• Journal of Radiation Protection and Research
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• v.11 no.1
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• pp.51-56
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• 1986

It is important to measure and protect from the radiation space dose and induced activity at the high energy medical linear accelerator facilities. These are to consider the additional risk to patients undergoing treatment, machine operators and staff members. Measurements of the space dose distribution and induced radioactivity at the 18 MeV medical linear accelerator facility in the Yonsei Cancer Center. 1. Exposure space dose for 300 rads monitor doses of 18 MeV electron are measured as 50 mR at 1 meter from patients. 2. Exposure space dose for 300 rads monitor doses of 10 MV X-ray are detected as 350 mR at 1 meter from phantom. 3. Induced radioactivity by photonuclear reaction was measured as 0.65 mR/hr from collimater after 30 Gy(3,000 rads) irradiated. 4. Analyzing the decay curves and energy spectrum of induced radioactivity, detected a few materials to be activated by photoneutron reaction, $^{65}Cu({\gamma}{\cdot}n)\;^{64}Cu,\;^{186}W({\gamma}{\cdot}n)\;^{185}W,\;^{181}Ta({\gamma}{\cdot}n)\;^{180}Ta,\;^{199}Au({\gamma}{\cdot}n)\;^{198}Au$.

• Progress in Medical Physics
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• v.9 no.4
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• pp.227-245
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• 1998

A most appropriate model of 3-D conformal radiotherapy has been induced by clinical evaluation and animal study, and therapeutic gains were evaluated by numerical equation of tumor control probability(TCP) and normal tissue complication probability (NTCP). The radiation dose to the tumor and the adjacent normal organs was accurately evaluated and compared using the dose volume histogram(DVH). The TCP and NTCP was derived from the distribution of given dosage and irradiated volume, and these numbers were used as the biological index for the assessment of the treatment effects. Ten patients with liver disease have been evaluated and 3 dogs were sacrificed for this study. Based on the 3-D images of the tumor and adjacent organs, the optimum radiation dose and the projection direction which could maximize the radiation effect while minimizing the effects to the adjacent organs could be decided. 3). The most effective collimation for the normal adjacent organs was made through the beams eye view with the use of multileaf collimator. When the dose was increased from 50Gy to 70Gy, the TCP for the conventional 2-port radiation and the 5-port multidimensional therapy was 0.982 and 0.995 respectively, while the NTCP was 0.725 and 0.142 respectively, suggesting that the 3-D conformal radiotherapy might be the appropriate therapy to apply sufficient radiation dose to the tumor while minimizing the damages to the normal areas of the liver. Positive correlation was observed between the NTCP and the actual complication of the normal liver in the animal study. The present study suggest that the use of 3-D conformal radiotherapy and the application of the mathematical models of TCP and NTCP may provide the improvements in the treatment of hepatoma with enhanced results.

• Journal of Radiation Protection and Research
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• v.22 no.2
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• pp.103-109
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• 1997

Adult male rats were exposed to a whole body with a single dose of 1.0, 2.0, 3.0, 5.0, and 7.0 Gy. The animals were sacrificed 48, 72, 96 and 216 hours following exposure. A competitive enzyme linked immunosorbent assay(ELISA) with antigen immobilized on the solid phase has been developed to measure ceruloplasmin in rat serum and complete dose response curves. Ceruloplasmin was purified from the plasma of turpentine treated male rats. Coating of ceruloplasmin had more effectiveness in 10 mM Tris-HCI, 150 mM sodium chloride, pH 7.4 than in 50 mM carbonate/bicarbonate buffer, pH 9.6. The coating range for ceruloplasmin was $70{\sim}140ng$/well. Levels of ceruloplasmin increased to maximum on the $72{\sim}96$ hours after irradiation. Slope of between response and dose was greatest value 96 hours following irradiation. Normal ceruloplasmin levels were not recorded 216 hours following exposure. In 0.1 Gy irradiated group, levels of ceruloplasmin also increased to maximum on the $72{\sim}96$ hours following irradiation. The concentration of this protein remained significantly different from control value, 196 hours after exposure. Ceruloplasmin was identified as one of the major acute phase protein following irradiation and further studies about gene expression and regulation would be necessary for radiation protection.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.5
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• pp.143-151
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• 2016

The aim of this study is to investigate the optimal algorithm to extract medical radiation induced pixel signal from complementary metal-oxide semiconductor (CMOS) sensors of smartphones camera. The pixel intensity and pixel number of smartphone camera were measured as the X-ray dose was increased. The front camera of the smartphone camera has low noise property and excellent dose response as compared to the back camera of the smartphone. The indirect method which uses scintillation crystal in front of the smartphone camera, couldn't improve the X-ray detection efficiency as compared to the direct method which does not use any scintillator in front of the smartphone camera. When we used the algorithm which employing threshold level on the pixel intensity and pixel number, the dose linearity was more higher for the pixel intensity rather for the pixel number. The use of pixel intensity of Y color component which represents the grey scale, would be efficient in terms of the radiation detection efficiency and reducing the complexity of the image processing. We expect that the radiation dose monitoring can be managed effectively and systematically by using the proposed radiation detection algorithm, thus eventually will contribute to the public healthcare.

• Nuclear Engineering and Technology
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• v.8 no.2
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• pp.89-99
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• 1976

The grafting of acrylic acid in aqueous solution to polyvinyl chloride fibers tab been studied in the presence of ferrous, ferric, and cupric salts, The mutual irradiation technique was adopted using a Co-60 source or a Van do Graaff accelerator. The grafting and homopolymerization were suppressed by the cations. Particularly the grafting was suppressed by the cations in the following order of effectiveness : $Cu^{2+}$>$Fe^{2+}$>$Cu^{3+}$. The rate of grafting (in %/hr) was proportional to the 0.76th power of the dose rate over the range from 8.5f $10^3$ rad/hr to $1.4\times10^5$ rad/dr. The apparent activation energy for the grafting was determined to be 6.1 Kcal/mole between $25^{\circ}$ and $75^{\circ}C$ for the mixture of AA-HaO-$(CH_2Cl)_2$, containing Mohr's salt, $4\times10^{-3}$ mole/l. The increase of the grafting was observed when total dose and dose intensity were raised, or when ethylene dichloride as a swelling agent was saturated in the monomer mixture. The grafted polyvinyl chloride fibers showed considerable improvement in moisture regain, heat shrinkage, and melting properties, but tensile properties were not significantly affected by grafting.

• Journal of Radiation Protection and Research
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• v.39 no.3
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• pp.134-141
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• 2014

Along with the wide use of radiotherapy in cancer treatment, there is growing interest in beneficial effect of low-dose irradiation (LDI) in cancer therapy. Therefore, we investigate how LDI affects immune responses in mice model. Total body irradiation (TBI) on C57BL/6 mice was given at low-dose rate of $1mGy{\cdot}min^{-1}$ using $^{137}Cs$ source at three times for consecutive three days. Hematological examination, total cell numbers of spleen, populations and characteristics of splenocytes were determined. Total numbers of RBC or platelet in irradiated mice showed no significant changes. WBC counts were decreased in a dose-dependent manner 2 days after TBI, however, these differences are gradually waned until 28 days. Dose-dependent decrease in the number of splenocytes of TBI mice at day 2 was also improved as time progressed. While the level of Foxp3 mRNA was decreased, the frequency of $CD4^+$ T cells and $CD69^+$ cells in spleen was increased at day 2 and 14. Fractionated low-dose TBI on mice exhibited normal body weight with no distinguishable behavior during whole experimental periods. These results suggest that some parameters of immune system could be altered and evaluated by fractionated low-dose TBI and be used to broaden boundary of low dose radiation research.

• Journal of the Korean Society of Radiology
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• v.8 no.7
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• pp.449-454
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• 2014

The purpose of this study is(was) to investigate the shielding ratio of 1 mmPb and the off axis ratio outside the field edge at depth of 1 cm from a phantom surface for 6 MV photon beam. A dose of 180 cGy was delivered to a depth of 10 cm for a $10{\times}10cm^2$ and $15{\times}15cm^2$ field in the SAD technique. The off axis ratio was calculated by measuring the dose of optically stimulated luminescent nanoDot dosimeters(OSLnDs) positioned at 2, 4 and 6 cm from the field edge, and the center axis of field. And the shielding ratio of 1 mmPb was calculated by measuring the dose of OSLnDs positioned at 2, 4 and 6 cm from the field edge.. As a result, for a $10{\times}10cm^2$ and $15{\times}15cm^2$ field, the off axis ratios were acquired 0.008-0.023 and 0.011-0.028, respectively. Also the shielding ratios of 1 mmPb were acquired 0.868-0.888 and 0.807-0.842, respectively. These results provide data to protect organs at risk outside the radiation treatment field.

• Progress in Medical Physics
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• v.13 no.2
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• pp.98-103
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• 2002

The purpose of this study was to evaluate the absorbed dose to the coronary artery segment from various sized balloon angio catheters. The liquid form of Ho-166 was produced at the KAERI by (n, ${\gamma}$ ) reaction. We used GafChromic film for the estimation of the absorbed dose by beta particles. The exposed films were read using a videodensitometer. Several film exposures were made with varying irradiation times and activities. A modified micrometer was used for the measurement of the absorbed dose distribution near the balloon surface. Four balloons of coronary catheters evaluated were 30 m long and 2.5, 3.0, 3.5 and 4.0 mm in diameter. All doses are plotted in units of Gy/min/GBq/ml as a function of radial distance in mm from the surface of balloon. The absorbed dose rate was 0.86, 1.01, 1.11 and 1.24 Gy/min/GBq/ml at a balloon surface for various balloon diameter 2.5, 3.0, 3.5 and 4.0 mm respectively. Using a vacuum pump, the air in the balloon was evacuated prior to instillation of the Ho-166 source. By removing air bubbles in the balloon, the absorbed dose distribution was more uniform.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.353-357
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• 2011

For the purpose of introducing hydrophilic function to pristine PVDF, pristine PVDF was modified under atmosphere and aqueous vapor by irradiating electron beam (EB). EB dose was varied from 0 to 125 K Gray, respectively. Their changes of chemical composition /structure were observed and evaluated by FT-IR, EDS and DSC. Also, their surface behaviors were evaluated by contact angle. In FT-IR study, it was confirmed that hydroxyl functions were introduced to pristine PVDF. In EDS analysis, mole ratio of F (fluoride) was almost constant (about 33%) in spite of increasing EB dose, meaning that hydroxyl function was introduced via dehydrozenation, not via deflurodination. In DSC study, $T_g$ increased with increasing EB dose, which was reconfirmed that hydroxyl function was introduced via dehydrozenation. $T_m$ increased with increasing EB dose, inferring that the increase in EB dose led to more outbreak of hydroxyl function which led to more enhanced hydrogen bond. In the result of contact angle, pristine PVDF film was $62^{\circ}$ and 125 K Gray-irradiated PVDF film was even $13^{\circ}$. All results showed that pristine PVDF was successfully changed to hydrophilic PVDF.

• Journal of the Korean Society of Radiology
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• v.15 no.6
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• pp.781-788
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• 2021

Due to the high sensitivity to radiation, excessive exposure needs to be prevented by accurately measuring the dose irradiated to the skin during radiation therapy. Although clinical trials use dosimeters such as film, OSLD, TLD, glass dosimeter, etc. to measure skin dose, these dosimeters have difficulty in accurate dosimetry on skin curves. In this study, to solve these problems, we developed a skin dosimeter that can be attached according to human flexion and evaluated its response characteristics. For the manufacture of the dosimeter, lead oxide (PbO) with high atomic number (Z_Pb: 82, Z_O: 8) and density (9.53 g/cm³) and silicon binders that can bend according to human flexion were used. In the case of a dosimeter made of PbO material, the performance degradation has been prevented by using parylene and others due to the presence of degradation due to oxidation, but the previously used parylene is affected by bending, so a new form of passive layer was produced and applied to the skin dosimeter. The characteristic evaluation of the skin dosimeter was evaluated by analyzing SEM, reproducibility, and linearity. Through SEM analysis, bending was evaluated, reproducibility and linearity at 6 MeV energy were evaluated, and applicability was assessed with a skin dosimeter. As a result of observing the dosimeter surface through SEM analysis, the parylene passive layer PbO dosimeter with the positive layer raised to the parylene produced cracks on the surface when bent. On the other hand, no crack was observed in the silicon passive layer PbO dosimeter, which was raised to silicon passive layer. In the reproducibility measurement results, the RSD of the silicon passive layer PbO dosimeter was 1.47% which satisfied the evaluation criteria RSD 1.5% and the linearity evaluation results showed the R² value of 0.9990, which satisfied the evaluation criteria R² 9990. The silicon passive layer PbO dosimeter was evaluated to be applicable to skin dosimeters by demonstrating high signal stability, precision, and accuracy in reproducibility and linearity, without cracking due to bending.