ABSTRACT

The known risks associated with exposure to radiation and the need for high-quality radiographic images to ensure accurate diagnoses make it essential that X-ray imaging systems be designed and maintained to provide high-quality images for low acceptable exposure levels. The ability of an X-ray detector to produce high signal-to-noise ratio images is described by the detective quantum efficiency (DQE). This chapter discusses the fundamental principles of the DQE and provides a summary of important linear systems concepts required to understand and interpret its meaning, including the modulation transfer function (MTF), line-spread function (LSF), sampling, signal aliasing, and noise aliasing. An introduction to cascaded-systems analysis is provided as a means of understanding signal and noise properties of X-ray detectors and generating theoretical models of the DQE. These models are important to establish performance benchmarks and to help guide the development of new detectors. It is shown there remains a large difference in DQE values between detectors in use today, and highlights the importance for informed purchase decisions and ongoing maintenance to ensure continuing high standards of care.