BASIC STUDIES ON THE DETECTABILITY OF SOLITARY-NODULES IN CHEST RADIOGRAPHY : DIFFERENCE OF SCREEN-FILM SYSTEM AND MAGNIFICATION RADIOGRAPHY

The chest phantom was modeled on that of a lung cancer. For the screen-film system and magnification radiography, the detectability of solitary-nodules in a chest radiograph was quantified in terms of the results of observer performance experiments by using ROC analysis. In contact radiography, high-resolution rare earth screen systems set a high value on the detection of solitary-nodules. Upon evaluation, high-resolution rare earth screen systems were found to be better than the medium-speed regular systems (Hiscreen-RX) being used mostly in clinical examinations at present. It was apparent that detectability in magnification radiography was improved as compared with detectability in contact radiography. In addition, there is little difference in detectability among the three screen-film systems used in magnification radiography. Considering the increase of exposure and the unsharpness caused by patient movement, it is better to use rare earth screen systems with high speed in magnification radiography. Sensitivity is improved, both in contact and magnification radiography, by Copper filtering.