishment rate of more than $80mm^2$ per month showed the fastest eruption speed of all(p<0.05). 5. The mesial angulated teeth in the test group were decreased more rapidly than the distal angulated teeth in the eruption speed(p>0.05). But, increased in the angulation change(p<0.05). 6. There was a tendency of faster tooth eruption with less deviation of tooth axis. Group with tooth axis deviation of less than $15^{\circ}$ showed the fastest angulation change of all(p<0.05). 7. The eruption speed and the angulation change rapidly decreased during the first 6 months following marsupialization. Based on the results of this study, a cyst-associated mandibular premolar erupted more rapidly after marsupializaton. We thought so that it's prognosis was good if the tooth had a little root maturity, a little devitation and cyst lesion healed faster. We recommend that if there is enough space for eruption, orthodontic traction and surgical treatment of the cyst-associated tooth should be postponed 6 months after marsupialization.

• The korean journal of orthodontics
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• v.35 no.1 s.108
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• pp.60-68
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• 2005

The evaluation of malocclusion has to be done quantitatively and qualitatively. This will be lead toward an analysis of malocclusion severity as well as treatment difficulty. The method of proper evaluation of malocclusion severity and treatment difficulty is necessary to assess treatment effect and efficiency for the orthodontists and to establish fundamentals for planning and executing the health-related policies in private and public institutions. The purposes of this study as the first part of the objective and quantitative analysis of malocclusion were 1) to measure treatment difficulty based on the opinions of several orthodontists. and 2) to investigate the relationships between objective malocclusion severity and subjective treatment difficulty 100 pairs of dental casts that had various types and severity of malocclusion were selected from the orthodontic departments of Kyurghee University and Samsung Medical Center The objective malocclusion severity was measured with the PAR (Peer Assessment Rating) index and the subjective treatment difficulty was evaluated by 8 experienced orthodontists. The relationships between objective malocclusion severity and subjective treatment difficulty were statistically evaluated. There were significant relationships between objective malocclusion severity and subjective treatment difficulty especially in the measurements of the upper anterior alignment, the buccal occlusion. the overjet, the overbite and the midline discrepancy en the malocclusion components. The results of this study can provide the background knowledge to develop a new occlusal index. which contains both the malocclusion severity and treatment difficulty for Korean orthodontists.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.2
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• pp.284-295
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• 1999

The purpose of this study was to measure and analyze the bond strength of bonded amalgam using dental adhesives and to compare this with light-curing composite resin. Sections 8mm in diameter were punched out from the labial surface of bovine anterior teeth. These were embedded in clear acrylic resin blocks with labial surface facing out. 55 specimens were made for enamel and dentin each. After dividing these into 5 groups, group 1: Superbond C&B, group 2: Panavia 21, group 3: All-Bond 2, group 4: Fuji I Glass Ionomer Luting Cement, group 5: Scotchbond Multi-Purpose(Restorative Z-100), molds with holes of 6.3mm in diameter and 1.5mm in depth were placed over the specimens. The exposed tooth surfaces were treated with adhesives and the molds were filled with amalgam. In group 5, the mold was filled with composite resin and light-cured for 40 seconds. The author measured all specimens for bond strength 24 hours after amalgam filing and analyzed fracture surfaces. The following results were obtained: 1. Among the dentin groups, groups 1, 2 and 4 showed significantly lower bond strength compared with group 5(P<0.05). 2. Among the enamel groups, group 4 showed significantly lower bond strength compared with group 5(P<0.05). 3. In group 2, 2D showed significantly lower bond strength compared with group 2E(P<0.05). Other adhesives showed no such differences in bond strength between dentin and enamel(P>0.05). 4. Cohesive failure was observed in groups 1E and 5D, while mixed failure was seen in groups 1 and 5. Only adhesive failures were noted in groups 2, 3, 4.

• Progress in Medical Physics
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• v.18 no.3
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• pp.107-117
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• 2007

In order to evaluate the radio-protective advantage of an enhanced dynamic wedge (EDW) over a physical wedge (PW), we measured peripheral doses scattered from both types of wedges using a 2D array of ion-chambers. A 2D array of ion-chambers was used for this purpose. In order to confirm the accuracy of the device we first compared measured profiles of open fields with the profiles calculated by our commissioned treatment planning system. Then, we measured peripheral doses for the wedge angles of $15^{\circ},\;30^{\circ},\;45^{\circ},\;and\;60^{\circ}$ at source to surface distances (SSD) of 80 cm and 90 cm. The measured points were located at 0.5 cm depth from 1 cm to 5 cm outside of the field edge. In addition, the measurements were repeated by using thermoluminescence dosimeters (TLD). The peripheral doses of EDW were (1.4% to 11.9%) lower than those of PW (2.5% to 12.4%). At 15 MV energy, the average peripheral doses of both wedges were 2.9% higher than those at 6MV energy. At a small SSD (80 cm vs. 90 cm), peripheral dose differences were more recognizable. The average peripheral doses to the heel direction were 0.9% lower than those to the toe direction. The results from the TLD measurements confirmed these findings with similar tendency. Dynamic wedges can reduce unnecessary scattered doses to normal tissues outside of the field edge in many clinical situations. Such an advantage is more profound in the treatment of steeper wedge angles, and shorter SSD.

• Korean Journal of Environmental Biology
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• v.22
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• pp.86-92
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• 2004

The marine viral density in the Gwangyang Bay was abundant about 2.0${\times}$10$^{8}$ particles ml$^{-1}$ . For each season, viral abundances were recorded from 9.0${\times}$10$^{8}$ particles ml$^{-1}$ in summer to 0.7${\times}$10$^{6}$ particles ml$^{-1}$ in winter. The spatial distributions of the viral, bacterial and phytoplankton biomass in the Gwangyang Bay were mostly highey in closed estuarine system (Station 2, 5, 10, 12, 16, 20) than open ocean system (Station 28, 38, 42, 46, 51), And the othey closed estuarine system (Station 22, 26, 32, 34) indicated higher viral abundances, lower bacterial and plankton biomass than open oceanic system. In depths of some stations, the bacterial abundances exceeded a hundred fold than viral abundances. Seasonal abundances of marine viruses and their host systems were dynamically changed, and their seasonal variations were closely correlated. In summer, viral and bacterial abundances were increased, and phytoplankton chlorophyll $\alpha$ concentrations were maintained in average values. In winter, viral and bacterial abundances were dramatically decreased, and chlorophyll a concentrations were decreased, but, immediately increased. The viral abundances were peaked in August 2001, and bacteyial abundance, in August 2001 and June 2002, while chlorophyll a concentrations were peaked in April. 2002. In total host and viral abundances, it was seemed that their pools were maintained to steady-states by viral mortality, and viral abundance maintained steady-states. In our assessments, this report is a unique research about marine viral ecology of the Gwangyang Bay in Korea.

• Progress in Medical Physics
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• v.23 no.3
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• pp.188-198
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• 2012

This study aims to evaluate the accuracy of the collapsed cone convolution (CCC) algorithm for dose calculation in a treatment planning system (TPS), CorePLAN$^{TM}$. We implemented beam models for various setup conditions in TPS and calculated radiation dose using CCC algorithm for 6 MV and 15 MV photon beam in $50{\times}50{\times}50cm^3$ water phantom. Field sizes were $4{\times}4cm^2$, $6{\times}6cm^2$, $10{\times}10cm^2$, $20{\times}20cm^2$, $30{\times}30cm^2$ and $40{\times}40cm^2$ and each case was classified as open beam cases and wedged beam cases, respectively. Generated beam models were evaluated by comparing calculated data and measured data of percent depth dose (PDD) and lateral profile. As a result, PDD showed good agreement within approximately 2% in open beam cases and 3% in wedged beam cases except for build-up region and lateral profile also correspond within approximately 1% in field and 4% in penumbra region. On the other hand, the discrepancies were found approximately 4% in wedged beam cases. This study has demonstrated the accuracy of beam model-based CCC algorithm in CorePLAN$^{TM}$ and the most of results from this study were acceptable according to international standards. Although, the area with large dose difference shown in this study was not significant region in clinical field, the result of our study would open the possibility to apply CorePLAN$^{TM}$ into clinical field.

• Progress in Medical Physics
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• v.20 no.2
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• pp.97-105
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• 2009

Absorbed dose to water based protocols recommended that plane-parallel chambers be calibrated against calibrated cylindrical chambers in a high energy electron beam with $R_{50}$>7 $g/cm^2$ (E${\gtrsim}$16 MeV). However, such high-energy electron beams are not available at all radiotherapy centers. In this study, we are compared the absorbed dose to water determined according to cross-calibration method in a high energy electron beam of 16 MeV and in electron beam energies of 12 MeV below the cross-calibration quality remark. Absorbed dose were performed for PTW 30013, Wellhofer FC65G Farmer type cylindrical chamber and for PTW 34001, Wellhofer PPC40 Roos type plane-parallel chamber. The cylindrical and the plane-parallel chamber to be calibrated are compared by alternately positioning each at reference depth, $Z_{ret}=0.6R_{50}-0.1$ in water phantom. The $D_W$ of plane-parallel chamber are derived using across-calibration method at high-energy electron beams of 16, 20 MeV. Then a good agreement is obtained the $D_W$ of plane-parallel chamber in 12 MeV. The agreement between 20 MeV and 12 MeV are within 0.2% for IAEA TRS-398.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.4
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• pp.305-319
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• 2000

A total of 50 diatom species and 1 subspecies belonging to 31 genera except Chaetoceros resting spores were identified in the 45 sediments subsampled from a gravity core GH98-1223 collected from the western Hokkaido Island located in the northeastern East Sea (Sea of Japan). The most dominant species is Thalassionema nitzschioides (Grunow) Hustedt, ranging 29 to 59% of the total assemblages, and most species including Denticulopsis seminae (Simonsen and Kanaya) Simonsen and Pseudoeunotia doliolus (Wallich) Grunow were less than 5% in average. Frequencies of cold-water species are generally higher than those of warm-water species and the vertical distribution of cold-water species was largely opposite to that of warm-water species in spite of ecological habitat difference. Frequency of cold-water species, D. seminae is reverse to that of P. doliolus, an indicator of the Tsushima Warm Current, which is consistent with diatom temperature value (T$_{d}$ value). The variation of T$_{d}$ values shows that the upper part of core with greater-than-average T$_{d}$ values represents postglacial warming trend. These T$_{d}$ values clearly demonstrate that the study area located in the northern part of the East Sea is gradually influenced by Tsushima Warm Current. In addition, the zig-zag variation in the lower part reflects the unstable seawater for diatom habitat. Chaetoceros resting spores indicating productivity and upwelling was 5.3 to 40%, with maximum peak at 80 cm. Chaetoceros resting spores/Chaetoceros vegetative cells, an indicator of relative amounts of biogenic material in the sediments was high at the upper 80 cm level, corresponding to the change of T$_{d}$ values. On the basis of diatom assemblages, the northeastern part of East Sea has experienced the effects of Tsushima Warm Current during the postglacial period of Holocene, which is similar to the modem climatic environment. However, the variation of P. doliolus reflects that the intensity of Tsushima Warm Current has been oscillated in the East Sea.

• Korean Journal of Soil Science and Fertilizer
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• v.15 no.4
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• pp.213-220
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• 1982

Soil water changes in lysimeters with four different soils and two different available soil depths were monitored during the growing seasons of the soybean-barley cropping from 1977 to 1980 in Suweon to evaluate evapotranspiration (ET) as a function of available soil water and evaporative demand of the atmosphere. ET was calculated with soil water profile and water balance. Soil water content was measured with a neutron moisture depth gauage and The evaporative demand of the atmosphere was estimated with a class A pan evaporation. Rainfall. solar radiation, and wind speed were observed to examine heat and water balances. The average ET of soybeans ranged from 1.6 mm/day at seedling to 6.5 mm/day at flowering, and that of barley ranged from 0.5 mm/day at the regrowth stage to 4.6 mm/day at heading; however, a large variability was observed. The ratio of ET to pan evaporation ($ET/E_o$) ranged from 0.5 to 1.1 for soybeans and 0.4 to 1.2 for barley. The soil evaporation factor ($K_e$) of the $ET/E_o$ component decreased as the soil water depleted and the canopy developed. The crop transpiration factor ($K_t$), another component of $ET/E_o$, also was a function of time and the soil water. $K_t$ was constant when the available soil water fraction (f) in the root zone was greater than a threshold value, and $K_e$ was decreased linearly when f was lower than this threshold. The threshold was 0.7 for the moderate evaporative demand days, 0.4 to 0.5 for the low evaporative demand days, and 0.9 to 0.96 for the high evaporative demand days. Conclusively, the ET can be estimated from the evaporative demand of the atmosphere, $E_o$, $K_e$ and $K_t$, and the available soil water content in the root zone.