Proceedings PaperDetectability of pulmonary nodules in linearly and logarithmically amplified digital images of the chest
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The purpose of this study was to compare detectability of pulmonary nodules in linearly and logarithmically amplified digital images of the chest. One hundred and sixty digital x-ray images of a frozen, unembalmed, human chest phantom with simulated pulmonary nodules were acquired using a 40 cm diameter image intensifier-television camera system. Signal from the video camera was digitized with a frame grabber using MicroVAX 3400 as the host computer. Each of these 160 images was processed using both linear and logarithmic amplification, resulting in 320 digital images of the chest. A free-response receiver operating characteristic (FROC) study was performed in which an experienced radiologist was asked to locate multiple simulated nodules on all 320 digital images and to record one of three levels of confidence for each assumed nodule. For each criterion, the total number of correct responses was divided by the total number of nodules to obtain the ordinate of the point. The total number of false-positive answers generated was divided by the number of images to obtain the abscissa of the point. Examination of FROC curves demonstrated that significantly more mediastinal nodules were identified in logarithmically amplified images.