5. 信頼性向上のための臨床撮影技術の実際 : 第44回総会シンポジウム : 放射線技術における信頼性の向上 : 胸部単純X線撮影技術に関して

概要

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For the optimization of image quality of the lung field, detection experiment of simulated tiny lung cancers and evaluation of clinical chest films were carried out, and these results were analyzed by making a comparison with the physical image characteristics. Detectability of shadows simulating tiny lung cancers against the background of lung field varies hardly in spite of depreciation of image characteristics (sharpness and granularity), as far as we use common screens and films, with high voltage technique. However with the low contrast system, a little deterioration of detectability was observed. With any systems, if the diameter of the shadows are 10 mm, detectability falls sharply compared with 12.5 mm. Judgments on clinical films by doctors show that poor graininess is the dominant cause affecting diagnostic utilities and secondly too low or too high contrast. Contrast coefficient (C) is defined. C=μ・(P/P+S)・G where μ=linear attenuation coefficient of primary x-ray reaching intensifying screens (mm^<-1>) P=primary x-ray fraction S=scatter x-ray fraction G=film contrast Adequate range of (C) is from 0.03 to a little over 0.04 (mm^<-1>). Keeping (C) in this range, by using a suitable combination of x-ray energy, anti-scatter grid and film contrast, it is reasonable to try for a better description of the mediastinal zone.
公益社団法人日本放射線技術学会の論文
1988-11-01