• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.26-26
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• 2012

The hydrophobic nature of the wool surface give rise to difficult penetration of dye molecules. Among all the methods of modification, graft polymerization is an attractive method to impart a variety of functional groups to a polymer. Grafting has been made by irradiating the light on the polymer in the presence of a solvent containing monomer. The energy source commonly used are high-energy electrons, X-rays, UV and visible light. UV irradiation is a relatively low-energy radiation in comparison with others since it has the least possibility to change bulk properties. In the present paper, a photo-reactive dye was synthesized from quinizarin by the reaction with methacryloyl chloride. The synthesized dye was continuously grafted onto wool fabric at room temperature by UV irradiation. Several key parameters including UV energy, dye concentration and pH have been examined to understand their influence on the photoreactive coloration.

• Journal of the Korean Society of Radiology
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• v.13 no.1
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• pp.81-86
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• 2019

In X-ray image, the role of filtration through the filter is to reduce the exposure of the patient by using photon which is useful in formation of the image, and at the same time, enhance the contrast of the image. During interaction between photon and object, low energy X-rays are absorbed from the site of a few cm of the first patient's tissue, and high energy X-rays are the one which form the image. Therefore, the radiation filter absorbs low energy X-ray in order to lower the exposure of the patient and improve the quality of the image. The purpose of this study is to compare the effect on the image quality by differences of added filter through simulation image and actual radiation image. For that purpose, we used Geant4 Application for Tomographic Emission (GATE) as a tool for Monte Carlo simulation. We set actual size, shape and material of Polymethylmethacrylate (PMMA) Phantom on GATE and differentiated the parameter of added filter. Also, we took image of PMMA phantom with same parameter of added filter by digital radiography (DR). Than we performed contrast-to-noise ratio (CNR) evaluation on both simulation image and actual DR image by Image J. Finally, we observed the effect on image quality due to different thickness of added filter, and compared two images' CNR evaluation's transitions of change. The result of this experiment showed decreasing in the progress of CNR on both DR and simulation image. It is ultimately caused by decreasing in contrast on image. In theory, contrast decrease with kVp increased. Given that condition, this study found out that filter makes not only decreasing total dose by absorbing low energy of X-ray, but also increasing average energy of X-ray.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.691-693
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• 2015

Radio sources are very weak, as they can travel through large distances. Radio sources also have photons with low energies compared to others electromagnetic waves (EM). Microwave photons have a little more energy than radio waves, infrared photons have still more, then visible, ultraviolet, X-rays, and the most energetic electromagnetic wave is gamma-rays. Radio astronomy studies are restricted due to radio frequency interference (RFI) produced by people. If this disturbance is not minimized, it poses critical problems for astrophysical studies. The purpose of this paper is to profile RFI maps in Peninsular Malaysia with a minimum mapping technique for RFI interference. Decision-making processes using GIS (Geographical Information System) for the selection requires gathering information for a variety of parameters. These factors affecting the selection process are also taken into account. In this study, various factors or parameters are involved, such as the availability of telecommunications transmission (including radio and television), rainfall, water lines and human activity. This mapping step must be followed by RFI site testing in order to identify areas of low RFI. This study will benefit radio astronomy research, especially regarding the RFI profile.

• 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.

• Journal of Radiation Protection and Research
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• v.46 no.3
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• pp.120-126
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• 2021

Background: This paper aims to evaluate the clinical utility and radiation dosimetry, for the mobile X-ray imaging of patients with known or suspected infectious diseases, through the window of an isolation room. The suitability of this technique for imaging coronavirus disease 2019 (COVID-19) patients is of particular focus here, although it is expected to have equal relevance to many infectious respiratory disease outbreaks. Materials and Methods: Two exposure levels were examined, a "typical" mobile exposure of 100 kVp/1.6 mAs and a "high" exposure of 120 kVp/5 mAs. Exposures of an anthropomorphic phantom were made, with and without a glass window present in the beam. The resultant phantom images were provided to experienced radiographers for image quality evaluation, using a Likert scale to rate the anatomical structure visibility. Results and Discussion: The incident air kerma doubled using the high exposure technique, from 29.47 µGy to 67.82 µGy and scattered radiation inside and outside the room increased. Despite an increase in beam energy, high exposure technique images received higher image quality scores than images acquired using lower exposure settings. Conclusion: Increased scattered radiation was very low and can be further mitigated by ensuring surrounding staff are appropriately distanced from both the patient and X-ray tube. Although an increase in incident air kerma was observed, practical advantages in infection control and personal protective equipment conservation were identified. Sites are encouraged to consider the use of this technique where appropriate, following the completion of standard justification practices.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.367-373
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• 2020

Most of the spatial scattered dose caused by the scattered rays generated by the collision between the object and X-rays is relatively easily absorbed by the human body as electromagnetic waves in the low energy region, thereby increasing the degree of radiation exposure. Such spatial scattering dose is also used as an indicator of the degree of radiation exposure of radiation workers and patients, and there is a need for a method to reduce exposure by reducing the spatial scattered dose that occurs indirectly. Therefore, in this study, a lead-free radiation shielding sheet was proposed as a way to reduce the spatial scattering dose, and a Monte Carlo (MC) simulation was performed based on a chest X-ray examination. The absorbed dose was calculated and the measured value and the shielding rate were compared and evaluated.

• Journal of the Korean Society of Radiology
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• v.12 no.7
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• pp.827-832
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• 2018

Research on effective dose analysis of actual conditions of use based on large data is scarce. In this study, the exposure conditions of Chest X-Ray examinations used by 324 medical institutions in Korea were calculated and evaluated using computer simulations. As a result of the experiment, the effective dose in the low energy parameter bands was 0.024 mSv, followed by spleen, adrenal glands, and lung. The effective dose in the high-energy exposure parameter band was 0.123 mSv, followed by height, spleen and adrenal glands. The effective dose was 0.017 mSv when the optimal conditions considered the quality and exposure proposed in Park's study were used. The results of the study will be a reference for chest X-rays and will help reduce patient exposure.

• Progress in Superconductivity
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• v.9 no.2
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• pp.162-166
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• 2008

We are developing a sensitive gamma ray spectrometer based on superconducting transition edge sensors. The detector consists of a small piece of high purity Sn as an absorber and a Ti/Au bilayer as a temperature sensor. It is designed to measure the thermal signal caused by absorption of gamma rays. The mechanical support and the thermal contact between the absorber and the thermometer were made with Stycast epoxy. The bilayer was formed by e-beam evaporation and patterned by wet etching on top of a $SiN_X$ membrane. A sharp superconducting transition of the film was measured near 100 mK. When the film was biased to the edge of the transition, signals were observed due to single photon absorption emitted from an $^{241}Am$ source. The measured spectrum showed several characteristic peaks of the source including 59.5 keV gamma line. The full with at half maximum was about 900 eV for the 59.5 keV gamma line. The background was low enough to resolve low energy lines. Considerations to improve the energy resolution of the gamma ray spectrometer are also discussed.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.214-216
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• 2005

The PAL (Pohang Accelerator Laboratory) is persuading to construct a SASE-XFEL facility (PAL XFEL) that supplies coherent X-rays. The bright and stable electron beam is essential for the PAL XEL. The electron beams has to have an emittance of 1.0 mm-mrad, a peak current of 3 kA, and a low energy spread of 1.0 MeV. In order to provide reasonably stable SASE output, the RF stability of 0.02% rms is required for both RF phase and amplitude. This is a technologically challenging issue for PAL XFEL. An inverter technology is to be applied to charge the PFN of a new modulator. Therefore, a new inverter system should provide very stable charging performances. This paper presents the development of an ultra stable klystron-modulator with an inverter power supply.

• The Journal of Korean Society for Radiation Therapy
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• v.7 no.1
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• pp.32-44
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• 1995

I. 제 목 고에너지 X-선 소조사야의 선량분포 및 계측에 관한 연구 II. 연구의 목적 및 중요성 최근 수술이 어려운 뇌종양등에 대한 방사선수술법(Radiosurgery)이 관심의 대상이 되고 있다. 방사선수술법은 크게 나누어 200여개의 Co-60이 장착된 장치(Gamma Knife)를 이용하는 방법과, X-선치료기를 이용하는 방법은 몇개의 보조기구를 설치하면 가능한 매우 경제적인 방법이다. 따라서 Microtron을 이용한 방사선수술의 기초자료확보를 위하여 소조사야에 대한 선량과 선량분포의 측정 및 계산을 실시하였다. III. 연구의 내용 및 범위 Microtron으로부터 조사되는 6MV, 10MV, 21MV X-선의 지름 3cm이하 소조사야에 대한 정확한 선량 및 선량분포 자료를 확보하기 위해, 가. Microtron치료기와 보조장치등에 대한 정밀도 계측 및 평가 나. 보조 Collimator의 적당한 크기와 재료의 선택 및 설계, 제작. 다. 에너지와 조사야 크기 각각에 대한 여러측정장치(Ion chamber, Diode detector, TLD 및 Film등)를 이용한 선량 및 선량분포 측정. 라. 측정값들의 비교, 검토 및 측정된 자료에 의한 선량 및 선량분포의 계산을 수행했다. IV. 연구결과 및 활용에 대한 건의 본 연구에서 얻은 결과는 다음과 같다. 가. Microtron치료기와 보조장치등의 정확도의 허용 오차범위내에서 잘 일치하였다. 나. 보조 collimater adpator는 총 길이 24cm로 하였으며 재질로는 두랄미늄을 사용하였고, 보조 collimator는 low melting alloy를 사용하였으며 소조사야 크기의 정확도는 0.5mm이내에서 매우 잘 일치 하였다. 다. 방사선 수술법의 에너지 선택에 중요한 요소중의 하나인 penumbra는 6MV X-선에서 가장 적게 나타났으며 라. 소조사면에 대한 깊이-선량 백분율곡선은 모든 에너지에서 조사면이 작아질수록 표면으로 이동하는 경향을 보였다. 이상의 결과로부터 방사선 수술을 시행할 경우 수십억원에 이르는 장비의 도입이나 새로운 시설 없이 Microtron에서 조사되는 고에너지 X-선을 이용할 수 있을 것으로 사료된다. 또한 새로 구입한 측정기나 보조 Collimator를 이용하여 소조사야에 대한 선량측정기술을 습득함으로써 일반적인 소조사야의 방사선치료나 회전치료등에 활용할 수 있다.