The value of observer performance studies in dose optimization: a focus on free-response receiver operating characteristic methods.

Receiver operating characteristic (ROC) analysis has been successfully used in radiology to help determine the combined success of system and observer. There is great value in these methods for assessing new and existing techniques to see if diagnostic accuracy can be improved. Within all aspects of radiology there should be compliance with the as-low-as-reasonably-achievable principle, which requires optimization of the diagnostic suitability of the image. Physical measures of image quality have long been used in the assessment of system performance, but these alone are not sufficient to assess diagnostic capability. It is imperative that the observer be included in any assessment of diagnostic performance. The free-response ROC paradigm has been developed as a statistically powerful advancement of traditional ROC analysis that allows a precise interpretation of complex images by adding location information to the level of observer confidence. The following review of free-response ROC methodology will explain how observer performance methods can be valuable in image optimization, including examples of how these have already been successful in hybrid imaging.