• Title, Summary, Keyword: angular dependence

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Evaluation of OSLD and EBT3 film for dose, energy, and angular dependence (OSLD와 EBT3 필름의 선량, 에너지, 방향의존성에 대한 평가)

  • Lee, Ju-seong;Kang, Bo-ram;Kwon, Hyeon-Kyung;Park, Ji-Young;Kim, Ju-Hye;Choi, Young-Se;Kim, Daehong
    • The Korean Journal of Food & Health Convergence
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    • v.4 no.1
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    • pp.15-22
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    • 2018
  • A radiation dosimeter is important to assess quality assurance (QA) of radiation therapy devices and to estimate the radiation dose in vivo dosimetry. Recently, optically stimulated luminescence detector (OSLD) is widely used in clinical filed. Therefore, the purpose of this study is to evaluate dose, energy, and angular dependence of OSLD and EBT3 film. The absorbed dose in clinical linear accelerator (Linac) beam is calibrated for dose per monitor unit (MU). Dose, energy, and angular dependence of OSLD and EBT3 film are estimated after the calibration procedure. The absorbed dose is measured at 50, 100, 150, and 200 cGy in an 6 MV X-ray beam for dose dependence. A dose of 150 cGy is delivered to OSLD and EBT3 film with 6 and 10 MV photon energies for energy dependence. For measurements of angular dependence, angular positions of gantry are $0^{\circ}{\pm}80^{\circ}$ with 6 MV at 150 cGy. The results of dose dependence is linear for OSLD and EBT3 film. For the results of energy dependence, errors were 0.39% and 0.03% for OSLD and EBT3 film, respectively. The results of dose for angular is decreased from $0^{\circ}$ to ${\pm}80^{\circ}$ for both OSLD and EBT3 film. When angle of $0^{\circ}$ is normalized to 1, and the dose is decreased to 60 and 66% at $80^{\circ}$ for OSLD and EBT3 film, respectively. Dose and energy dependence of OSLD and EBT3 film are measured within the recommendation of manufacturer. Angular dependence is increased from $0^{\circ}$ to ${\pm}80^{\circ}$ for OSLD and EBT3 film. The characteristics of OSLD and EBT3 film are similar and expected to useful for clinical field.

Fundamental Study of nanoDot OSL Dosimeters for Entrance Skin Dose Measurement in Diagnostic X-ray Examinations

  • Okazaki, Tohru;Hayashi, Hiroaki;Takegami, Kazuki;Okino, Hiroki;Kimoto, Natsumi;Maehata, Itsumi;Kobayashi, Ikuo
    • Journal of Radiation Protection and Research
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    • v.41 no.3
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    • pp.229-236
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    • 2016
  • Background: In order to manage the patient exposure dose in X-ray diagnosis, it is preferred to evaluate the entrance skin dose; although there are some evaluations about entrance skin dose, a small number of report has been published for direct measurement of patient. We think that a small-type optically stimulated luminescence (OSL) dosimeter, named nanoDot, can achieve a direct measurement. For evaluations, the corrections of angular and energy dependences play an important role. In this study, we aimed to evaluate the angular and the energy dependences of nanoDot. Materials and Methods: We used commercially available X-ray diagnostic equipment. For angular dependence measurement, a relative response of every 15 degrees of nanoDot was measured in 40-140 kV X-ray. And for energy dependence measurement, mono-energetic characteristic X-rays were generated using several materials by irradiating the diagnostic X-rays, and the nanoDot was irradiated by the characteristic X-rays. We evaluated the measured response in an energy range of 8.1-75.5 keV. In addition, we performed Monte-Carlo simulation to compare experimental results. Results and Discussion: The experimental results were in good agreement with those of Monte-Carlo simulation. The angular dependence of nanoDot was almost steady with the response of 0 degrees except for 90 and 270 degrees. Furthermore, we found that difference of the response of nanoDot, where the nanoDot was irradiated from the randomly set directions, was estimated to be at most 5%. On the other hand, the response of nanoDot varies with the energy of incident X-rays; slightly increased to 20 keV and gradually decreased to 80 keV. These results are valuable to perform the precise evaluation of entrance skin dose with nanoDot in X-ray diagnosis. Conclusion: The influence of angular dependence and energy dependence in X-ray diagnosis is not so large, and the nanoDot OSL dosimeter is considered to be suitable dosimeter for direct measurement of entrance surface dose of patient.

Spin Transfer Torque in Ferromagnet-Normal Metal-Antiferromagnet Junctions

  • Lee, Hyun-Woo;Yang, Hyun-Soo
    • Journal of Magnetics
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    • v.16 no.2
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    • pp.92-96
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    • 2011
  • This study investigated theoretically the properties of the spin transfer torque acting on a ferromagnet in a ferromagnet-normal metal-antiferromagnet junction. Earlier work showed that the angular dependence of the spin transfer torque can be a wavy-type if the junction satisfies a special symmetry. This paper reports a simple model analysis that allows a derivation of the wavy angular dependence without taking advantage of the symmetry. This result suggests that the wavy angular dependence can appear even when the symmetry is broken. As an illustration, the angular dependence was calculated as a function of the degree of the compensation at the normal metal-antiferromagnet interface. The implications of the result for the current-induced magnetization precession are discussed.

Evaluation for Performance of a Military Radiation Detecter PDR-1K : Focused on Dependence of Angular and Energy (군사용 방사선 계측기 PDR-1K 반응도 평가 : 방향 및 에너지 의존성을 중심으로)

  • Park, Wonseok;Choi, Junhyuk;Jung, Doyoung;Kim, Jango;Min, Byungin
    • Journal of the Korea Institute of Military Science and Technology
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    • v.20 no.2
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    • pp.300-305
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    • 2017
  • In this paper, we performed a evaluation for angular and energy dependence of military radiation detector PDR-1K. Its measuring range is divided into two section, low and high, and each range has a GM tube separately owing to broad scale. We observed a change in relative angular reactivity within 0.928 ~ 1.188 in low range and within 0.743 ~ 1.000 in high range from $-90^{\circ}$ to $+90^{\circ}$. The evaluation for energy dependence appeared a relative reactivity within 0.892 ~ 1.000 above 83 keV. This means PDR-1K isn't possible to use below 83 keV of radiation energy. It is possible to provide response information to user and to increase reliability of radiation measurement through this paper.

A Theoretical Calculation for Angular Dependence of X-ray Beams on Extremity Phantom (말단팬텀에서 X-선 빔의 방향의존성에 관한 이론적 계산)

  • Kim, Jong-Soo;Yoon, Suk-Chul;Kim, Jang-Lyul;Kim, Kwang-Pyo
    • Journal of Radiation Protection and Research
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    • v.21 no.4
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    • pp.263-271
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    • 1996
  • The ANSI N13.32 recommends that a study of the angular response of a dosimeter be carried out once, although no pass/fail criterion is given for angular response. Gamma dose equivalent conversion and angular dependence factors were calculated by using MCNP code for the case of ANSI N13.32 extremity phantoms(finger and arm) at the depth of $7mg/cm^2$. Those extremity dosimeters were assumed to be irradiated from both monoenergitic photons and ISO X-ray narrow beams. These calculated gamma dose equivalent conversion and angular dependence factors were compared to B. Grosswendt's result calculated by using X-ray beams. The result showed that the dose equivalent conversion factors of this study agreed well with that of B. Grosswendt for all energies within 2% except 7% in the case of the low energies. In the case of angular dependence factors comparison, they agreed within 3%. It was shown that angular dependence factors of the finger phantom decreased as the horizontal angle of the phantom increased for the ISO X-ray beams less than 60keV. For the higher energy X-ray beams range they decreased slightly around 40 degree, but then increased from this energy to 90 degree.

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Angular Dependence of Exchange Bias in NiFe/MnIr Bilayers (NiFe/MnIr 박막에서 교환 바이어스의 각도 의존성 연구)

  • Yoon, Seok Soo;Kim, Dong Young
    • Journal of the Korean Magnetics Society
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    • v.27 no.1
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    • pp.30-34
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    • 2017
  • In this report, we calculated the angular dependence of exchange bias ($H_{ex}$) by using single domain model in exchange coupled ferromagnetic (F)/antiferromagnetic (AF) bilayers, which results with AF thickness ($t_{AF}$) were used for the analysis of measured ones in NiFe/MnIr bilayers. Angular dependence of $H_{ex}$ calculated at $t_{AF}$ > $t_c$ showed typical unidirectional behaviors, however, calculated one at $0.5t_c$ < $t_{AF}$ < $t_c$ showed peculiar angular behaviors by fixed AF spins at specified angle near ${\theta}_H=90^{\circ}$. Angular dependence of $H_{ex}$ measured in NiFe/MnIr (20 nm) bilayers showed typical unidirectional behaviors. However, measured one in NiFe/MnIr (4 nm) bilayers showed mixed behaviors including both of unidirectional and peculiar angular behaviors, which was explained by the grain size distribution of polycrystalline MnIr.

Dependence of solar proton peak flux on 3-dimensional CME parameter

  • Park, Jinhye;Moon, Yong-Jae;Lee, Harim
    • The Bulletin of The Korean Astronomical Society
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    • v.40 no.1
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    • pp.64.1-64.1
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    • 2015
  • In the present study, we examine the dependence of solar proton peak flux at SOHO and STEREO on 3-D CME parameters (radial speed, angular width, and longitudinal angular separation between its source region and the magnetic footpoints of spacecraft). For this we consider 38 proton enhancements of 16 SEP events observed by SOHO, STEREO-A, and/or B from 2010 August to 2013 June. As a result, we find that the enhancements are strongly dependent on these three parameters. The correlation coefficient between proton peak flux and CME speed is about 0.42 for the cases the footpoints are located inside the lateral boundaries of angular widths, while there is no correlation for the events outside the boundaries. The correlation coefficient between peak flux and angular separation is -0.51. We find that most of strong proton events occur when their angular separations are closer to zero, supporting that most of the proton fluxes are generated near the CME noses rather than their flanks.

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The comparison of angular dependence for optical stimulated luminescence dosimeter(OSLD) and electronic personal dosimeter(EPD) used in Diagnostic Radiology (영상의학과에서 사용되는 광자극 형광선량계와 전자식 개인선량계의 방향 의존성 비교)

  • Kwon, Soon-mu;Park, Jeong-kyu;Kim, Boo-soon
    • Journal of Digital Contents Society
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    • v.16 no.3
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    • pp.463-470
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    • 2015
  • The angular dependence of active dosimeters, EPD, is analysed and compared with that of passive dosimeters, OSLD, after evaluating their relative response and uncertainty of measurement, where it is known that the personal use of them has been increased recently. There appeared a minor variation for average relative response of OSLD in the horizontal and vertical directions within the range $0^{\circ}{\sim}{\pm}90^{\circ}$, which are 0.97 and 0.95 respectively. The variations of angular dependence in the same situations with OSLD are 0.65 and 0.62, respectively, which also reveals a negligible effect on the overall uncertainty. EPDs within the interval $0^{\circ}{\sim}{\pm}60^{\circ}$ for horizontal and vertical directions are 0.94 and 0.97, respectively. These satisfy the requirements of IEC 61526. Uncertainties about the dependence of direction from horizontal and vertical directions are 0.44, 0.40, respectively. The impact of these uncertainties on the overall uncertainty was negligible. However, we observed a significant change in reactivity: the relative reactivities for $+90^{\circ}$ and $-90^{\circ}$ from the horizontal direction are 0.60, 0.37, while that form vertical direction is 0.06. The direction dependence of OSLD was superior to EPD in the range of $0^{\circ}{\sim}{\pm}90^{\circ}$. There appeared a rapidly changing structural features in EPD response for a certain direction. Therefore, we conclude that concurrent use of passive dosimeters and auxiliary dosimeter provides accurate data for personal dose measurements.

A Study on the Angular Dependence of the PB-3 Dosimeter Using Teledyne 9150 TLD Reader System (열형광선량계(도시메터타입 : PB-3)의 방향의존성에 관한 연구)

  • Son, Jung-Kwon;Kim, Jong-Kyung;Yoon, Suk-Chul
    • Journal of Radiation Protection and Research
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    • v.19 no.3
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    • pp.189-198
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    • 1994
  • An angular dependence experiment was made and a performance test of the Teledyne dosimetry system was done in accordance with the ANSI N13.11-1992. The angular dependence experiment was performed with $^{137}Cs$ and low energy X-ray beam. Teledyne dosimetry system performed well at the $0^{\circ}$ angle of incidence for all dosimeters in both vertical and horizontal irradiations. It would have easily passed the 0.5 tolerance limit. But the dosimetry system was not performed well at the ${\pm}60^{\circ}$ angle of incidence for low energy X-ray beam. The accuracy for $^{137}Cs$ beam at all angles of incidence was within the 0.5 tolerance limit. Therefore performance of the dosimetry system could be considered acceptable in case that the dosimeter is irradiated to $^{137}Cs$ beam. However, it could not be acceptable for the dosimeter irradiated to low energy X-ray, especially at more than ${\pm}40^{\circ}$

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