Peripheral vision, structured noise and film reader error.

The ability of film readers to detect a nodular target abnormality with the peripheral vision was studied using a gray structureless background, chest radiographs with a bilateral pneumothorax and chest radiographs with pulmonary vasculature. Peripheral detection of the nodular abnormality was profoundly decreased by the presence of the normal structures even though the nodule properties such as size and contrast were not different and, in the case of the pneumothorax, the nodules did not overlap normal structures. Structured noise is an important and often neglected variable in studies of visual search, film reader error and image processing in radiology.