• Journal of Radiation Protection and Research
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• v.37 no.3
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• pp.138-145
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• 2012

As of the end of 2010, 21 nuclear power reactors were operating in Korea. Radioactive effluents from nuclear power plants (NPPs) had been increased continuously and the radioactivity of effluents released in 2010 was 547.12 TBq. From 2001 to 2010, the annual average radioactivity of gaseous and liquid effluents per reactor was 11.61 TBq for pressurized water reactor (PWR) plants and 118.12 TBq for PHWR (pressurized heavy water reactor) plants. Most of the radioactivity from gaseous and liquid effluents was came from $^3H$. Based on the results of release trends and analysis, effluents characteristics was suggested for the management of radioactive effluents from NPPs.

• Macromolecular Research
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• v.15 no.4
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• pp.285-290
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• 2007

Ag nanoparticles were distributed onto polystyrene nanoparticle (PS-Ag) beads using two synthetic methodologies. In the first methodology, polystyrene (PS) beads were prepared via emulsion polymerization, with Ag nanoparticles subsequently loaded onto the surface of the PS beads. The polymerization of styrene was radiolytically induced in an ethanol (EtOH)/water medium, generating PS beads. Subsequently, Ag nanoparticles were loaded onto the PS beads via the reduction of Ag ions. The results from the morphological studies, using field emission transmission electron microscopy (FE-TEM), reveal the PS particles were spherical and nanosized, and the average size of the PS spherical particles decreased with increasing volume % of water in the polymerization medium. The size of the PS spherical particles increases with increasing radiation dose for the polymerization. Also, the amount of Ag nanoparticle loading could be increased by increasing the irradiation dose for the reduction of the Ag ions. In the second methodology, the polymerization of styrene and reduction of Ag ions were simultaneously performed by irradiating a solution containing styrene and Ag ions in an EtOH/water medium. Interestingly, the Ag nanoparticles were preferentially homogeneously distributed within the PS particles (not on the surface of the PS particles). Thus, Ag nanoparticles were distributed onto the surface of the PS particles using the first approach, but into the PS clusters of the particles via the second. The antimicrobial efficiency of a cloth coated with the Ag-PS composite nanoparticles was tested against bacteria, such as Staphylococcus aureus and Klebsiella pneumoniase, for 100 water washing cycles.

• The Journal of Korean Physical Therapy
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• v.9 no.1
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• pp.71-79
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• 1997

The purpose of this study were to determined the effect of laser irradiation on the fibroblast activity. Cultures of 3T3 fibroblasts were subjected to Helium Neon laser(632.8 nm) irradiation of various energy density. On one, two and three consecutive days the fibroblast monolayers wert irradiated for period from 0 to 32 minutes with 8 mW of average output power. The fibroblast activity was determined by the quantitative assay of MTT, SRB and NR after incubation of the fibroblasts for 24 hours. Results show that exposure duration from 2 min to 32 min could increase MTT at three consecutive days, whereas control and 1 min, one and two days irradiation had were not inclosed. The SRB and NR were inclosed at two and three consecutive days from 2 min to 32 min, whereas control and 1 min, and once radiation were not increased. These result demonstrate that energy density from 0.48 to 7.64 J/cm could increase cellular protein contents and fibroblast activity at more than twice irradiation of laser, whereas low energy density (less than 0.24 J/m) and once irradiation of laser had no effect. The results suggest that the beneficial effect of the He-Ne laser with adequate dose on fibroblast activity in vitro.

• Radiation Oncology Journal
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• v.20 no.3
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• pp.206-214
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• 2002

Purpose : The aim of this study was to assess the effectiveness, survival rate and complications of radiation therapy and chemoradiation treatment in hypopharyngeal cancer. Methods and Materials : From January 1984 to December 1999, 56 patients who had hypopharyngeal carcinoma treated with curative radiation therapy were retrospectively studied. Twenty four patients $(42.9\%)$ were treated with radiation therapy alone (Group I) and $32\;(57.1\%)$ treated with a combination of chemotherapy and radiation (Group II). Total radiation dose ranged from 40.5 to 83. 5 Gy (median 67.9 Gy). Radiotherapy was given with conventional technique in 9 patients $(16.4\%)$, with hyperfractionation I ($1.15\~1.2$ Gy/fr., BID) in 26 $(47.2\%)$, hyperfractionation II (1.35 Gy/fr., BID) in 18 $(32.7\%)$, and accelerated fractionation (1.6 Gy/fr., BID) in 2 $(3.6\%)$. In chemotherapy, 5-FU ($1,000\;mg/m^2$ daily for 5 consecutive days) and cisplatin ($100\;mg/m^2$ on day 1) were administered in a cycle of 3 weeks interval, and a total of 1 to 3 cycles (average 2..3 cycles) were given prior to radiation therapy. Follow up duration was $1\~195$ months (median 28 months). Results : Overall 2 and 5 year survival rates were $40.6\%\;and\;27.6\%;\;50.0\%\;and\;30.0\%$ in Group I, and $36.4\%\;and\;26.3\%$ in Group II, respectively. Complete local control rates in Group I and II were $70.0\%\;and\;67.7\%$, respectively. The response to radiotherapy and nodal stage were statistically significant prognostic factors. The complication rate was increased in Group II and was decreased in hyperfractionation. Conclusion : The response to radiotherapy and nodal stage were valid factors to indicate the degree of control over the hypopharyngeal cancer. The induction cisplatin, 5-Fu chemotherapy was not valid in terms of local control rate and survival rate, but did contribute to an increased complication rate. The use of hyperfractionation was valid to reduce the late radiation complications.

• Progress in Medical Physics
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• v.19 no.4
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• pp.263-268
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• 2008

The application of a respiratory gated radiotherpy method to the lung radiation surgery was evaluated compared with the conventional method in which the whole tumor motion range is considered in the delineation of PTV (Planning target volume). The four dimensional CT simulation images were acquired for the five NSCLC (Non-small cell lung cancer) patients for radiation surgery. The respiratory gated plan was prepared with the 50% phase CT images and the conventional method was planned based on the ITV (Internal target volume) which include all the target volumes created in each phase CT images within a whole respiratory period. The DVH (Dose volume histogram) of OAR (Organ at risk) which calculated in each method was compared for the evaluation of the plan properness. The relative decrease of OARs' DVH were verified in the application of respiratory gated method. The average decrease rate were $16.88{\pm}9.97%$ in the bronchus, $34.13{\pm}19.15%$ in the spinal cord, $28.42{\pm}18.49%$ in the chest wall and $32.48{\pm}16.66%$ in the lung. Based on these results, we can verified the applicability and the effectiveness of the respiratory gated method in the lung radiation surgery.

• Progress in Medical Physics
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• v.17 no.2
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• pp.105-113
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• 2006

This study peformed to confirm the corrected dose In different electron density materials using the superposition/FFT convolution method in radiotherapy Planning system. The experiments of the $K_2HPO_4$ diluted solution for bone substitute, Cork for lung and n-Glucose for soft tissue are very close to effective atomic number of tissue materials. The image data acquisited from the 110 KVp and 130 KVp CT scanner (Siemes, Singo emotions). The electron density was derived from the CT number (H) and adapted to planning system (Xio, CMS) for heterogeneity correction. The heterogeneity tissue phantom used for measurement dose comparison to that of delivered computer planning system. In the results, this investigations showed the CT number is highly affected in photoelectric effect in high Z materials. The electron density in a given energy spectrum showed the relation of first order as a function of H in soft tissue and bone materials, respectively. In our experiments, the ratio of electron density as a function of H was obtained the 0.001026H+1.00 in soft tissue and 0.000304H+1.07 for bone at 130 KVp spectrum and showed 0.000274H+1.10 for bone tissue in low 110 KVp. This experiments of electron density calibrations from CT number used to decide depth and length of photon transportation. The Computed superposition and FFT convolution dose showed very close to measurements within 1.0% discrepancy in homogeneous phantom for 6 and 15 MV X rays, but it showed -5.0% large discrepancy in FFT convolution for bone tissue correction of 6 MV X rays. In this experiments, the evaluated doses showed acceptable discrepancy within -1.2% of average for lung and -2.9% for bone equivalent materials with superposition method in 6 MV X rays. However the FFT convolution method showed more a large discrepancy than superposition in the low electron density medium in 6 and 15 MV X rays. As the CT number depends on energy spectrum of X rays, it should be confirm gradient of function of CT number-electron density regularly.

• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.1
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• pp.134-139
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• 2014

Purpose: Adaptive statistical iterative reconstruction (ASIR) technique is a reconstruction method of CT image using statistical noise modeling which is known to reduce image noise and to preserve image quality despite reducing radiation dose. The aim of this study is to evaluate images using ASIR on bone SPECT/CT which is primarily performed in our hospital. Materials and Methods: We compared the images of applied ASIR (ASIR level: 20-80%) and none ASIR by changing the mA based on 120 kVp, 100 mA using Discovery NM/CT 670 (GE, U.S.A). First, we evaluated attenuation correction in SPECT image by changing the ASIR level using Anthropomorphic phantom. Second, we compared the contrast to noise ratio (CNR), image noise and spatial resolution in CT image using ACR phantom. Third, after selecting the ASIR level applicable patient using lower torso phantom, we examined 2 patients who followed up bone SPECT/CT and we performed blind test. Results: The degree of attenuation correction in SPECT image showed no significant difference between applied ASIR and none ASIR (P>0.05). When applied ASIR, the noise of CT image were reduced at least 17 up to 52% by changing the mA. The CNR of image with ASIR was maintained more than 0.8 at 40 mA (ASIR 60%) while those without ASIR showed 0.42 at standard 40 mA. In comparison of the high contrast object, we distinguished 12 line pairs/cm at 40 mA regardless of appling ASIR. Comparison of the patients image applied ASIR level 60% (40 mA) which found out by spine image of lower torso phantom showed no signigicant difference between applied ASIR and none ASIR in blind test. The CTDIvol and DLP for applied ASIR 60% showed decreased by 60%, 60% on average than using standard mA. Conclusion: The study show that the radiation dose in SPECT/CT using ASIR can be reduced despite degradation of SPECT and CT images. In addition, higher ASIR level could be possibly applied characteristics of SPECT/CT that region of interest is limited to bone.

• Journal of dental hygiene science
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• v.14 no.4
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• pp.442-447
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• 2014

The aim of this study was to analyze perception of risk and using status of hand-held dental x-ray unit among dental hygienists in metropolitan area. This research was based on perception of risk and using status of hand-held dental x-ray unit survey in 257 dental hygienists from July 7 to 31, 2014. Data were analyzed with t-test, one way ANOVA, and multivariable logistic regression analysis using SPSS Windows 21.0 program and significance level was set at p<0.05. The hand-held dental x-ray unit to cover all type patients was 24.8%. The 62.6% of patients and 81.3% of operator doesn't wear lead apron, the experience rate of radiation education was 40.1%. The average of risk perception was 3.08 points. The associated factors of risk perception were career, number of radiation exposure per day, and possession of fixed x-ray unit. The increased of accumulated dose when the occupationally exposed work continues, it is necessary to effort of defense against dental radiation.

• Radiation Oncology Journal
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• v.19 no.4
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• pp.306-311
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• 2001

Purpose : In this retrospective study, we attempted to evaluate the treatment outcome and the prognostic factors of thymoma treated with surgery, radiotherapy and chemotherapy. Methods and materials : Between 1979 and 1998, 55 patients with thymoma were treated at the Seoul National University Hospital. Of these, 11 patients underwent surgery only, 33 patients received post-operative radiotherapy and 11 patients received radiotherapy only. Twenty-three patients had gross total resection and 21 patients subtotal resection. For postoperative radiotherapy, the radiation dose consisted of $41.4\~55.8\;Gy$. The average follow-up was 64 months, and ranged from 2 to 160 months. The sex ratio was 1:1 and the median age was 48 years $(15\~74\;years)$. Overall survival and disease-free survival were determined via the Kaplan-Meier method, and the log-rank was employed to evaluate for differences in prognostic factor. Results : The five- and 10-year survivai rates were $87\%\;and\;65\%$ respectively, and the median survival was 103 months. By univariate analysis, only stage (p=0.0017) turned out to be significant prognostic factors of overall survival. Also, stage (p=0.0007) was significantly predictive for overall survival in mutivariated analysis. Conclusion : This study showed the stage was found to be important prognostic factors, which influenced survival. Especially, as incomplete resection is related with poor results, complete resection is important to cure the invasive thymoma.

• Journal of the Korean Society of Radiology
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• v.15 no.4
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• pp.429-435
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• 2021

In intracavitary radiotherapy, incorrect location of the source can cause excessive dose to normal tissue, so it is essential to evaluate the location accuracy of the source. In this study, basic research was performed on digital line dosimeter based on lead (II) oxide (PbO) to improve analog verification method. Therefore, a polycrystalline PbO unit cell dosimeter was manufactured and the measurement performance for Ir-192 sources was evaluated. As a result, the reproducibility satisfies the evaluation criteria of 1.5% with a relative standard deviation of 0.85%. Linearity showed excellent results with a linear coefficient of R² of 0.9998. In the case of distance dependence evaluation, the power function R² showed 0.9855 for PbO and 0.9974 for diode, and the overall average difference was 1.66% for PbO and 2.18% for diode. This study presents the basic detection performance of the polycrystalline PbO dosimeter for the Ir-192 source and can provide basic data in the field of radiation measurement.