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Maehata I, Hayashi H, Kimoto N, Takegami K, Okino H, Kanazawa Y, Tominaga M. Practical method for determination of air kerma by use of an ionization chamber toward construction of a secondary X-ray field to be used in clinical examination rooms. Radiol Phys Technol 2016; 9:193-201. [PMID: 26994011 DOI: 10.1007/s12194-016-0352-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Revised: 02/10/2016] [Accepted: 02/16/2016] [Indexed: 11/28/2022]
Abstract
We propose a new practical method for the construction of an accurate secondary X-ray field using medical diagnostic X-ray equipment. For accurate measurement of the air kerma of an X-ray field, it is important to reduce and evaluate the contamination rate of scattered X-rays. To determine the rate quantitatively, we performed the following studies. First, we developed a shield box in which an ionization chamber could be set at an inner of the box to prevent detection of the X-rays scattered from the air. In addition, we made collimator plates which were placed near the X-ray source for estimation of the contamination rate by scattered X-rays from the movable diaphragm which is a component of the X-ray equipment. Then, we measured the exposure dose while changing the collimator plates, which had diameters of 25-90 mm(ϕ). The ideal value of the exposure dose was derived mathematically by extrapolation to 0 mm(ϕ). Tube voltages ranged from 40 to 130 kV. Under these irradiation conditions, we analyzed the contamination rate by the scattered X-rays. We found that the contamination rates were less than 1.7 and 2.3 %, caused by air and the movable diaphragm, respectively. The extrapolated value of the exposure dose has been determined to have an uncertainty of 0.7 %. The ionization chamber used in this study was calibrated with an accuracy of 5 %. Using this kind of ionization chamber, we can construct a secondary X-ray field with an uncertainty of 5 %.
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Affiliation(s)
- Itsumi Maehata
- School of Health Sciences, Tokushima University, 3-18-15 Kuramoto-Cho, Tokushima, Tokushima, 770-8503, Japan
| | - Hiroaki Hayashi
- Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-Cho, Tokushima, Tokushima, 770-8503, Japan.
| | - Natsumi Kimoto
- School of Health Sciences, Tokushima University, 3-18-15 Kuramoto-Cho, Tokushima, Tokushima, 770-8503, Japan
| | - Kazuki Takegami
- Graduate School of Health Sciences, Tokushima University, 3-18-15 Kuramoto-Cho, Tokushima, Tokushima, 770-8503, Japan
| | - Hiroki Okino
- Graduate School of Health Sciences, Tokushima University, 3-18-15 Kuramoto-Cho, Tokushima, Tokushima, 770-8503, Japan
| | - Yuki Kanazawa
- Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-Cho, Tokushima, Tokushima, 770-8503, Japan
| | - Masahide Tominaga
- Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-Cho, Tokushima, Tokushima, 770-8503, Japan
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