マエハタ, イツミ School of Health Sciences, Tokushima University
キモト, ナツミ School of Health Sciences, Tokushima University
タケガミ, カズキ Graduate School of Health Sciences, Tokushima University
オキノ, ヒロキ Graduate School of Health Sciences, Tokushima University
金澤, 裕樹 Institute of Biomedical Sciences, Tokushima University Graduate School 徳島大学 教育研究者総覧 KAKEN研究者をさがす
Diagnostic X-ray equipment
Secondary X-ray field
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 mmϕ. The ideal value of the exposure dose was derived mathematically by extrapolation to 0 mmϕ. 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 %.
Radiological Physics and Technology
Copyright © Japanese Society of Radiological Technology and Japan Society of Medical Physics 2016
The final publication is available at Springer via http://dx.doi.org/10.1007/s12194-016-0352-7.
rpt_9_2_193.pdf 1.49 MB