著者

中田 好抒 杣沢 繁

出版者

公益社団法人日本放射線技術学会

雑誌

日本放射線技術學會雜誌 (ISSN:03694305)

巻号頁・発行日

vol.27, no.3, pp.217-225, 1971-10-31

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Tte distribution of the radiation dose within a uniform, circular, 'Phantom' column (30cm. in diameter) was measured in terms of the eccentric angle, θ, between the zero axis of the column and the central axis of the eccentric beam, for the point P' which lies at the same distance, n, from the source as does the center of rotation of the 'Phantom', at a distance γ from the center of rotation (taken as the eccentric radius from the center of rotation of the section of the beam passing through P'). In the calculations, the 100% reference level was taken to be that at the point P, a distance equal to the eccentric radius along the zero axis of the 'Phantom' in the direction of the source. Gregory's method was applied to calculation at intervals ^o_ff 10 degrees. The absolute radiation dose, Dp, at the datum point P can be expressed theoretically by the ollowing formulas. [numerical formula] R : the angle of beam rotation T_R : the time required to rotate the beam R degrees [numerical formula] (W : width of the rotation field) In these formulas, TAR means the values of the distance P'Q from a point P' to the surface of the 'Phantom' along the eccentric beam, and it can be obtained from the following expression : [numerical formula] PR : radius of the 'Phantom' The difference between the values obtained from this formula and practical measuremets in a 28cm. diameter Mix Dp- 'Phantom' was within ± 4%.