小川憲一 京都大学医学部附属病院放射線部 1. 方法 1-1. A System of Setting Exposure Conditions in General X-rays Using a Calculating Formula

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1 X 885 臨床技術 論文受付 2009 年 12 月 10 日 論文受理 2010 年 5 月 22 日 一般 X 線撮影時の照射条件設定システムの構築 小川憲一 京都大学医学部附属病院放射線部 Code No. 620 緒言 X X X X 1 1. 方法 X KXO-80G 1 1 mmal A System of Setting Exposure Conditions in General X-rays Using a Calculating Formula Kenichi Ogawa Kyoto University Hospital, Clinical Radiology Service Received December 10, 2009; Revision accepted May 22, 2010; Code No. 620 Summary The purpose of this study was to determine the exposure conditions for general X-rays by calculation. The concept of the basic equation for the calculation is that the dose after transmitting an object is determined by entering the exposure conditions. For this purpose, we formulated a basic equation by mathematically representing all factors that influence imaging conditions. Using the basic equation, we succeeded in determining the optimal exposure condition for a patient s body thickness by calculation. Even if another equipment, grid, added filter, etc., is used, optimal exposure conditions can be determined by adding correction factors determined by simple added measurements; this confirmed the versatility of the system. The calculation accuracy was verified to be within 15%. By using this system, we succeeded in optimizing exposure conditions for general X-rays. Key words: general X-rays, exposure condition, calculating formula, grid, added filter

2 mmal X 1 DHF-1510H II mmal 1.5 mmal 8: cm ALCO ELECTRIC MODEL F-11D RAMTEC-150E DC300 FS 1-3 TD=V I T (150/FDD) 2 R A(d) S AF F B B1 1 TD transmission dose C/ kg V X kv I ma T ms FDD cm R C/kg/mAs A(d) X 1 d cma(d) S A(d) AF added filter A(d) F B B1 B Fig cm 4 mm 30 cm cm cm 200 ma 50 ms X kv 140 kv 80 kv 1.0 V Fig. 1 Figure showing arrangement for measurement. The radiation field is the size on the position of the dose meter R 1 TD R cm 80 kv 200 ma 50 ms FDD 150 cm R X 2 R C (C/kg)/C 1 R A(d) S AF F B B1 1.0 R=TD/(V I T (150/FDD) 2 ) R FDD 80 kv 150 cm 1.0 R 1 mas A(d) cm cm 200 ma 50 ms d cm 3 cm 25 cm 40 kv 140 kv 1.0 A(d) A(d) 66 8

3 X X S 1 S S 8 cm 17 cm cm 50 kv 130 kv A(d) 1 S 2 1 A(d) AF AF AF 0.05 mmcu+0.5 mmal 2 8 cm 17 cm cm 50 kv 130 kv A(d) AF AF= F cm 200 ma 50 ms 40 kv 140 kv 3 cm 25 cm 5 5 cm cm cm A(d) B B cm 40 kv 140 kv 3 cm 20 cm cm cm X T t B B1 B B1 T t X T t1 80 kv 20 cm cm B1 T t1/t t Fig. 2 Relationship between tube voltage and fluorescence values using X-rays device of two companies. Fluorescence values are relative values for 80 kv to 1.0. Water phantom, grid and addition filter are not used. 2. 結果 2-1 Fig. 2 1 V= (kv) (kv) (kv) R pc (C/kg)/C 200 ma 50 ms 10 mas R R 1 mas 0.54 μc/kg 2-3 A(d) 40 kv 140 kv Fig kv 140 kv 120 kv A(d)=e d 2-4 X S 1 2 S Table 1 2 A(d) S

4 888 Fig. 3 Relationship between thickness of water phantom and fluorescence values for field of cm. Fluorescence values are relative values for no water phantom to 1.0. Table 1 Table shows S value for tube voltage using water phantom of 8 cm and 17 cm for X-rays device of two companies A(d) are relative values for without the water phantom to 1.0. S values are the rate of attenuation dose (A(d)) for Hitachi (H) and Toshiba (T). Tube voltage water (-) water 8 cm water 17 cm kv A(d)T, A(d)H A(d)T A(d)H S=A(d)H/A(d)T A(d)T A(d)H S=A(d)H/A(d)T T: Toshiba H: Hitachi 70 kv 8 cm 17 cm 6 60 kv 10 S 8 cm S= (kv) (kv) (kv) AF AF Table 2 8 cm 17 cm A(d) A(d) AF 8 cm 17 cm 60 kv 17 cm AF 4 AF 8 cm AF= (kv) (kv) (kv) F 40 kv 140 kv 80 kv 120 kv Fig. 4a b cm cm 30 cm 1 cm 10 kv FA cm 2 80 kv 20 cm 5 F= (FA) (FA) (FA) (FA) (FA) Fig cm 40 kv 10 Fig cm 66 8

5 X 889 Table 2 Table show AF value for tube voltage using water phantom of 8 cm and 17 cm for the added filter in and out A(d) are relative values for no water phantom to 1.0. X-ray device is Hitachi and added filter is 0.05 mmcu+0.5 mmal. AF values are A(d)filter+/A(d)filter-. Tube voltage water (-) water 8 cm water 17 cm kv A(d) f +, - A(d) f - A(d) f + AF A(d) f - A(d) f + AF added filter: f Fig. 4 Relationship between thickness of water phantom and field factor. Field factors are relative values for cm and fluorescence values of each water thickness to 1.0. (a) tube voltage 80 kv. (b) tube voltage 120 kv. a b Fig. 5 Field factor for field area and tube voltage using water phantom of 15 cm. Fig. 6 Field factor for thickness of water phantom and tube voltage using field of cm

6 890 Fig. 7 Transmission of total radiation for tube voltage changing thickness of the water phantom. Field size is cm. Fig. 8 Transmission of total radiation for tube voltage changing field. Thickness of the water phantom is 15 cm. 25 cm cm X Fig. 7 X 10 cm 15 cm X Fig. 8 X cm X X T t cm 80 kv B= d d d 考察 X 1 Fig. 9 Transmission of total radiation for tube voltage changing grid ratio. Values of is measurement value and other values are values in the document. Thickness of water phantom is 20 cm. Strip frequency of grids is cm cm X X 66 8

7 X 891 Fig X 2 80 kv 120 kv 120 kv 80 kv 120 kv X 80 kv 120 kv 120 kv 1 B1=T t1/t t T t1 T t 80 kv 20 cm T t1 80 kv 20 cm T t1 3-2 X 1 2 X X 1 R 1 A(d) S 8 cm 17 cm S S 2 S 60 kv 10 S A(d) 60 kv 10 A(d) S A(d) X S 8 cm 17 cm S 12 cm 15 cm S 3-3 X 1 R AF AF AF 5 8 cm 17 cm AF 4 AF AF AF 12 cm 15 cm μc/kg μc/kg

8 結語 X X 15 謝辞 参考文献 ; 65(1): JIS X 2004; 60(8): 図表の説明 Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 2 X 80 kv cm cm 1.0 a 80 kv b 120 kv 15 cm cm X cm X 15 cm X 20 cm 60 Table 1 2 X 8 cm 17 cm S A(d) 1.0 S A(d) Table 2 8 cm 17 cm AF A(d) 1.0 X 0.05 mmcu+0.5 mmal AF A(d) filter+/a(d) filter- 66 8