Visual psychophysics and medical imaging: nonparametric adaptive method for rapid threshold estimation in sensitivity...

The M-AFC (alternatively forced choice) transformed up-down adaptive method for the rapid determination of visual thresholds in medical images is described. The method is very efficient in obtaining thresholds to medical imaging parameters; in addition, it is free from criterion bias, an important concern in radiology, and it is free from parametric assumptions about the stimulus scale, which is often unknown due to the complexity of medical images. Issues of experimental design are presented that arise in the use of this method, and the psychological caveats which should be followed with human observers are noted. Two experiments are presented to demonstrate the method's efficacy in determining thresholds and psychometric functions in medical images.