反転現像処理X線写真に関する研究

抄録

The X-ray film used for intensifying screens consists of silver halide grains of various size and having large dispersion. In conventional radiographs, film emulsion is blackened gradually from silver halide grains of large size and higher sensitivity to those of smaller size and lower sensitivity. In black-and-white reversal processing, larger size grains are mainly removed by bleach. It is thus expected that the final image of reversal-processed film will be formed by blackening of minute silver halide grains. Basing on this assumption, the image quality of reversal-processed radiograph was investigated from the staved point of spatial frequency characeristics, entropy and redundancy analysis. The radiographic granularity measured by Wiener spectrum showed reversal development to be better than conventional development at same density, and reversal development at high exposures and conventional development at low exposures to be advantageous. From the entropy analysis, optimum conditions under which transmitted information or the relative efficiency of transmission η is a maximum were found to exist for both conventional and reversal-processed radiographs. Also, from redundancy analysis, the reversal-processed radiograph at low subject contrast was better than conventional radiographs. Radiographs by reversal processing should thus prove excellent for clinical and detailed diagnostic purposes.