Changes in lesion detectability caused by light adaptation in retinal photoreceptors.

This paper deals with specific physiologic mechanisms in the retina that can decrease apparent contrast in dark parts of an image. A new signal processing model based on these mechanisms is described which can be used to predict observer contrast thresholds for circular test patches superimposed on both uniform and nonuniform backgrounds. Experiments conducted using this model suggest that several types of viewing conditions commonly encountered in clinical practice may interfere with the radiologist's ability to detect low-contrast lesions. The authors' long-term objective is to use this model to predict observer performance when searching for marginally visible anatomic and pathologic detail in radiographic examinations.