Modeling visual search during mammogram viewing

The purpose of this study was to determine if quantitative parameters derived from visual scanpaths obtained by eye-position recording and parsed using a search and error model can be used to separate readers with different levels of expertise. Expertise was established on the basis of level of training and scores on an image reading test. The eye-position recordings of 9 readers, who searched 31, two view (cc and mlo) mammograms for breast cancer were reviewed. The likelihood of hitting a lesion with a "useful visual field" of 5 degrees of visual angle circumscribed about the center of the gaze location was measured as well as the time required to first hit a lesion and the fixation dwell time on the lesion zone. The hits and misses were classified, using the search model, into scanning, recognition and decision categories. The mammographers were significantly different from the trainees when compared using the categories of the search model.