Japanese Journal of Radiological Technology

For the purepose of the reduction of the exposure dose to the patient in X-ray diagonosis, the techniques which affer the maximum diagonostic informations by the minimum doses are indispensable. This paper is discussed the following problems of the techniques to be solnel. 1) The problems before X-ray exposure.(a)Strict order for the X-ray diagnosis (b)Adequate apparatus and accessaries (c)Ideal design of X-ray room 2) The problems during X-ray exposure (a)Choice of the adequate tube voltages (b)Field sizes (c)Intensifying screens 3) The problems after X-ray exposure (a)Excellent X-ray diagonostic ability (doctor) (b)Improvement of techniques by the film check (c)Developping process (d)Adequate system for the filing of the films

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On thu reduction of the radiation exposure to the patient; the gonad dose reducton in radiography of the infant hip joints, abdomen and fetus io Verg important. This artile refer to our study about a factors for them, especially, the tube voltages, screens, filters and protectiod. The result are as follows : - 1) Infant hip joint 60kVp, HS or high speed film, with protection, without Lysholm grid. 2) Abdomen 80〜90kVp, 2〜3mm Al filter, high speed screen and film are preferable. 3) Fetus Low tension apparatus-90kVp. 0.15〜0.2mm Cu filter. High tension apparatus-120kVp. 0.2〜0.3mm Cu filter. Make use of high speed screen or film.

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In the symposium the author would like to advocated the high sensitive radiography which is primarily based on the exposure reduction technique, in contrast to conventional high contrast radiography with high exposure. Assuming to the stomach examination, this paper mainly discusses the diagnostic evaluation and the image quality for the several factors which affect on the image quality, such as filter, grid, film, fluorescent screen, and film processor. Prior to the experiment, the questionnaire is distributed to 170 hospitals all over Japan to investigate the actual situation in the field. As a result of the study 6 subjects for the experiment are selected. The followings are the summary of the results. 1) 0.2 to 0.3mm Cu filter on the radiation window is suitable for exposure reduction. 2) The grids having different grid ratio should be selectable according to the patient thickness. Selectable grid ratio, for example, are 4 to 1,6 to 1,10 to 1,and no grid. 3) Exposure time should be in the range from 0.02 to 0.05 seconds. 4) Image quality should be decided after discussion with the doctor. 5) The fluorescent screen and the film should be high speed type.

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On programing radiotherapy, it is one of most essential procedure to choose irradiation field as much protective to normal tissue as possible. Extension of carcinoma is always variform, while mechanical fields provided from Co-60 installation are unvariably rectangular. There are two types of beam shaping equipment available, one is "trimming table" equiped to stretcher side and another is "shadow tray" equiped to sourcehead side, the latter being desirable for the moving techniques. Almost all conventional shadow trays have very complexed structure and too much weight to handle on every treatment, for instance, complete box-type shadow tray offers troublesome work to mount on sourcehead, or to reset the lead trimmer. Auther designed a very simple structutures for its purpose, comprised two transparent acrylite plates and four metalic columns to connect the plates each other. Each column has screw on each end of it and the each screw on one end is designed as reversewise against another one. Two plates are loosened or teightened easily by screwing the columns to one direction. For the purpose of stopping slip off of lead trimmers, lower plate has metalic frame offering slight elvation on every side of the margin except one, that is a gate for the lead trimmers. Since there can be equiped wedge filter under the lower plate, combination use for lead trimmer and wedge filter together is also possible at same time. As beam direction from Co-60 source makes radial line on its course, lead trimmers should be made slightly trapezoidal on their sectional view, to fit to the beam direction. Thickness of two acrylite plates being 10mm in total, 7.3% of dose are absorbed.

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