Predictive value and threshold detectability of lung tumors.

The visibility limit of soft tissue nodules in the lungs is 3 mm on a chest radiography, yet lung cancers are rarely detected until the tumors are 8-10 mm in size. This paper presents data on the size distribution of nodular lung cancers and noncancerous nodular noise on chest radiographs. These data are analyzed in decision-making terms and show that when the size is 8-10 mm, observers can separate true cancers from noise that mimics cancer, with a probability of being correct, or a predictive value, of 90% or more.