Abstract
Image qualities were evaluated in terms of the noise equivalent quanta number (NEQ (u)), which is the total evaluation method including the gamma, modulation transfer function (MTF) and Wiener spectrum. Then, we carried out some experiments to observed the usefullness. NEQ (u) was applied for evaluating various systems with large differences regarcling gamma and speed. As a result, it was found that NEQ (u) was affected to great extent by gamma and it was seen as not being sfficient for evaluating the image quality by MTF and Wiener spectrum only. In some systems with the same system speed, it was shown by calculating NEQ (u) that a combination of high-speed film with a low-speed screen is available for the fine structure object and a combination low-speed film with high-speed screen is available for large structure object. These results are in good agreement with the clinical evaluations carried out. NEQ (u) is a usefull method for evaluating of the radiographic image quality.
