ABSTRACT
This chapter introduces metrics that are used to characterize image quality and system performance. It identifies key physical factors that determine performance characteristics. The chapter describes the modulation transfer function and detective quantum efficiency. It discusses linear systems theory and presents a description of important principles and relationships required to characterize system performance in the spatial frequency domain. The chapter examines how Fourier methods are used, and how to develop an understanding of image noise in both the spatial and spatial frequency domains. Digital images consist of a matrix of numerical values that represent image brightness on a uniformly-spaced grid of picture elements. One consequence of this is that both signal and noise may exhibit spectral aliasing artifacts. Quantum-based imaging systems generate images through a cascade of random physical processes. For example, X-ray interactions and energy absorption are random processes.
