Informational Performance In Radiography

Paper presented at Symposium on “Photographic Aspects of Ionizing Radiations”, organized by the Science Committee on 15–17 April 1964, at Oxford.

Abstract

An “information index” as a measure of informational performance of a radiographic system is derived, taking into account visual threshold concepts of the human eye. Theoretically, this information index is related to the Wiener spectrum, describing the noise power spectrum in a detection system as a function of spatial frequency, and to the informational sensitivity. It is found that the “spread” (unsharpness or blur) in a radiographic system determines the smallest image size for which the information index may be found whereas the maximum scan of the eye (~02 inch) determines the largest image size. The information index depends on quantum-statistical fluctuations and varies with the speed of the radiographic film, its gradient and the optical density to which It is developed. These conclusions are borne out in experiments. Practically, the information index is a useful tool to judge the adequacy of different photographic materials for radiographic applications. A procedure for routine evaluation of the informational performance of radiographic systems is described.

Notes

Paper presented at Symposium on “Photographic Aspects of Ionizing Radiations”, organized by the Science Committee on 15–17 April 1964, at Oxford.