Physical and Psychophysical Measurement of Images

Abstract

In this chapter, we consider how medical images may be evaluated in terms of the information they provide to human observers. Much of this book discusses what is known about the registration and interpretation of visual data within the human visual system. This knowledge, the product of a large psychophysical and neurophysiological literature, is fundamental to any attempt to characterize imagery: it specifies the dimensions, properties, and aspects of images that are informative. An understanding of visual perception should educate our attempts to characterize images by means of physical measurements. Beyond this, the psychophysical literature provides a family of methodologies for assessing diagnostic performance of imaging systems in which human observers serve as pattern recognizers. Psychophysical methods assess psychological response to variation in physical stimuli. These procedures can be applied even where little is known about the underlying recognition process itself or where the physics of the imaging process is not well understood. The best known and most widely used psychophysical method in medical imaging research generates receiver operating characteristic (ROC) curves. The second part of this chapter is devoted to an introduction to current use of these methods.