• Progress in Medical Physics
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• v.22 no.1
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• pp.52-58
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• 2011

Our goal is to assess the suitability of a glass dosimeter on detection of high-energy electron beams for clinical use, especially for radiation therapy. We examined the dosimetric characteristics of glass dosimeters including dose linearity, reproducibility, angular dependence, dose rate dependence, and energy dependence of 5 different electron energy qualities. The GD was irradiated with high-energy electron beams from the medical linear accelerator andgamma rays from a cobalt-60 teletherapy unit. All irradiations were performed in a water phantom. The result of the dose linearity for high-energy electron beams showed well fitted regression line with the coefficient of determination; $R^2$ of 0.999 between 6 and 20 MeV. The reproducibility of GDs exposed to the nominal electron energies 6, 9, 12, 16, and 20 MeV was ${\pm}1.2%$. In terms of the angular dependence to electron beams,GD response differences to the electron beam were within 1.5% for angles ranging from $0^{\circ}$ to $90^{\circ}$ and GD's maximum response differencewas 14% lower at 180o. In the dose rate dependence, measured dose values were normalized to the value obtained from 500 MU/min. The uncertainties of dose rate were measured within ${\pm}1.5%$ except for the value from 100 MU/min. In the evaluation of the energy dependence of the GD at nominal electron energies between 6 and 20 MeV, we obtained lower responses between 1.1% and 4.5% based on cobalt-60 beam. Our results show that GDs have a considerable potentiality for measuring doses delivered by high-energy electron beams.

• The Journal of Korean Society for Radiation Therapy
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• v.6 no.1
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• pp.89-93
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• 1994

Authors have measured virtual source distance of electron beam from CL/1800 medical linear accelerator, with newly designed method. Beam scanning was performed with the direction of beam axis in the air. Compared results between this study and well established in phantom measurement shows good agreement with in experimental error. And we have found that build-up cap plays very important role in air measurement because of charge build up. The method of in-air measurement of virtual source distance is very easy to set-up and generate accurate results.

• Applied Microscopy
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• v.45 no.1
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• pp.1-8
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• 2015

We have developed a new HD-2700 (Hitachi High-Technologies Corp., Japan) scanning transmission electron microscope (STEM) that includes an automatic aberration correction function, and a large-solid-angle energy-dispersive X-ray spectroscopy detector that enables high-resolution and sensitive analysis. For observation with atomic resolution, using spherical-aberration-corrected STEM, in order that satisfactory performance of the device can be achieved readily, and within a short time, irrespective of the operator's skill level, a spherical-aberration-correction device with an automatic aberration-correction function was developed. This automatic aberration-correction function carries out the entire correction-related process (aberration measurement, selection and correction) automatically, with automatic selection of the aberrations that require correction, and automatic measurement of the appropriate corrections.

• Radiation Oncology Journal
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• v.15 no.2
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• pp.159-165
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• 1997

Purpose : Secondary electrons generated by interaction between Primary X-rar beam and block tray in megavoltage irradiation, result in excess soft radiation dose to the surface layer To reduce the surface dose from the electron contamination, electron filters were attached under the tray when a customized block was used. Materials and Methods : Cu, Al or Cu/Al combined Plate with different thickness was used as a filter and the surface dose reduction was measured for each case. The measurement to find optimal filter was performed with $10m\times10cm$ field size and 78.5cm source to surface distance. The measurement points are positioned with 2mm intervals from surface to maximum build-up point. To acquire the effect of field size dependence on optimal electron filter, the measurement was performed from $4cm\times4cm\;to\;25cm\times25cm$ field sizes. Results : The surface dose was slowly increased by increasing irradiation field but rapidly increased beyond $15cm\times15cm$ field size. Al plate was found to be inadequate filter because of the failure to have surface dose kept lowering than the dose of deep area. Cu 0.5mm plate and Cu/Al=0.28mm/1.5mm combined plate were found to be optimal filters. By using these 2 filters, the absorbed dose to the surface layer was effectively reduced by $5.5\%,\;11.3\%,\;and\;22.3\%$ for the field size $4cm\times4cm,\;10m\times10cm,\;and\;25cm\times25cm$, respectively. Conclusion : The surface dose attributable to electron contamination had a dependence on field size. The electron contamination was increased when tray was used. Specially the electron contamination in the surface layer was greater when the larger field was used. 0.5mm Cu Plate and Cu/Al=0.28mm/15mm combined plates were selected as optimal electron filters. When the optimal electron filter was attached under the tray, excessive surface dose was decreased effectively The effect of these electron filters was better when a larger field was used.

• Progress in Medical Physics
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• v.25 no.2
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• pp.95-99
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• 2014

Radiation monitoring is one of the most important process in all places where radioactive material is used including hospital. In this preliminary study, we made GAS electron multiplier (GEM) detector and acquired relative efficiencies in order to see if GEM detector can be useful in radiation monitoring system. The relative efficiency was acquired by using the ratio of GEM detector efficiency to CdTe detector efficiency. The relative efficiency of 72% and 4% was acquired for beta-ray and gamma-ray respectively.

• The Journal of Korean Society for Radiation Therapy
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• v.9 no.1
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• pp.40-45
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• 1997

When therapeutic irradiation is indicated for the orbital tumors, the greatest concern is the risk of radiation-induced cataract. Conjunctival lymphoma is one of the good examples. We would like to report the procedure of the lens shielding device(L.S.D) and the result of irradiated dose to the lens. L.S.D. consistes of two parts : load alloy to attenuate electron beam, and dental acryl which completely covers the lead alloy to avoid discomfort of cornea from contacting directly with cerrobend and side scattering by cerrobend. And for easy location and removal, side bars were made on each side. Radiation doses were meaured with TLD(TLD 3500 Hawshaw). Markus chamber in a polystyrene phantom. The phantom was irradiated with 9MeV electron beams from Clinac 2100C with $6{\times}6cm$ electron cone. The relative dose at 6mm depth where the lens is located was $4.2\%$ with TLD and $5.1\%$ with Markus chamber clinically when 2600 cGy are irradiated to the eyeball, the mapinary dose to the lens will be 109 cGy or 132 cGy, which will significently reduce the cataract.

• Progress in Medical Physics
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• v.9 no.1
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• pp.29-35
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• 1998

There has been necessity of an air free ionization chamber using the gold-crystal-aluminium plates, henceforth called the crystal chamber. The crystal chamber formed of parallel plates is very small in size and has more response for absorbed dose of therapeutic radiation beams. The gold plate on the crystal facing the photon and electron beam acts as an intensifier of signals and crystal plate as an ionization medium respectively. Both the copper guard ring and the aluminum collecting electrode are connected to an electrometer. Using high energy photon (6, 15 MV) and electron (9, 12, 15, 18 MeV) beams, the responses of the crystal chamber are evaluated against a PTW Farmer-type chamber at a field size of 10${\times}$10cm$^2$ and 100 cm SSD. The responses of crystal chamber for therapeutic radiation electron and photon beams are greater in magnitude by several order than Farmer. The crystal chamber has good linearity without correction factor C$\_$t,p/ with respect to the signals, a reading reproduction with good accuracy and precision less than 0.5%, and has other useful functions in measuring radiation beams.

• Journal of Biomedical Engineering Research
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• v.7 no.2
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• pp.111-112
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• 1986

Radiation-induced fibrosarcoma tumors were grown on the flanks of C3H mice. The mice were divided into two groups. One group was injected with Photofrin II, intravenously (2.5mg/kg body weight). The other group received no Photofrin II. Mice from both groups were irradialed for approximately 15 minutes at 100, 300, or 500 mW/cm2 with the argon (488nm/514.5 nm), dye(628nm) and gold vapor (pulsed 628 nm) laser light. A photosensitizer behaved as an added absorber. Under our experimental conditions, the presence of Photolfrin II increased surface temperature by at least 40% and the temperature rise due to 300 mW/cm2 irradiation exceeded values for hyperthermia. Light and temperature distributions with depth were estimated by a computer model. The model demonstrated the influence of wavelength on the thermal process and proved to be a valuable tool to investigate internal temperature rise.

• Proceedings of the Korean Society of Medical Physics Conference
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• 1999.11a
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• pp.100-103
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• 1999

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.988-989
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• 2005