Prediction of human observer performance by numerical observers: an experimental study

Numerical observers are investigated for predicting the outcome of a free-r esponse human observer study involving the detection of simulated pulmonary nodules in images reconstructed from low-dose computed tomography projecti on data by use of several reconstruction algorithms. A new way of calculati ng the figure of merit of a numerical observer is proposed wherein the dete ctability of signals in a particular image depends on the noise properties associated with that image and not the other images in the data set. The re sulting variants of numerical observers are found to perform better than th eir traditional counterparts. In particular, the imagewise variant of the r egion-of-interest observer is found to predict best the rank ordering of al gorithms by human observers for the free-response task. (C) 1999 Optical So ciety of America [S0740-3232(99)00303-8].