• Title/Summary/Keyword: 중심 선속도

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The Dependence of the Wedge Factor with the Variation of High Energy Photon Beam Fluences (고에너지 광자선의 선속 변화에 따른 쐬기인자의 의존성)

  • 오영기;윤상모;김재철;박인규;김성규
    • Progress in Medical Physics
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    • v.11 no.1
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    • pp.1-18
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    • 2000
  • For wedged photon beams, the variation of the wedge factor with field size was reported by several authors. However, until now such variation with field size had not been explained quantitatively. Therefore, the variation of the wedge factor was investigated by measuring outputs with field sizes increasing from 4 cm $\times$ 4 cm to 25 cm $\times$ 25 cm for open and wedged 6 and 10MV X-ray beams. The relative outputs for wedged fields to 10 cm $\times$ 10 cm have been obtained. The results show the Increase of the wedge factor caused by the change in fluence of high energy Photon beam with field size, up to 8.0% for KD77-6MV X-ray beam. This increase could be explained as a linear function of the irradiated wedge volume except small field size up to about 10 cm. In the cases of the narrow rectangular beam parallel to the wedge direction, the wedge factor decreases slightly with increasing field size up to about 10-15 cm due to a relatively reduced photon fluence from the change of the wedge thickness. We could explain the causes of a wedge factor variation with field size as the fluences of primary photon passed throughout the wedge, contributing to the dose at the central beam axis and that the fluences were affected by the gradient of the wedge with the change of field size. For clinical use, the formula developed to describe the wedge factor variation with field size has been corrected.

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Actual Condition of Quality Control of X-ray Imaging System in Primary Care Institution: focused on Gwangju Metropolitan City (1차 의료기관의 엑스선 발생장치 정도관리에 관한 현황조사:광주광역시 지역을 중심으로)

  • Dong, Kyung-Rae;Lee, Seun-Joo;Kweon, Dae-Cheol;Goo, Eun-Hoe;Jung, Jae-Eun;Lee, Kyu-Su
    • Journal of Radiation Protection and Research
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    • v.35 no.1
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    • pp.34-42
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    • 2010
  • With the expanded use of radiation in modern medical practices, the most important issue in regards to efforts to reduce individual exposure dose is quality assurance. Therefore in order to study the present condition of quality assurance, the Gwangju Metropolitan City area was divided into five districts each containing ten hospitals. Four experiments were conducted: a reproducibility experiment for kVp, mA, and examination time (sec) intensity of illumination; half-value layer (HVL) measurement; and beam perpendicularity test matching experiment. The tube voltage reproducibility experiment for all fifty hospitals resulted in a 95.33% passing rate and mA and examination time both resulted in a 77.0% passing rate. The passing rate for intensity of illumination was 86.0% and 52.0% for HVL, which was the lowest passing rate of all four factors. For the beam perpendicularity test matching experiment, generally the central flux is matched to within $1.5^{\circ}$. Of all fifty hospitals 30.0% were beyond $3^{\circ}$. The results of the survey showed that 58% responded that they knew about quality assurance cycle. All fifty respondents stated that they have not received any training in regards to quality assurance at their current place of employment. Although quality assurance is making relative progress, the most urgent issue is awareness of the importance of quality assurance. Therefore, the implementation of professional training focusing on safety management and accurate quality assurance of radiation will reduce the exposure to radiation for radiologists and patients and higher quality imaging using less dosage will also be possible.

Prediction of the Flow Characteristics of Jet Fan in a Confined Space (제한공간에 설치된 제트팬의 기류특성 예측)

  • 이재헌;환유준;김경환;임윤철;오명도;김종필
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.3
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    • pp.206-213
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    • 2002
  • In this paper, the flow characteristics of an axial fan spraying isothermal compact jet in a confined space were investigated by the experimental methods, the numerical method, and the free jet theory According to the results, the numerical result and the experimental result are agreed well qualitatively and different quantitatively within $\pm1.0%$ for the centerline velocity, the entrainment ratio, and the maximum throw. However, the free jet theory can reasonably predict the centerline velocity except the entrainment ratio and the maximum throw. In other words, the entrainment ratio and the maximum throw by 1.he free jet theory are hard to estimate the characteristics of jet because of restriction of c confined space.

Study on the 6 MV Photon Beam Characteristics and Analysis Method from Medical Linear Accelerators Using Geant4 Medical Linac2 Example (GEANT4 Medical Linac2 예제를 이용한 6 MV 선형가속기 광자선속의 기초특성과 연구방법)

  • Kim, Byung-Yong;Kim, Hyung-Dong;Kim, Sung-Jin;Oh, Se-An;Kang, Jung-Gu;Kim, Sung-Kyu
    • Progress in Medical Physics
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    • v.22 no.2
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    • pp.79-84
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    • 2011
  • In this study, Geant4 based Monte Carlo simulations were carried out for medical linear accelerator. Modified Medical Linac2 toolkit was used for calculation. The energy spectrum, most probable energy and the photon mean energy compared with the published results using the EGS4 code. The results well agreed with published results. The calculated results of photon fluence, energy fluence and mean energy according to the radius from the centre of the beam were analyzed. Monte Carlo simulation using Medical Linac2 code is considered to be useful for analysis of medical linear accelerator. Because the calculated results varies depending on Physics List model for same head structure. It it important to choose the right model for research purpose. Monte Carlo simulation using GEANT4 Medical Linac2 is a valuable for any novice to adopt this code to the study related to 6 MV photon fluence from medical linear accelerator.

Application of Real Time Currents Prediction in Ship Speed Correction of Sea Trial Test (실선시운전 선속 보정을 위한 실시간 해수유동 예측 활용)

  • Lee, Moonjin;Lee, Han-Jin;Shin, Myung-Soo;Jung, Soo-Won
    • Journal of Navigation and Port Research
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    • v.38 no.6
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    • pp.593-600
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    • 2014
  • Information supporting system which is based on real-time prediction of currents to be applicable to the sea trial test of ship is developed. In the system, the spatial distribution of currents at specific time and the trends of variability of currents occurring at specific sites are also given as valuable information for sea trial test of ship. In addition, the system has a capability to connect with a GPS which provides information including speed loss of the ship caused by currents on the way of voyage. With information from the sea trial test, the system is also capable of delivering optimum time and pathways by considering calculated speed loss of ship at specific time and its pathway. Having information described as above, the real-time current prediction system supports and provides functions of not only running the test in an efficient way but also providing valuable information which is encouraged to be used during the test by installing at the ship.

Calculation of Neutron Energy Distribution from the Components of Proton Therapy Accelerator Using MCNPX (MCNPX를 이용한 양성자 치료기의 구성품에서 발생하는 중성자 에너지 분포계산)

  • Bae, Sang-Il;Shin, Sang-Hwa
    • Journal of the Korean Society of Radiology
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    • v.13 no.7
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    • pp.917-924
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    • 2019
  • The passive scattering system nozzle of the proton therapy accelerator was simulated to evaluate the neutrons generated by each component in each nozzle by energy. The Monte Carlo N-Particle code was used to implement spread out Bragg peak with proton energy 220 MeV, reach 20 cm, and 6 cm length used in the treatment environment. Among the proton accelerator components, neutrons were the highest in scatterers, and the neutron flux decreased as it moved away from the central flux of the proton. This study can be used as a basic data for the evaluation of the radiation necessary for the maintenance and dismantling of proton accelerators.

Measurement of the fast Neutron Flux Density in the Bulk Shielding Experimental Tank of the TRIGA Mark-II Reactor Using Solid State Track Detector

  • Ro, Seung-Gy;Jun, Jae-Shik;Cho, Sae-Hyung
    • Nuclear Engineering and Technology
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    • v.5 no.4
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    • pp.334-338
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    • 1973
  • The horizontal distribution of the fast neutron flux density in the Bulk Shielding Experimental Tank of the TRIGA Mark-II reactor at the steady power of 250 KW has been measured using a solid state track detector which is natural mica placed in contact with $^{232}$ Th fissile foil. The neutron flux density was calculated on the assumption that the fast neutron spectrum is similar to that from the thermal-induced $^{235}$ U fission. The resulting flux density distribution along the horizontal line from the center of the thermalizing column door is presented in tabular and graphical forms.

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The Measurements of Energy and Distribution of Scattered Electrons in Therapeutic X-Ray Beam (치료 방사선 선속(Flux)에 포함된 산란전자의 분포와 에너지 측정)

  • Vahc, Young-Woo;Park, Kyung-Ran;Ohyun Kwon;Lee, Yong-Ha;Kim, Tae-Hong;Kim, Sookil
    • Progress in Medical Physics
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    • v.13 no.1
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    • pp.1-8
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    • 2002
  • Accurate knowledge of the distribution of contamination electrons ( which comes from mainly gantry head by Compton scattering, pair production, and tray: henceforth called leptons ) at the surface and in the first centimeters of tissue is essential for the clinical practice of radiation oncology. Such lepton tends to reduce or eliminate the ‘skin-sparing’ advantage of megavoltage photon beam radiotherapy, This information is needed to prescribe a absorbed dose to a skin volume at a few millimeter depth in high energy therapeutic radiation photon beam All experiments were done with 15 MV photon beam from a dual energy linear accelerator (Clinac 1800, Varian). Field size is defined by ranged from 10.0$\times$10.0 to 30.0$\times$30.0 $\textrm{cm}^2$. The absorbed dose and distribution of leptons in therapeutic radiation beam (15 MV) are investigated by means of variable blocked beams of 30.0$\times$30.0 $\textrm{cm}^2$ and dose beam profiles partly removed leptons with a copper plate. A numerous leptons mainly are distributed as shape of broad cone in the central photon beam and leptons path length in the water are shorter than 2.5 cm because of the leptons energy having around 3.0 MeV. These results clearly appears that the subtraction of leptons from the total depth dose curve not only lower the absolute dose in the buildup region and surface dose, it also causes a shift of d$_{max}$ to a deeper depth.

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A Study on the Stability of a Low Freeboard Coastwise Tanker Capsized in Turning (2) -Experimental Examination of the Outward Heel Moment Induced by Flooding of Seawater onto the Deck- (선회중 전복한 저건현 내항 탱커의 복원성에 관한 연구 (2) -갑판상 해수 침입이 경사 모멘트에 미치는 영향에 대한 실험적 조사 -)

  • Lee, Yun-Sok;Kim, Chol-Seong;Lee, Sang-Min
    • Journal of Navigation and Port Research
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    • v.27 no.5
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    • pp.465-471
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    • 2003
  • A coastwise chemical tanker sailing at full speed has capsized during turning in calm water. In the previous paper, we investigated the reasons of the accident by demonstrating the proper correction for the free surface effect of the liquid cargo and the bow-sinkage effect. In this paper, we also carry out model experiments of a transverse pressure under the seawater and an outward heel moment according to the heel angle and rudder angle, on the basis of radius of turning circle, ship's speed and drift angle of model ship occurring in turning. It is also shown that the flooding of seawater onto the deck occurring in turning generated a significant outward heel moment and increased the vertical distance between the center of gravity of the ship and the center of lateral water drag.

Methodologic Aspect of LINAC-based Stereotactic Radiosurgery (선형가속기 기반 뇌정위 방사선 수술기법)

  • Choi, Tae Jin
    • Progress in Medical Physics
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    • v.23 no.3
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    • pp.127-137
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    • 2012
  • A conversing beam is firstly designed for radiosurgery by a neurosugern Lars Leksell in 1949 with orthogonal x-rays tube moving through horizontal moving arc to focusing the beam at target center. After 2 decades he composits 201 source of the Co-60 for gamma knife which beams focused at locus. Sveral linac-based stereotactic radiosurgery using the circular collimated beam which size range for 0.4~4.0 cm in a diameter by non-coplanar multiarc have been developed over the decades. The irregular lesions can be treated by superimposing with several spherical shots of radiation over the tumour volume. Linac based techniques include the use of between 4 and 11 non-co-planar arcs and a dynamic rotation technique and use photon beam energies in the range of 6~10 MV. Reviews of the characteristics of several treatment techniques can be found in the literature (Podgorsak 1989, Schell 1991). More in recent, static conformal beams defined by custom shaped collimators or a mini- or micro-multileaf collimator (mMLC) have been used in SRS. Finally, in the last few years, intensity-modulated mMLC SRS has also been introduced. Today, many commercial and in-house SRS programs have also introduced non-invasive immobilization systems include the cyberknife and tomotherapy and proton beam. This document will be compared the characteristics of dose distribution of radiosurgery as introduced gamma knife, BrainLab include photon knife in-house SRS program and cyberknife in currently wide used for a cranial SRS.