• Title, Summary, Keyword: air kerma

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Calibration of an $^{192}Ir$ Source Used for High Dose Rate RALS. (RALS에 장착한 Ir-192 선원의 강도측정에 대한 고찰)

  • Moon, Un-Chull
    • The Journal of Korean Society for Radiation Therapy
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    • v.6 no.1
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    • pp.56-60
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    • 1994
  • In the past, brachytherapy was carried out mostly with radium or radon sources. Currently. use of artificially produced radionuclially produced radionuclides such as $^{137}Cs,\;^{192}Ir,\;^{198}Au,\;and\;^{125}I$ is rapidly increasing. Although electrons are often used as an alternative to interstitial implants, brachytherapy continues to remain an important mode of therapy, either alone or combined with external beam. The National Council on Radiation Protection and Measurements(NCRP) recommends that the strength of any ${\gamma}$ emitter should be specified directly in terms of exposure rate in air at a specified distance such as 1m. The air kerma strength is defined as the product of air kerma rate in 'free space' and the square of the disrance of the calibration point from the source center along the perpendicular bisector, i. e., $S_k=K_L{\times}L^2$. Where $S_K$ is the the air kerma strength and K is the air kerma rate at a specified distance L. (usually 1m). Recommended units for all kerma strength are ${\mu}Gym^{2}h^{-1}$.

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Quality Assurance of Air Kerma Strength for Ir-192 High Dose Rate Source (Ir-192 고선량률 선원에 대한 공기커마강도의 품질보증)

  • Kim, Jong-Eon;Yoon, Chun-Sil;Kim, Sung-Hyun
    • Journal of radiological science and technology
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    • v.30 no.2
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    • pp.147-151
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    • 2007
  • AAPM TG43 report has recommended to measure air kerma strength with the strength of source. Main purpose of this study is to verify the accuracy of air kerma strength provided by manufacturer. Materials for this study were MAX-4001 Electrometer, HDR 1000 Plus of the corporation of standard imaging, and 6 french bronchial Applicator with 1000 mm. we measured ionization current in 10-90 mm range from the bottom of the central axis of chamber. The reference point of calibration displayed by the maximum ionization current in the ionization current curve was measured, and air kerma strength was computed from the maximum ionization current. we acquired 50 mm distance to correspond with the maximum ionization current in the ionization current curve. Its distance has perfectly fitted to the source reference point of calibration certificate of UW-ADCL. Air kerma strength computed value has measured about 0.5% more than calibration value provided by manufacturer. Air kerma strength of calibration certificate provided by manufacturer has acquired reliable results. This study shows that considering the move error of dwell position of source and the dead space length in well-type chamber is a good way to get an accurate result.

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Consistent Comparison for The Linearity Air Kerma of IEC Standards and Commercial Load in Diagnosing DR Generators (진단용 DR 발생장치에서 IEC 표준규격과 상용부하의 공기커마 직선성에 대한 일관성 비교)

  • Han, Beom-Hui;Kim, Chong-Yeal;Lee, Sang-Ho;Han, Sang-Hyun;You, In-Gyu
    • Journal of the Korean Society of Radiology
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    • v.6 no.5
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    • pp.389-394
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    • 2012
  • In this study, based on IEC 60601-2-54 standard load conditions presented in the limited interval over the air kerma at the absolute linearity closely evaluated by measuring the X-ray results were as follows: 10 units targeted all Diagnostic X-ray generating device (DR) presented in the IEC 60601-2-54 standard linearity of air kerma emerged as inappropriate, the general evaluation of the dose linearity from four in the top 50% and 80 kVp % of the two measurement series were as irrelevant all the rest from six of the top tube voltage of 50% and 80% of the two measurement series, appeared in all suitable. Presented in IEC 60601-2-54 standard dose linearity testing and conventional linearity tests showed many differences. IEC 60601-2-54 standard linearity in the proposed international standards of air kerma is the recommendation of the existing dose linearity considerably more feasible, and to quantify the amount of radiation as the standard suggested by the standard IEC 60601-2-54 air kerma of a diagnostic X-ray imaging device linearity performance management is considered key elements in the critical appraisal.

Calculation of Concrete Shielding Wall Thickness for 450 kVp X-ray Tube with MCNP Simulation and Result Comparison with Half Value Layer Method Calculation (MCNP 시뮬레이션을 통한 450 kVp 엑스레이 튜브의 콘크리트 차폐벽 두께 계산 및 반가층 방법을 이용한 계산과의 결과 비교)

  • Lee, Sangheon;Hur, SamSurk;Lee, Eunjoong;Kim, Chankyu;Cho, Gyu-seong
    • Journal of Radiation Industry
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    • v.10 no.1
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    • pp.29-35
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    • 2016
  • Radiation generating devices must be properly shielded for their safe application. Although institutes such as US National Bureau of Standards and National Council on Radiation Protection and Measurements (NCRP) have provided guidelines for shielding X-ray tube of various purposes, industry people tend to rely on 'Half Value Layer (HVL) method' which requires relatively simple calculation compared to the case of those guidelines. The method is based on the fact that the intensity, dose, and air kerma of narrow beam incident on shielding wall decreases by about half as the beam penetrates the HVL thickness of the wall. One can adjust shielding wall thickness to satisfy outside wall dose or air kerma requirements with this calculation. However, this may not always be the case because 1) The strict definition of HVL deals with only Intensity, 2) The situation is different when the beam is not 'narrow'; the beam quality inside the wall is distorted and related changes on outside wall dose or air kerma such as buildup effect occurs. Therefore, sometimes more careful research should be done in order to verify the effect of shielding specific radiation generating device. High energy X-ray tubes which is operated at the voltage above 400 kV that are used for 'heavy' nondestructive inspection is an example. People have less experience in running and shielding such device than in the case of widely-used low energy X-ray tubes operated at the voltage below 300 kV. In this study, Air Kerma value per week, outside concrete shielding wall of various thickness surrounding 450 kVp X-ray tube were calculated using MCNP simulation with the aid of Geometry Splitting method which is a famous Variance Reduction technique. The comparison between simulated result, HVL method result, and NCRP Report 147 safety goal $0.02mGy\;wk^{-1}$ on Air Kerma for the place where the public are free to pass showed that concrete wall of thickness 80 cm is needed to achieve the safety goal. Essentially same result was obtained from the application of HVL method except that it suggest the need of additional 5 cm concrete wall thickness. Therefore, employing the result from HVL method calculation as an conservative upper limit of concrete shielding wall thickness was found to be useful; It would be easy, economic, and reasonable way to set shielding wall thickness.

Experimental Measurement and Monte Carlo Simulation the Correction Factor for the Medium-Energy X-ray Free-air Ionization Chamber

  • Yu, Jili;Wu, Jinjie;Liao, Zhenyu;Zhou, Zhenjie
    • Journal of the Korean Physical Society
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    • v.73 no.10
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    • pp.1466-1472
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    • 2018
  • A key comparison has been made between the air-kerma standards of the National Institute of Metrology (NIM), China, and other Asia Pacific Metrology Programme (APMP) members in the medium-energy X-ray. This paper reviews the primary standard Free-air ionization chamber correction factor experimental method and Monte Carlo simulation method in the NIM. The experimental method and the Monte Carlo simulation method are adopted to obtain the correction factor for the medium-energy X-ray primary standard free-air ionization chamber at 100 kV, 135 kV, 180 kV, 250 kV four CCRI reference qualities. The correction factor has already been submitted to the APMP as key comparison data and the results are in good agreement with those obtained in previous studies. This study shows that the experimental method and the EGSnrc simulation method are usually used in the measurement of the correction factor. In particular, the application of the simulation methods is more common.

Comparison of Air Kerma and Absorbed Dose to Water Based Protocols for High Energy Photon Beams: Theoretical and Experimental Study

  • Shin, Dong-Oh;Kim, Seong-Hoon;Seo, Won-Seop;Park, Sung-Yong;Park, Jin-Ho;Kang, Jin-Oh;Hong, Seong-Eon;Ahn, Hee-Kyung
    • Proceedings of the Korean Society of Medical Physics Conference
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    • pp.241-243
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    • 2002
  • New types of protocols have been recently in development, all based on an absorbed dose-to-water with the aim of improving the accuracy of measurements of absorbed dose to water. IAEA TRS-277, the air-kerma standard-based present protocol, and IAEA TRS-398 and AAPM TG-51, the absorbed dose-to-water standard-based new one, were studied and compared theoretically and experimentally for photon beams of 6, 10, and 15 MV. NE 2571 and 3 Farmer types of ionization chambers in widely commercial use were used to determine an absorbed dose to water at the reference depth in water. Two different kinds of calibration factors were given respectively for every chamber calibrated in $\^$60/CO gamma ray beams from a Korean Secondary Standard Dosimetry Laboratory (KFDA). This work shows that there is around 1 % of difference of absorbed doses measured between two different types of calibration systems owing to different physical parameters and reference conditions used. We hope this work to help form the basis on development of new type of protocol in Korea.

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Comparison of Air Kerma­based and Absorbed Dose to Water­based Protocols in the Dosimetry of High Energy Electron Beams (고 에너지 전자선에 대한 공기커마와 물 흡수선량에 기반한 프로토콜간의 비교)

  • 박창현;신동오;박성용
    • Progress in Medical Physics
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    • v.14 no.4
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    • pp.249-258
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    • 2003
  • A few years ago, a proposal was made to change the dosimetry from the air kerma-based reference dosimetry to the absorbed dose-based reference dosimetry for all radiotherapy beams of ionizing radiation to improve the accuracy of dosimetry. Here, we present a dosimetry study in which the two most widespread absorbed dose­based protocols (IAEA TRS­398 and AAPM TG­51) were compared with an air kerma­based protocol (IAEA TRS-277) by measuring the absorbed dose in the same reference depth. Measurements were performed in three clinical electron beam energies using a PTW 30002 cylindrical chamber, and Markus and Roos plane­parallel chambers. $^{60}$ Co calibration factors were obtained from the KFDA. The absorbed dose differences between the air kerma­based and absorbed dose­based protocols were within 2.0% for all chambers in all beams. The results thus show that the obtained absolute dose values will be not significantly altered by changing from the air kerma­based dosimetry to the absorbed dose­based dosimetry. It was also shown that absorbed dose values between the absorbed dose­based protocols agreed by deviations of less than 0.5% for a cylindrical chamber and less than 0.7% for plane­parallel chambers using cross­calibration factors. Although the use of a cylindrical chamber and plane­parallel chambers resulted in a difference of less than 2% for all situations investigated here, to reduce errors, the plane­parallel chambers are recommended for electron energies in which the use of cylindrical chamber is not permitted in each protocol.

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Evaluation of Energy Dependency for Air Kerma Area Product by RQR Beam Quality and Indirect Calibration (RQR 선질에 따른 공기커마 면적선량계의 에너지 의존성 평가와 간접 교정)

  • Kim, Jung-Su;Kim, Sung-Hwan;Kim, Mi-Jeong;Lee, Seung-Youl;Lee, Tae-Hee;Seoung, Youl-Hun
    • Journal of the Korean Society of Radiology
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    • v.12 no.6
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    • pp.769-776
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    • 2018
  • According IEC 60601-1 ed3.1 and IEC 60601-2-45 regulation, diagnostic X-ray equipment should be display to measured and calculated air kerma area product. On the clinical X ray equipment, air kerma area product dosimeter would like to have an evidence for dosimeter accuracy and energy dependency. This study was performed to indirect calibration and energy dependency test for attached type air kerma area product (KAP) dosimeter by RQR standards beam quality. On the RQR5 beam quality, attached KAP dosimeter error showed -7.5%, respectably. On the RQR9 beam quality, attached KAP dosimeter error showed -10.4%, respectably. All RQR beam quality, average absolute error was $8.30%{\pm}2.85%$, respectably. On this study, attached KAP dosimeter was satisfied to IEC 60580 and AAPM TG 190. This calibration method of KAP dosimeter will help to performance maintain for clinical KAP dosimeter.

Quality Correction for Ir-192 Gamma Rays in Air Kerma Strength Dosimetry Using Cylindrical Ionization Chambers (원통형 전리함을 이용한 Ir-192 선원에 대한 공기커마세기 측정 시 선질보정에 관한 연구)

  • Jeong, Dong-Hyeok;Kim, Jhin-Kee;Kim, Ki-Hwan;Oh, Young-Kee;Kim, Soo-Kon;Lee, Kang-Kyoo;Moon, Sun-Rock
    • Progress in Medical Physics
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    • v.20 no.1
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    • pp.30-36
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    • 2009
  • The quality correction in the air kerma dosimetry for Ir-192 using farmer type ionization chambers calibrated by Co-60 quality is required. In this study we determined quality factor ($k_u$) of two ionization chambers of PTW-N30001 and N23333 for Ir-192 source using dosimetric method. The quality factors for energy spectrum of microSelectron were determined as $k_u$=1.016 and 1.017 for PTW-N30001 and N23333 ionization chambers respectively. We applied quality factors in air kerma dosimetry for microSelectron source and compared with reference values. As a results we found that the differences between reference air kerma rate and measured it with and without quality correction were about -0.5% and -2.0% respectively.

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