• 제목/요약/키워드: Small field irradiation

검색결과 61건 처리시간 0.024초

얇은 산화막의 wear out에 관한 광 조사 효과 (The effect of irradiation on the wear out of thin oxide film)

  • 김재호;최복길;성영권
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1989년도 추계학술대회 논문집 학회본부
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    • pp.114-118
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    • 1989
  • Due to the increased integration density of VLSI circuits a highly reliable thin oxide film is required to fabricate a small geometry MOS device. The behavior of thermal $SiO_2$ under high electric field and current condition has a major effect on MOS device degration and also the practical use of MOS device under irradiation has cause the degration of thin oxide films. In this paper, in order to evaluate the reliability of thin oxides with no stress applied and stressed by the irradiation under low electric field, the tests of TDDB (Time-dependent-dielectric breakdown) are used. Failure times against electric field are examined and acceleration factor is obtained for each case. Based on the experimental data, breakdown wear out limitation for thin oxide films is characterised.

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Linear Accelerator를 이용한 Stereotactic Radiosurgery 방법 (A Method of Stereotactic Radiosurgery Using A Linear Accelerator)

  • 나수경;박재일
    • 대한방사선치료학회지
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    • 제6권1호
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    • pp.146-153
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    • 1994
  • A modified irradiation technique utilizing a linear accelerator for radiation surgery within the brain was performed in 41 cases of patients with anteriovenous malformation(AVM), astrocytoma, meningioma. etc. The treatment planning and dosimetry of small field for stereotactic radiosurgery with 10 MV X-ray isocentically mounted linear accelerator will be presented dose with field size, the central axis persent depth dose and the combined moving beam dose distribution. The three dimensional dose planning of stereotactic focusing irradiation on small size tumor region was perfomed with dose planning computer system(Therac 2300) and was verified with film dosimetry. The more the number of strip and the wider the angle of arc rotation, the larger were the dose delivered on tumor and the less the dose to surrounding the normal tissues. In this study, the using machine and method was as fellowing. 1) Apparatus : NELAC-1018 10MV X-ray 2) Strip No. : Select the 5-7 strips 3) Cone and field size are from $1{\times}1cm^2$ to $3.5{\times}3.5cm^2$, and special circular cone designed for the purpose of minimized the risk to normal tissue and those size are $0.7{\~}3.6cm{\phi}$.

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송과선종의 방사선치료 (Radiation Therapy of Midline Pineal Tumors and Suprasellar Germinoma)

  • 서창옥;김귀언;서정호;박창윤;추성실
    • Radiation Oncology Journal
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    • 제1권1호
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    • pp.69-77
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    • 1983
  • 20 cases of midline pineal tumors and 3 suprasellar germinomas received radiation therapy at Yonsei University Medical College, Severance hospital from 1971 to 1982 were reviewed. 12 cases were pathologically proved; 10 germinomas, 1 pineoblastoma, and 1 pineocytoma. 11 cases received radiotherapy without biopsy confirmation. Although treatment fields varied from small field to whole brain irradiation, but not to the spinal cord, most patients received 4000-5000 rads irradiation to the primary tumor site. 17 patients are alive without evidence of disease and 5 year actuarial NED survival is 73.2%. 9 of 10 biopsy proved germinomas and all 6 presumed germinomas are alive and well. Optimum radiation dose, adequate irradiation field, tumor response to radiation observed in serial CT scan and role of radiation therapy in the management of pineal tumors are also discussed.

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Philips LINAC 6 MV와 8 MV X선 소조사연에 대한 선량분포 측정 (Measurement of Dose Distribution in Small Beams of Philips 6 and 8 MVX Linear Accelerator)

  • 서태석;윤세철;신경섭;박용휘
    • Radiation Oncology Journal
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    • 제9권1호
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    • pp.143-152
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    • 1991
  • 본 논문에서는 소조사면에 대한 X-선의 선량분포를 일반실험식으로 계산될 수 있도록 beam 측정 데이타를 종합 처리하는 방법에 대하여 기술하고 있다. Beam 데이타는 philips LINAC 6 MV, 8 MV X-ray에 대하여 측정 되었으며, 측정된 요소는 tissue maximum ratio (TMR), off-axis-ratio (OAH), 그리고 relative output factor (ROF)를 포함한다. 소조사면에 의한 방사선 치료를 위하여 isocenter에서 지름이 1 내지 3cm되도록 실린더 형태의 특수 collimator가 2 mm 간격으로 제작되었다. 본 측정을 위하여 다이오드 detector가 이용되었으며 Film 및 TLO 측정기로 측정된 값과 비교검토 되었다. 제한된 조사면으로 측정된 TMR, OAR data로부터 beam 데이타를 나타내는 실험식을 유도하였으며 이 실험식은 임의의 Set-UP조건에 따른 측정값을 예상할 수 있는 일반 실험식으로 확장되었고 측정된 TMR과 OAR 값들은 잘 일치되었다.

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넓은 광자선 조사면($40{\times}40cm^2$ 이상)의 선량분포 특성 (The characteristics on dose distribution of a large field)

  • 이상록;정덕양;이병구;권영호
    • 대한방사선치료학회지
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    • 제15권1호
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    • pp.19-27
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    • 2003
  • I. 목적 Total Body Irradiation(TBI)와 Half Body Irradiation(HBI), Non-Hodgkin's lymphoma, E-Wing's sarcoma, lymphosarcoma, neuroblastoma 등의 특수한 경우에 넓은 광자선 조사면($40{\times}40cm2$ 이상)이 임상적으로 사용될 수 있다. 넓은 광자선 조사면의 선량분포는 매번 실제 측정 대신 좁은 광자선 조사면 (표준 SSD 100cm, 조사면의 크기 $40{\times}40cm2$ 미만)에서 얻은 측정결과를 이용하여 보정할 수 있으나, 단 순한 계산에 의한 방법만으로는 산란 방사선의 여러 가지 요인에 의한 실제 신체 각 부위의 선량 및 그 균일성을 알기는 힘들다. 본 연구에서는 치료거리 증가에 따른 넓은 광자선 조사면의 기본 parameter(PDD, TMR, Output, Sc, Sp)를 측정하고, 좁은 광자선 조사면에서 얻은 측정결과와 비교하여 그 차이를 확인해 보고 실제 적용여부를 알아보고자 한다. II. 대상 및 방법 표준 SSD 100cm에서 Multidata water phantom을 이용하여 조사면의 크기 변화에 따라 기본parameter(PDD, TMR, Output, Sc, Sp)를 측정하였다. 먼저 SSD 180cm에서(phantom이 치료실 바닥으로 수직방향) 조사면 증가에 따른 기본 parameter를 측정하였고, SSD 350cm에서(phantom이 치료실 벽면으로 수평방향이고 horizotal beam의 측정이 가능한 mylar를 가진 small water phantom을 이용) 같은 방법으로 측정하여 서로 비교해보았다. III. 결과 및 결론 SSD 180cm과 350cm에서 측정한 parameter들이 표준 선량측정 자료와 비교해서 오차범위가 실험적 오차에 있을 정도로 큰 차이가 없었음을 알 수 있었다. 정확한 자료를 얻기 위해 anthropomorphous phantom에서 선량측정을 하거나 이런 목적을 위해 특별히 고안된 unlimited phantom을 이용한 절대값을 얻을 수 있는 선량 측정이 요구된다. 부가적으로 작은 부피의 ionization chamber 사용과 넓은 조사면에 의한 cable과 stem effect를 고려해야 할 필요가 있다.

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Theoretical Study of the Strong Field Emission of Electrons inside a Nanogap Due to an Enhanced Terahertz Field

  • Choi, Soo Bong;Byeon, Clare Chisu;Park, Doo Jae
    • Current Optics and Photonics
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    • 제2권6호
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    • pp.508-513
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    • 2018
  • We report the development of a theoretical model describing the strong field tunneling of electrons in an extremely small nanogap (having a width of a few nanometers) that is driven by terahertz-pulse irradiation, by modifying a conventional semiclassical model that is widely applied for near-infrared wavelengths. We demonstrate the effects of carrier-envelope phase difference and strength of the incident THz field on the tunneling current across the nanogap. Additionally, we show that the dc bias also contributes to the generation of tunneling current, but the nature of the contribution is completely different for different carrier-envelope phases.

전자선 에너지 및 조사야에 따른 유효선원 피부 간 거리 변화 (Variation of Effective SSD According to Electron Energies and Irradiated Field Sizes)

  • 양칠용;염하용;정태식
    • Radiation Oncology Journal
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    • 제5권2호
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    • pp.157-163
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    • 1987
  • It is known that fixed source to skin distance (SSD) cannot be used when the treatment field is sloped or larger than the size of second collimator in electron beam irradiation and inverse square law using effective ssd should be adopted. Effective SSDs were measured in different field sizes in each 6, 9, 12, 15 and 18MeV electron energy by suing NELAC 1018D linear accelerator of Kosin Medical Center. We found important parmeters of effective SSD. 1. Minimum effective SSD was 58.8cm in small field size of $6\pm6cm$ and maximum effective SSD was 94.9cm in large field size of $25\pm25cm$, with 6MeV energy. It's difference was 36.1cm. The dose rate at measuring point was quite different even with a small difference of SSD in small field $(6\times6cm)$ and low energy (6 MeV). 2. Effective SSD increased with field size in same electron energy. 3. Effective SSDs gradually increased with the electron energies and reached maximum at 12 or 15 MeV electron energy and decreased again at 18MeV electron energy in each identical field size. And so the effective SSD should be measured in each energy and field size for practical radiotherapy.

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선형가속기의 6MV X선에 대한 소형조사면의 선량측정 (Dose Characteristics of Small Radiation Fields for 6MV X-ray of Linear Accelerator)

  • 최태진;김옥배;김영훈;손은익;김인홍
    • Radiation Oncology Journal
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    • 제7권2호
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    • pp.287-291
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    • 1989
  • Radiation dosimetry has been extended to small fields less than $4\times4cm^2$ which may be suitable for irradiation of small intracranial tumors. Special consideration was given to the percentage depth dose and scatter correction factors with 0.14ml ion chamber, film dosimetry and TLD measurement. Calculated dose distributions were compared with measured data.

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방사선 치료용 고에너지 전자선의 조직 내 선량분포 특성에 관한 연구 (Study on Characteristics of Dose Distribution in Tissue of High Energy Electron Beam for Radiation Therapy)

  • 나수경
    • 대한방사선치료학회지
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    • 제14권1호
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    • pp.175-186
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    • 2002
  • The purpose of this study is directly measure and evaluate about absorbed dose change according to nominal energy and electron cone or medical accelerator on isodose curve, percentage depth dose, contaminated X-ray, inhomogeneous tissue, oblique surface and irradiation on intracavitary that electron beam with high energy distributed in tissue, and it settled standard data of hish energy electron beam treatment, and offer to exactly data for new dote distribution modeling study based on experimental resuls and theory. Electron beam with hish energy of $6{\sim}20$ MeV is used that generated from medical linear accelerator (Clinac 2100C/D, Varian) for the experiment, andwater phantom and Farmer chamber md Markus chamber und for absorbe d dose measurement of electron beam, and standard absorbed dose is calculated by standard measurements of International Atomic Energy Agency(IAEA) TRS 277. Dose analyzer (700i dose distribution analyzer, Wellhofer), film (X-OmatV, Kodak), external cone, intracavitary cone, cork, animal compact bone and air were used for don distribution measurement. As the results of absorbed dose ratio increased while irradiation field was increased, it appeared maximum at some irradiation field size and decreased though irradiation field size was more increased, and it decreased greatly while energy of electron beam was increased, and scattered dose on wall of electron cone was the cause. In percentage depth dose curve of electron beam, Effective depth dose(R80) for nominal energy of 6, 9, 12, 16 and 20 MeV are 1.85, 2.93, 4.07, 5.37 and 6.53 cm respectively, which seems to be one third of electron beam energy (MeV). Contaminated X-ray was generated from interaction between electron beam with high energy and material, and it was about $0.3{\sim}2.3\%$ of maximum dose and increased with increasing energy. Change of depth dose ratio of electron beam was compared with theory by Monte Carlo simulation, and calculation and measured value by Pencil beam model reciprocally, and percentage depth dose and measured value by Pencil beam were agreed almost, however, there were a little lack on build up area and error increased in pendulum and multi treatment since there was no contaminated X-ray part. Percentage depth dose calculated by Monte Carlo simulation appeared to be less from all part except maximum dose area from the curve. The change of percentage depth dose by inhomogeneous tissue, maximum range after penetration the 1 cm bone was moved 1 cm toward to surface then polystyrene phantom. In case of 1 cm and 2 cm cork, it was moved 0.5 cm and 1 cm toward to depth, respectively. In case of air, practical range was extended toward depth without energy loss. Irradiation on intracavitary is using straight and beveled type cones of 2.5, 3.0, 3.5 $cm{\phi}$, and maximum and effective $80\%$ dose depth increases while electron beam energy and size of electron cone increase. In case of contaminated X-ray, as the energy increase, straight type cones were more highly appeared then beveled type. The output factor of intracavitary small field electron cone was $15{\sim}86\%$ of standard external electron cone($15{\times}15cm^2$) and straight type was slightly higher then beveled type.

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