• 연구논문집
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• s.32
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• pp.65-76
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• 2002

The intensity of x-ray or gamma-ray is attenuated according to density and thickness of the transmitted medium. In this study, by using this principle, on-line real-time radiometric system was developed using a 128 channels linear array of solid state detectors to measure wall thickness of insulated piping system. This system uses a Ir-192 as a gamma ray source and detector is composed of BGO scintillator and photodiode. Ir-192 gamma ray source and linear detector array mounted on a computer controlled robotic crawler. The Ir-192 gamma ray source is located on one side of the piping components and the detector array on the other side. The individual detectors of the detector array measure the intensity of the gamma rays after passing through the walls and the insulation of the piping component under measurement. The output of the detector array is amplified by amplifier and transmitted to the computer. This system collects and analyses the data from the detector array in real-time. The maximum measurable length of pipe is 120cm/mm. in the case of 1mm scanning interval.

• The Journal of Korean Society for Radiation Therapy
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• v.6 no.1
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• pp.56-60
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• 1994

In the past, brachytherapy was carried out mostly with radium or radon sources. Currently. use of artificially produced radionuclially produced radionuclides such as $^{137}Cs,\;^{192}Ir,\;^{198}Au,\;and\;^{125}I$ is rapidly increasing. Although electrons are often used as an alternative to interstitial implants, brachytherapy continues to remain an important mode of therapy, either alone or combined with external beam. The National Council on Radiation Protection and Measurements(NCRP) recommends that the strength of any ${\gamma}$ emitter should be specified directly in terms of exposure rate in air at a specified distance such as 1m. The air kerma strength is defined as the product of air kerma rate in 'free space' and the square of the disrance of the calibration point from the source center along the perpendicular bisector, i. e., $S_k=K_L{\times}L^2$. Where $S_K$ is the the air kerma strength and K is the air kerma rate at a specified distance L. (usually 1m). Recommended units for all kerma strength are ${\mu}Gym^{2}h^{-1}$.

• Journal of radiological science and technology
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• v.4 no.1
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• pp.63-71
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• 1981

The metal-plates(Aluminium. Copper, Lead) of change the variation thickness have been penetrated by the collimated beam($450mm{\times}4mm{\phi}$) of Gamma-ray from $^{192}Ir$. Then, the scattered $\gamma$-ray dose in variable angle and the directly transmitted $\gamma$-ray dose were measured using the electrometer of ionization chamber. The results were summarized as follows: 1. Obtained the mass attenuation coefficients of $Al;0.0937cm^2g^{-1},\;Cu;0.0937cm^2g^{-1},\;pb;0.244cm^2g^{-1}$. 2. Total intensity of front scattered $\gamma$-ray follow the order of Al>Cu>pb. 3. The scattered $\gamma$-ray intensity with the lager angle of scattering was saturated after increase rapidly, and the scattering angle of the more larger was decreased. 4. The scattered $\gamma$-ray intensity through plates of aluminium or copper was saturated after increase with thicker scatterer, and the intensity was decreased at the more thicker. But the variation of scattered $\gamma$-ray dose in the lead plate made the fewest than Al and Cu. 5. The ratio of the scattered $\gamma$-ray dose and the directly transmitted $\gamma$-ray dose was saturated after increase with the thicker scatterer, and the scatterer of the more thicker was decreased. Degree of total intensity in these ratios was followed the order of Cu>Al>Pb.

• Progress in Medical Physics
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• v.13 no.4
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• pp.187-194
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• 2002

In this work we investigated through Monte Carlo calculations the physical characteristics of the absorbed dose from the Ir-192 source used in brachytherapy The Monte Carlo calculations were performed using the code EGS4, which was extensively modified in order to handle cylindrical sources, phantoms, and energy distributions to suit out own purpose. From the results of the calculations for the $\beta$ -rays, it was found that they contribute on the average 0.02% to The total absorbed dose in the distance range of 0.5-5.0 cm from the source. This is due to the face that, although most of the primary $\beta$ -rays are absorbed in the source and encapsulation material, the resulting low energy braking radiation from them contribute to such a distance. The absorbed dose in the encapsulation material varied on the average from 2.8% for platinum down to 1.1% for iron. The radial dose functions obtained by our Monte Carlo calculations were consistent within $\pm$3% with those of the TG-43 report for the radial distance interval 0.5-10.0 cm from the source. The user code we wrote in this work can be used for other sources of different sizes and so it can be very useful in designing and producing the sources for brachytherapy.

• The Journal of Korean Society for Radiation Therapy
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• v.8 no.1
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• pp.19-27
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• 1996

I. Project Title A Study of Brachytherapy for intraocular tumor II. Objective and Importance of the project The eye enucleation or external-beam radiation therapy that has been commonly used for the treatment of intraocular tumor have demerits of visual loss and in deficiency of effective tumor dose. Recently, brachytherapy using the plaques containing radioisotope-now treatment method that decrease the demerits of the above mentioned treatment methods and increase the treatment effect-is introduced and performed in the countries, Our purpose of this research is to design suitable shape of plaque for the ophthalmic brachytherapy, and to measure absorbed doses of Ir-192 ophthalmic plaque and thereby calculate the exact radiation dose of tumor and it's adjacent normal tissue. III. Scope and Contents of the project In order to brachytherapy for intraocular tumor, 1. to determine the eye model and selected suitable radioisotope 2. to design the suitable shape of plaque 3. to measure transmission factor and dose distribution for custom made plaques 4. to compare with the these data and results of computer dose calculation models IV. Results and Proposal for Applications The result were as followed. 1. Eye model was determined as a 25mm diameter sphere, Ir-192 was considered the most appropriate as radioisotope for brachytherapy, because of the size, half, energy and availability. 2. Considering the biological response with human tissue and protection of exposed dose, we made the plaques with gold, of which size were 15mm, 17mm and 20mm in diameter, and 1.5mm in thickness. 3. Transmission factor of plaques are all 0.71 with TLD and film dosimetry at the surface of plaques and 0.45, 0.49 at 1.5mm distance of surface, respectively. 4. As compared the measured data for the plaque with Ir-192 seeds to results of computer dose calculation model by Gary Luxton et al. and CAP-PLAN (Radiation Treatment Planning System), absorbed doses are within ${\pm}10\%$ and distance deviations are within 0.4mm Maximum error is $-11.3\%$ and 0.8mm, respectively. As a result of it, we can treat the intraocular tumor more effectively by using custom made gold plaque and Ir-192 seeds.

• The Journal of Korean Society for Radiation Therapy
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• v.19 no.1
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• pp.19-26
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• 2007

Purpose: To compare of the accuracy among various measurement procedures of HDR Brachytherapy, and to evaluate the clinical suitability and usefulness of alternative PMMA (polymethylmethacrylateplastics: $C_5H_8O_2$) plate phantom without any additional cost due to the purchase of measuring apparatus. Materials and Methods: We made a comparative study on three types of measuring systems: well type chamber, source calibration jig, and PMMA plate phantom. Farmer type chamber was used for source calibration jig method and PMMA plate phantom method. Measurement was done 5 times each in comparison with the measurement values from manufacturer. Measurement results from experiment were compared with that from the manufacturer which is offered with the source whenever a source is substituted by a new one and evaluate the accuracy of source activity. Results: As a consequence of Ir-192 source measurement using well type chamber, source calibration jig and PMMA plate phantom, RMS (Root Mean Square) values for the relative error are 0.6%, 1.57%, 2.1%, respectively, compared with the data from manufacturer. And the mean errors with standard deviation are given $-0.2{\pm}0.5%$, $0.97{\pm}1.23%$, $-0.89{\pm}1.87%$ respectively. Conclusion: From the results shown by the three types of measurement system (well type chamber, source calibration jig, and PMMA plate phantom), the measurement with well type chamber produced the best accuracy. It turns out that we can also use the alternative system of PMMA plate phantom clinically without purchasing any additional particular apparatus since the system does not exceed the recommendation of AAPM (American Association of Physicists in Medicine), which requires the error range of within ${\pm}5%$.

• Radioisotope journal
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• v.13 no.1
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• pp.23-30
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• 1998

• Proceedings of the Korean Nuclear Society Conference
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• 1977.06a
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• pp.109.5-110
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• 1977

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.521-522
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• 2005

• The Journal of Korean Society for Radiation Therapy
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• v.6 no.1
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• pp.61-63
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• 1994