Digital Image Quality Descriptors and Performance Characteristics

Abstract

This chapter first introduces three characteristics of a digital image, including the matrix, the pixel, and the bit depth. Three important descriptors in digital image quality are spatial resolution, contrast resolution, and noise. While spatial resolution refers to the imaging system to show detail or sharpness, contrast resolution describes the ability of the imaging system to show differences in tissue contrast on the image (image contrast). Noise on the other hand refers to the grainy or mottle appearance of the image due to the number of photons used to create the image. Fewer photons will produce more noise (quantum noise). Finally, performance characteristics of digital detectors are introduced such as the point spread function (PSF), the edge spread function (ESP), the modulation transfer function (MTF) and the detective quantum efficiency (DQE). Of these four characteristics, only the DQE was described as it is an important metric used to describe the noise characteristics of a digital detector and has practical implications in clinical imaging. Finally, the notion of image artifacts arising from several sources, including the detector, software, and the object being imaged, was introduced.