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Development and characterization of air kerma cavity standard
摘要： Ionization chambers are the most common detectors for precise measurements such as these required in radiation protection and radiotherapy. This paper presents the design, development and characterization of a new graphite–walled cavity ionization chamber used as a primary standard for air kerma rate for 137Cs and 60Co gamma radiation of the Central Office of Measures (GUM). The paper describes particularly methods for a cavity volume determination and the cavity volume relation to an electric field. The various correction factors to be applied to the primary standards and their determination by experimental and Monte Carlo methods are discussed. Re–evaluation of the standard according to the recommendations of ICRU90 Report for the new primary standard is presented. A typical uncertainty budget for the graphite-walled cavity ionization chamber as a primary standard for air kerma rate for gamma radiation is presented and results of internal comparisons between standards are summarized and discussed.
关键词： ionization chamber,air kerma cavity standard,Monte Carlo simulation,gamma radiation
更新于2025-09-23 15:23:52
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An evaluation of computed tomography dose index measurements using a pencil ionization chamber and small detectors
摘要： The aim of this study was to compare the values of the computed tomography dose index 100 (CTDI100) obtained using two small detectors (i.e. a small ionization chamber and a small solid state detector) with those obtained from a 100-mm pencil ionization chamber for various input CT parameters: beam width, kVp, mAs, pitch, and head-body phantom variation. The measurement of CTDI100 using the 100-mm pencil chamber was carried out in a single rotation of axial mode, while the measurement using small detectors was carried out in helical mode. The differences of CTDI100 values obtained with two small detectors were about 7% for all variations. The differences of CTDI100 values obtained with small detectors and a 100-mm pencil ionization chamber for beam widths of more than 4 mm were within 40%. However, for the narrowest beam widths (4 mm), the difference between them was very large (about 150%).
关键词： computed tomography dose index (CTDI),CT dose profiler,small solid state detector,CT dosimetry,small detector,small ionization chamber
更新于2025-09-23 15:21:21
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Experimental Measurement and Monte Carlo Simulation the Correction Factor for the Medium-Energy X-ray Free-air Ionization Chamber
摘要： 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.
关键词： Correction factor,Air-kerma,Experimental method,Free-air ionization chamber,Monte Carlo simulation
更新于2025-09-04 15:30:14